Abstract
Objective Heart rate modulation therapy using ivabradine reduces both morbidity and mortality in patients with systolic heart failure. However, the target heart rate for this patient population remains to be elucidated. Methods In this prospective observational study, we included patients with heart failure and a reduced ejection fraction who received 5.0 mg/day of ivabradine for three days. At baseline and three days later, the overlap length between E-wave and A-wave using trans-mitral Doppler echocardiography, as well as the cardiac output using AESCLONE mini, were simultaneously measured. The associations between Δ overlap length and Δ cardiac output were then investigated. Results Eight patients [77 (53, 87) years old, 2 men] were included. The heart rate decreased from 81 (69, 104) bpm down to 64 (57, 79) bpm (p=0.012). The overlap length increased in four patients and decreased in the other four patients. During the time period of ivabradine therapy, patients who had a greater decrease in overlap length had a greater increase in cardiac output (r=0.84, p=0.009). Conclusion Decreases in the overlap length between E-wave and A-wave by Doppler echocardiography were associated with an increase in the cardiac output while on ivabradine therapy. The implications of Doppler echocardiography-guided heart rate modulation therapy targeting a minimal overlap length therefore require further evaluation in larger, prospective studies.