|
Systolic time intervals were determined in 56 cases of hyperthyroidism by a noninvasive polygraphic method and a comparative study of the results was done, according to the severity of the disease. Except for the transformation time, all the systolic time intervals, namely, electromechanical systole, mechanical systole, left ventricular ejection time, preejection period and isovolumic contraction time, were significantly shortened in proportion to the severity of the disease. It was noted that the shortening of the isovolumic contraction time was the most pronounced. By correcting these observed systolic time intervals for the heart rate, the left ventricular ejection time was normalized fully and both the electromechanical systole and the mechanical. systole were partially normalized, whereas the isovolumic contraction time and the pree jection period remained significantly shortened in spite of the correction. These facts suggested that the shortening of the left ventricular ejection time, the electromechanical systole and the mechanical systole was caused primarily or largely by tachycardia, but the shortening of the isovolumic contraction time and the preejection period resulted from hyperthyroidism per se, without being related to tachycardia. It was also noted that the left ventricular ejection timeJisovolumic contraction time ratio was significantly increased by the marked shortening of the isovolumic contraction time.
|