Figure 2
From: WEB downloadable software for training in cardiovascular hemodynamics in the (3-D) stress echo lab
Contractility changes with heart rate changes. The force-frequency relationship is defined up-sloping (upper panel) when the peak exercise SP/ESV index is higher than baseline and intermediate stress values; flat or negative (lower panel), when the peak exercise systolic pressure/end-systolic volume index is equal to or lower than baseline stress values. The critical heart rate (or optimum stimulation frequency) is defined as the heart rate at which systolic pressure/end-systolic volume index reaches the maximum value during progressive increase in heart rate.