Techniques for Cardiac Resynchronization Therapy in Patients with Congenital Heart Disease.

Cardiac resynchronization therapy (CRT) for congenital heart disease has shown promising suucess as an adjunct to medical therapy for heart failure. While cardiac conduction defects and need for ventricular pacing are common in congential heart disease, CRT indications, techniques and long term outcomes have not been well establaished. This is a review of the techniques nad short term outcomes of CRT for the following complex congenital heart disease conditions: single ventricle physiology, systemic right ventricle, and the subpulmonic right ventricle.

Belhassen Ventricular Tachycardia in a Child.

First reported in 1981, idiopathic left ventricular tachycardia (VT) of the Belhassen type is characterized during electrocardiography (ECG) by a right bundle branch pattern and left axis deviation. We report the case of a 15-year-old Hispanic male who, during a routine evaluation ECG to support sports participation, was found to have nonsustained monomorphic VT. Prior to his exercise treadmill test, his physical examination and echocardiogram were normal. Then, during preparation for the exercise treadmill test, the ECG showed sustained monomorphic VT with a right bundle branch block pattern and superior QRS axis, suggesting a diagnosis of Belhassen VT.

Loss of ventricular preexcitation during noninvasive testing does not exclude high-risk accessory pathways: A multicenter study of WPW in children.

BACKGROUND: Abrupt loss of ventricular preexcitation on noninvasive evaluation, or nonpersistent preexcitation, in Wolff-Parkinson-White syndrome (WPW) is thought to indicate a low risk of life-threatening events. OBJECTIVE: The purpose of this study was to compare accessory pathway (AP) characteristics and occurrences of sudden cardiac arrest (SCA) and rapidly conducted preexcited atrial fibrillation (RC-AF) in patients with nonpersistent and persistent preexcitation. METHODS: Patients 21 years or younger with WPW and invasive electrophysiology study (EPS) data, SCA, or RC-AF were identified from multicenter databases. Nonpersistent preexcitation was defined as absence/sudden loss of preexcitation on electrocardiogram, Holter monitoring, or exercise stress test. RC-AF was defined as clinical preexcited atrial fibrillation with shortest preexcited R-R interval (SPERRI) ≤ 250 ms. AP effective refractory period (APERP), SPERRI at EPS , and shortest preexcited paced cycle length (SPPCL) were collected. High-risk APs were defined as APERP, SPERRI, or SPPCL ≤ 250 ms. RESULTS: Of 1589 patients, 244 (15%) had nonpersistent preexcitation and 1345 (85%) had persistent preexcitation. There were no differences in sex (58% vs 60% male; P=.49) or age (13.3±3.6 years vs 13.1±3.9 years; P=.43) between groups. Although APERP (344±76 ms vs 312±61 ms; P<.001) and SPPCL (394±123 ms vs 317±82 ms; P<.001) were longer in nonpersistent vs persistent preexcitation, there was no difference in SPERRI at EPS (331±71 ms vs 316±73 ms; P=.15). Nonpersistent preexcitation was associated with fewer high-risk APs (13% vs 23%; P<.001) than persistent preexcitation. Of 61 patients with SCA or RC-AF, 6 (10%) had nonpersistent preexcitation (3 SCA, 3 RC-AF). CONCLUSION: Nonpersistent preexcitation was associated with fewer high-risk APs, though it did not exclude the risk of SCA or RC-AF in children with WPW.

Ventricular pacing in single ventricles-A bad combination.

BACKGROUND: Chronic ventricular pacing (VP) is associated with systolic dysfunction in a subset of pediatric patients with heart block and structurally normal hearts. The effect of chronic VP in congenital heart disease is less well understood, specifically in the single-ventricle (SV) population. OBJECTIVE: To determine the longitudinal effect of VP in SV patients. METHODS: SV patients with heart block and dual-chamber pacemakers requiring >50% VP were compared with nonpaced (controls) SV patients matched for age, sex, and SV morphology. Patients were excluded if a prepacing echocardiogram was not available. Echocardiogram and clinical parameters were compared at baseline (prepacing) and at last follow-up in the paced group, and in controls when they were at ages similar to those of their paced-group matches. RESULTS: Twenty-two paced and 53 control patients from 2 institutions were followed for similar durations (6.6±5 years vs 7.6±7.6 years; P = .59). There was no difference between groups regarding baseline ventricular function or the presence of moderate-to-severe atrioventricular valvar regurgitation (AVVR). Paced patients were more likely to develop moderate-to-severe systolic dysfunction (68% vs 15%; P < .01) and AVVR (55% vs 8%; P < .001) and require heart failure medications (65% vs 21%; P < .001). Chronic VP was also associated with a higher risk of transplantation or death (odds ratio, 4.9; 95% confidence interval, 1.05-22.7; P = .04). CONCLUSIONS: SV patients requiring chronic VP are at higher risk of developing moderate-to-severe ventricular dysfunction and AVVR with an increased risk of death or transplantation compared with controls. New strategies to either limit VP or improve synchronization in this vulnerable population is imperative.

Cardiac conduction disturbances seen after transcatheter device closure of muscular ventricular septal defects with the Amplatzer occluder.

This study examined the incidence of cardiac conduction abnormalities and ventricular arrhythmias after the transcatheter closure of muscular ventricular septal defects (MVSDs) using the Amplatzer device occluder. From the records of 27 patients who underwent 33 consecutive MVSD device closures, a low incidence of permanent and transient cardiac conduction disturbances was observed. Heart rate variability was less after the closure of multiple MVSDs compared with single MVSDs.

Acute hemodynamic benefit of multisite ventricular pacing after congenital heart surgery.

