Tammy S. Wieand

Permanent Epicardial Pacing in Pediatric Patients Seventeen Years of Experience and 1200 Outpatient Visits

Background—The purpose of this study was to evaluate the long-term outcome of all pediatric epicardial pacing leads. Methods and Results—All epicardial leads and 1239 outpatient visits between January 1, 1983, and June 30, 2000, were retrospectively reviewed. Pacing and sensing thresholds were reviewed at implant, at 1 month, and at subsequent 6-month intervals. Lead failure was defined as the need for replacement or abandonment due to pacing or sensing problems, lead fracture, or phrenic/muscle stimulation. A total of 123 patients underwent 207 epicardial lead (60 atrial/147 ventricular, 40% steroid) implantations (median age at implant was 4.1 years [range 1 day to 21 years]). Congenital heart disease was present in 103 (84%) of the patients. Epicardial leads were followed for 29 months (range 1 to 207 months). The 1-, 2-, and 5-year lead survival was 96%, 90%, and 74%, respectively. Compared with conventional epicardial leads, both atrial and ventricular steroid leads had better stimulation thresholds 1 month after implantation; however, only ventricular steroid leads had improved chronic pacing thresholds (at 2 years: for steroid leads, 1.9 &mgr;J [from 0.26 to 16 &mgr;J]; for nonsteroid leads, 4.7 &mgr;J [from 0.6 to 25 &mgr;J];P <0.01). Ventricular sensing was significantly better in steroid leads 1 month after lead implantation (at 2 years: for steroid leads, 8 mV [from 4 to 31 mV]; for nonsteroid leads, 4 mV [from 0.7 to 10 mV];P <0.01). Neither congenital heart disease, lead implantation with a concomitant cardiac operation, age or weight at implantation, nor the chamber paced was predictive of lead failure. Conclusions—Steroid epicardial leads demonstrated relatively stable acute and chronic pacing and sensing thresholds. In this evaluation of >200 epicardial leads, lead survival was good, with steroid-eluting leads demonstrating results similar to those found with historical conventional endocardial leads.

Postoperative junctional ectopic tachycardia in children : Incidence, risk factors, and treatment

BACKGROUND Junctional ectopic tachycardia (JET) occurs commonly after pediatric cardiac operation. The cause of JET is thought to be the result of an injury to the conduction system during the procedure and may be perpetuated by hemodynamic disturbances or postoperative electrolyte disturbances, namely hypomagnesemia. The purpose of this study was to determine perioperative risk factors for the development of JET. METHODS Telemetry for each patient admitted to the cardiac intensive care unit from December 1997 through November 1998 for postoperative cardiac surgical care was examined daily for postoperative JET. A nested case-cohort analysis of 33 patients who experienced JET from 594 consecutively monitored patients who underwent cardiac operation was performed. Univariate and multivariate analyses were conducted to determine factors associated with the occurrence of JET. RESULTS The age range of patients with JET was 1 day to 10.5 years (median, 1.8 months). Univariate analysis revealed that dopamine or milrinone use postoperatively, longer cardiopulmonary bypass times, and younger age were associated with JET. Multivariate modeling elicited that dopamine use postoperatively (odds ratio, 6.2; p = 0.01) and age less than 6 months (odds ratio, 4.0; p = 0.02) were associated with JET. Only 13 (39%) of the patients with JET received therapeutic interventions. CONCLUSIONS Junctional ectopic tachycardia occurred in 33 (5.6%) of 594 patients who underwent cardiac operation during the study period. Postoperative dopamine use and younger age were associated with JET. It may be speculated that dopamine should be discontinued in the presence of postoperative JET.

