Different characteristics of heart failure due to pump failure and bradyarrhythmia

BACKGROUND Heart failure (HF) can be caused by left ventricular (LV) pump failure as well as by bradyarrhythmias. Hemodynamic differences between HF by LV pump failure and that by bradyarrhythmia have not been fully investigated. We hypothesized that HF by LV pump failure could be associated with both reduced cardiac output (CO) and increased LV filling pressure due to associated LV diastolic dysfunction, whereas HF by bradyarrhythmia could be associated with reduced CO but only modestly increased LV filling pressure due to the absence of LV diastolic dysfunction. METHODS In 39 patients with HF by LV pump failure (LV ejection fraction <35%), 24 with HF by bradyarrhythmia, and 22 normal controls, LV volume, ejection fraction, stroke volume, left atrial volume, and early diastolic mitral valve flow to tissue annular velocity ratio (E/E') were measured by echocardiography. RESULTS Compared to patients with HF by LV pump failure, those with HF by bradyarrhythmia had significantly lower heart rates, less LV dilatation, preserved LV ejection fraction, preserved stroke volume, similarly reduced cardiac index (1.8 ± 0.4 vs. 1.6 ± 0.4 L/min/m(2), n.s.), preserved LV diastolic function (E') (4.4 ± 2.1 vs. 7.1 ± 2.9 cm/s, p < 0.001), less dilated end-systolic LA volume, and preserved E/E' (24 ± 10 vs. 13 ± 7, p < 0.001). CONCLUSIONS HF by LV pump failure is characterized by both significantly reduced CO and increased LV filling pressure, whereas HF by bradyarrhythmia is characterized by a similar reduction in CO but only modestly increased LV filling pressure.