Background:Percutaneous transluminal septal myocardial ablation (PTSMA) and modified Morrow septal myectomy (MMSM) are two invasive strategies used to relieve obstruction in patients with hypertrophic cardiomyopathy (HCM).This study aimed to determine the clinical outcome of these two strategies.Methods:From January 2011 to January 2015,226 patients with HCM were treated,68 by PTSMA and 158 by MMSM.Both ultrasonic cardiograms and heart functional class were recorded before,after operations and in the follow-up.Categorical variables were compared using Chi-square or Fisher's exact tests.Quantitative variables were compared using the paired samples t-test.Results:Interventricular septal thickness was significantly reduced in both groups (21.27 ± 4.43 mm vs.18.72 ± 4.13 mm for PTSMA,t =3.469,P ＜ 0.001,and 21.83 ± 5.03 mm vs.16.57 ± 3.95 mm for MMSM,t =10.349,P ＜ 0.001,respectively).The left ventricular outflow tract (LVOT) pressure gradient (PG) significantly decreased after the operations in two groups (70.30 ± 44.79 mmHg vs.39.78 ± 22.07 mmHg for PTSMA,t =5.041,P ＜ 0.001,and 74.58 ± 45.52 mmHg vs.13.95 ± 9.94 mmHg for MMSM,t =16.357,P ＜ 0.001,respectively).Seven patients (10.29％) in the PTSMA group required a repeat operation in the follow-up.Eight (11.76％)patients were evaluated for New York Heart Association (NYHA) Ⅲ/Ⅳ in the PTSMA group,which was significantly more than the five (3.16％) in the same NYHA classes for the MMSM group at follow-up.Less than 15％ of patients in the PTSMA group and none of the patients in the MMSM group complained of chest pain during follow-up.Conclusions:Both strategies can not only relieve LVOT PG but also improve heart function in patients with HCM.However,MMSM might provide a more reliable reduction in gradients compared to PTSMA.