The effect of long-term continuous positive airway pressure treatment on systolic and diastolic function in patients with obstructive sleep apnoea syndrome: a five year observational study.

Objective: Evaluation of the long-term effects of continuous positive airway presure (CPAP) on mean heart rate and left ventricular systolic and diastolic parameters in obstructive sleep apnea syndrome (OSAS) using conventional and tissue Doppler techniques.

Methods: This prospective cohort study is designed to evaluate the long-term effects of CPAP treatments in normotensive OSAS patients. Initially 40 patients aged from eighteen to fifty five with documented OSAS syndrome were evaluated within one month of CPAP treatment. All had high self-reported compliance with treatment. From the latter, 21 patients with uninterrupted CPAP therapy (for at least 5 years, 5 hours per day) were included in the study and further evaluated with treatment. The left ventricular systolic function was assessed on apical four- chamber view using modified Simpson method and diastolic function was evaluated with classic transmitral pulsed and tissue Doppler techniques. Paired t test and Wilcoxon signed rank test had been used to compare the clinical and echocardiography data before and after treatment period.

Results: A comparison of values assessed after one month and after 5 years of CPAP therapy, revealed a significant increase in the acceleration time(AT) Em/Am ratio and ejection time (ET) (AT: p=0.04; Em/Am ratio p=0.03 ET: p=0.04) while a significant decrease was observed on deceleration time (DT), isovolumetric relaxation time (IRT), myocardial performance index (MPI), mitral regurgitation (MR) and 24 hour mean heart rate (HR) in all subjects (DT: p=0.02; IVRT: p=0,04; MPI: p=0,01; MR: p≤0.001; HR: p=0.004).

Conclusion: We observed a significant improvement in the left ventricular systolic and diastolic function and a significant decrease of 24-hour heart rate and mitral regurgitation with unchanged ejection fraction of the left ventricle with long-term CPAP treatment similar to short-term treatment studies. The long-term maintenance of the beneficial effect of CPAP throughout the 5 year long-term treatment can be one of the pathophysiologic mechanisms that may explain the decrease of cardiovascular mortality observed with long-term CPAP therapy in OSAS patients.