CALCIUM CHANNEL BLOCKADE AND SHORT-TERM SURVIVAL FOLLOWING ACUTE MYOCARDIAL INFARCTION
R.W. Parsons, I. Hanemaaijer, R.J. Broadhurst, K. Jamrojik, M.S.T. Hobbs, J. Hung*.
Department of Public Health, University of Western Australia, and Cardiology, Sir Charles Gairdner Hospital, Nedlands, Western Australia.
There is concern that calcium channel blockers (CCBs) may adversely affect patient outcome following with acute myocardial infarction (AMI). We therefore assessed the impact on short-term (28-day) case fatality of AMI in patients while taking CCBs at the time of admission by comparison to those on b-blockers or neither medication. This was a retrospective cohort study of 7766 patients who reached hospital alive between 1984 to 1993 with symptoms of an AMI. Cases were derived from a population-based register of major coronary events (AMI and coronary deaths) covering all residents of Perth, aged 26-64 years, as part of the WHO MONICA project. Clinical and drug treatment variables at the time of hospital admission predictive of death within 28 days of AMI were assessed using multivariate logistic regression. Among 7766 patients at AMI onset, 1291 (16.6%) were taking a CCB, alone or with a b-blocker, and 1259 (16.2%) a b-blocker alone. Patients taking a CCB or b-blocker at admission were more likely to have a prior history of angina, MI, coronary bypass surgery, hypertension, diabetes, or heart failure compared to those on neither medication. This was associated with a higher 28-day case fatality in patients taking any CCB, compared to those on b-blockers alone or neither medication (17.6% vs 9.3% and 11.1% respectively, P<.001). the mortality was similar among patients taking nifedipine, diltiazem, or verapamil (P=.21). When a statistical model was used to adjust for factors predictive of death at 28 days, patients taking any CCB were not found to have an excess risk of death compared to those on neither CCB nor b-blocker (relative risk [RR] 1.06, 95% confidence interval [CI] 0.87 to 1.30). However, there was an increased risk of death when compared to those on b-blockers alone (RR 1.34, 95% CI 1.06 to 1.69).
Conclusion: These results indicate that prior calcium blockade is not associated with an excess risk or death following AMI once differences in baseline risk profile are taken into account. However, patients taking CCBs compared to b-blockers have a worse outcome primarily because prior b-blockade confers a survival advantage following AMI. Thus b-blockers should generally be preferred to CCBs for the treatment of patients at risk of myocardial infarction.
