Are beta-blockers effective or contraindicated in pulmonary arterial hypertension?

Pulmonary arterial hypertension (PAH) is a life-threatening disease characterized by progressively elevated pulmonary vascular resistance. Sustained elevation of pulmonary vascular resistance causes severe right ventricular hypertrophy and failure. Sympathetic nerve activity is increased in patients with left ventricular failure, and treatment with beta-adrenergic receptor blockers was found to improve survival rate and cardiac function of patients with left ventricular failure. Sympathetic nerve activity is also increased in patients with PAH. Muscle sympathetic nerve activity in patients with PAH was correlated with heart rate and NYHA class. These findings indicate that treatment with adrenergic receptor blockers may be effective in patients with PAH. However, neurohormonal modulation with beta-adrenergic receptor blockers carries the risks of decreased cardiac contractility and cardiac output. The safety of treatment with beta-adrenergic receptor blockers in clinical settings has been uncertain. Meanwhile, several experimental studies have shown beneficial effects of adrenergic receptor blockers in PAH. Carvedilol inhibited the exaggerated proliferation of pulmonary artery smooth muscle cells of patients with idiopathic PAH. Treatment with carvedilol improved survival of rats with monocrotaline-induced PAH. Bisoprolol also delays progression to right heart failure in rats with PAH. Careful use of beta blockers in selected patients might be beneficial. Further studies are needed to determine whether beta-adrenergic receptor blockers are tolerable and effective in patients with PAH.