Obstructive sleep apnoea-hypoapnoea syndrome reversibly depresses cardiac response to exercise

To evaluate cardiac response to exercise in middle-aged normotensive obstructive sleep apnoea-hypoapnoea syndrome (OSAHS) adults with normal resting left ventricular systolic function and to test the hypothesis that nasal continuous positive airway pressure (CPAP) therapy might improve cardiac performance during exercise.

We performed a prospective, randomized, double-blind, placebo-controlled, cross-over clinical trial including 31 consecutive newly diagnosed OSAHS patients and 15 healthy subjects. Cardiopulmonary exercise testing with cardiac output measurement, blood pressure (BP) recordings, and urinary excretion of catecholamine levels were obtained at baseline and after 3 months on both effective and sham CPAP. OSAHS subjects had higher systolic and mean nocturnal BP and higher nocturnal levels of catecholamines. In contrast, they had lower increments in cardiac output (Qt) and in stroke volume (SV) in response to exercise than control subjects. CPAP therapy was associated with highly significant improvements in all the indices of left ventricular systolic performance response during exercise, whereas with sham CPAP, all of them remained unchanged.

OSAHS patients with normal resting left ventricular systolic function and no hypertension had a worse cardiac response to exercise than healthy subjects. In these patients, 3 months of CPAP improved both Qt and SV responses to exercise.