Introduction: Dual chamber coupled pacing (DCCP) has potential as a therapy for patients with heart failure (HF) by increasing atrial and ventricular contractility and reducing the mechanical heart rate (MHR). Ventricular coupled pacing has been shown to improve cardiac efficiency in animal models of atrial fibrillation and LV dysfunction via high-dose isoflurane, but it has not been studied in an ischemic model of HF. We hypothesized that in an ischemic model of HF, we could apply DCCP with moderate rate support and improve cardiac efficiency. Methods: We compared the metabolic and hemodynamic effects of DCCP at 3 heart rates with normal sinus rhythm (NSR) in 8 anesthetized dogs with EF's < 35% from serial embolizations. A coupled stimulus was delivered to the right ventricle 10 ms after the effective refractory period. An atrial premature stimulus was delivered 60 ms prior to the ventricular stimulus. DCCP was applied with no atrial pacing (DCCP-low), with atrial pacing that increased the MHR by 5 bpm (DCCP-mid), and with atrial pacing that increased the MHR by 15 bpm (DCCP-high). Each setting was maintained for 15 minutes. There were 2 baselines in the protocol – one before and one after the DCCP steps. The two baselines were averaged to obtain a single baseline with which to compare the DCCP rates. The order of the DCCP rates was randomized. Left ventricular and aortic pressure, and aortic and total coronary flow were continuously measured. Arterial and coronary sinus samples were taken to measure blood gases. Results: DCCP at all rates significantly increased mean coronary flow (mCorFlow) (26%, 22%, 44% for low, mid and high respectively) and LVdPdtmax (125%, 120%, 117% respectively) and decreased MHR (-44%, -42%, -30% respectively). Only DCCP-high showed an increase in cardiac output (CO, 17 ± 11%) and external cardiac work (CW, 19 ± 21%) but this did not translate into a significant increase in efficiency due to the larger increase in mCorFlow (44% ± 48%). Conclusion: These results suggest that, unlike during atrial fibrillation or an isoflurane model of LV dysfunction, coupled pacing does not improve cardiac efficiency in an ischemic model of HF.

AIMSPrevious studies have demonstrated that ambulatory atrial defibrillation shocks delivered by an implantable cardioverter-defibrillator (ICD) are safe and effective, but poorly tolerated. Separate studies have demonstrated the utility of single oral bolus propafenone for conversion of recent-onset atrial fibrillation (AF); however, most patients were hospitalized, had no structural heart disease, were taking no other antiarrhythmic drugs, and were not exposed to concomitant shock. We hypothesized that a single oral bolus dose of propafenone given early after onset would be a safe and effective adjunct to ICD-based AF therapy and improve overall therapy tolerance.METHODS AND RESULTSA randomized three-way crossover study design was used to compare three strategies, deployed in the ambulatory setting early after AF episode onset in 35 ICD patients with advanced, drug refractory episodic/persistent syndromes, many of whom had structural heart disease and were taking other antiarrhythmic drugs: (i) single oral bolus propafenone (600 mg), followed by ICD shock if necessary; (ii) single oral bolus placebo, followed by ICD shock if necessary; and (iii) no oral bolus therapy and ICD shock if necessary (no bolus). Antiarrhythmic efficacy, defined by the restoration of sinus rhythm within 24 h, was similar during propafenone (81%) and no-bolus strategies (84%); both were significantly higher than during placebo strategy (62%). Propafenone was well tolerated and not associated with proarrhythmia. Shock use was significantly lower during propafenone strategy (19%) than during no-bolus strategy (55%); this was correlated with improved patient tolerance.CONCLUSIONAdjunctive use of single oral bolus propafenone is safe and effective in patients with an ICD and improves patient tolerance of device-based AF therapy.

Background: We sought to characterize atrial tachyarrhythmia (AT) burden and frequency after implantation of a dual‐chamber implantable cardioverter‐defibrillator (D‐ICD).

Introduction: This prospective, multicenter, randomized trial evaluated the effects of atrial prevention and termination therapies on atrial tachyarrhythmia (ATA) burden in patients with a standard indication for an implantable cardioverter defibrillator (ICD).