Physiological Replacement of T3 Improves Left Ventricular Function in an Animal Model of Myocardial Infarction-Induced Congestive Heart Failure

Background— Patients with congestive heart failure (CHF) often have low serum triiodothyronine (T3) concentrations. In a rodent model of myocardial infarction-induced CHF and low serum T3, we hypothesized that replacing T3 to euthyroid levels would improve left ventricular function without producing untoward signs of thyrotoxicosis. Methods and Results— Adult male Sprague-Dawley rats were subjected to left anterior descending coronary artery ligation (myocardial infarction). One week post-myocardial infarction, left ventricular fractional shortening was significantly reduced to 22�1% in CHF animals versus 38�1% for sham-operated controls (P<0.001). Serum T3 concentration was also significantly reduced (80�3 versus 103�6 ng/dL; P<0.001), in CHF animals versus Shams. At 9 weeks post-myocardial infarction, systolic function (+dP/dt max) was significantly attenuated in CHF animals (4773�259 versus 6310�267 mmHg/s; P<0.001) as well as diastolic function measured by half time to relaxation (15.9�1.2 versus 11.1...