summarises the process of identifying studies eligible for inclusion in our analysis. We reviewed the full text of 128 articles from 2742 studies identified from our initial literature search and hand search. A total of 24 studies met criteria for inclusion, and we could ascertain data on myocardial infarction for 19.
13,14,21-37 We excluded four controlled studies identified in the literature search because the control arms were usual care,
38 atenolol,
39 amlodipine,
40 and hydrochlorothiazide.
41 Agreement between two investigators for final study inclusion, measured by the κ statistic, was 0.75. All trials had a prospective, parallel design. Nine trials had the maximum Jadad score of 5; four trials scored 4, five scored 3, and one scored 2 (). Allocation concealment was adequate in eight studies (42%), inadequate in two studies (11%), and unclear in the remaining nine studies (47%). With the exception of the study by Di Pasquale et al,
36 treatment was assigned in a randomised fashion. Participants were blinded in 19 studies (100%), investigators in 17 studies (89%), and outcome assessors in 18 (95%). Finally, patients were analysed by the intention to treat principle in 15 of the studies (79%).
| Table 1Characteristics of controlled trials of angiotensin receptor blocker use that report myocardial infarction |
In our data set, the study by Bakris et al
22 compared losartan with both a placebo arm and an enalapril arm; we therefore included the study in both analyses. We did not use information from the amlodipine arm of the irbesartan diabetic nephropathy trial.
25 Two studies investigated the use of angiotensin receptor blockers in hypertensive patients,
21,22 four studies in patients with diabetes mellitus and nephropathy,
23-26 10 studies in patients with heart failure,
14,27-35 and three studies in patients with a recent myocardial infarction or ischaemic syndrome.
13,36,37 Myocardial infarction, major adverse cardiac events, or cardiac mortality was an adjudicated study end point in nine studies,
13,14,21,24,25,28-30,33 whereas myocardial infarction was reported as an adverse event or was reported by the investigators in 10 studies that had primarily physiological or drug tolerability outcomes.
22,23,26,27,31,32,34-37 Finally, nine studies allowed for comparison between angiotensin receptor blockers and ACE inhibitors,
13,14,22,26,33-37 and 11 studies allowed for comparison between angiotensin receptor blockers and placebo.
21-25,27-32 Funnel plots for the angiotensin receptor blockers compared with placebo studies and angiotensin receptor blockers compared with ACE inhibitor studies are qualitatively symmetrical, indicating the absence of publication bias (). Other important study characteristics, including number of subjects, mean age, sex, and duration of follow-up, are summarised in the .
Effect of angiotensin receptor blockers compared with placebo on risk of myocardial infarction
In this analysis we included two hypertension trials, three trials of patients with diabetes and nephropathy, and six heart failure trials, with a total of 10 656 subjects allocated to treatment with angiotensin receptor blockers and 10 406 subjects allocated to placebo. In the group that was treated with angiotensin receptor blockers, 436 myocardial infarctions occurred (4.09%), compared with 450 myocardial infarctions in the placebo group (4.32%). Overall, using angiotensin receptor blockers was not associated with a significant increase in the risk of myocardial infarction, with a pooled odds ratio of 0.94 (95% confidence interval 0.75 to 1.16) from the random effects model (). Analysis using the fixed effects model similarly showed no significant association of using angiotensin receptor blockers with risk of myocardial infarction (pooled odds ratio 0.95, 0.83 to 1.09).
Effect of angiotensin receptor blockers compared with angiotensin converting enzyme inhibitors on risk of myocardial infarction
shows the results of the comparison of treatment with angiotensin receptor blockers and ACE inhibitors with respect to risk of myocardial infarction in one hypertension study, one diabetes and nephropathy study, four heart failure studies, and three recent studies of myocardial infarction or ischaemic syndrome. Among 5406 patients receiving angiotensin receptor blockers, 435 myocardial events occurred (8.05%), compared with 433 events (8.30%) in 5219 patients receiving ACE inhibitors, resulting in a pooled odds ratio close to unity (1.01, 0.87 to 1.16 by random effects analysis; 1.00, 0.87 to 1.16 by fixed effects analysis). This summary effect size was driven mainly by the OPTIMAAL study,
13 which accounted for 86.8% of the weighted odds ratio in the random effects model, with an individual study odds ratio of 1.01 (0.87 to 1.16).