Too little aspirin for secondary prevention after acute myocardial infarction in patients at high risk for cardiovascular events: Results from the MITRA study

Background A meta-analysis of randomized trials has shown a significant reduction of mortality rate in patients receiving aspirin for secondary prevention after acute myocardial infarction (AMI). However, a significant number of patients do not receive aspirin after AMI. Little is known about why aspirin is withheld or the long-term outcome of these patients today. Methods The Maximal Individual Therapy in Acute Myocardial Infarction (MITRA) registry is a multicenter registry of patients with AMI in Germany. Results Of 4902 patients, 509 (10%) did not receive aspirin at the time of discharge from the hospital. The mean follow-up period for these patients was 17 months. Relative contraindications to aspirin were significantly associated with the withholding of aspirin (in-hospital bleeding: odds ratio [OR], 3.56; 95% CI, 1.86–6.80; history of peptic ulcer: OR, 2.49; 95% CI, 1.62–3.83). Absolute contraindications to aspirin were rare (2.2%). Other medications of proven benefit were also given less often in these patients (β-blockers: 49.0% vs 61.9%, P <.001; angiotensin-converting enzyme inhibitors: 65.6% vs 70.2%, P = .06; statins: 12.2% vs 15.1%, P = .10). Patients who were not given aspirin were at high risk for vascular events. They were more likely to have a history of prior AMI (OR, 1.34; 95% CI, 1.02–1.79), were in critical clinical condition at admission more often (cardiogenic shock: OR, 1.98; 95% CI, 1.09–3.56; overt heart failure: OR, 1.6; 95% CI, 1.05–2.3), and received acute revascularization less often (OR, 1.32; 95% CI, 1.05–1.67). The 1-year mortality was 2-times higher in patients who did not receive aspirin than in patients who did receive aspirin (16.5% vs 8.3%, P <.001). A significant association of withheld aspirin at discharge with a higher long-term mortality rate was confirmed with multivariate analysis (OR, 1.62; 95% CI, 1.15–2.29). Conclusions Ten percent of patients who sustained an AMI did not receive aspirin at the time of hospital discharge. Most of these patients were at high risk for cardiovascular events. Withheld aspirin was significantly associated with higher mortality rate during follow up.