The duration of the systolic time intervals in nondigitalized patients with heart failure was determined from simultaneous fast speed recordings of the electrocardiogram, phonocardiogram, and carotid arterial pulsation. These were compared with the systolic time intervals corrected for heart rate and sex in 211 normal subjects. The failing left ventricle is characterized by a prolongation in the systolic pre-ejection period and a diminution in the left ventricular ejection time while total electromechanical systole remains relatively unaltered. Both components of the pre-ejection period, the Q-1 interval and the isovolumic contraction time, were prolonged. These alterations in the phases of systole occur in the absence of a measurable change in ventricular depolarization time. The prolongation in the pre-ejection period is well correlated with the reduced stroke volume and cardiac output in heart failure and is independently augmented by high levels of arterial pressure. The abbreviation in left ventricular ejection time is also correlated significantly with the stroke volume and cardiac output. It is postulated that a defect in the mechanical performance of the heart is responsible for the abnormal systolic time intervals in human heart failure.

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The relationships between the systolic time intervals determined from simultaneous recordings of the electrocardiogram, the phonocardiogram, the carotid arterial pulse tracing, and direct measures of left ventricular performance as assessed angiographically by measurement of left ventricular stroke volume (SV), end-diastolic volume (EDV), and ejection fraction (EF) were studied in 68 patients with a wide variety of cardiac diseases. The systolic intervals, the pre-ejection period (PEP), the left ventricular ejection time (LVET), and the ratio PEP/LVET, each correlated significantly with angiographically determined EF and EDV. Closest correlation was observed between PEP/LVET and EF (r = -0.90). The systolic intervals correlated only slightly with the angiographically determined SV. These data lend additional evidence supporting the use of systolic time intervals as a non-invasive measure of left ventricular performance in patients with cardiac disease.

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