Mechanical alternans in patients with chronic heart failure

Background: Clinical implications of mechanical alternans in patients with chronic heart failure have remained uncertain. In this study, prevalence, c haracteristics, and prognostic implications of mechanical alternans were in vestigated. Methods and Results: Consecutive 51 patients with dilated cardiomyopathy un derwent diagnostic cardiac catheterization using a micromanometer-tipped ca theter. Under basal conditions, 7 of 35 patients with sinus rhythm showed m echanical alternans. Physiologic tachycardia (110 bpm) induced mechanical a lternans in another 15 patients with sinus rhythm and in another 10 of 16 p atients with atrial fibrillation. Low doses of dobutamine also induced mech anical alternans in another 8 patients, but a high dose of dobutamine elimi nated mechanical alternans. Consequently, 40 patients (78%) showed mechanic al alternans. Mechanical alternans was always accompanied by alternating ch anges of positive dP/dt, a parameter of contractility during isovolumetric contraction time, but negative dP/dt was occasionally constant. Concordant mechanical alternans between both ventricles was more prevalent than discor dant alternans. The left ventricular end-diastolic volume indices and end-s ystolic volume indices of patients with mechanical alternans were larger th an those of patients without. The left ventricular ejection fraction of pat ients with alternans was significantly lower than that of patients without. Conclusions: Mechanical alternans was highly prevalent in patients with chr onic heart failure. The origin of mechanical alternans seems to exist befor e or at the isovolumetric contraction time.