Excess coronary artery bypass graft mortality among women with hypothyroidism

Background The impact of thyroid disease on patients undergoing coronary artery bypass grafting has been reported in only small series of selected patients. Methods We investigated 30-day mortality of patients on thyroxine replacement therapy undergoing isolated coronary artery bypass grafting from 1993 to 2000 and identified variables of importance for outcome. Results A total of 3,631 patients (606 women) had isolated coronary artery bypass grafting of whom 58 patients (30 women) were treated for hypothyroidism. The mortality rate was higher among women with thyroxine replacement (16.7%, 95% confidence interval [CI] 5.6 to 34.7) than those without thyroxine replacement (5.9%, 95% CI 4.1 to 8.2; p = 0.02) and no difference between men with (3.6%, 95% CI 0.1 to 17.8) and without (2.6%, 95% CI 2.0 to 3.2) thyroxine treatment (p = 0.8). Intake of diuretics (p< 0.001) was directly associated with mortality whereas intake of aspirin (p = 0.01), levothyroxine dose (p = 0.03), and serum thyroxine level (p = 0.01) were inversely associated with mortality among women on thyroxine replacement. Conclusions Women on thyroxine replacement therapy undergoing coronary artery bypass grafting had an increased mortality rate. We speculate that insufficient thyroid hormone replacement could partly play a role in this outcome