Systolic ventricular function in acute hypothyroidism: a study using Doppler echocardiography

Summary

The influence of thyroid State on left ventricular systolic function was studied in 11 patients (5 men, 6 women, aged 20-55 years) without cardiac disease, who had undergone total thyroidectomy and radioiodine treatment for thyroid cancer before. Pulsed-wave Doppler echocardiographic measuring of aortic blood flow and two-dimensional/time-motion (2D/M-mode) echocardiography were performed on two occasions once while the patients were mildly hyperthyroid on thyroxine replacement therapy and once when they were hypothyroid. During hypothyroidism left ventricular end-diastolic diameter decreased from 48 ± 5 mm to 46 ± 5 mm (p < 0.05). The diameter of the aortic ring, the left ventricular end-systolic diameter, the thickness of the interventricular septum and posterior wall, and fractional shortening did not differ significantly between the two studies. The following parameter of aortic blood flow changed significantly when passing from the hyperthyroid to the hypothyroid State: peak velocity (0.86 ±0.15 m/s versus 0.72 ±0.15 m/s, p < 0.01); mean velocity (0.49 ± 0.08 m/s versus 0.44 ± 0.08 m/s, p < 0.01); time- velocity integral (14.1 ± 3.0 cm versus 12.3 ± 3.1 cm, p <0.05); stroke volume (43.0 ± 9.7 ml versus 35.2 ± 8.2 ml, p < 0.05); and preejection period (124 ± 23 ms versus 147 ± 21 ms, p < 0.01). Peak acceleration, mean acceleration, acceleration time and left ventricular ejection time did not change when the thyroid State was altered.

It is concluded that left ventricular contractile function was not affected by acute hypothyroidism. The changes of aortic blood flow can be explained by a reduction in left ventricular preload when the patients were rendered hypothyroid.

Key words

hypothroidism - Doppler echocardiography - left ventricular systolic function