Effects of β-blocker therapy on exercise oscillatory ventilation in reduced ejection fraction heart failure patients: A case series study.

Abstract

Exercise oscillatory ventilation (EOV) is an abnormal breathing pattern that occurs in ~20% of patients with heart failure (HF) and is associated with poor prognosis and exercise intolerance. β-blockers (βb) are prescribed for most HF patients; however, their effect on EOV remains unclear. We evaluated the effect of βb on EOV in HF patients with reduced ejection fraction (HFrEF). Fifteen patients diagnosed with HF, ejection fraction <45%, aged from 18 to 65 years, were included before starting βb therapy. Patients underwent clinical evaluation, cardiopulmonary exercise testing, echocardiography, laboratory exams (norepinephrine levels, B type natriuretic peptide) at baseline and after βb therapy optimized for six months. Presence of exercise oscillatory breathing was determined by two experienced observers who were blinded to the moment of the test (pre or post). Fifteen patients (1 female), aged 49.5±2.5 years, with HFrEF, NYHA I-III enrolled in the study. The etiologies of the HFrEF were idiopathic (n=8) and hypertensive (n=7). LVEF increased after βb therapy from 25.9±2.5% to 33±2.6%, P=0.02; peak VO2 did not significantly change (21.8±1.7 vs 24.7±1.9, P=0.4); VE/VCO2 slope changed from 32.1±10.6-27.5±9.1, P=0.03. Before βb initiation, nine patients (60%) had EOV, but only two (13%) did after optimized therapy. McNemar test was used to evaluate the significance of the association between the two moments (P=0.02). In patients with HF, medical therapy with βb can reverse EOV. This may explain why these patients experience symptom improvement after βb therapy.