The role of wall stress in the assessment of ventricular function.

Over the past decade there has been a steady proliferation of indices which have been proposed for assessing ventricular function. Many of these indices are based on single measurements and often are insensitive and have limited clinical utility. The present article focuses on the role of wall stress in assessing ventricular function from the point of view of the heart as a muscle. For many clinical applications (excluding coronary artery disease), average stress formulae developed by Falsetti et al. and Mirsky are adequate. Based on these formulae one may describe the mechanical properties of heart muscle in terms of stress-strain or stiffness-stress relations. Such analyses yield useful information with regard to the degree of fibrosis present and should be of importance in biopsy studies on the cardiomyopathies and in hypertrophied ventricles. Furthermore, regional muscle function may be simply quantitated by these methods, employing simultaneous measurements of pressure and wall thickness. Pressure-volume relations obtained during diastole or systole at best yield limited information on ventricular function and should be replaced by a corresponding stress-strain analysis. Finally, it is recommended that relationships (rather than single points) be developed for assessing both muscle and pump function. Furthermore, these relationships should first be based on invasive measurements before proceeding with the more attractive but less accurate noninvasive approach.