The Incidence of Arrhythmias in a Pediatric Cardiac Intensive Care Unit

A pediatric cardiac intensive care unit (CICU) manages critically ill children and adults with congenital or acquired heart disease. These patients are at increased risk for arrhythmias. The purpose of this study was to prospectively evaluate the incidence of arrhythmias in a pediatric CICU patient population. All patients admitted to the CICU at the Cardiac Center at The Childrens Hospital of Philadelphia between December 1, 1997, and November 30, 1998, were evaluated prospectively from CICU admission to hospital discharge via full disclosure telemetry reviewed every 24 hours. Arrhythmias reviewed included nonsustained and sustained ventricular tachycardia (VT), nonsustained and sustained supraventricular tachycardia (SVT), atrial flutter and fibrillation, junctional ectopic tachycardia, and complete heart block. We reviewed 789 admissions consisting of 629 patients (age range, 1 day–45.5 years; median, 8.1 months). Hospital stay ranged from 1 to 155 days (total of 8116 patient days). Surgical interventions (n = 602) included 482 utilizing cardiopulmonary bypass. During the study period, there were 44 deaths [44/629 patients (7.0%)], none of which were directly attributable to a primary arrhythmia. The operative mortality was 5.1%. Overall, 29.0% of admissions had one or more arrhythmias the most common arrhythmia was nonsustained VT (18.0% of admissions), followed by nonsustained SVT (12.9% of admissions). Patients admitted to a pediatric CICU have a high incidence of arrhythmias, most likely associated with their underlying pathophysiology and to the breadth of medical and surgical interventions conducted.

Electrophysiologic properties of the atrioventricular node in pediatric patients.

OBJECTIVES The purpose of this study was to characterize anterograde and retrograde properties of the atrioventricular (AV) node in children and to determine the presence of ventriculoatrial (VA) conduction and dual AV node pathways. BACKGROUND Although AV node reentry is common in adults, it accounts for 13% of pediatric supraventricular tachycardia (SVT). The age-related changes in the AV node with development are poorly understood. The incidence of dual AV node pathways and VA conduction in the pediatric population is unknown. METHODS Electrophysiologic studies were performed in 79 patients with normal hearts and no evidence of AV node arrhythmias. Patients were classified into two groups by age: group I = 49 patients (0.39 to 12.8 years old, mean [+/- SD] age 8.5 +/- 3.6); group II = 30 patients (13.4 to 20.0 years old, mean age 15.6 +/- 1.8). RESULTS There was a significant difference (p < 0.05) in the cycle length (CL) at which anterograde AV block occurred between group I (305 +/- 63 ms) and group II (350 +/- 91 ms). Sixty-one percent of children had VA conduction with no age-related differences. There was no significant difference in the mean CL of retrograde VA block (360 ms). The incidence of dual AV node pathways in group I was 15% and 44% in group II (p < 0.05). CONCLUSIONS These findings suggest that AV node electrophysiology undergoes maturational changes. The increase in AV node reentrant tachycardia in adults may relate to changes in the relative refractoriness and conduction of the AV node or to differences in autonomic input into the AV node that allow dual pathway physiology to progress to SVT.

Genotype- and mutation site-specific QT adaptation during exercise, recovery, and postural changes in children with long-QT syndrome.

Background— Exercise stress testing has shown diagnostic utility in adult patients with long-QT syndrome (LQTS); however, the QT interval adaptation in response to exercise in pediatric patients with LQTS has received little attention. Methods and Results— One-hundred fifty-eight patients were divided into 3 groups: Those with LQTS type 1 (LQT1) or LQTS type 2 (LQT2) and normal control subjects without cardiovascular disease. Each patient underwent a uniform exercise protocol with a cycle ergometer followed by a 9-minute recovery phase with continuous 12-lead ECG monitoring. Each patient underwent a baseline ECG while resting in the supine position and in a standstill position during continuous ECG recording to determine changes in the QT and RR intervals. Fifty patients were gene-positive for LQTS (n=29 for LQT1 and n=21 for LQT2), and the control group consisted of 108 patients. QT interval adaptation was abnormal in the LQT1 patients compared with LQT2 and control patients (P<0.001). A corrected QT interval (QTc) >460 ms in the late recovery phase at 7 minutes predicted LQT1 or LQT2 versus control subjects with 96% specificity, 86% sensitivity, and a 91% positive predictive value. A recovery &Dgr;QTc(7 min−1 min) >30 ms predicted LQT2 versus LQT1 with 75% sensitivity, 82% specificity, and a 75% positive predictive value. The postural &Dgr;QT was significantly different between LQTS and control groups (P=0.005). Conclusions— Genotype-specific changes in repolarization response to exercise and recovery exist in the pediatric population and are of diagnostic utility in LQTS. An extended recovery phase is preferable to assess the repolarization response after exercise in the pediatric population.

