Quantification of the contractile response to injury: assessment of the work-length relationship in the intact heart.

We used a sonomicrometric determination of ventricular dimension to examine the effect of ischemia and reperfusion on the work-length relationship in the intact heart to develop a useful and precise variable of ventricular contractile response to injury. Twenty anesthetized dogs were instrumented with epicardial ultrasonic dimension transducers to record right ventricular free wall chord length and left ventricular minor-axis length, micromanometers to record ventricular pressures, and an electromagnetic probe to record pulmonary arterial (n = 8) or aortic (n = 7) flow. Dogs were subjected to either 20 min (n = 7) or 30 min (n = 13) of global cardiac ischemia supported by cardiopulmonary bypass. Data were acquired over a range of end-diastolic volumes produced by transient (5 to 10 sec) vena caval occlusion before and after ischemia. In both ventricles, systolic epicardial dimensional shortening correlated with flow probe-measured stroke volume (mean r = .969) and regional stroke work calculated as the integral of instantaneous ventricular pressure and epicardial dimension correlated with measured global stroke work (mean r = .960), confirming the validity of dimensional measurements. Regression analysis demonstrated a highly linear relationship between calculated regional stroke work and end-diastolic length in the right ventricle (mean r = .973) and left ventricle (mean r = .967), quantifiable by a slope (Mw) and x intercept (Lw). Change in afterload produced by pulmonary arterial or aortic constriction resulted in no significant changes in Mw or Lw in either ventricle. Ischemia and reperfusion decreased Mw and shifted Lw to the right in both ventricles. The decrease in Mw with 30 min ischemia exceeded the decrease with 20 min ischemia by 29% in the right ventricle and by 32% in the left (p less than .04) with up to 1 hr of reperfusion. Changes in Lw were not related to severity of injury. After ischemia, infusion of calcium increased Mw by 177% in the right ventricle and by 67% in the left (p less than .03) without significant changes in Lw. Independent of load conditions, the slope Mw, of the linear stroke work vs end-diastolic length relationship is a valid and precise index of right and left ventricular contractile response to global ischemia in the intact circulation. This variable may be useful in evaluating therapies designed to limit myocardial injury and enhance ventricular functional performance.

A new information system for medical practice.

A data bank containing our clinical experience with more than 3,000 patients with suspected and documented ischemic heart disease is being used to expand our ability to care for patients. This report describes how the experience is documented, stored, and retrieved so that it can be used in patient management. Data acquisition is integrated with patient care by means of forms that are part of the patient record. Follow-up information is obtained at six months, one year, and yearly thereafter. All data are stored in a computer information system that allows the doctor to recall the experience of patients like his new patient. Prognostic information is available on each new patient both on-line and in the form of a printed laboratory report. The data bank represents an initial chapter of a computer textbook of medicine.