Background : Subnormal baroreflex sensitivity(BRS) is an important risk indicator for sudden death. The open artery hypothesis that late restoration of antegrade flow in the infarct-related artery(IRA) renders the border zone of the infarction more electrically stable, thereby diminishing the incidence of ventricular tachyarrhythmias and sudden death, does not have definite backgrounds to influence revascularization strategy in post-myocardial infarction(MI) patient. Objectives : We studied the effect of acute coronary reocclusion on the change of arterial baroreflex function in MI patients with already depressed BRS. Methods: Forty-three(31 men, 55짹11years) consecutive MI patients, who presented late(>24hrs) after MI onset and fixed necrosis on MIBI myocardial perfusion scan, were included. ECG RR intervals and invasive beat to beat systolic blood pressure(SBP) were acquired before and during 3-min coronary occlusions. BRS was determined by conventional phenylephrine method. Heart rate variability(HRV) parameters, LF, HF power, it���s normalized power and LF/HF ratio were also calculated just before phenylephrine injection in each period before and during coronary occlusion. Results: No significant changes of SBP and HRV parameters, except shortening of RR interval(768짹27ms vs 796짹27ms of baseline, p=0.043) were observed during coronary occlusion. The BRS decreased from 5.02짹1.00 to 2.67짹0.75ms��mmHg-1(p=0.01) by coronary occlusion in 32 patients with adequate pressure rise and correlation coefficient of the baroreflex slope after phenylephrine injection. Correlation coefficients of the baroreflex regressions decreased from 0.86짹0.02 to 0.76짹0.07(p=0.212) during coronary occlusion. Six of 11patients who showed loss of baroreflex function had negative LV remodelling on echocardiographic examinations 6짹3 months later. Conclusions: Abrupt coronary reocclusion further deteriorate residual baroreflex function in postMI patients without significant hemodynamic changes. This result support the evidence that patency of IRA should be warranted even in case of late presented MI.