Effects of long-term thyroid hormone suppressive treatment on the cardiac functions.

Long-term effects of thyroid hormone suppressive therapy on the heart were evaluated in 45 patients by non-invasive techniques. Fifteen patients were athyreotic after surgery for differentiated thyroid cancer and 30 had diffuse or nodular goiter. Mean age of the group was 42 +/- 12 years. Twenty-four age- and sex-matched subjects were taken as controls. Mean daily dose of levothyroxine was 158 +/- 36 micrograms. Plasma thyroid stimulating hormone (TSH) levels were within normal range. Mean serum T4 and free T4 were significantly higher (p < 0.001) whereas mean serum T3 and free T3 did not differ from the control levels. Non-invasive cardiac assessment was done by a standard 12 lead electrocardiogram (ECG), ambulatory electrocardiographic (Holter) monitoring and echocardiographic study. Six patients had left ventricular hypertrophy in ECG. Holter monitoring demonstrated a higher average heart rate in patients compared to controls (86 +/- 10 vs 72 +/- 6 beats/min; p < 0.001). Supraventricular premature beats were more frequent in patients than in the control group (98% vs 60%; p < 0.06). Echocardiogram showed an increased left ventricular (LV) mass index in patient group (98 +/- 28 vs 78 +/- 16 gm/m2; p < 0.02). LV systolic function was increased with higher values of fractional shortening (40 +/- 8% vs 34 +/- 6%; p < 0.05) and rate-adjusted velocity of shortening (1.4 +/- 0.12 vs 1.02 +/- 0.16 circumferences/sec; p < 0.01). It is concluded that long-term levothyroxine suppressive therapy has significant effects on the cardiac functions.

Response to exercise and ambulatory blood pressure monitoring in essential hypertension.

To evaluate the relationship of ambulatory blood pressure (ABP) recording and blood pressure response to exercise, 58 essential hypertensive patients, not taking any drugs, had symptom-limited treadmill stress test (TST) within 48-96 hours of ABP, TST time, blood pressure increase, decrease, mode of increase and decrease, were independent of ABP systolic (SBP) and diastolic blood pressure (DBP) over 24 hours, day time and night time (p = ns). SBP decrease immediately after exercise were independent of ABP data. TST achieved heart rate was related to both 24 hours SBP (r = -0.64, p = 0.00005) and DBP (r = -0.55, p = 0.00001) in both day (r = -0.64, p = 0.00001 and r = -0.54, p = 0.002) and night (r = -0.52, p = 0.0001 and r = -0.46, p = 0.003) time periods. Therefore patients with achieved heart rate < 100% (n = 18) had higher 24 hour SBP (148 vs 132 +/- 2 mm Hg, p = 0.0006) and DBP (92.4 +/- 6.4 vs 84 +/- 6.2 mm Hg, P = 0.006) day and night. It is concluded that there is no overlap of diagnostic information using blood pressure. Values in TST or ABP although achieved heart rate in exercise is inversely related to severity of hypertension.