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 been too complex for accurate quantification in situ. We have developed a new tactile sensor system for measuring accurately myocardial stiffness in situ and validated its use for estimation of myocardial contractile function. The tactile sensor was placed on the left ventricle of five mongrel dogs, (weighing 12-17 kg) and myocardial stiffness (g/mm2) was measured. Dobutamine (5.0 micrograms/kg/min) and propranolol (0.25 mg/kg) were sequentially administrated intravenously, and the change in 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/mm2. After administration of dobutamine, end-systolic stiffness increased to 3.26 +/- 0.32 g/mm2 (p < 0.01). After the administration of propranolol, end-systolic stiffness decreased significantly to 1.83 +/- 0.19 g/mm2 (p < 0.01), compared with the baseline values. Regional myocardial stiffness of a beating heart can be measured precisely using our new tactile sensor system. End-systolic stiffness is a useful index for accurate quantification of the regional myocardial contractile state.