Effectiveness of Cardiac Resynchronization Therapy in Diabetic Patients with Ischemic and Nonischemic Cardiomyopathy

Background: Diabetes mellitus (DM) increases the risk for the development of both ischemic and nonischemic cardiomyopathy. We aimed to identify differences in response to cardiac resynchronization therapy with a defibrillator (CRT‐D) among DM patients with ischemic or nonischemic cardiomyopathy. Methods: Cox proportional hazards regression modeling was used to assess clinical response to CRT‐D (defined as CRT‐D vs. defibrillator‐only reduction in the risk of heart failure [HF] or death) and echocardiographic response (defined as percent reduction in left ventricular end diastolic and systolic volume [LVEDV and LVESV, respectively] at 12 month of follow‐up compared with baseline values) among 552 diabetic patients with ischemic (n = 367) or nonischemic (n = 185) cardiomyopathy enrolled in MADIT‐CRT. Results: The clinical benefit of CRT‐D was more pronounced among nonischemic patients (HR = 0.30 [P < 0.001] than among ischemic patients (HR = 0.59 [P = 0.004]; P for interaction = 0.10). Nonischemic patients also experienced significantly greater reductions in LVESV and LVEDV at 12 months with CRT‐D compared with ischemic patients (P < 0.001 for both). Subgroup analysis showed that the most pronounced reduction in HF or death with CRT‐D therapy occurred in nonischemic patients who were women (83% risk‐reduction [P < 0.001]), had a lower BMI (<30/kg/m²: 79% risk‐reduction [P < 0.001]), or had left bundle branch block at enrollment (82% risk‐reduction [P < 0.001]). Conclusions: The present study shows that treatment with CRT‐D in at‐risk cardiac patients with DM is associated with substantial reductions in the risk of HF or death and improvement in cardiac remodeling in those with ischemic and nonischemic cardiomyopathy, with a more pronounced benefit in patients with nonischemic disease. Ann Noninvasive Electrocardiol 2012;17(1):14–21     

Atrial Burst Pacing with Biphasic and Monophasic Waveforms for Atrial Fibrillation

Background: Biphasic pacing is a novel mode of pacing that was suggested to increase cardiac conduction velocity as compared with cathodal monophasic pacing. We aimed to evaluate the safety and efficacy of rapid atrial pacing to convert atrial fibrillation (AF) to normal sinus rhythm. Methods: Multiple biphasic (anodal/cathodal), reverse biphasic (cathodal/anodal), and monophasic (cathodal) atrial pacing therapies were performed among 12 patients undergoing left atrial catheter ablation for AF. The efficacy end point was successful conversion of AF to sinus rhythm, and safety end point no induction of ventricular arrhythmias. Patients were paced at three cycle lengths (100, 200, and 333 msec) for 60 seconds at three locations (right and left atrial appendages and coronary sinus). Results: Among the 66 biphasic (anodal/cathodal) pacing procedures one procedure in a patient with chronic AF, which involved pacing at the left atrial appendage with a cycle length of 200 msec, led to conversion of AF to sinus rhythm. None of the 66 monophasic pacing procedures or the 66 reverse biphasic (cathodal/anodal) pacing procedures was associated with AF termination. None of the biphasic pacing procedures was associated with induction of ventricular arrhythmias. Conclusions: Rapid atrial pacing using a variety of waveforms at the cycle length and output used in the current study was found to be safe. There was a single success in converting a chronic AF to sinus rhythm. Ann Noninvasive Electrocardiol 2012;17(1):22–27     

Relation of bundle branch block to long-term (four-year) mortality in hospitalized patients with systolic heart failure

There is controversy regarding type of bundle branch block (BBB) that is associated with increased mortality risk in patients with heart failure (HF). The present study was designed to explore the association between BBB pattern and long-term mortality in hospitalized patients with systolic HF. Risk of 4-year all-cause mortality was assessed in 1,888 hospitalized patients with systolic HF (left ventricular ejection function <50%) without a pacemaker in a prospective national survey. Cox proportional hazards regression modeling was used to compare mortality risk in patients with right BBB (RBBB; 10%), left BBB (LBBB; 14%), and no BBB (76%) on admission electrocardiogram. At 4 years of follow up, mortality rates were highest in patients with RBBB (69%), intermediate in those with LBBB (63%), and lowest in those without BBB (50%, p <0.001). Multivariate analysis demonstrated a significant 36% increased mortality risk in patients with RBBB versus no BBB (p = 0.002) but no significant difference in mortality risk for patients with LBBB versus no BBB (hazard ratio 1.04, p = 0.66). RBBB versus LBBB was associated with a 29% (p = 0.035) increased risk for 4-year mortality in the total population and with a 58% (p = 0.015) increased risk in patients with ejection fraction <30%. In conclusion, RBBB but not LBBB on admission electrocardiogram is associated with a significant increased long-term mortality risk in hospitalized patients with systolic HF. Deleterious effects of RBBB compared to LBBB appear to be more pronounced in patients with more advanced left ventricular dysfunction.