The short cardiac pre-ejection period: an index to thyrotoxicosis

Systolic time intervals (STI) were determined from simultaneous records of the electrocardiogram, carotid pulse and phonocardiogram in 17 consecutive patients with thyrotoxicosis and sinus rhythm. None of the patients had clinical evidence of congestive heart failure. Intervals measured included electromechanical systole (Q-S 2 ), heart sound interval (S 1 -S 2 ) and left ventricular ejection time (LVET). From these, the pre-ejection period (PEP), isovolumetric contraction time (ICT) and Q-S 1 intervals were derived. Deviations (ΔSTI) of observed values from expected values (Weissler equations) for the same heart rate were obtained by subtraction. The mean deviation of the thyrotoxic patients ± sem from the normal population were ΔQ- S 2 * = –37.8 ± 4.2; ΔLVET = –4.0 ± 4.1; ΔPEP * = –33.8 ± 1.8. The shortening of PEP was due largely to a shortened ICT (ΔICT * = –27.2 ± 1.1). In eight patients studied serially during treatment the short PEP returned to the normal range concurrently with serum T 4 measurements. This study indicates that the PEP is a unique noninvasive measurement of biological end organ responsiveness with thyroid dysfunction; a short PEP is characteristic of uncomplicated thyrotoxicosis and serial changes in PEP may be a useful index of therapeutic response. * P < .001.