Background: The aim of this study was to test the efficacy of a low-dose pravastatin regimen (20 mg daily) in patients with myocardial infarction.
Methods: GISSI Prevenzione (GISSI-P) is an open trial on secondary coronary heart disease prevention: 4271 recent acute myocardial infarction patients (< or = 6 months) with total blood cholesterol > or = 200 mg/dl were randomized to low-dose cholesterol-lowering treatment (pravastatin 20 mg daily) or no treatment. GISSI-P was started in 1993 and its story was crossed by the publication of the results of similarly designed clinical trials. The publication of 4S results in 1994 prompted the Data Safety and Monitoring Board (DSMB) and the Steering Committee (SC) to change the protocol so that only patients whose total blood cholesterol was < 250 mg/dl could be randomized whilst patients with total blood cholesterol > 250 mg/dl who had already been enrolled in the study had to be re-evaluated and, if appropriate, pharmacologically treated. The DSMB and the SC agreed to stop randomization prematurely in late 1996 after the publication of CARE results.
Results: Mean follow-up time was 23.0 +/- 6.7 months (median 24.3 months). The two treatment groups were well matched at baseline. Pharmacological interventions recommended by the protocol were widely prescribed (antiplatelet agents > 90%, beta-blockers 42.7%, and ACE-inhibitors 40.2%). Mainly because of the on-course modification of the study protocol, 402/2133 (18.8%) patients in the control group started a cholesterol-lowering treatment during follow-up. Conversely, 296/2138 (13.8%) patients permanently stopped taking their tablets. Side effects, however, were the reason for discontinuing therapy in 57 (2.7%) patients in the pravastatin group, and patient reluctance to continue accounted for most of the remainder. After excluding control patients who had started a cholesterol-lowering treatment during follow-up, the following changes of median lipid concentrations in the control group over the whole course were observed: total cholesterol -1.9%; LDL cholesterol -2.9%; triglycerides -2.0%; HDL cholesterol +1.4%. The analysis carried out excluding patients randomized to pravastatin treatment and actually not assuming the drug clearly indicated the cholesterol-lowering efficacy of low-dose pravastatin (total cholesterol -12.5%; LDL cholesterol -18.8%; triglycerides -7.9%; HDL cholesterol +3.4%). During the study 256 (6.0%) patients either died or had a non-fatal stroke or a myocardial infarction, 136 (6.4%) in the control group and 120 (5.6%) in the pravastatin group (relative risk 0.90, 95% confidence interval 0.71-1.15, p = 0.41); 160 patients died, 88 (4.1%) in the control group and 72 (3.4%) in the pravastatin group (relative risk 0.84, 94% confidence interval 0.61-1.14, p = 0.26). The few (n = 28) non-cardiovascular deaths were balanced: 16 (0.8%) in the control group and 15 (0.6%) in the pravastatin group. The reduction of cardiovascular events was more evident in the by-treatment analysis, with coronary heart disease deaths being significantly decreased (relative risk 0.60, 95% confidence interval 0.38-0.96, p = 0.04). The overall frequency of adverse events was similar in the two groups. No significant difference between treatment groups was found for total cases of cancer or at any particular site.
Conclusions: Despite the decreased statistical power due to its premature stopping, the results of the GISSI-P suggest that a low-dose treatment with pravastatin (20 mg daily) is effective in reducing blood lipids, and underline the importance of long-term compliance with treatments in the search for a maximal effective dosage. Furthermore, the effects of a statin on total and coronary mortality quantified for the first time in a population exposed to Mediterranean dietary and lifestyle habits are markedly consistent with those obtained in different settings.