Comparison of left and right atrial epicardial pacing in patients with congenital heart disease

BACKGROUND Complex congenital heart disease (CHD) often necessitates the use of epicardial pacing. Adequate right atrial (RA) sensing and pacing thresholds are often difficult to obtain due to suture line scarring and RA dilatation. The purpose of this study was to evaluate the placement of left atrial (LA) epicardial leads in children. METHODS Patient demographics, pacing, and sensing data of atrial pacing systems implanted between January 1994 and January 1997 were collected. RESULTS Forty-nine pacing systems were implanted: 14 LA epicardial, 19 RA epicardial, and 16 transvenous in the right atrium. Lead impedance, current, and energy were similar in the two epicardial groups throughout the study. Energy thresholds (ET) were lower in the LA than RA at 6 months, and 1 and 2 years (p < 0.05). Analysis of post-Fontan patients performed alone revealed a lower ET in the LA as compared with the RA. Pacing and sensing parameters from transvenous leads are presented for relative comparison. CONCLUSIONS Transvenous leads are most efficient but often contraindicated in complex CHD. LA leads offer lower energy thresholds than RA leads with similar sensing parameters.

Time and temperature profile of catheter cryoablation of right septal and free wall accessory pathways in children.

Introduction: The overall acute success with cryoablation for accessory pathways (APs) has been reported to be lower than with radiofrequency ablation. Generally, prior cryomapping (limited to −30°C) has been used to test for loss of AP conduction and absence of atrioventricular (AV) node impairment. However, the temperature at which loss of AP conduction occurs may be variable. The purpose of this study was to evaluate the time and temperature profile at which loss of AP conduction occurs.

QT and JT dispersion in children with long QT syndrome.

QT and JT Dispersion in Long QT Syndrome. Introduction: Abnormalities of ventricular repolarization leading to ventricular arrhythmias place children with long QT syndrome at high risk for sudden death. Dispersion of the QT (QTd) and JT (JTd) intervals, as markers of cardiac electrical heterogeneity, may be helpful in evaluating children with long QT syndrome and identifying a subset of patients at high risk for development of critical ventricular arrhythmias (ventricular tachycardia, torsades de pointes, and/or cardiac arrest).

Cryoablation of Congenital Familial Ectopic Tachycardia with Preservation of Atrioventircular Nodal Function in an Infant

A 1‐year‐old child weighing 8 kg with familial congenital junctional ectopic tachycardia that was difficult to treat with antiarrhythmic medications underwent successful cryoablation with preservation of atrioventricular (AV) nodal function. This report describes a strategy of cryoablation in conjunction with a 3‐D mapping system and the use of atrial overdrive pacing during cryothermal application to assess AV nodal function.

Perioperative conduction and rhythm disturbances after the Ross procedure in young patients

BACKGROUND The Ross procedure is performed for a variety of left ventricular outflow tract diseases in children. The preoperative hemodynamic burden of pressure or volume overload and associated ventricular hypertrophy can predispose to ventricular arrhythmias. Additional procedures performed with the Ross procedure (eg, Konno) may damage the conduction system. METHODS Between January 1995 and February 1997, the Ross procedure was performed in 42 patients, 31 (74%) of whom had 71 prior interventions. Concomitant procedures (n = 42 in 23 patients) included 17 annular-enlarging procedures. Screening was performed for perioperative conduction and rhythm abnormalities. RESULTS There was one postoperative death. Perioperative ventricular tachycardia occurred in 12 patients (29%), with 2 receiving antiarrhythmic medication for ventricular tachycardia at discharge. Transient complete heart block occurred in 3 patients, all of whom had concomitant procedures performed in the subaortic area; all patients were discharged in sinus rhythm and no patient received a permanent pacemaker. CONCLUSIONS The Ross procedure can be performed successfully in children with complex cardiac disease with low mortality and perioperative morbidity. The incidence of perioperative ventricular tachycardia is high (29%), suggesting the need for vigilant perioperative monitoring and long-term surveillance.