The response of right ventricular size, function, and pressure to supine exercise: A comparison of patients with chronic obstructive lung disease and normal subjects
The response of right ventricular ejection fraction (RVEF) and right ventricular end-diastolic volume (RVEDV) to exercise was studied in 11 patients with severe (FEF25%–75%=0.32±0.13, mean ±SD) chronic obstructive pulmonary disease (COPD). Using gated radionuclide cardiac blood pool imaging techniques, the response of the patients with COPD was compared with that of 15 control subjects. Arterial blood gases, pulmonary arterial pressures, wedge pressure, and right ventricular pressures also were monitored in patients with COPD. The resting R VEF was lower and the resting RVEDV was higher in patients with COPD than in normals (both,P<0.01). Two of the 11 COPD patients had a RVEF during rest that was below lower limits, while 10 of 11 patients had RV dilation. Right ventricular end-diastolic pressure, measured during rest in patients with COPD, was normal (6.1±2.1 mm Hg) and cardiac index was within normal limits (3.55±0.82 l/min/m2). With exercise this cardiac index rose to 5.52±1.7/min/m2 (P<0.01) due to the increase in heart rate (83±18 to 125±25 beats/min;P<0.01) while stroke volume did not significantly change. During exercise, normal subjects showed and increase in RVEF while RVEDV did not change; in patients with COPD, the RVEF fell and the RVEDV increased. In the patients with COPD, mild resting arterial hypoxemia and hypercapnia were both exaggerated during exercise; and mild resting pulmonary arterial hypertension (PAm=24.3±7.6 mm Hg) also worsened with exercise (PAm=41±19 mm Hg,P<0.01). Correlation between change in RVEF and PAm was-0.58, and between change in RVEDV and PAm was 0.63. We conclude that patients with severe COPD often have right ventricular dilation at rest and commonly respond to supine exercise with a fall in LV ejection fraction and further dilation of the right ventricle.