Therapeutic trials in coronary thrombosis should measure left ventricular function as primary end-point of treatment.

Clinical trials in coronary thrombosis can record as end-points either death or an index of left ventricular function (ejection fraction or end-systolic volume) which can be used as a surrogate for long-term mortality. Hospital mortality for patients under 70 years of age in whom effective thrombolysis is achieved should now be no more than about 5%. To show a 20% reduction (to 4%) in mortality with an alpha error (two-sided) of 0.05 and a beta error of 0.2 requires 15,000 patients. By contrast, a 25% improvement towards normal in ejection fraction (from about 59% to about 62%) requires only 384 patients. Since it is likely that one of several thrombolytic agents will be effective in conjunction with one or more myocardial protective agents, many trials will be required, and it may be more appropriate in future studies to measure left ventricular function rather than mortality as the principal end-point.