First-in-man trial of β3-adrenoceptor agonist treatment in chronic heart failure - impact on diastolic function.

Diastolic dysfunction (DD) in heart failure (HF) is associated with increased myocardial cytosolic calcium, and calcium-efflux via the sodium-calcium-exchanger depends on the sodium gradient. Beta-3-adrenoceptor (β3-AR) agonists lower cytosolic sodium and have reversed organ congestion. Accordingly, β3-AR agonists might improve diastolic function, which we aimed to assess. In a first-in-man, randomized, double-blinded trial, we assigned 70 patients with HF with reduced ejection fraction (HFrEF), NYHA II-III, and LVEF<40% to receive the β3-AR agonist mirabegron (300 mg/day) or placebo for six months, in addition to recommended HF therapy. We performed echocardiography and cardiac computed tomography (CCT) and measured N-terminal pro-brain natriuretic peptide (NT-proBNP) at baseline and follow-up. DD was graded per multiple renowned algorithms. Baseline and follow-up data were available in 57 patients (59±11 years, 88% male, 49% ischemic heart disease). No clinically significant changes in diastolic measurements were found within or between groups by echocardiography (E/e' placebo: 13±7 to 13±5, p=0.21 vs mirabegron: 12±6 to 13±8, p=0.74, between group follow-up difference 0.2 [95% CI -3 to 4], p=0.89), or CCT (left atrial volume index: between group follow-up difference 9 ml/m2 [95% CI -3 to 19], p=0.15). DD gradings did not change within or between groups following two algorithms (p=0.72, p=0.75). NT-proBNP remained unchanged in both groups (p=0.74, p=0.64). In patients with HFrEF, no changes were identified in diastolic measurements, gradings or biomarker after β3-AR stimulation compared to placebo. The findings add to previous literature questioning the role of impaired Na+-Ca2+ mediated calcium-export as a major culprit in DD. NCT01876433.

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