Myocardial Tactile Stiffness: A Variable of Regional Myocardial Function

Abstract

Objectives. We developed a new sensor system for in situ measurement of myocardial tactile stiffness—stiffness in a direction perpendicular to the wall—and validated its use for providing a reasonable estimation of regional myocardial function.Background. Numerous attempts have been made to directly assess regional myocardial function. The complexity and highly invasive nature of the measuring devices have hampered their in situ application.Methods. In open chest mongrel dogs, myocardial tactile stiffness, ventricular pressure and ventricular volume were monitored. Under the preload reduction, these variables were measured to determine the relation between the end-systolic pressure–volume relation (ESPVR) and the end-systolic tactile stiffness–volume relation (ESSVR). The changes in myocardial tactile stiffness were monitored in the regional ischemic myocardial model and infarcted model to evaluate their usefulness as indexes of regional myocardial function.Results. Myocardial tactile stiffness changed cyclically and followed a time course similar to left ventricular pressure. When preload was altered, the ESSVR was as linear as the ESPVR. The slope of the ESSVR and that of the ESPVR showed a strong correlation over a wide range of contractility. These results suggest that myocardial tactile stiffness can be a good index of regional wall stress or fiber stress. End-systolic myocardial tactile stiffness of ischemic and infarcted regions decreased significantly, with a concomitant increase in end-diastolic stiffness compared with that of intact myocardium.Conclusions. Using our tactile sensor system, regional myocardial tactile stiffness of a beating heart was measured with reasonable temporal resolution. We consider myocardial tactile stiffness to be a useful index of regional myocardial function.