The impact of arterial hypertension on the results of coronary artery bypass grafting

Abstract

Arterial hypertension is though to be associated with reduced coronary vasodilator reserve in the coronary microcirculation. Increased ventricular mass and coronary arteriolar abnormalities are the dominant features in patients with severe hypertension, while large-vessel coronary disease is the predominant feature in patients with mild hypertension. In the present study we have evaluated how hypertension influences the outcome of coronary artery bypass grafting (CABG), with emphasis on patients with preoperative left-ventricular ejection fraction (LVEF) < or = 25%. Between January 1, 1990 and November 1, 1994, 77 consecutive patients with LVEF < or = 25% (Hypertensive, n = 38 [group I] and normotensive, n = 39 [group II] underwent CABG. During the same time period 2289 patients with LVEF > 25% underwent CABG (Hypertensive, n = 870 [group III] and normotensive, n = 1419 [group IV]) and were studied for comparison. Mean age (64 years), sex distribution (86% men), and other classical risk factors did not differ between the groups, except a higher incidence of insulin-dependent diabetes in patients with LVEF < or = 25%. There were 18% reoperative CABG, 91% of the patients were Canadian Cardiovascular Society's (CCS) angina class 3 and 4 preoperatively, 38% had unstable angina, and 35% underwent urgent surgery (within 24 hours of admission). Angiography and operation data did not differ significantly between the groups. Hospital mortality in group I was 5.3% and in group II 15.4%, p < 0.008. In group III it was 6.3% and in group IV 2.2%, p < 0.001. Postoperative low cardiac output occurred in 18% (group I) and 39% (group II), p < 0.05, and only in 5% in groups III and IV, p < 0.001. Non-fatal myocardial infarction and other postoperative complications revealed no group differences. LVEF and CCS class improved from 1 month postoperatively in groups I and II, however, significantly more in group I (hypertensives), p < 0.001. Hypertensive patients with poor left-ventricular function preoperative to were found to have a lower hospital mortality and incidence of postoperative low cardiac output than normotensiven with LVEF < or = 25%. Hypertensive patients also had a better improvement of their left-ventricular function and CCS class than normotensiven. Left-ventricular hypertrophy and previous myocardial infarction were predictors for mortality in patients with LVEF > 25%. Patients with LVEF < or = 25% showed the same tendency, though not statistically significant.