Abstract Body (Do not enter title and authors here): Background: Obstructive sleep apnoea (OSA) is highly prevalent in patients with obstructive hypertrophic cardiomyopathy (oHCM), and the severity of OSA appears to worsen following septal myoectomy. The effect of OSA on the survival of oHCM following myoectomy remains uncertain. In this study, we aimed to investigate the clinical outcomes in oHCM patients with different severities of OSA.

Method: We prospectively enrolled 330 oHCM who underwent septal myoectomy at our institution from January 2015 to December 2019. All patient underwent a standard polysomnography was performed on . The total apnea-hypopnea index (AHI), representing the number of respiratory events per hour of sleep, was calculated using the total recording time as the denominator. Mild, moderate, and severe OSA were respectively defined as an AHI >5 events/h, ≥15 events/h, and ≥30 events/h.

Result: Of 330 patients, 152 patients had OSA including 87 patients with mild OSA and 65 patients with moderate or severe OSA. Compared to patients without OSA, patients with OSA were much older ( 44.00 ± 12.18 vs. 52.22 ± 10.33 vs. 51.38 ± 10.31, p <0.001), less likely to be female [75 (42.1%) vs. 27 (31.0%) vs. 10 (15.4%), p<0.001], had a higher body mass index (24.81 ± 3.35 vs. 26.32 ± 3.00 vs. 27.77 ± 3.26, p<0.001), a higher proportion of atrial fibrillation, hypertension, and history of smoking. The proportion of coronary artery bypass graft and valvular intervention were comparable between patients with and without OSA. The Cox maze procedure seems higher in patients with OSA than that in patients without OSA [ 10(5.6%) vs. 12 (13.8%) vs. 4 (6.2%) , p= 0.057]. During a median follow-up of 23.1 (16.8-44.6) months, 2 death, 35composite endpoint (2 death, 10 patients readmitted for atrial fibrillation ablation, 21 patients for heart failure, and 2 patients for other arrhythmias, 1 patient experienced a stroke) were observed. The Kaplan-Meier survival curve showed no difference in all cause mortality but higher composite endpoints in patients with moderate or severe OSA(Image 1). Cox hazard regression model revealed that compared to patients without OSA, patients with moderate or severe OSA was independently associated with a worse survival [HR: 2.54, 95%CI (1.08 - 6.00), p=0.033)(Image 2).

Conclusion: OSA is common in patients with oHCM, and patients with moderate or severe OSA may indicate a worse survival.