Differences in pulmonary function and exercise capacity in patients with idiopathic dilated cardiomyopathy and idiopathic pulmonary arterial hypertension.

OBJECTIVES: We observed the pulmonary function and exercise capacity of idiopathic dilated cardiomyopathy (IDCM) and idiopathic pulmonary arterial hypertension (IPAH) patients using cardiopulmonary exercise testing (CPX). We evaluated and compared the two groups.

BACKGROUND: Pulmonary abnormalities and decreased exercise capacity are common in IDCM and IPAH. Little is known about the differences in these two syndromes.

METHODS: Sixty-three patients were involved the study, 23 with IDCM and 40 with IPAH. All patients underwent pulmonary function testing at rest and CPX.

RESULTS: Patients with IPAH had a higher peak respiratory frequency (32.40 ± 7.88 vs 29.60 ± 6.50 b/min), peak dead space volume/tidal volume (29.33 ± 4.55 vs 26.30  ± 3.31%), peak end-tidal partial pressure of O2 (125.18 ± 5.88 vs 115.17 ± 6.06 mm Hg), peak minute ventilation/CO2 production (50.14 ± 13.26 vs 33.50 ± 6.80 L/min/L/min), and a lower peak oxygen uptake (1262.70 ± 333.34 vs 742.76 ± 194.72 ml/min), peak minute ventilation (38.20 ± 13.07 vs 45.33 ± 12.31 L), peak oxygen uptake/heart rate (5.11 ± 1.47 vs 9.43 ± 2.79 ml/b) and peak end-tidal partial pressure of CO2 (23.73 ± 5.39 vs 35.30 ± 5.45 mm Hg) during exercise.

CONCLUSIONS: Compared to IDCM, patients with IPAH had worse pulmonary function and exercise capacity resulting from severe ventilation/perfusion mismatching and gas exchange abnormalities.