Evaluation of the Contractile State of the Human Heart from the First Derivative of the Apexcardiogram

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Abstract
The first derivatives of the left ventricular pressure pulse (dp/dt LV) and of the apexcardiogram (Δ ACG) were recorded 73 times in 45 subjects, and the time intervals from the peak of the R wave of the electrocardiogram to the peak of the derivatives (t-dp/dt LV and t-Δ ACG) were determined under different circulatory conditions. These parameters express the duration of the development of maximum tension during isometric contraction of the ventricle. The values obtained from the left ventricular pressure pulse and from the ACG showed close correlation both at rest and after pharmacological interventions which enhanced or depressed the myocardial contractile state. During orciprenaline infusion, t-dp/dt LV and t-Δ ACG were consistently shortened, while they increased in most cases after beta-adrenergic receptor blockade. Determination of the time to peak derivative of the ACG, a parameter so far unexplored, is proposed as a simple method of detecting changes in the myocardial contractile state in the intact human being.