Anjan S. Batra

A multicenter experience with novel implantable cardioverter defibrillator configurations in the pediatric and congenital heart disease population.

Both slowed and regularized ventricular rate provide hemodynamic benefits to patients with atrial fibrillation and thus constitute a primary therapeutic goal. The return to sinus rhythm obviously reaches this goal and has been the preferred strategy over several decades. Given that recurrence of atrial fibrillation is frequent in the face of both pharmacological and ablation-based invasive therapy, and that side effects may limit their use, rhythm control approaches may frequently fall short of expected clinical benefits. In that situation, rate control becomes the alternate strategy. In fact, a number of recent clinical trials comparing rhythm and rate control strategies consistently reported net benefits of rate control therapy (see1,2 for review). Accordingly, for many patients rate control is becoming the preferred strategy while rhythm control is being targeted when needed and/or possible.1 Rate control is primarily achieved by drug-induced conduction impairment of the AV node. When this approach fails, ablation-induced third-degree AV block coupled with ventricular pacing may be considered.3,4 Several other approaches are currently under scrutiny: ventricular pacing without AV block, slow pathway ablation, gene therapy, and selective ganglionic parasympathetic stimulation.3 The modulation of AV nodal function by cardiac ganglionic stimulation may prove to be of significant value in heart failure patients in whom antiarrhythmic drug-induced depression of ventricular function must be avoided.5-8 An added benefit is that a normal ventricular activation sequence is maintained. Selective ganglionic stimulation combined with ventricular pacing may provide further benefits by achieving a slowed and regularized ventricular rate in spite of persistent atrial fibrillation.9 The Soos et al. study in the current issue10 raises the possibility that ganglionic stimulation may be feasible with currently available pacemaker technology. The concept of rate control through parasympathetic stimulation is derived from pioneering experimental work showing that selective AV node conduction slowing can be achieved through local cardiac nerve stimulation.11-15 Effective parasympathetic ventricular rate slowing during atrial fibrillation has been reached in animals with nerve stimulation applied endocardially in the vicinity of AV node,16 transvenous catheter stimulation from the coronary sinus,5 and local electrical stimulation of inferior interatrial parasympathetic ganglionated plexus.7-10 In humans, transvenous

A Prospective Analysis of the Incidence and Risk Factors Associated with Junctional Ectopic Tachycardia Following Surgery for Congenital Heart Disease

This study was designed to evaluate the incidence and risk factors associated with the occurrence of junctional ectopic tachycardia (JET) in patients after congenital heart surgery. We prospectively analyzed cardiac rhythm status in 336 consecutive patients undergoing surgery for congenital heart disease at our institution during a 1-year period. The incidence of JET was 8% (27/336). Repairs with the highest incidence of JET were arterial switch operation (3/13, 23%), atrioventricular (AV) canal repair (4/19, 21%), and Norwood repair (2/10, 20%). Compared to patients with no arrhythmias, patients with JET were more likely to be younger (2.75 ± 2.44 vs 5.38 ± 7.25 years, p < 0.01), have had longer cardiopulmonary bypass times (126 ± 50 vs 85 ± 73, p < 0.01), and have a higher inotrope score (6.26 ± 7.55 vs 2.41 ± 8.11, p < 0.01). By multivariate analysis, ischemic time was the only factor associated with JET [odds ratio, 1.01 (confidence interval, 1.005–1.02); p = 0.0014). The presence of JET did not correlate with electrolyte abnormalities. JET is not necessarily related to surgery near the His bundle or hypomagnesemia. Longer ischemic time is the best predictor of JET. Patients undergoing arterial switch operation, AV canal repair, and Norwood repair are at highest risk of postoperative JET and should be considered for prophylactic therapy.

The Clinical Course of Acquired Complete Heart Block in Children with Acute Myocarditis

A case of biopsy-proven myocarditis in a 7-year-old complicated by advanced atrioventricular (AV) block prompted a review of the medical literature to determine the prognosis for recovery of AV conduction or need for pacemaker implantation. A total of 40 patients younger than 20 years of age were identified, with return of AV conduction within 7 days in 27 patients (67%), permanent pacing in 11 patients (28%) with persistent AV block, and death in 2 patients (5%).

Efficacy of Biphasic Waveform Compared to Monophasic Waveform for Cardioversion of Atrial Flutter in Pediatric Patients

The efficacy of biphasic waveform cardioversion of atrial flutter in pediatric patients has not previously been demonstrated. Cardioversion outcomes were compared in two sequential groups of patients with atrial flutter undergoing transthoracic cardioversion using monophasic and biphasic waveforms at a single pediatric institution. The mean energy required for procedural success was 1.7 ± 1.2 J/kg in the monophasic group compared to 0.9 ± 0.6 J/kg in the biphasic group (p = 0.002). The mean number of attempts before achieving procedural success was 1.9 ± 1.2 for the monophasic group and 1.3 ± 1.0 for the biphasic group (p = 0.019). Procedure success rate was 89.5% (33/38) in the monophasic group compared to 100% (27/27) in the biphasic group (p = 0.13). Success rate for biphasic waveform cardioversion was 83% (5/6) when using energy less than 0.5 J/kg. These findings provide the impetus for lower starting energies and more widespread use of devices utilizing biphasic waveforms in pediatric patients.

A PROSPECTIVE STUDY OF THE IMPACT OF MELODY VALVE IMPLANT ON THE FREQUENCY OF ARRHYTHMIAS DURING EXERCISE TESTING

Percutaneous pulmonary valve implant (Melody) for conduit related pulmonary stenosis (PS) or pulmonary insufficiency (PI) has gained rapid acceptance. However, objective data regarding the benefit of this therapy with regard to the incidence of arrhythmias remains limited. As part of the phase I