ObjectiveTo evaluate the efficacy and safety of modified maze Ⅳ (Cox-maze Ⅳ) in hypertrophic obstructive cardiomyopathy (HOCM) patients.MethodsFrom June 2016 to June 2019, 30 HOCM and persistent atrial fibrillation (pAF) patients received Cox-maze Ⅳ operation with modified extended Morrow operation, including 21 males and 9 females. The average age was 51.36±10.27 years and the average weight was 72.48±11.29 kg. All patients underwent left atrial appendectomy. Recurrence of AF, improvement of symptoms, cardiac function (NYHA) were assessed during follow-up.ResultsThere was no death during the perioperative period. Postoperative left ventricular outflow tract gradient was significantly decreased compared with that before operation (P<0.01), and all systolic anterior motion (SAM) signs disappeared after operation. Thirty patients were all effectively followed up for 3-40 (16.24±8.26) months. During the follow-up period, there was no death, and the cardiac function (NYHA) of all patients recovered to gradeⅠ-Ⅱ. At the end of follow-up, twenty-four patients (80.00%) maintained sinus rhythm, and twenty-seven patients (90.00%) maintained sinus rhythm after amiodarone conversion. Univariate analysis showed that the smoking history (P=0.04), left atrial diameter≥55 mm before operation (P=0.03), left atrial diameter≥50 mm after operation (P=0.02), postoperative tricuspid regurgitation (P=0.02) were closely related to postoperative AF recurrence. The increase of left atrial diameter after operation was an independent risk factor for AF recurrence (P=0.02).ConclusionMorrow/Cox-maze Ⅳ procedure is safe and effective in treatment of patients with HOCM complicated with pAF, which helps to maintain postoperative sinus rhythm, and to improve the cardiac function. The increase of left atrial diameter after operation is an independent risk factor for AF recurrence.