CLINICAL INVESTIGATIONS Effect of chronic intercurrent medication with β-adrenoceptor blockade or calcium channel entry blockade on postoperative silent myocardial ischaemia†

We have examined observational data from four published studies investigating the incidence of postoperative silent myocardial ischaemia (post-SMI) for the effects of chronic intercurrent therapy with β-adrenoceptor blockade or chronic calcium channel entry blockade. A total of 453 patients underwent ambulatory ECG monitoring before and for 2 days after non-cardiac surgery; 79 patients were receiving chronic intercurrent β-adrenoceptor blockade and 70 calcium channel entry blockade for ischaemic heart disease or arterial hypertension. Using logistic regression analysis, we defined a model for post-SMI that included four significant terms: β-adrenoceptor blockade; calcium channel entry blockade; arterial hypertension; and vascular surgery. Using univariate regression, there was no effect of chronic β-adrenoceptor blocking therapy on post-SMI (odds ratio 0.94 (95% confidence intervals 0.54–1.65)), but there was a higher incidence of post-SMI in patients receiving chronic calcium channel entry blocking drugs (odds ratio 1.95 (1.15–3.32); P 0.015). There was no interaction between β-adrenoceptor blockade and calcium channel entry blockade for postoperative SMI (odds ratio 2.48 (0.71– 8.73)), but there was an interaction between β-adrenoceptor blockade, calcium channel entry blockade, hypertension and vascular surgery (P 0.0201). These findings are at variance with those which have shown effects of preoperative β-adrenoceptor blockade on the incidence of post-SMI over the first 7 days after operation, and on mortality rates to 2 yr. There are no comparable data examining the effects of chronic intercurrent calcium channel entry blockade.