Carbon monoxide diffusing capacity and mortality in pulmonary arterial hypertension

Area of Science:

• Pulmonary Medicine
• Cardiovascular Research
• Clinical Prognostics

Background:

• Abnormal carbon monoxide diffusing capacity (DLCO) indicates pulmonary vascular disease.
• DLCO predicts pulmonary arterial hypertension (PAH) and poor outcomes in systemic sclerosis and idiopathic pulmonary fibrosis.
• The prognostic value of DLCO in World Health Organization (WHO) Group I PAH is not well-established.

Purpose of the Study:

• To investigate the prognostic utility of DLCO in patients with WHO Group I PAH.
• To determine if DLCO is an independent predictor of mortality in this patient population.

Main Methods:

• A cohort study of 408 WHO Group I PAH patients (1982-2006) was conducted.
• Data included demographics, comorbidities, medications, functional class, laboratory tests, exercise testing, and hemodynamics.
• Cox proportional hazards analysis assessed the association of DLCO with mortality, adjusting for multiple clinical and hemodynamic variables.

Main Results:

• The lowest tertile of DLCO was independently associated with an increased risk of death (multivariate HR = 2.4, P = 0.025).
• The multivariate model including DLCO demonstrated improved predictive accuracy (c-statistic = 0.78) compared to the model without DLCO (c-statistic = 0.75).
• A model with hemodynamic variables alone was inferior to the model incorporating DLCO.

Conclusions:

• Carbon monoxide diffusing capacity (DLCO) is an independent predictor of mortality in patients with WHO Group I PAH.
• DLCO provides significant prognostic information beyond traditional hemodynamic variables.