Does clopidogrel worsen the outcomes of patients submitted to CABG during hospitalization for acute myocardial infarction?

Introduction

Clopidogrel is recommended for patients with acute myocardial infarction (AMI); however concern exists regarding those patients submitted to coronary artery bypass surgery (CABG). We estimated the incidence of CABG during AMI hospitalization, and evaluated whether early treatment with clopidogrel is harmful to this population.

Methods

We studied 941 patients with AMI (71% male, age 68 ± 15 years) using prospective data recorded between 2003 and 2008. Variables are presented as the median and interquartile range, or relative frequencies. The effect of clopidogrel on hospital mortality and the hospitalization period was adjusted for prognostic markers (left ventricular ejection fraction, age and Killip class) using logistic or Cox regression, respectively. We also evaluated the effects of clopidogrel on the subgroup of patients submitted to CABG through the inclusion of interaction terms in a multivariate analysis.

Results

Clopidogrel was used in 641 (69%) patients. CABG was performed in 44 patients (4.6%), and 17 of them (40%) received clopidogrel. Clopidogrel was interrupted before surgery in all patients (time without clopidogrel: 4.5 days (1.5 to 6.5)). Among patients submitted to CABG, the hospitalization period (13 days (12 to 30) with clopidogrel vs 12 days (10 to 18) without clopidogrel; P = 0.12) and blood transfusions (3.7 units (2.4 to 5.4) with clopidogrel vs 2.2 units (0.9 to 2.3) without clopidogrel; P = 0.24) were not affected by clopidogrel. The mortality rate remained the same in both groups (15% with clopidogrel vs 20% without clopidogrel; P = 0.7). After an adjusted analysis, we compared the effects of clopidogrel in the RM subgroup with the rest of the population. In analyses adjusted for possible confounders, clopidogrel was associated with reduced length of stay (hazard ratio for discharge = 1.3; 95% CI = 1.1 to 1.5) and reduced mortality rate (odds ratio = 0.36; 95% CI = 0.2 to 0.7). However, in the subgroup of patients submitted to CABG, clopidogrel increased the length of stay (hazard ratio for discharge = 0.62; 95% CI = 0.3 to 1.2; test for heterogeneity P = 0.04), and, although not statistically significant, it might also have an adverse effect on mortality (odds ratio = 1.8; 95% CI = 0.2 to 15.7; test for heterogeneity P = 0.156).

Conclusion

The early use of clopidogrel increased the length of stay in patients submitted to CABG during hospitalization for AMI. Clopidogrel's effect on mortality in the CABG subgroup could not be estimated with precision in this sample.