Figure 9

Scatter plots demonstrating relationship between sensor isovolumic contraction force (y axis) and SP/ESV index ratio (x axis) as delta % rest-peak values in the whole group of 88 patients. Green symbols: dipyridamole stress; blue symbols: pacing stress; red symbols: exercise stress. Despite cardiac vibrations propagate as mechanical shear waves, and the intervening viscoelastic thoracic tissue attenuates the higher frequencies and introduces a variable propagation delay, the sensor recorded force value shows good correlation with the standard stress-echo end-systolic elastance index (SP/ESV index ratio).