QRS Duration (qr + duration)

Distribution by Scientific Domains


Selected Abstracts


ABSENCE OF CORRELATION BETWEEN QRS DURATION AND ECHOGRAPHIC PARAMETERS OF VENTRICULAR DESYNCHRONIZATION.

ECHOCARDIOGRAPHY, Issue 2 2004
CAN WE STILL TRUST THE ELECTROCARDIOGRAPHIC CRITERIA?
Background: Identification of the responder candidates for multisite pacing is still difficult and severe heart failure, dilated left ventricle with reduced ejection fraction, prolonged QRS with left bundle branch block (LBBB) are still considered the principal indicators of ventricular desynchronization. The aim of the study was to assess if echographic ventricular desynchronization parameters measured in patients with dilated cardiomyopathy and severe heart failure are correlated with the duration of the QRS on surface electrocardiogram. Methods: This study included 51 patients aged 58.8 ± 7.4 years with idiopathic DCM. The following parameters were measured: QRS duration; effective contraction time (ECT) measured as the interval between QRS onset and closure of aortic valve, interventricular delay (IVD) measured as the time between onset of aortic and pulmonary flow, left ventricular mechanical delay (LVD) as the time from maximal interventricular septum contraction and posterior wall contraction, posterior (P), lateral (L), and posterolateral (PL) wall delays, as the time from QRS onset to maximal wall contraction. Regional post-systolic contraction was defined in a given wall as the difference (contraction delay , ECT)> 50 ms. Results: 29 patients presented complete LBBB, 22 patients had QRS duration < 120 ms. 39 patients had a post-systolic contraction of the PL wall (32 patients of the L wall and 26 patients of the P wall). 16 patients with QRS duration <120 had a post-systolic contraction of the PL wall (as for the LBBB the rest of 39 patients). In 40 patients the sequence of regional ventricular contraction was: P-L-PL wall (16 patients with QRS < 120). LVD was > 100 ms in 36 patients (26 patients with LBBB and 10 with QRS < 120). 27 patients with LBBB and 6 with QRS < 120 ms presented IVD > 30 ms. There was no correlation between the QRS duration and the parameters listed above. Conclusions: In a population of patients with severe heart failure and dilated cardiomyopathy there is no correlation between the duration of the QRS and echocardiographic parameters of ventricular desynchronization. These results show that mechanical ventricular desynchronization can be observed in patients with a QRS duration < 120 ms. Further studies are needed to evaluate if this population could beneficiate of multisite pacing therapy. [source]


Aspects of Left Ventricular Morphology Outperform Left Ventricular Mass for Prediction of QRS Duration

ANNALS OF NONINVASIVE ELECTROCARDIOLOGY, Issue 2 2010
Nina Hakacova M.D., Ph.D.
Background: The knowledge of the case-specific normal QRS duration in each individual is needed when determining the onset, severity and progression of the heart disease. However, large interindividual variability even of the normal QRS duration exists. The aims of the study were to develop a model for prediction of normal QRS complex duration and to test it on healthy individuals. Methods: The study population of healthy adult volunteers was divided into a sample for development of a prediction model (n = 63) and a testing sample (n = 30). Magnetic resonance imaging data were used to assess anatomical characteristics of the left ventricle: the angle between papillary muscles (PMA), the length of the left ventricle (LVL) and left ventricular mass (LVM). Twelve-lead electrocardiogram (ECG) was used for measurement of the QRS duration. Multiple linear regression analysis was used to develop a prediction model to estimate the QRS duration. The accuracy of the prediction model was assessed by comparing predicted with measured QRS duration in the test set. Results: The angle between PMA and the length of the LVL were statistically significant predictors of QRS duration. Correlation between QRS duration and PMA and LVL was r = 0.57, P = 0.0001 and r = 0.45, P = 0.0002, respectively. The final model for prediction of the QRS was: QRSPredicted= 97 + (0.35 × LVL) , (0.45 × PMA). The predicted and real QRS duration differed with median 1 ms. Conclusions: The model for prediction of QRS duration opens the ability to predict case-specific normal QRS duration. This knowledge can have clinical importance, when determining the normality on case-specific basis. Ann Noninvasive Electrocardiol 2010;15(2):124,129 [source]


QRS Duration in the Selection of Patients for Cardiac Resynchronization Therapy

ANNALS OF NONINVASIVE ELECTROCARDIOLOGY, Issue 4 2009
Arthur J. Moss M.D.
No abstract is available for this article. [source]


Clinical Implications of QRS Duration and QT Peak Prolongation in Patients with Suspected Coronary Disease Referred for Elective Cardiac Catheterization

ANNALS OF NONINVASIVE ELECTROCARDIOLOGY, Issue 2 2008
M. Nadeem Attar M.D., M.R.C.P.
Background: The electrocardiogram (ECG) remains a simple, universally available, and prognostically powerful investigation in heart failure, and acute coronary syndromes. We sought to assess the prognostic utility of clinical, angiographic, and simple ECG parameters in a large cohort of patients undergoing elective cardiac catheterization (CC) for known or suspected coronary artery disease. Methods: Consecutive consenting patients undergoing CC for coronary disease were enrolled at a single tertiary center. Patient data, drug therapy, catheter reports, and ECG recordings were prospectively recorded in a validated electronic archive. The primary outcome measure was death or nonfatal myocardial infarction (MI) over 1 year or until percutaneous or cardiac surgical intervention. Independent prognostic markers were identified using the Cox proportional hazard model. Results: A total of 682 individuals were recruited of whom 17(2.5%) died or suffered a nonfatal MI in 1 year. In multivariate analysis QRS duration (ms) (HR 1.03 95% CI 1.01,1.05, P = 0.003), extent of coronary disease (HR 2.01 95% CI 1.24,3.58, P = 0.006), and prolonged corrected QT peak interval in lead I (HR 1.02 95% CI 1.00,1.03, P = 0.044) were independently associated with death or nonfatal MI. Receiver-operator characteristic (ROC) analysis for the multivariate model against the primary end point yielded an area under the curve of 0.759 (95% CI 0.660,0.858), P < 0.001. Conclusions: QRS duration and QT peak are independently associated with increased risk of death or nonfatal MI in stable patients attending for coronary angiography. [source]


Brain Natriuretic Peptide Levels and Response to Cardiac Resynchronization Therapy in Heart Failure Patients

