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Postoperative Left Ventricular Contractility in the Cardiac Surgical Patient: An Evaluation of the Force-Interval Relationship
Journal article   Open access   Peer reviewed

Postoperative Left Ventricular Contractility in the Cardiac Surgical Patient: An Evaluation of the Force-Interval Relationship

James D. Sink, Page A.W. Anderson and Andrew S. Wechsler
The Annals of thoracic surgery, v 40(5), pp 475-482
Nov 1985
DOI: https://doi.org/10.1016/S0003-4975(10)60103-8
PMID: 4062400
Featured in Collection :   UN Sustainable Development Goals @ Drexel
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https://doi.org/10.1016/S0003-4975(10)60103-8View
Published, Version of Record (VoR)Maybe Open Access (Publisher Bronze),  Open

Abstract

The force-interval relationship—the dependence of cardiac contractility on the rate and pattern of stimulation—was evaluated for its potential use in monitoring patients in the period immediately following heart surgery. Six patients were studied for three days after coronary artery bypass grafting. The monitoring instrumentation used during operation included a catheter-tip micromanometer introduced into the left ventricle, a pair of ultrasonic transducers placed on the left ventricular (LV) epicardium to monitor minor-axis dimension, pacing electrodes placed on the right atrium, and systemic arterial and venous catheters. During the experiments, heart rate was controlled by atrial pacing. After every twentieth systole (the control systole), a pause in the heart rate was introduced during which an extrasystole (S E) and a postex-trasystole (S PES) were elicited at test intervals t E and t PES, respectively. The intervals between the control systole and test systoles S E and S PES were experimentally manipulated. When the test intervals were increased, the peak first derivative of LV pressure ( ▪ max) of S E and of S PES increased monophasically. To eliminate the effects of LV end-diastolic volume, we used only S PES and control systoles with the same LV end-diastolic dimension in construction of PES ratio curves ( ▪ max of S PES/ ▪ max of the control systole, as a function of t PES). The PES ratio rose monophasically with an increase in t PES; these curves were well fitted by an exponential relationship. The PES ratio exceeded unity at long t PES intervals. This ratio, denoting postextrasystolic potentiation, was inversely dependent on t E. The patients experienced no complications. Our findings, identical to those in isolated myocardium and in the isolated, isovolumically contracting heart, suggest that the force-interval relationship can be used to safely and easily monitor postoperative ventricular contractility.

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Web of Science research areas
Cardiac & Cardiovascular Systems
Respiratory System
Surgery
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