Systolic Time Intervals in the Evaluation of Thyroid Dysfunction

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Abstract
Systolic time intervals, the pre-ejection period (PEP), left ventricular ejection time (LEVT) and PEP/LVET ratio were studied in 10 thyrotoxic and 10 hypothyroid patients. LVET and PEP intervals were corrected for heart rate (LVETc and PEPc). The measurements were repeated after 1-28 mo. when the patients were euthyroid following appropriate therapy. Compared with the euthyroid values, the PEPc intervals and PEP/LVET ratios were significantly decreased (P < 0.01) in the thyrotoxic and increased (P < 0.001) in the hypothyroid patients. In both groups the LVETc intervals were significantly prolonged (P < 0.001). In 4 of the hypothyroid patients the PEP/LVET ratios were markedly increased (> 0.60, mean 0.66), and above 0.41 in the euthyroid state (reference value 0.35 .+-. 0.05). In the other hypothyroid patients and in thyrotoxic patients the euthyroid PEP/LVET ratios were within the reference values. The systolic time intervals were not influenced by propranolol therapy in the thyrotoxic patients. Increased myocardial contractility unaffected by adrenergic blockade in thyrotoxicosis, and reduced contractility in hypothyroidism are indicated.