HbA1c in pulmonary arterial hypertension: a marker of prognostic relevance?

Patients with pulmonary arterial hypertension (PAH) exhibit impaired glucose metabolism and increased insulin resistance. The clinical consequences of these metabolic changes are not known.

We assessed HbA1c levels in 115 patients newly diagnosed with PAH (79 females and 36 males; mean age 49.2 years; idiopathic n = 67, collagen vascular disease n = 16, congenital heart defect n = 19, pulmonary veno-occlusive disease n = 8, portopulmonary n = 5). No patients had diabetes or were receiving anti-diabetic medication or systemic steroids. After initiation of pulmonary vasoactive treatment, patients remained in long-term follow-up.

Initially, patients were in an advanced stage of disease (mean pulmonary arterial pressure 53 ± 18 mm Hg, cardiac index 2.3 ± 0.8 liters/min/m2) with a 6-minute-walk distance of 337 ± 123 meters, and in NYHA Functional Class 3.0 ± 0.7. The HbA1c was 5.73 ± 0.75%. A moderate but statistically significant positive correlation was observed between HbA1c levels and BNP (r(p) = 0.41, p = 0.014), but no correlation was found with hemodynamics or 6-minute-walk distance. The 5-year survival rate for the entire group was 68%. Kaplan-Meier analysis and multivariate Cox proportional hazard models correcting for demographic and clinical covariates revealed that patients with HbA1c < 5.7% had a significantly better 5-year survival compared with those having higher initial values (85.1% vs. 55.9%; log rank p = 0.002). HbA1c was a predictor of all-cause mortality with a hazard ratio of 2.23 (95% CI 1.06 to 4.70; p = 0.034) per 1-unit increase of HbA1c.

In patients with pulmonary arterial hypertension, the HbA1c level at time of diagnosis is an independent predictor of long-term prognosis.