Obstructive sleep apnea syndrome: More insights on structural and functional cardiac alterations, and the effects of treatment with continuous positive airway pressure

OBJECTIVES: We studied structural and functional cardiac alterations in obstructive sleep apnea (OSA), their relationship to the severity of OSA, and the effects of treatment with continuous positive airway pressure (CPAP). BACKGROUND: Obstructive sleep apnea may influence the cardiac function by several mechanisms in the awake patient. METHODS: Left and right ventricular morphology and function were studied using echocardiography before and after treatment with CPAP in symptomatic patients (Epworth sleepiness score, 10 ± 4.8) with severe OSA (apnea-hypopnea index [AHI], 42 ± 24). The patients (n = 43, 32 men) had no known cardiac disease and were obese (body mass index, 31.6 ± 5.4 kg/m²). The same echocardiographic parameters were studied in age-matched overweight patients (n = 40; body mass index, 26.4 ± 2.3 kg/m²). RESULTS: The patients were hypertensive (systolic blood pressure, 153 ± 25 mm Hg), with a higher resting heart rate (77 ± 10 beats/min, p = 0.008) compared with age-matched control patients (n = 40). There was right ventricular dilatation, hypertrophic interventricular septum, reduced left ventricular stroke volume, tissue Doppler-determined systolic and diastolic velocities of the left and right ventricle, and normal pulmonary artery pressure. The structural and functional parameters were significantly associated with AHI (p < 0.004). Multiple stepwise regression showed the interventricular septum thickness, right ventricular free wall, and mitral annulus tissue Doppler systolic velocities to be predictive of a higher AHI (p < 0.001). Six months after treatment with CPAP, significant improvements were observed in the symptoms and hemodynamics, as well as left and right ventricular morphology and function. CONCLUSIONS: The structural and functional consequences of OSA on the heart are influenced by the severity of AHI. These effects are reversible if the apneic episodes are abolished.