Meta-analysis of monotherapy versus combination therapy for pulmonary arterial hypertension

Previous studies comparing combination therapy (CT) of pulmonary vasodilators to monotherapy (MT) in patients with pulmonary arterial hypertension (PAH) report conflicting results as to whether CT is more efficacious than MT. We systematically searched the Cochrane Library, EMBASE, and MEDLINE databases for randomized controlled trials comparing CT to MT for patients with PAH. Data were pooled using the DerSimonian-Laird random-effects model. Six randomized controlled trials including 729 patients met our inclusion criteria. Follow-up ranged from 12 to 16 weeks. Compared to MT, CT resulted in a modest increase in 6-minute walk distance at the end of follow-up (weighted mean difference 25.2 m, 95% confidence interval [CI] 13.3 to 37.2). CT did not decrease mortality (risk ratio [RR] 0.42, 95% CI 0.08 to 2.25), admissions for worsening PAH (RR 0.72, 95% CI 0.36 to 1.44), or escalation of therapy (RR 0.36, 95% CI 0.09 to 1.39) and did not improve New York Heart Association functional class (RR 1.32, 95% CI 0.38 to 4.5) compared to MT. Incidence of study-drug discontinuation was similar between groups (RR 0.89, 95% CI 0.53 to 1.48). CT did not decrease the combined end point of mortality, admission for worsening PAH, lung transplantation, or escalation of PAH therapy (RR 0.42, 95% CI 0.17 to 1.04). In conclusion, this meta-analysis suggests that in PAH CT does not offer an advantage over MT apart from modestly increasing exercise capacity. However, given the paucity of good-quality data, more studies are required to define the efficacy of CT in this population before establishing final guidelines.