Implantable defibrillators with and without resynchronization for patients with left ventricular dysfunction.

In conclusion, sudden cardiac arrest is a major cause of mortality in patients with LV dysfunction, even in asymptomatic patients. Low EF and heart failure may contribute synergistically to this risk, and may confer a risk of sudden death that accumulates over time. Several studies confirm that ICDs are more effective than optimal medical therapy at reducing SCA, although efforts must focus on optimizing medical therapy. Finally, ventricular dyssynchrony is a major risk factor for cardiac mortality that is best ameliorated by CRT. Future studies using markers of mechanical dyssynchrony will likely enhance the ability of CRT to reduce symptoms, hospitalization, and mortality.