on behalf of the Multicenter InSync ICD II Study GroupBackground-The effects of cardiac resynchronization therapy (CRT) in patients with mildly symptomatic heart failure have not been fully elucidated. Methods and Results-The Multicenter InSync ICD Randomized Clinical Evaluation II (MIRACLE ICD II) was a randomized, double-blind, parallel-controlled clinical trial of CRT in NYHA class II heart failure patients on optimal medical therapy with a left ventricular (LV) ejection fraction Յ35%, a QRS Ն130 ms, and a class I indication for an ICD. One hundred eighty-six patients were randomized: 101 to the control group (ICD activated, CRT off) and 85 to the CRT group (ICD activated, CRT on). End points included peak V O 2 , V E/V CO 2 , NYHA class, quality of life, 6-minute walk distance, LV volumes and ejection fraction, and composite clinical response. Compared with the control group at 6 months, no significant improvement was noted in peak V O 2 , yet there were significant improvements in ventricular remodeling indexes, specifically LV diastolic and systolic volumes (Pϭ0.04 and Pϭ0.01, respectively), and LV ejection fraction (Pϭ0.02). CRT patients showed statistically significant improvement in V E/V CO 2 (Pϭ0.01), NYHA class (Pϭ0.05), and clinical composite response (Pϭ0.01). No significant differences were noted in 6-minute walk distance or quality of life scores. Conclusions-In patients with mild heart failure symptoms on optimal medical therapy with a wide QRS complex and an ICD indication, CRT did not alter exercise capacity but did result in significant improvement in cardiac structure and function and composite clinical response over 6 months.

N IMPORTANT SUBSET OF PAtients who have chronic heart failure (HF) also have cardiac dyssynchrony. Delays in interventricular or intraventricular electrical activation cause marked abnormalities in the sequence of global and segmental right and left ventricular (LV) activation and impair mechanical performance. 1-3 The ability of new methods of cardiac stimulation to resynchronize ventricular function, improve overall cardiac performance, and increase exercise capacity has been shown by the results of several observational and controlled studies. 4-10 The Multicenter InSync Randomized Clinical Evaluation (MIRACLE), the first ran-Author Affiliations and Financial Disclosures are listed at the end of this article.

VNS does not reduce the rate of death or HF events in chronic HF patients. (INcrease Of VAgal TonE in CHF [INOVATE-HF]; NCT01303718).

Transvenous CRT system implantation appears safe, well-tolerated, has a high success rate, and improves with operator experience and the addition of new technologies.

Right ventricular pacing worsens LV function in patients with and without LV dysfunction unless the RV pacing site is optimized. Left ventricular and BiV pacing preserve LV function in patients with EF >40% and improve function in patients with EF <40% despite no clinical indication for BiV pacing.

Selective site right ventricular pacing has been suggested as an approach to reduce the incidence of ventricular dysfunction and hopefully influence the morbidity resulting from traditional right ventricular apical pacing. Pacing from the right ventricular apex allows a stable ventricular rate, and together with atrial pacing and sensing, helps maintain atrioventricular synchrony but does not allow physiological activation of the left ventricle. Traditional atrial pacing sites like the right atrial appendage may encourage atrial tachyarrhythmias, whereas lead placement in right atrial septal sites may reduce the frequency of symptomatic atrial tachyarrhythmia episodes, especially when combined with prevention algorithms. Researchers attempting to pace the heart from these selective sites have been hindered by the lack of uniform definitions of where these sites actually lie and the inadequacy of tools to consistently reach these locations and verify correct placement. This lack of definition consensus may have contributed to the apparent conflict of data, particularly in the right ventricle. There is an urgent need for a standardization of terms and identifying measures for selective pacing sites.

With the use of recommended implant techniques, the study results support the electrical efficacy and safety of a catheter-delivered, lumenless lead in traditional or alternate right atrium or right ventricle sites through 18 months post-implant.

Biventricular, alternative, and multisite pacing are currently being explored to improve cardiac function among patients with medically refractory, end-stage dilated cardiomyopathies. Although, due to inherent myocardial abnormalities, patients with repaired congenital heart defects may be at a greater risk than others to develop heart failure, often requiring cardiac transplantation. The efficacy of biventricular pacing among these patients is unknown. This report presents a patient with successfully repaired congenital heart disease in infancy who developed a symptomatic dilated cardiomyopathy at 22 years of age. Following biventricular pacing, systemic ventricular function showed a 14% improvement in ventricular dP/dt. One month later, subjective symptoms improved and cardiac ultrasound illustrated a 125% increase in fractional area of change. Exercise stress testing showed a 17% improvement in aerobic work capacity.