Heart rate per se impacts cardiac function in patients with systolic heart failure and pacing: a pilot study

Aims This study was designed to compare the specific effects of two heart rates (HR), 55 and 75 b.p.m., in patients with heart failure (HF). Methods and results Patients with chronic HF, left ventricular ejection fraction (LVEF) <= 35%, and a pacemaker with >90% of paced QRS, were included in a randomized cross-over trial of two 3-month periods where pacing rate was set at either 55 or 75 b.p.m. At the end of each period, patients were examined and radionuclide ventriculography, echocardiography, and blood sampling were performed for centralized and blinded analysis. Two patients did not complete the study because of early worsening while paced at 75 b.p.m. Twelve patients completed the study. Compared with 75 b.p.m., pacing at 55 b.p.m. was associated with a higher LVEF [+4.7% (2.6-6.7), P < 0.001], lower B-type natriuretic peptide levels [-91 pg/mL (-148 to -33), P < 0.01], lower systolic pulmonary artery pressure (41 +/- 10 vs. 47 +/- 10 mmHg, P = 0.02) and lower NYHA (New York Heart Association) class (2.2 +/- 0.6 vs. 2.6 +/- 0.5, = 0.03). The baseline pacing rate prior to inclusion had no effect on results. Conclusion HR per se may impact cardiac function and low HR might be beneficial in patients with systolic HF compared with intermediate HR.