BACKGROUND: Cardiac dysfunction after congenital heart surgery is a major cause of morbidity and mortality. Cardiac resynchronization through multisite ventricular pacing (MSVP) improves cardiac index and ventricular function, and lowers systemic vascular resistance (SVR) in adults with heart failure and interventricular conduction delay. METHODS: The acute hemodynamic effects of MSVP after congenital heart surgery were assessed. Twenty-nine patients (aged 1 week to 17 years) with prolonged QRS interval had atrial and ventricular unipolar epicardial temporary pacing leads placed at surgery. Group 1 consisted of patients with a single ventricle (n = 14); group 2 included patients with two-ventricle anatomy (tetralogy of Fallot, ventricular septal defect) undergoing ventricular surgery (n = 10); and group 3 included patients with two-ventricle anatomy undergoing other cardiac surgery (n = 5). At a mean postoperative day 1 (range, 0 to 6), blood pressure, systemic and mixed venous oxygen saturations, electrocardiograms, and echocardiograms were obtained before and after 20 minutes of MSVP. RESULTS: The QRS duration decreased with MSVP in all patients (mean, 23%, p < 0.005). Systolic blood pressure improved in all patients (mean, 9.7%, p < 0.005). Cardiac index improved in 19 of 21 patients tested, with no change in 2 patients (mean, 15.1%, p = 0.0001). In 2 patients, MSVP facilitated weaning from cardiopulmonary bypass. Echocardiographic mitral or tricuspid valve inflow was not significantly different with MSVP. CONCLUSIONS: Multisite ventricular pacing results in improved cardiac index and increased systolic blood pressure, and it can also facilitate weaning from cardiopulmonary bypass. Multisite ventricular pacing may be used as adjunct to standard postoperative treatment of cardiac dysfunction after congenital heart surgery.

Resynchronization therapy in pediatric and congenital heart disease patients: an international multicenter study.

OBJECTIVES: Our objective was to evaluate the short-term safety and efficacy of cardiac resynchronization therapy (CRT) in children. BACKGROUND: Cardiac resynchronization therapy has been beneficial for adult patients with poor left ventricular function and intraventricular conduction delay. The efficacy of this therapy in the young and in those with congenital heart disease (CHD) has not yet been established. METHODS: This is a multi-center, retrospective evaluation of CRT in 103 patients from 22 institutions. RESULTS: Median age at time of implantation was 12.8 years (3 months to 55.4 years). Median duration of follow-up was four months (22 days to 1 year). The diagnosis was CHD in 73 patients (71%), cardiomyopathy in 16 (16%), and congenital complete atrioventricular block in 14 (13%). The QRS duration before pacing was 166.1 +/- 33.3 ms, which decreased after CRT by 37.7 +/- 30.7 ms (p < 0.01). Pre-CRT systemic ventricular ejection fraction (EF) was 26.2 +/- 11.6%. The EF increased by 12.8 +/- 12.7 EF units with a mean EF after CRT of 39.9 +/- 14.8% (p < 0.05). Of 18 patients who underwent CRT while listed for heart transplantation, 3 improved sufficiently to allow removal from the transplant waiting list, 5 underwent transplant, 2 died, and 8 others are currently awaiting transplant. CONCLUSIONS: Cardiac resynchronization therapy appears to offer benefit in pediatric and CHD patients who differ substantially from the adult populations in whom this therapy has been most thoroughly evaluated to date. Further studies looking at the long-term benefit of this therapy in this population are needed.

Ventricular resynchronization by multisite pacing improves myocardial performance in the postoperative single-ventricle patient.

BACKGROUND: Ventricular resynchronization with multisite pacing in heart failure patients results in acute improvement of myocardial performance, but the mechanism is unknown. Our goals were to determine whether multisite pacing results in acute improvement of myocardial performance in postoperative single-ventricle patients, and to elucidate the mechanism by assessing the synchronization of regional ventricular contraction during multisite pacing using real-time three-dimensional echocardiographic imaging. METHODS: Multisite pacing studies were performed in 26 single-ventricle patients (mean age, 28 months; range, 7 days to 11 years) undergoing some form of single-ventricle palliation (stage I Norwood, 4; aortopulmonary shunt, 1; cavopulmonary shunt, 9; Fontan, 8; Fontan revision, 3; valve replacement, 1). Electrocardiogram, blood pressure, mixed-venous oxygen saturation, and three-dimensional echocardiograms (n = 10) were recorded at baseline and during multisite pacing. Data were analyzed to obtain regional volume-time curves for 16 three-dimensional segments of the systemic ventricle. An index of asynchrony was calculated at baseline and during pacing as the standard deviation of all segmental volume-time curves from onset to end of ejection. RESULTS: With multisite pacing performed at a median postoperative day 2 (range, 0 to 9), QRS duration decreased in 24 of 26 patients (93.9 +/- 17.5 versus 71.7 +/- 10.8 ms; p < 0.001); systolic blood pressure increased in 25 of 26 patients (86.3 +/- 20.0 versus 93.8 +/- 20.2 mm Hg; p < 0.001); cardiac index increased in 21 of 22 patients (3.2 +/- 0.8 versus 3.7 +/- 1.0 L x min(-1) x m(-2); p < 0.001); and the index of asynchrony improved in 8 of 10 patients (10.3 +/- 4.8 versus 6.0 +/- 1.4; p < 0.04). CONCLUSIONS: Multisite pacing improves cardiac performance after single-ventricle palliation. Real-time three-dimensional echocardiography demonstrated that multisite pacing improved the synchrony of ventricular contraction.