The pattern of left ventricular contraction or relaxation is not uniform and also changes depending on hemodynamic states. Accordingly, the measurement of myocardial segment length only may have limitations for the analysis of regional myocardial function, and a two-dimensional analysis of regional myocardial function was developed and characterized by utilizing measurement of regional myocardial surface area on the epicardial surface. In eight anesthetized open-chest dogs, the relationship between regional myocardial function and total cardiac function was examined. The extent of the reduction of regional myocardial surface area during the ejection phase or during the systolic phase correlated more closely with stroke volume over wide ranges of left ventricular end-diastolic pressure, aortic pressure, left ventricular contractility, and heart rate (r = 0.75 - 0.96) than the shortening of myocardial segment length alone. Thus, the results demonstrated that regional myocardial function estimated by the measurement of regional myocardial surface area represents total cardiac function more accurately than myocardial segment length over wide ranges of hemodynamic states despite the changes in the left ventricular contraction and relaxation pattern.