CONGESTIVE HEART FAILURE, Issue 5 2006
Reynolds M. Delgado MD
The authors used brain natriuretic peptide (BNP) as a reliable marker to identify nonresponders to cardiac resynchronization therapy (CRT) in patients with advanced heart failure. The study included 70 patients with left ventricular dysfunction (mean ejection fraction, 21±4%) and left bundle branch block (QRS duration, 164±25 milliseconds) treated with CRT. The authors reviewed data on New York Heart Association functional class, baseline ejection fraction, sodium, creatinine, QRS duration, and BNP levels 3 months before and after CRT therapy. The authors compared results of 42 patients who survived (973+192 days) after CRT implantation (responders) to those of 28 patients (nonresponders) who either expired (n=21) or underwent heart transplantation (n=5) or left ventricular assist device implantation (n=2) after an average of 371+220 days. Mean BNP levels after 3 months of CRT decreased in responders from 758±611 pg/mLto 479±451 pg/mL (P=.044), while in nonresponders there was increase in BNP levels from 1191 ±466 pg/mL to 1611 ±1583; P=.046. A rise in BNP levels was associated with poor response (death or need for transplantation or left ventricular assist device and impaired long-term outcome), which makes it a good predictor to identify such patients. [source]


Contractile Reserve Assessed Using Dobutamine Echocardiography Predicts Left Ventricular Reverse Remodeling after Cardiac Resynchronization Therapy: Prospective Validation in Patients with Left Ventricular Dyssynchrony

ECHOCARDIOGRAPHY, Issue 6 2010
F.R.C.P.C., Mario Sénéchal M.D.
Background: The presence of viable myocardium may predict response to cardiac resynchronization therapy (CRT). The aim of this study is to evaluate in patients with left ventricular (LV) dyssynchrony whether response to CRT is related to myocardial viability in the region of the pacing lead. Methods: Forty-nine consecutive patients with advanced heart failure, LV ejection fraction < 35%, QRS duration > 120 ms and intraventricular asynchronism , 50 ms were included. Dobutamine stress echocardiography was performed within the week before CRT implantation. Resting echocardiography was performed 6 months after CRT implantation. Viability in the region of LV pacing lead was defined as the presence of viability in two contiguous segments. Response to CRT was defined by evidence of reverse LV remodeling (,15% reduction in LV end-systolic volume). Results: Thirty-one patients (63%) were identified as responders at follow-up. The average of viable segments was 5.9 ± 2 in responders and 3.2 ± 3 in nonresponders (P = 0.0003). Viability in the region of the pacing lead had a sensitivity of 94%, a specificity of 67%, a positive predictive value of 83%, and a negative predictive value of 86% for the prediction of response to CRT. Conclusions: In patients with LV dyssynchrony, reverse remodeling after CRT requires viability in the region of the pacing lead. This simple method using echocardiography dobutamine for the evaluation of local viability (i.e., viability in two contiguous segments) may be useful to the clinician in choosing the best LV lead positioning. (Echocardiography 2010;27:668-676) [source]


Usefulness and Limitation of Dobutamine Stress Echocardiography to Predict Acute Response to Cardiac Resynchronization Therapy

ECHOCARDIOGRAPHY, Issue 1 2010
F.R.C.P.C., Mario Sénéchal M.D.
Background: It has been hypothesized that a long-term response to cardiac resynchronization therapy (CRT) could correlate with myocardial viability in patients with left ventricular (LV) dysfunction. Contractile reserve and viability in the region of the pacing lead have not been investigated in regard to acute response after CRT. Methods: Fifty-one consecutive patients with advanced heart failure, LV ejection fraction , 35%, QRS duration > 120 ms, and intraventricular asynchronism , 50 ms were prospectively included. The week before CRT implantation, the presence of viability was evaluated using dobutamine stress echocardiography. Acute responders were defined as a ,15% increase in LV stroke volume. Results: The average of viable segments was 5.8 ± 1.9 in responders and 3.9 ± 3 in nonresponders (P = 0.03). Viability in the region of the pacing lead had an excellent sensitivity (96%), but a low specificity (56%) to predict acute response to CRT. Mitral regurgitation (MR) was reduced in 21 patients (84%) with acute response. The presence of MR was a poor predictor of response (sensibility 93% and specificity 17%). However, combining the presence of MR and viability in the region of the pacing lead yields a sensibility (89%) and a specificity (70%) to predict acute response to CRT. Conclusion: Myocardial viability is an important factor influencing acute hemodynamic response to CRT. In acute responders, significant MR reduction is frequent. The combined presence of MR and viability in the region of the pacing lead predicts acute response to CRT with the best accuracy. (Echocardiography 2010;27:50-57) [source]


ABSENCE OF CORRELATION BETWEEN QRS DURATION AND ECHOGRAPHIC PARAMETERS OF VENTRICULAR DESYNCHRONIZATION.

ECHOCARDIOGRAPHY, Issue 2 2004
CAN WE STILL TRUST THE ELECTROCARDIOGRAPHIC CRITERIA?
Background: Identification of the responder candidates for multisite pacing is still difficult and severe heart failure, dilated left ventricle with reduced ejection fraction, prolonged QRS with left bundle branch block (LBBB) are still considered the principal indicators of ventricular desynchronization. The aim of the study was to assess if echographic ventricular desynchronization parameters measured in patients with dilated cardiomyopathy and severe heart failure are correlated with the duration of the QRS on surface electrocardiogram. Methods: This study included 51 patients aged 58.8 ± 7.4 years with idiopathic DCM. The following parameters were measured: QRS duration; effective contraction time (ECT) measured as the interval between QRS onset and closure of aortic valve, interventricular delay (IVD) measured as the time between onset of aortic and pulmonary flow, left ventricular mechanical delay (LVD) as the time from maximal interventricular septum contraction and posterior wall contraction, posterior (P), lateral (L), and posterolateral (PL) wall delays, as the time from QRS onset to maximal wall contraction. Regional post-systolic contraction was defined in a given wall as the difference (contraction delay , ECT)> 50 ms. Results: 29 patients presented complete LBBB, 22 patients had QRS duration < 120 ms. 39 patients had a post-systolic contraction of the PL wall (32 patients of the L wall and 26 patients of the P wall). 16 patients with QRS duration <120 had a post-systolic contraction of the PL wall (as for the LBBB the rest of 39 patients). In 40 patients the sequence of regional ventricular contraction was: P-L-PL wall (16 patients with QRS < 120). LVD was > 100 ms in 36 patients (26 patients with LBBB and 10 with QRS < 120). 27 patients with LBBB and 6 with QRS < 120 ms presented IVD > 30 ms. There was no correlation between the QRS duration and the parameters listed above. Conclusions: In a population of patients with severe heart failure and dilated cardiomyopathy there is no correlation between the duration of the QRS and echocardiographic parameters of ventricular desynchronization. These results show that mechanical ventricular desynchronization can be observed in patients with a QRS duration < 120 ms. Further studies are needed to evaluate if this population could beneficiate of multisite pacing therapy. [source]


Echocardiographic Features of Patients With Heart Failure Who May Benefit From Biventricular Pacing

