REGIONAL MYOCARDIAL STIFFNESS MEASURED BY A NEW TACTILE SENSOR SYSTEM

Numerous investigators have attempted to measure regional wall stress directly. However, the measurement systems and devices employed have b een too complex for accurate quantification in situ. We have developed a new tactile sensor system for measuring accurately myocardial stiff ness in situ and validated its use for estimation of myocardial contra ctile function. The tactile sensor was placed on the left ventricle of five mongrel dogs, (weighing 12-17 kg) and myocardial stiffness (g/mm (2)) was measured. Dobutamine (5.0 mu g/kg/min) and propranolol (0.25 mg/kg) were sequentially administrated intravenously, and the change i n myocardial stiffness was monitored. Myocardial stiffness followed a time course similar to that of left ventricular pressure, indicating a close relationship-with wall stress. Baseline end-systolic stiffness in 5 dogs was 2.38 +/- 0.19 g/mm(2). After administration of dobutamin e, end-systolic stiffness increased to 3.26 +/- 0.32 g/mm(2) (P < 0.01 ). After the administration of propranolol, end-systolic stiffness dec reased significantly to 1.83 +/- 0.19 g/mm(2) (p < 0.01), compared wit h the baseline values. Regional myocardial stiffness of a beating hear t can be measured precisely using our new tactile sensor system. End-s ystolic stiffness is a useful index for accurate quantification of the regional myocardial contractile state.