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Higher mortality after coronary-artery surgery in women treated with thyroxine than other women

(March 2003)

The background of the study. Patients with hypothyroidism may also have coronary artery disease, and need coronary-artery bypass grafting. The short-term outcome of this operation was compared in patients with hypothyroidism receiving long-term thyroxine (T4) therapy and other patients.

How the study was done. Between 1993 and 2000, 606 women and 3025 men underwent coronary-artery bypass grafting at the Hammersmith Hospital in London, England. They included 30 women and 28 men with a history of hypothyroidism who were being treated with T4. The characteristics and the surgical details in these 58 women and men were compared, and their 30-day mortality rates were compared with the rates in the other women and men.

The results of the study. The characteristics of the women and men treated with T4 were similar, except that the women had a slightly higher mean serum free T4 concentration, more were taking a diuretic drug, and the operation took longer in the women.

Among the 58 T4-treated hypothyroid patients, there were 6 deaths (5 women, 1 man) within 30 days after surgery. The mortality rate in the 30 women (17 percent) was statistically significantly higher than in the other 576 women (6 percent). The mortality rate in the T4-treated hypothyroid men (4 percent) was similar to that in the other 2997 men (3 percent). Four of the women and the 1 man died of progressive heart failure; the other woman died of an arrhythmia. Among the women with hypothyroidism, independent variables associated with death were lower T4 dose and diuretic therapy.

The conclusions of the study. Short-term mortality after coronary-artery bypass graft surgery is higher in women with hypothyroidism receiving T4 therapy than in other women.

The original article. Zindrou D, Taylor KM, Bagger JP. Excess coronary artery bypass graft mortality among women with hypothyroidism. Ann Thorac Surg 2002;74:2121-5.