Ventilatory limitation to exercise in patients with HFpEF and obesity: No room to breathe.

BACKGROUND

Lowering pulmonary capillary wedge pressure (PCWP) by sublingual nitroglycerin (NTG) fails to increase exercise capacity in patients with heart failure with preserved ejection fraction (HFpEF). These findings beg the question as to the origin of exercise limitation. Our objective was to determine whether exercise tolerance could be ventilatory limited in older patients with HFpEF and obesity.

METHODS

Patients with HFpEF and obesity (n = 42) underwent pulmonary artery and radial artery catheterizations. Cardiorespiratory responses, breathing mechanics, and arterial blood gases were measured at rest, 20 W, and at peak exercise before and after NTG.

RESULTS

At rest, there was a drop in cardiac output and PaO2 (p < 0.01) with subsequent increases in HR, a-v¯O2 difference, and A-aO2 difference (p < 0.001) after NTG. At 20 W, there were increases in HR, a-v¯O2 difference, V̇E/V̇CO2, lactate, PaO2, and A-aO2 difference (p < 0.05). At peak exercise, there was an increase in V̇E/V̇CO2 and pH (p < 0.01), and a decrease in PaCO2 (p < 0.001). However, before and after treatment, there was a qualitative decline in V̇E/V̇CO2 from 20 W to peak exercise suggesting these patients could not increase V̇E further. There were no differences in breathing mechanics at rest, 20 W, or peak exercise after NTG.

CONCLUSIONS

We conclude that mechanical ventilatory constraints coupled with increased ventilatory inefficiency impose a ventilatory limitation to exercise in patients with HFpEF and obesity.

CLINICAL TRIAL INFORMATION: Clinical Trials number: NCT04068844.