The effects of digitalis on survival in high-risk patients with coronary artery disease. The Coronary Artery Surgery Study (CASS)

To examine whether digitalis use is associated with an increased mortality in certain high-risk subsets of patients with coronary artery disease, we analyzed the data of 14,547 patients in the Coronary Artery Surgery Study (CASS) registry who had significant coronary artery stenosis (≥70% narrowing) and received medical treatment for their disease. At the time of entry, 2600 patients (18%) were taking a digitalis preparation. At a mean follow-up of 4 1/2 years, the cumulative mortality rate for these patients was 18%, compared with 5% for the 11,947 patients not taking digitalis (p<0.001). Univariate analysis showed significant differences between the two groups in the following baseline variables: prior infarction, multiple infarction, age, degree of congestive heart failure (CHF), extent of disease, cardiomegaly and wall motion abnormalities. Cox regression analysis of the entire population failed to show digitalis to be one of the 13 variables independently predictive of survival. High-risk subsets of patients with CHF, myocardial infarction within 2 months preceding entry and patients with prior cardiac arrest or arrhythmia were analyzed separately by Cox analysis. The number of vessels diseased and left ventricular wall motion were the two most important variables predictive of survival in each group. Digitalis therapy failed to enter the final model in any subset of patients studied. The expected mortality of our study population classified according to the degree of CHF was similar to the observed mortality whether the patients were on or off digitalis. This study fails to confirm the findings of earlier reports showing a substantial mortality associated with digitalis use in certain high-risk subsets of patients with coronary artery disease. Although we could demonstrate no benefit in terms of survival for patients receiving digitalis in this population study, we conclude that digitalis therapy is not likely to be an independent risk factor contributing significantly to mortality in patients with coronary artery disease.