ECHOCARDIOGRAPHY, Issue 3 2003
Amgad N. Makaryus
Background: Recent studies suggest that cardiac resynchronization therapy through biventricular pacing (BVP) may be a promising new treatment for patients with advanced congestive heart failure (CHF). This method involves implantation of pacer leads into the right atrium (RA), right ventricle (RV), and coronary sinus (CS) in patients with ventricular dyssynchrony as evidenced by a bundle branch block pattern on electrocardiogram (ECG). Clinical trials are enrolling stable patients with ejection fractions (EF) , 35%, left ventricular end-diastolic diameters (LVIDd) , 54 mm, and QRS duration ,140 msec. We compared echocardiography features of these patients (group 1) with other patients with EF , 35%, LVIDd , 54 mm, and QRS < 140 msec (group 2 = presumably no dyssynchrony). Methods: Nine hundred fifty-one patients with CHF, LVID 54 mm, EF 35% by echocardiography were retrospectively evaluated. One hundred forty-five patients remained after those with primary valvular disease, prior pacing systems, or chronic atrial arrhythmias were excluded. From this group of 145 patients, a subset of 50 randomly selected patients were further studied (25 patients [7 females, 18 males] from group 1, and 25 patients [7 females, 18 males] from group 2). Mean age group 1 = 75 years old, mean age group 2 = 67 years old. Mean QRS group 1 = 161 msec, mean QRS group 2 = 110 msec. Each group was compared for presence of paradoxical septal motion, atrial and ventricular chamber sizes, LV mass, LVEF, and RV systolic function. Results: Of the initial group of 951 patients, 145 (15%) met inclusion criteria. In the substudy, 20/25 (80%) of group l and 7/25 (28%) of group 2 subjects had paradoxical septal motion on echo (Fisher's exact test, P = 0.0005). The t-tests performed on the other echocardiography variables demonstrated no differences in chamber size, function, or LV mass. Conclusions: Cardiac resynchronization therapy with BVP appears to target a relatively small population of our advanced CHF patients (15% or less). Although increasing QRS duration on ECG is associated with more frequent paradoxical septal motion on echo, it is not entirely predictive. Paradoxical septal motion on echo may therefore be more sensitive at identifying patients who respond to BVP. Further prospective studies are needed. (ECHOCARDIOGRAPHY, Volume 20, April 2003) [source]


Acute Cardiac Effects of Nicotine in Healthy Young Adults

ECHOCARDIOGRAPHY, Issue 6 2002
Catherine D. Jolma M.D.
Background: Nicotine is known to have many physiologic effects. The influence of nicotine delivered in chewing gum upon cardiac hemodynamics and conduction has not been well-characterized. Methods: We studied the effects of nicotine in nonsmoking adults (6 male, 5 female; ages 23,36 years) using a double-blind, randomized, cross-over study. Subjects chewed nicotine gum (4 mg) or placebo. After 20 minutes (approximate time to peak nicotine levels), echocardiograms and signal-averaged electrocardiograms (SAECG) were obtained. After 40 minutes, subjects were again given nicotine gum or placebo in cross-over fashion. Standard echocardiographic measurements were made from two-dimensional images. We then calculated end-systolic wall stress (ESWS), shortening fraction (SF), systemic vascular resistance (SVR), velocity for circumferential fiber shortening corrected for heart rate (Vcfc), stroke volume, and cardiac output. P wave and QRS duration were measured from SAECG. Results: Significant differences (P < 0.05) from control or placebo were found for ESWS, mean blood pressure, cardiac output, SVR, heart rate, and P wave duration. No significant changes were seen in left ventricular ejection time (LVET), LV dimensions, SF, contractility (Vcfc), or QRS duration. Conclusions: These results suggest that nicotine chewing gum increases afterload and cardiac output. Cardiac contractility does not change acutely in response to nicotine gum. Heart rate and P wave duration are increased by chewing nicotine gum. [source]


Cardiac function and antiepileptic drug treatment in the elderly: A comparison between lamotrigine and sustained-release carbamazepine

EPILEPSIA, Issue 8 2009
Erik Saetre
Summary Purpose:, To investigate the comparative effects of carbamazepine (CBZ) and lamotrigine (LTG) on electrocardiography (ECG) parameters in elderly patients with newly diagnosed epilepsy. Methods:,, The study was conducted in the Norwegian subcohort (n = 108) of an international randomized double-blind 40-week trial, which compared the efficacy and tolerability of LTG and sustained-release CBZ in patients aged 65 and older with newly diagnosed epilepsy. Target maintenance doses were 400 mg/day for CBZ and 100 mg/day for LTG, with adjustments based on clinical response. Patients with significant unpaced atrioventricular (AV) conduction defect were excluded. Resting 12-lead ECG recordings were made under standardized conditions at pretreatment (baseline) and at the 40-week study visit (treatment visit). Changes in QRS interval (primary endpoint), heart rate (HR), PQ, and QTc (HR-corrected QT) intervals were assessed and compared between groups. Results:, Of the 108 patients randomized, 33 discontinued prematurely because of adverse events (n = 24, none of which was cardiac) or other reasons (n = 9), and 15 were nonevaluable due to incomplete ECG data. None of the assessed ECG parameters differed significantly between groups at baseline. No significant ECG changes were recorded between baseline and treatment visit for QRS duration and QTc intervals, whereas HR fell and PQ intervals increased slightly on both treatments. However, there were no differences between groups in changes from baseline to treatment visit. There were no significant relationships between individual ECG changes and serum drug concentrations, except for QTc intervals, which decreased slightly with increasing CBZ concentrations. The proportion of patients with ECG parameters outside the normal range at treatment visit was similar to that recorded at baseline. Discussion:, Clinically significant ECG changes are not common during treatment with CBZ or LTG in elderly patients with no preexisting significant AV conduction defects. [source]


Safety of Deferring the Reimplantation of Pacing Systems After Their Removal for Infectious Complications in Selected Patients: A 1-Year Follow-Up Study

JOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 5 2010
ELOI MARIJON M.D.
Introduction: Recent expert consensus guidelines mention that one of the principles for infected device replacement following removal is to "reevaluate carefully if there is a continued need for a new cardiac device replacement." This is a Class I recommendation, which nevertheless suffers from a very low level of evidence (level of evidence C), since no study has revisited the systematic practice of reimplanting the same device based on a meticulous clinical reassessment. In the present paper, we examined the safety of withholding the implantation of pacing systems in selected patients. Methods and Results: Between January 2005 and December 2007, 188 consecutive patients underwent extractions of infected pacing systems at 2 medical centers. "Low-risk" patients were identified by (1) a spontaneous heart rate >45 bpm, (2) no symptomatic asystole during monitoring, (3) QRS duration <120 ms when history of AV block was noted, (4) no high-degree AV block during continuous monitoring. They remained device-free, unless an adverse clinical event occurred mandating the reimplantation. The primary study endpoint was rate of sudden death and syncope after a 12-month follow-up. Among the 74 (39.4%) "low-risk" patients, a single patient suffered a bradycardia-related syncopal event corresponding to a 1.3% (95% CI, 0.0,3.9) rate of primary endpoint. Pacing systems were also reimplanted in 24 patients (32.4%) for syncope (n = 1), nonsevere bradycardia-reated symptoms (n = 17), cardiac resynchronization (n = 2), and for reassurance in 4 asymptomatic patients. Conclusion: After removal of infected pacing systems, these preliminary data demonstrated that a strategy of nonsystematic device reimplantation associated with close surveillance was safe in "low-risk" patients, allowing the administration of antimicrobials in a device-free state. (J Cardiovasc Electrophysiol, Vol. 21, pp. 540-544, May 2010) [source]


