Objective To assess the long-term effects of pacing in patients with hypertrophic obstructive eardiomyopathy(HOCM),and explore the most specific echocardiographic indexes.MethodsA total of 37 consecutive HOCM patients implanted dual-chamber pacemakers were enrolled and followed up.Thirty-seven cases were followed up for 1 year,26 cases were followed up for 2 years,and 10 cases were followed up for 3 years.After 1,2 and 3 years pacemaker implantation,pacing frequency,pacing threshold,impedance,atrioventricular delay and cumulative percent atrial and ventricular pacing were respectively tested,and left atrial dimension (LAD),left ventricular end-diastolic dimension (LVEDd),left ventricular posterior wall thickness (LVPW),interventricular septum thickness (IVS),left ventricular outflow tract diameter(LVOTd),left ventricular outflow tract pressure gradient (LVOTPG),left ventricular ejection fraction(LVEF),pulmonary artery systolic pressure (PASP) were measured and mitral valve systolic anterior motion(SAM) was observed.Pacing parameters and echocardiography indexes were dynamically compared before and after pacemaker implantation.ResultsPacing frequency was adjusted 60～70 bpm,atrioventricular delay was adjusted 90～ 180 ms,in order to achieve more than 95％ ventricular pacing,pacing threshold,pacing impedance were normal.The difference of various pacing parameters were no statistically significant within 3 years ( P ＞ 0.05).Compared with before pacing,after 1,2 and 3 years pacemaker implantation,IVS and LVOTPG declined significantly (P ＜ 0.01 ),LVOTd widened significantly ( P ＜0.01),SAM phenomenon improved obviously ( P ＜0.01 ),but the difference of LAD,LVEDd,LVPW,LVEF,PASP were no statistically significant ( P ＞ 0.05 ).Conclusions The heart structure reconstruction of patients with HOCM can been chronically improved by dual-chamber pacing treatment.IVS,LVOTd and LVOTPG can be used as the sensitive and specific indexes to evaluate pacing treatment.