Myocardial tactile stiffness during acute reduction of coronary blood flow

Background. Evaluation of regional myocardial contractile function is of clinical importance. We have developed a new tactile sensor system for accurate measurement of myocardial stiffness in situ. We found that the myocardial stiffness measured by this sensor, which we call tactile stiffness, can be a very useful index for accurate quantification of regional myocardial function. In this study, we used a coronary stenosis model to investigate regional myocardial tactile stiffness under conditions of reduced coronary blood flow. Methods. The myocardial tactile stiffness, coronary blood flow, and ventricular pressure and volume, of five open chest mongrel dogs weighing 15 to 17 kg, were measured. After measuring the baseline myocardial stiffness, coronary arterial stenosis was induced with a balloon occluder. Results. Reducing the coronary flow to 50% and 25% of the baseline level reduced the end-systolic tactile stiffness significantly from 2.20 ± 0.16 g/mm2 to 2.05 ± 0.20 g/mm2 (p< 0.05) and from 2.21 ± 0.16 g/mm2 to 1.96 ± 0.18 g/mm2 (p< 0.01), respectively. Reducing the flow, to 50% and 25%, increased the end-diastolic stiffness significantly from 1.29 ± 0.15 g/mm2 to 1.39 ± 0.14 g/mm2 (p< 0.01) and from 1.30 ± 0.16 g/mm2 to 1.46 ± 0.14 g/mm2 (p< 0.05), respectively. Conclusions. We consider that the regional myocardial tactile stiffness will be a useful index sensitive enough to detect changes in regional contractile function under conditions of reduced coronary blood flow.