Septal Dyskinesia and Global Left Ventricular Dysfunction in Pediatric Wolff-Parkinson-White Syndrome with Septal Accessory Pathway

JOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 3 2010
BO SANG KWON M.D.
LV Dysfunction in WPW Syndrome.,Introduction: Echocardiographic studies have shown that some patients with Wolff-Parkinson-White (WPW) syndrome have myocardial dyskinesia in the segments precociously activated by an accessory pathway (AP). The aim of the present study was to determine the extent to which the AP contributes to global left ventricular (LV) dysfunction. Methods: Electrophysiological and echocardiographic data from 62 children with WPW (age at diagnosis = 5.9 ± 4.2 years) were retrospectively analyzed. Results: The left ventricular ejection fraction (LVEF) of patients with septal APs (53 ± 11%) was significantly lower than that of patients with right (62 ± 5%) or left (61 ± 4%) APs (P = 0.001). Compared to patients with normal septal motion (n = 56), patients with septal dyskinesia (n = 6) had a reduced LVEF (61 ± 4% and 42 ± 5%, respectively) and an increased LV end diastolic dimension (P < 0.001 for both comparisons). Multivariate analysis identified septal dyskinesia as the only significant risk factor for reduced LVEF. All 6 patients with septal dyskinesia had right septal APs, and a preexcited QRS duration that was longer than that of patients with normal septal motion (140 ± 18 ms and 113 ± 32 ms, respectively; P = 0.045). After RFA there were improvements in both intraventricular dyssynchrony (septal-to-posterior wall motion delay, from 154 ± 91 ms to 33 ± 17 ms) and interventricular septal thinning (from 3.0 ± 0.5 mm to 5.3 ± 2.6 mm), and a significant increase in LVEF (from 42 ± 5% to 67 ± 8%; P = 0.001). Conclusion: The dyskinetic segment activated by a right septal AP in WPW syndrome may lead to ventricular dilation and dysfunction. RFA produced mechanical resynchronization, reverse remodeling, and improvements in LV function. (J Cardiovasc Electrophysiol, Vol. 21, pp. 290,295, March 2010) [source]


Clustering of Ventricular Tachyarrhythmias in Heart Failure Patients Implanted with a Biventricular Cardioverter Defibrillator

JOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 12 2006
MAURIZIO LUNATI M.D.
Background: Temporal patterns of ventricular tachyarrhythmia (VT/VF) have been studied only in patients who have received implantable cardioverter defibrillators (ICD) for secondary prevention of sudden death, and mainly in ischemic patients. The aim of this study was to evaluate VT/VF recurrence patterns in heart failure (HF) patients with biventricular ICD and to stratify results according to HF etiology and ICD indication. Methods and Results: We studied 421 patients (91% male, 66 ± 9 years). HF etiology was ischemic in 292 patients and nonischemic in 129. ICD indication was for primary prevention in 227 patients and secondary prevention in 194. Baseline left ventricular ejection fraction (LVEF) was 26 ± 7%, QRS duration 168 ± 32 msec, and NYHA class 2.9 ± 0.6. In a follow-up of 19 ± 11 months, 1,838 VT/VF in 110 patients were appropriately detected. In 59 patients who had ,4 episodes, we tried to determine whether VT/VF occurred randomly or rather tended to cluster by fitting the frequency distribution of tachycardia interdetection intervals with exponential functions: VT/VF clusters were observed in 46 patients (78% of the subgroup of patients with ,4 episodes and 11% of the overall population). On multivariate logistic analysis, VT/VF clusters were significantly (P < 0.01) associated with ICD indication for secondary prevention (odds ratio [OR]= 3.12; confidence interval [CI]= 1.56,6.92), nonischemic HF etiology (OR = 4.34; CI = 2.02,9.32), monomorphic VT (OR = 4.96; CI = 2.28,10.8), and LVEF < 25% (OR = 3.34; CI = 1.54,7.23). Cardiovascular hospitalizations and deaths occurred more frequently in cluster (21/46 [46%]) than in noncluster patients (63/375 (17%), P < 0.0001). Conclusions: In HF patients with biventricular ICDs, VT/VF clusters may be regarded as the epiphenomenon of HF deterioration or as a marker of suboptimal response to cardiac resynchronization therapy. [source]


Diagnostic Value of Flecainide Testing in Unmasking SCN5A-Related Brugada Syndrome

JOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 8 2006
PAOLA G. MEREGALLI M.D.
Introduction: Provocation tests with sodium channel blockers are often required to unmask ECG abnormalities in Brugada syndrome (BrS). However, their diagnostic value is only partially established, while life-threatening ventricular arrhythmias during these tests were reported. We aimed to establish sensitivity, specificity, and safety of flecainide testing, and to predict a positive test outcome from the baseline ECG. Methods and Results: We performed 160 tests with flecainide in subjects determined to be at risk for BrS. P wave width, PQ duration, QRS width, S wave amplitude and duration in leads II-III, in addition to ST morphology and J point elevation in V1-V3 were measured before and after flecainide administration. Moreover, leads were positioned over the third intercostal space (V1IC3 -V2IC3). Flecainide tests were considered positive if criteria from the First Consensus Report on BrS were fulfilled. In 64 cases, the test was positive, while 95 were negative (1 test was prematurely interrupted). The sensitivity and specificity, calculated in SCN5A-positive probands and their family members, were 77% and 80%, respectively. Baseline ECGs exhibited significant group differences in P, PQ, and QRS duration, J point elevation (leads V1-V2 and V1IC3 -V2IC3), and S duration in II, but an attempt to predict the outcome of flecainide testing from these baseline ECG parameters failed. No malignant arrhythmias were observed. Conclusion: Flecainide testing is a valid and safe tool to identify SCN5A-related BrS patients. Baseline ECGs do not predict test outcomes, but point to conduction slowing as a core mechanism in BrS. [source]


Evaluation of Myocardial Performance with Conventional Single-Site Ventricular Pacing and Biventricular Pacing in a Canine Model of Atrioventricular Block

JOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 9 2003
PATRICIO A. FRIAS M.D.
Introduction: The aim of this study was to evaluate epicardial biventricular pacing as a means of maintaining synchronous ventricular activation in an acute canine model of AV block with normal ventricular anatomy and function. Chronic single-site ventricular pacing results in dyssynchronous ventricular activation and may contribute to ventricular dysfunction. Biventricular pacing has been used successfully in adult patients with congestive heart failure. Methods and Results: This was an acute study of open chest mongrel dogs (n = 13). ECG, left ventricular (LV), aortic, and pulmonary arterial pressures were measured. LV impedance catheters were used to assess cardiodynamics using instantaneous LV pressure-volume relations (PVR). Following radiofrequency ablation of the AV node, a temporary pacemaker was programmed 10 beats/min above the intrinsic atrial rate, with an AV interval similar to the baseline intrinsic PR interval. The pacing protocol consisted of 5-minute intervals with the following lead configurations: right atrium-right ventricular apex (RA-RVA), RA-LV apex (LVA), and RA-biventricular using combinations of four ventricular sites (RVA, RV outflow tract [RVOT], LVA, LV base [LVB]). RA-RVA was used as the experimental control. LV systolic mechanics, as measured by the slope of the end-systolic (Ees) PVR (ESPVR, mmHg/cc), was statistically greater (P < 0.05) with all modes of biventricular pacing (RA-RVA/LVA 20.0 ± 2.9, RA-RVA/LVB 18.4 ± 2.9, RA-RVOT/LVA 15.1 ± 1.8, RA-RVOT/LVB 17.6 ± 2.9) compared to single-site ventricular pacing (RA-RVA 12.8 ± 1.6). Concurrent with this improvement in myocardial performance was a shortening of the QRS duration (RA-RVA 97.7 ± 2.9 vs RA-RVA/LVA 75.7 ± 4.9, RA-RVA/LVB 70.3 ± 4.9, RA-RVOT/LVA 65.3 ± 4.4, and RA-RVOT/LVB 76.7 ± 5.9, P < 0.05). Conclusion: In this acute canine model of AV block, QRS duration shortened and LV performance improved with epicardial biventricular pacing compared to standard single-site ventricular pacing. (J Cardiovasc Electrophysiol, Vol. 14, pp. 996-1000, September 2003) [source]


Acute Effects of Low Doses of Red Wine on Cardiac Conduction and Repolarization in Young Healthy Subjects

ALCOHOLISM, Issue 12 2009
Matteo Cameli
Background:, Moderate to high blood concentrations of ethanol have been shown to yield acute changes in cardiac electrophysiological properties, but the effect of low concentrations have never been assessed. The role of concomitant changes in clinical variables or cardiac dimensions is also still unknown. This study aimed at exploring the acute effects of low doses of ethanol, administered as Italian red wine, on conduction, depolarization, and repolarization electrocardiographic (ECG) intervals in a population of healthy subjects. Methods:, Forty healthy young volunteers drank a low quantity of red wine (5 ml/kg), and an equal volume of fruit juice in separate experiments. Heart rate, P-wave duration, PR interval, QRS duration, QT interval, corrected QT interval, QT dispersion, and corrected QT dispersion were assessed at baseline and after 60 minutes from challenge. Results:, Mean blood ethanol concentration after drinking was 0.48 ± 0.06 g/l. Compared to the control challenge, significant changes after red wine intake were observed in P-wave duration (from 101 ± 11 to 108 ± 14 milliseconds, p = 0.0006), PR interval (from 153 ± 15 to 167 ± 17 milliseconds, p < 0.0001), QT interval (from 346 ± 28 to 361 ± 24 milliseconds, p < 0.0001), and corrected QT interval (from 388 ± 24 to 402 ± 30 milliseconds, p = 0.0006). None of these changes showed correlations with modifications in clinical or echocardiographic variables. In multivariate analyses aimed at exploring predictors of ECG changes, none of the variables entered the final models. Conclusions:, Low doses of red wine acutely slow cardiac conduction and prolong repolarization in normal individuals. These changes are poorly predictable. The potential arrhythmogenic impact of these effects is worthy of exploration. [source]


Right Ventricular Septal Pacing: A Comparative Study of Outflow Tract and Mid Ventricular Sites

PACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 10 2010
RAPHAEL ROSSO M.D.
Background: Prolonged right ventricle (RV) apical pacing is associated with left ventricle (LV) dysfunction due to dysynchronous ventricular activation and contraction. Alternative RV pacing sites with a narrower QRS compared to RV pacing might reflect a more physiological and synchronous LV activation. The purpose of this study was to compare the QRS morphology, duration, and suitability of RV outflow tract (RVOT) septal and mid-RV septal pacing. Methods: Seventeen consecutive patients with indication for dual-chamber pacing were enrolled in the study. Two standard 58-cm active fixation leads were passed to the RV and positioned in the RVOT septum and mid-RV septum using a commercially available septal stylet (model 4140, St. Jude Medical, St. Paul, MN, USA). QRS duration, morphology, and pacing parameters were compared at the two sites. The RV lead with less-satisfactory electrical parameters was withdrawn and deployed in the right atrium. Results: Successful positioning of the pacing leads at the RVOT septum and mid-RV septum was achieved in 15 patients (88.2%). There were no significant differences in the mean stimulation threshold, R-wave sensing, and lead impedance between the two sites. The QRS duration in the RVOT septum was 151 ± 14 ms and in the mid-RV septum 145 ± 13 ms (P = 0.150). Conclusions: This prospective observational study shows that septal pacing can be reliably achieved both in the RVOT and mid-RV with active fixation leads using a specifically shaped stylet. There are no preferences in regard to acute lead performance or paced QRS duration with either position. (PACE 2010; 33:1169,1173) [source]


Impact of Right Ventricular Pacing Sites on Exercise Capacity during Ventricular Rate Regularization in Patients with Permanent Atrial Fibrillation

PACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 12 2009
HUNG-FAT TSE M.D., Ph.D.
Background:The deleterious effects of right ventricular apical (RVA) pacing may offset the potential benefit of ventricular rate (VR) regularization and rate adaptation during an exercise in patient's atrial fibrillation (AF). Methods:We studied 30 patients with permanent AF and symptomatic bradycardia who receive pacemaker implantation with RVA (n = 15) or right ventricular septal (RVS, n = 15) pacing. All the patients underwent an acute cardiopulmonary exercise testing using VVI-mode (VVI-OFF) and VVI-mode with VR regularization (VRR) algorithm on (VVI-ON). Results:There were no significant differences in the baseline characteristics between the two groups, except pacing QRS duration was significantly shorter during RVS pacing than RVA pacing (138.9 ± 5 vs 158.4 ± 6.1 ms, P = 0.035). Overall, VVI-ON mode increased the peak exercise VR, exercise time, metabolic equivalents (METs), and peak oxygen consumption (VO2max), and decreased the VR variability compared with VVI-OFF mode during exercise (P < 0.05), suggesting that VRR pacing improved exercise capacity during exercise. However, further analysis on the impact of VRR pacing with different pacing sites revealed that only patients with RVS pacing but not patients with RVA pacing had significant increased exercise time, METs, and VO2max during VVI-ON compared with VVI-OFF, despite similar changes in peaked exercise VR and VR variability. Conclusion:In patients with permanent AF, VRR pacing at RVS, but not at RVA, improved exercise capacity during exercise. [source]


