Noninvasive evaluation of left ventricular force−frequency relationships by measuring carotid arterial wave intensity during exercise stress

Background and purpose Estimation of the contractility of the left ventricle during exercise is important in drawing up a protocol of cardiac rehabilitation. It has been demonstrated that color Doppler- and echo tracking-derived carotid arterial wave intensity is a sensitive index of global left ventricular (LV) contractility. We assessed the feasibility of measuring carotid arterial wave intensity and determining force−frequency (contractility−heart rate) relations (FFRs) during exercise totally noninvasively. Methods We measured carotid arterial wave intensity with a combined color Doppler and echo tracking system in 25 healthy young male volunteers (age 20.8 ± 1.2 years) at rest and during exercise. FFRs were constructed by plotting the maximum value of wave intensity (WD 1 ) against heart rate (HR). Results We first confirmed that HR increased linearly with an increase in work load in each subject ( r 2 = 0.95 ± 0.04). WD 1 increased linearly with an increase in HR. The goodness-of-fit of the regression line of WD 1 on HR in each subject was very high ( r 2 = 0.48−0.94, p