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Ventricular Tachycardia and Atrioventricular Block Introduction In pediatric patients with pacemakers implanted for atrioventricular block (AVB), nonsustained ventricular tachycardia (NSVT) detected during routine surveillance is a finding of unknown significance. We sought to describe the incidence of NSVT and determine if there was an association between NSVT and adverse outcomes in these patients. Methods and Results This is a single-center retrospective study of 136 patients (1971-2013) with pacemakers implanted for advanced and complete AVB. Exclusion criteria: structural heart disease, diagnoses of myocarditis, cardiomyopathy or channelopathy preceding AVB diagnosis, and sustained or polymorphic ventricular tachycardia (VT) as the first occurring arrhythmia after pacemaker implant. During median follow-up of 11.6 years (IQR 4.3 years, 17 years), 14 (10%) patients had NSVT. There were 6 (4.4%) deaths. Overall, Kaplan-Meier 20-year survival from time of implant was 93%. By univariate analysis, earlier mortality was associated with NSVT (P = 0.010), sustained left ventricular (LV) dysfunction (P = 0.004), maternal autoantibodies (P = 0.017), and acquired AVB (P = 0.049). By multivariate analysis, earlier mortality was associated with NSVT (HR: 5.39 [95% CI: 1.02-28.41]; P = 0.047) and sustained LV dysfunction (HR: 10.24 [95% CI: 1.83-57.32]; P = 0.008). Conclusions In children with pacemakers implanted for AVB, NSVT is not uncommon and may be associated with increased mortality. Persistent LV dysfunction may also be a potential factor associated with death. Closer follow-up should be considered in patients with these findings. Large, multicenter studies should be considered to confirm these findings and identify risk stratification methods for this unique patient population. [ABSTRACT FROM AUTHOR]

In African-American (AA) adults, β-blockers (BB) have been reported to be less efficacious treating cardiac disease compared with whites (CAUC). This has been attributed to genetic polymorphisms of β-receptors. It is unknown if racial differences affect response to BB in pediatric patients with arrhythmias. AA and CAUC ≤18 years of age were included if they underwent treadmill stress testing while receiving metoprolol, atenolol, nadolol, or carvedilol. Patient demographics, resting heart rate (HR), maximum HR, and BB variables were collected. CAUC patients were matched on a 2:1 basis by age and sex to AA patients. Patients were blunted if HR was <90 % of maximum predicted HR for same-age patients on a modified Bruce protocol treadmill stress test. Long-term follow-up for breakthrough arrhythmias was documented. 78 patients were included (26 AA, 52 CAUC). No differences were noted in demographics, medication dose, BB or arrhythmia type, or baseline, maximal, or % HR change ( p = not significant [NS]). On univariate analysis, fewer AA achieved a blunted HR during treadmill testing compared with CAUC (65 vs. 86 %, p = 0.03). On multivariate analysis, AA were less likely to have an HR blunted by BB (OR 0.18, 95 % confidence interval [CI] 0.04-0.75, p = 0.02) compared with CAUC. During the 1-year follow-up period, AA trended toward having one (58 vs. 40 %, p = 0.14) or multiple instances (38 vs. 26 %, p = 0.26) of breakthrough arrhythmia on cardiac Holter monitor testing. Race appears to affect the efficacy of BB therapy in pediatric patients with arrhythmias. Future studies to identify genetic polymorphisms in this patient subset are necessary. [ABSTRACT FROM AUTHOR]

Flecainide is frequently used for treatment of cardiac arrhythmias in children. Due to concerns regarding increased mortality, there has been hesitancy to use flecainide in children with congenital heart disease (CHD) or cardiomyopathy (CM). The objective of this study was to describe trends in use of flecainide in children with CHD or CM and assess its association with cardiac arrest or death. Data from 42 children's hospitals contained in the PHIS database (2004-2011) were analyzed. All patients with CHD or CM receiving anti-arrhythmic therapy for supraventricular arrhythmias were reviewed. Trends in flecainide use were analyzed, and the incidence of cardiac arrest or death was compared to patients receiving other anti-arrhythmics. There were 3,544 pts with CHD or CM who received anti-arrhythmic therapy (median age 73 days). Flecainide was administered in 229 pts (6.5 %). There was a trend toward increased use of flecainide in this population, increasing from 4.6 % in 2004 to 8.7 % in 2011 ( p = 0.07). The incidence of cardiac arrest in patients with CHD or CM receiving flecainide was 3.0 % with an overall mortality of 4.3 %. The mortality was 2.9 % in pts with CM and nobody with single ventricle physiology died. Based on multivariable analysis, when compared to pts with CHD or CM receiving other anti-arrhythmics, there was no difference in the incidence of cardiac arrest ( p = 0.31) or death ( p = 0.28). Flecainide use in children with CHD or CM has increased in recent years. The incidence of cardiac arrest or death with flecainide administration in this cohort appears comparable to other anti-arrhythmic agents. [ABSTRACT FROM AUTHOR]