Transthoracic echocardiography and exercise echocardiography
All patients underwent transthoracic echocardiography at baseline and after 3 months in both the CPAP and sham treatment groups using a 2.5-MHz transducer ultrasound machine (Vivid 7 or Vivid E9 system, GE Healthcare). Conventional 2D, M-mode, and Doppler images were obtained and measured according to the current recommendationsExercise stress echocardiography was performed for all patients at baseline and the 3-month follow-up. Symptom-limited supine bicycle exercise stress echocardiography was performed according to current guidelines using a cycle ergometer