Evidence for Electrical Remodeling of the Native Conduction System with Cardiac Resynchronization Therapy

PACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 5 2007
CHARLES A. HENRIKSON M.D.
Background:Cardiac resynchronization therapy (CRT) improves hemodynamics and decreases heart failure symptoms. However, the potential of CRT to bring about electrical remodeling of the heart has not been investigated. Methods and Results:We studied 25 patients, of whom 17 had a nonischemic cardiomyopathy, and 8 had an ischemic cardiomyopathy; 16 had left bundle branch block (LBBB), 1 right bundle branch block (RBBB), and 8 nonspecific intraventricular conduction delay. During routine device clinic visits, patients with chronic biventricular pacing (>6 months) were reprogrammed to VVI 40 to allow for native conduction to resume. After 5 minutes of native rhythm, a surface electrocardiogram (ECG) was recorded, and then the previous device settings were restored. This ECG was compared to the preimplant ECG. Preimplant mean ejection fraction was 19% (range, 10%,35%), and follow-up mean ejection fraction was 35% (12.5%,65%). Mean time from implant to follow-up ECG was 14 months (range, 6,31). The QRS interval prior to CRT was 155 ± 29 ms, and shortened to 144 ± 31 ms (P = 0.0006), and the QRS axis shifted from ,1 ± 59 to ,26 ± 53 (P = 0.03). There was no significant change in PR or QTc interval, or in heart rate. Conclusion:CRT leads to a decrease in the surface QRS duration, without affecting other surface ECG parameters. The reduced electrical activation time may reflect changes in the specialized conduction system or in intramyocardial impulse transmission. [source]


Activation Sequence Modification During Cardiac Resynchronization by Manipulation of Left Ventricular Epicardial Pacing Stimulus Strength

PACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 1 2007
USHA B. TEDROW M.D.
Background: Success of cardiac resynchronization therapy (CRT) depends on altering electrical ventricular activation (VA) to achieve mechanical benefit. That increases in stimulus strength (SS) can affect VA has been demonstrated previously in cardiomyopathy patients undergoing ablation. Objective: To determine whether increasing SS can alter VA during CRT. Methods: In 71 patients with CRT devices, left ventricle (LV) pacing was performed at escalating SS. Timing from pacing stimulus to right ventricular (RV) electrogram, ECG morphology, and maximal QRS duration on 12 lead ECG were recorded. Results: Demographics: Baseline QRS duration 153 ± 25 ms, ischemic cardiomyopathy 48%, ejection fraction 24%± 7%. With increased SS, conduction time from LV to right ventricle (RV) decreased from 125 ± 56 ms to 111 ± 59 ms (P = 0.006). QRS duration decreased from 212 ± 46 ms to 194 ± 42 ms (P = 0.0002). A marked change in QRS morphology occurred in 11/71 patients (15%). The RV ring was the anode in 6, while the RV coil was the anode in 5. Sites with change in QRS morphology showed decrease in conduction time from LV to RV from 110 ± 60 ms to 64 ± 68 ms (P = 0.04). Twelve patients (16%) had diaphragmatic stimulation with increased SS. Conclusions: Increasing LV SS reduces QRS duration and conduction time from LV to RV. Recognition of significant QRS morphology change is likely clinically important during LV threshold programming to avoid unintended VA change. [source]


Relationship Between Global Myocardial Index and Automatic Left Ventricular Border Detection Pattern to Identify Biventricular Pacing Candidates

PACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 2007
DRAGOS COZMA M.D., Ph.D.
Objective of the Study: to evaluate the relation between global myocardial index (GMI) and the pattern of left ventricular (LV) volume curves variation, using automatic border detection (ABD), and their role in assessing LV asynchrony. Methods: We studied 52 patients (mean age = 55 ± 17 years) with dilated cardiomyopathy. QRS duration (QRSd) and GMI were measured. Currently accepted TDI and M-mode parameters were used to indicate LV dyssynchrony. On-line continuous LV volume changes were recorded using ABD. Ejection time (ET ABD) was measured from the ABD wave-forms as time interval between maximal and minimal volume variation during LV electromechanical systole. We derived the ejection time index (ETiABD) as the ratio between ET ABD and RR interval (ETiABD = ET/RR). Results: 31 patients had a QRSd >120 ms and 21 patients had a QRSd <120 ms. Ventricular dyssynchrony was observed in 39 patients (29 patients had a QRSd > 120 ms). GMI was significantly higher in patients with, than in patients without ventricular dyssynchrony (1.06 ± 0.18 vs 0.73 ± 0.13, P = 0.0001), while ETABD was significantly smaller (233 ± 39 ms vs 321 ± 28 ms, P = 0.0001). The corresponding difference for ETiABD was 26.9 ± 6.8% vs 6.3 ± 4%, P < 0.0001. By simple regression analysis an inverse linear correlation was observed between GMI and ETiABD (r2=,0.51, P < 0.0001). The pattern of ABD waveforms showed increased isovolumic contraction and relaxation times in patients with LV asynchrony, similar to the GMI pattern. Conclusions: Regional delays in ventricular activation cause uncoordinated and prolonged ventricular contractions, with lengthening of the isovolumic contraction and relaxation times and shortening of the time available for filling and ejection. GMI explores these parameters and together with ABD might be useful to identify patients with ventricular asynchrony. [source]


Long-Term Survival in Patients Treated with Cardiac Resynchronization Therapy: A 3-Year Follow-Up Study from the InSync/InSync ICD Italian Registry

PACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 2006
MAURIZIO GASPARINI
Background: Studies reporting the long-term survival of patients treated with cardiac resynchronization therapy (CRT) outside the realm of randomized controlled trials are still lacking. The aim of this study was to quantify the survival of patients treated with CRT in clinical practice and to investigate the long-term effects of CRT on clinical status and echocardiographic parameters. Methods: The study population consisted of 317 consecutive patients with implanted CRT devices from eight Italian University/Teaching Hospitals. The patients were enrolled in a national observational registry and had a minimum follow-up of 2 years. A visit was performed in surviving patients and mortality data were obtained by hospital file review or direct telephone contact. Results: During the study period, 83 (26%) patients died. The rate of all-cause mortality was significantly higher in ischemic than nonischemic patients (14% vs 8%, P = 0.002). Multivariate analysis showed that ischemic etiology (HR 1.72, CI 1.06,2.79; P = 0.028) and New York Heart Association (NYHA) class IV (HR 2.87, CI 1.24,6.64; P = 0.014) were the strongest predictors of all-cause mortality. The effects of CRT persisted at long-term follow-up (for at least 2 years) in terms of NYHA class improvement, increase of left ventricular ejection fraction, decrease of QRS duration (all P = 0.0001), and reduction of left ventricular end-diastolic and end-systolic diameters (P = 0.024 and P = 0.011, respectively). Conclusions: During long-term (3 years) follow-up after CRT, total mortality rate was 10%/year. The outcome of ischemic patients was worse mainly due to a higher rate of death from progressive heart failure. Ischemic etiology along with NYHA class IV was identified as predictors of death. Benefits of CRT in terms of clinical function and echocardiographic parameters persisted at the time of long-term follow-up. [source]


