- OBJECTIVE: To describe the rationale and design of the Prospective Reinfarction Outcomes in the Thrombolytic Era Cardizem CD Trial (PROTECT). DESIGN: A multicentre, randomized, double-blind, parallel-group comparison of once daily beta-therapy versus heart rate lowering calcium channel blocker therapy, in the reduction of one-year nonfatal reinfarction and cardiovascular death (combined primary end-point) initiated 24 to 96 h post non-Q wave myocardial infarction. SETTING: One hundred and twenty hospitals across Canada. PATIENTS: Over 7500 women and men aged 21 years or older with enzyme-confirmed non-Q wave infarction and without significant left ventricular systolic dysfunction will be recruited over two years. INTERVENTIONS: Once daily beta-blocker therapy (oral atenolol, 50 to 200 mg) versus once daily calcium channel blocker therapy (oral diltiazem 120 to 360 mg) with follow-up for up to three years. CONCLUSIONS: The PROTECT will be the largest all-Canadian cardiovascular trial to date and will compare two commonly prescribed agents for secondary prophylaxis following non-Q wave infarction. The scientific question addressed by the PROTECT is of major public health importance and the results of the study will directly affect current clinical practice.