PATENCY OF INFARCT-RELATED ARTERY - EFFECT OF RESTORATION OF ANTEROGRADE FLOW ON VAGAL REFLEXES

Background In post-myocardial infarction (MI) patients. the restoratio n of anterograde flow in the infarct-related artery (IRA) significantl y improves survival. Limitation of infarct size and increased electric al stability of the myocardium are likely operating mechanisms for thi s beneficial effect. We tested the hypothesis that patency of the IRA may enhance vagal reflexes, a factor known to affect electrical stabil ity of the infarcted myocardium. Methods and Results Analysis of angio graphic data was performed in 359 of 1284 post-MI patients enrolled in a multicenter prospective study within 8 weeks after the index MI. Al l the patients underwent baroreflex sensitivity (BRS) assessment by th e phenylephrine method. The BRS of the entire population averaged 8.2/-5.5 ms/mm Hg, and was significantly related to age but not to ejecti on fraction (EF). One-, two-, and three-vessel disease was present in 138, 96, and 99 patients. respectively, while no coronary stenosis was observed in 26. IRA patency was documented in 234 patients (65%), whi le in the remaining 125 (35%), the artery remained occluded. Patients with occluded IRAs had more extensive coronary disease (2 to 3 vessels , 71% versus 46%, P<.01) and more depressed left ventricular (LV) func tion (LVEF, 48+/-13% versus 53+/-12%, P<.001). Patency of the IRA was associated with higher BRS values (BRS, 8.9+/-5.8 versus 7.1+/-4.7 ms/ mm HE, P<.005) and with a lower incidence (9% versus 18%, P<.02) of ma rkedly depressed BRS (<3 ms/mm Hg), a condition suggested by prelimina ry studies to be associated with an increased risk of post-MI mortalit y. The association between IRA patency and BRS was more evident in ant erior than in inferior MI. Multivariate regression analysis showed tha t age of the patient and patency of the IRA were the major independent determinants of BRS, while LVEF was weakly related to BRS and only wh en analyzed as a categorized variable. Conclusions The presence of an open IRA is associated with a higher baroreflex sensitivity, and this effect is largely independent of limitation of infarct size by IRA pat ency. These data offer new insights into the mechanisms by which coron ary artery patency map affect cardiac electrical stability and surviva l.