Determinants of Mortality in Patients Undergoing Cardiac Resynchronization Therapy: Baseline Clinical, Echocardiographic, and Angioscintigraphic Evaluation Prior to Resynchronization

PACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 12 2005
ANTONIO DE SISTI
Background: In dilated cardiomyopathy (DCM) patients (pts) with cardiac resynchronization therapy (CRT) for ventricular dyssynchrony, long-term predictors of mortality and morbidity remain poorly investigated. Method and Results: We reviewed data of 102 pts, 68 ± 10 years, NYHA Class II,IV (14 Class II, 67 Class III, 21 Class IV), who benefited from CRT (69 CRT, 33 CRT-ICD). Fifty-two patients had an ischemic DCM, 36 a previously implanted conventional PM/ICD, 29 a permanent atrial fibrillation, and 19 needed dobutamine in the month preceding implant. QRS duration was 187 ± 35 ms, left ventricular end-diastolic diameter 72 ± 10 mm, mitral regurgitation severity 1.9 ± 0.8, echographic aorto-pulmonary electromechanical delay 61.5 ± 25 ms and septo-lateral left intraventricular delay 86 ± 56 ms, pulmonary artery pressure (PAP) 43 ± 11 mmHg, angioscintigraphic left ventricular ejection fraction (EF) 20 ± 9%, and right ventricular EF 30.5 ± 14%. Over a mean follow-up of 23 ± 20 months, 26 pts died (18 heart failures (HFs), 1 arrhythmic storm, 7 noncardiac deaths). Positive univariate predictors of death from any cause were NYHA Class IV (P < 0.001), and need for dobutamine the month preceding CRT (P < 0.008), while use of ,-blocking agents (P < 0.08) and left ventricular EF (P < 0.09) were negative ones. NYHA Class IV was the only independent predictor at multivariate analysis (P < 0.01). Survival at 24 months was 85% in Class II, 80% in Class III, and 37% in Class IV (II vs III, P = ns; III vs IV, P < 0.001). When using a composite endpoint of death from any cause and unplanned rehospitalization for a major cardiovascular event, there were 48 events (14 HF deaths, 3 noncardiac deaths, 26 HF rehospitalizations, 2 paroxysmal atrial fibrillation, 2 sustained ventricular tachycardia, 1 nonfatal pulmonary embolism). Predictors of death from any cause/unplanned rehospitalization for a major cardiovascular event in the follow-up were NYHA Class IV (P < 0.001), need for dobutamine during the month preceding CRT (P < 0.002), and PAP (<0.02). NYHA Class IV was the only independent predictor at multivariate analysis (P < 0.05). Event-free proportion at 24 months was 70% in Class II, 64% in Class III, and 37% in Class IV (II vs III, P = ns; III vs IV, P < 0.01). When considering determinants of mortality only in NYHA Class IV patients, no variable was significantly correlated to mortality. Need for dobutamine during the last month preceding CRT did not add an adjunctive mortality risk. Conclusion: Baseline NYHA Class IV at implantation appears as the most important determinant of a poor clinical outcome in terms of both mortality and morbidity. No predictive criteria seem available for NYHA Class IV patients, in order to discriminate who will die after CRT and who will not. NYHA Class IV strongly influences the clinical outcome, suggesting that, in future studies planned on mortality and rehospitalization as major endpoints, baseline NYHA Class IV should be separately taken into account. [source]


Is the Fascicle of Left Bundle Branch Involved in the Reentrant Circuit of Verapamil-Sensitive Idiopathic Left Ventricular Tachycardia?

PACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 10 2003
JEN-YUAN KUO
The exact reentrant circuit of the verapamil-sensitive idiopathic left VT with a RBBB configuration remains unclear. Furthermore, if the fascicle of left bundle branch is involved in the reentrant circuit has not been well studied. Forty-nine patients with verapamil-sensitive idiopathic left VT underwent electrophysiological study and RF catheter ablation. Group I included 11 patients (10 men, 1 woman; mean age 25 ± 8 years) with left anterior fascicular block (4 patients), or left posterior fascicular block (7 patients) during sinus rhythm. Group II included 38 patients (29 men, 9 women; mean age 35 ± 16 years) without fascicular block during sinus rhythm. Duration of QRS complex during sinus rhythm before RF catheter ablation in group I patients was significant longer than that of group II patients (104 ± 12 vs 95 ± 11 ms, respectively, P = 0.02). Duration of QRS complex during VT was similar between group I and group II patients (141 ± 13 vs 140 ± 14 ms, respectively, P = 0.78). Transitional zones of QRS complexes in the precordial leads during VT were similar between group I and group II patients. After ablation, the QRS duration did not prolong in group I or group II patients (104 ± 11 vs 95 ± 10 ms, P = 0.02); fascicular block did not occur in group II patients. Duration and transitional zone of QRS complex during VT were similar between the two groups, and new fascicular block did not occur after ablation. These findings suggest the fascicle of left bundle branch may be not involved in the antegrade limb of reentry circuit in idiopathic left VT. (PACE 2003; 26:1986,1992) [source]


The Monolithic Fetal Pacemaker:

PACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 4p1 2003
Prototype Lead Design for Closed Thorax Deployment
DELL'ORFANO, J., et al.: The Monolithic Fetal Pacemaker: Prototype Lead Design for Closed Thorax Deployment.Prenatal sudden cardiac death and hydrops fetalis are often due to complete heart block. However, no pacing modality exists for intrauterine application for fetal bradycardia. A prototype lead for a novel fetal pacemaker has been developed and used in a direct pacing model. It has been demonstrated that the lead can be safely and successfully deployed using a hypochondriac and transdiaphragmatic or subxiphoid approach. Pacing with ventricular capture was evident with the widening of QRS duration from50.2 ± 9.8to95.1 ± 12.8 ms (P = 0.0001). Further studies by echocardiogram revealed an increase in the pulse with pacing, confirming pacing. This study documents proof-of-concept for closed thorax over-the-wire deployment of a novel lead design applicable to fetal pacing. By combining the lead design with microcircuitry and a small power source, it is possible to create a monolithic fetal pacemaker system capable of being deployed in utero. (PACE 2003; 26[Pt. I]:805,811) [source]


Which Patients with Congestive Heart Failure May Benefit from Biventricular Pacing?

PACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 1p2 2003
NESTOR O. GALIZIO
GALIZIO, N.O., et al.: Which Patients with Congestive Heart Failure May Benefit from Biventricular Pacing?Background: Biventricular pacing improves the clinical status and ventricular function in patients with congestive heart failure (CHF) and intraventricular conduction delay. However, patient selection criteria including NYHA functional class, rhythm, PR interval, QRS duration (QRSd), left ventricular ejection fraction (LVEF), left ventricular diastolic diameter (LVDD), and other variables are not clearly defined. Objective: To determine which and how many patients referred for an initial cardiac transplantation evaluation may be eligible for biventricular pacing (BP) according to the criteria of recently completed trials of cardiac resynchronization therapy (CRT). Methods: This was a retrospective review of 200 patients, whose mean age was51 ± 13years (173 men). Sinus rhythm was present in 88% of the patients, 107 had a QRSd >120 ms, and 38% had left bundle branch block. LVDD was72.5 ± 12 mmand LVEF21.7 ± 9.3%; 54% had mitral regurgitation. Results: When NYHA class, electrocardiographic, and ventricular function criteria were considered separately, a high proportion of patients appeared to be candidates for CRT: 70.5% were in NYHA functional class III/IV, 34% had QRSd ,150 ms, 60% had LVDD ,60 mm and 53.5% LVEF ,35%. However, the proportions of patients eligible for CRT were different according to the selection criteria of recently completed trials: 18% of the patients with InSync criteria, 13% of the patients with MUSTIC SR criteria, 0.5% with MUSTIC AF criteria, 27% of patients with MIRACLE criteria, and 35% of the patients with CONTAK CD criteria (without considering indications for implantable cardioverter defibrillator). Conclusion: In this population-based study, a wide range of patients (13% to 35%) would have been candidates for CRT, according to the selection criteria of different completed trials.(PACE 2003; 26[Pt. II]:158,161) [source]


Relation Between the Pacing Induced Sequence of Activation and Left Ventricular Pump Function in Animals

PACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 4 2002
FRITS W. PRINZEN
PRINZEN, F.W., et al.: Relation Between the Pacing Induced Sequence of Activation and Left Ventricu-lar Pump Function in Animals. The main goal of this article was to review animal experimental work on the effect of asynchronous activation on ventricular pump function. During normal sinus rhythm and atrial pacing, the Purkinje system contributes significantly to the rapid electrical activation of the ventricles. In contrast, during ventricular pacing the impulse is almost exclusively conducted through the normal myocardium. As a consequence, electrical activation of the ventricles becomes asynchronous and has an abnormal sequence. The abnormal impulse conduction causes considerable disturbances to occur in regional systolic fiber shortening, mechanical work, blood flow, and oxygen consumption; low values occurring in early activated regions and values above normal being present in late activated regions. Many animal studies have now shown that the abnormal electrical activation, induced by ventricular pacing, leads to a depression of systolic and diastolic LV function. Pacing at the right ventricular apex (the conventional pacing site) reduces LV function more than pacing at the high ventricular septum or at LV sites. In canine hearts with experimental LBBB, LV pacing significantly improves LV pump function. Differences in LV pump function between (combinations of) pacing sites are poorly correlated with QRS duration. Therefore, the cause of the depression of LV function during abnormal electrical activation appears to be a combination of the asynchrony and the sequence of activation. These experimental findings justify continuing attention for optimizing the site(s) of ventricular pacing in patients with normal and abnormal ventricular impulse conduction. [source]


Alternans in QRS Amplitude During Ventricular Tachycardia

PACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 2 2002
PHILIPPE MAURY
MAURY, P., et al.: Alternans in QRS Amplitude During Ventricular Tachycardia. Although the value of T wave alternans as an index of electrical instability has been extensively investigated, little is known about QRS alternans during VT. Intracardiac electrograms of 111 episodes of spontaneous monomorphic regular VT retrieved from implantable defibrillators in 25 patients were retrospectively selected. Three beat series, representing the total amplitudes and amplitudes from baseline to summit and from baseline to lower point of 16 or 32 successive QRS complexes before deliverance of electrical therapy were generated for each episode. Spectral analysis was then performed using the fast Fourrier transform. VT was considered as alternans if the magnitude of the spectral power at the 0.5-cycle/beat frequency was greater than the mean ± 3 SD of the noise in at least one of the three spectral curves. QRS alternans was present in 23 (20%) of 111 episodes and in 9 (36%) of 25 patients. Alternans was not related to the VT cycle length, QRS duration, QRS amplitude, signal amplification, nor to clinical variables. Alternans was more frequently detected in unipolar configuration and when a higher number of complexes was included in analysis. Failure of antitachycardia pacing was more frequent in case of alternans VT (50% vs 75% success in non-alternans VT, P = 0.05). Spontaneous termination before deliverance of therapy occurred in 16 nonalternans VT but never in alternans episodes (P = 0.02). Alternans in QRS amplitude is a relatively common finding during VT and could be associated with failure of antitachycardia pacing and lack of spontaneous termination. Lower efficacy of electrical therapies in case of QRS alternans must be confirmed in a way to improve the effectiveness of antitachycardia pacing. [source]


Magnetocardiographic Intra-QRS Fragmentation Analysis in the Identification of Patients with Sustained Ventricular Tachycardia after Myocardial Infarction

PACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 8 2001
PETRI KORHONEN
KORHONEN, P., et al.: Magnetocardiographic Intra-QRS Fragmentation Analysis in the Identification of Patients with Sustained Ventricular Tachycardia after Myocardial Infarction. The aim of this study was to investigate if magnetocardiographic (MCG) analysis of cardiac micropotentials within the QRS complex can identity patients prone to ventricular arrhythmias, and to compare it to MCG time-domain, late-field analysis. The study population consisted of 136 patients with remote MI, 53 with and 83 without a history of VT. After averaging and high pass filtering of multichannel MCG signals, time-domain parameters describing the end-QRS activity and fragmentation index M and score S describing the whole QRS complex were computed. Fragmentation and time-domain parameters differed between the VT and control groups: fragmentation index M was 12 ± 3 versus 9 ± 2 (P < 0.001), fragmentation score S was 83 ± 42 versus 56 ± 21 (P < 0.001), and filtered QRS duration was 144 ± 32 versus 114 ± 19 ms (P < 0.001) in VT and control groups, respectively. A combination of fragmentation parameters yielded 87% sensitivity and 61% specificity in VT identification. Corresponding figures for a time-domain parameter combination were 81% and 72%. Sensitivity of time-domain analysis was 88% and specificity was 75% in a subgroup with anterior MI. In multivariate analysis, fragmentation and time-domain analyses discriminated VT patients from controls independently of the extent of coronary artery disease or left ventricular dysfunction. MCG in postinfarction patients reveals pathology associated with propensity to ventricular arrhythmias inside and not only at the end of the QRS complex. MCG seems most accurate in the anterior infarct location. [source]