Noninvasive assessment of cardiac contractility by using (dP/dt)/P of carotid artery pulses during exercise.

In earlier studies we have shown that both the pressure (P) of the carotid artery pulse (CAP) and its first derivative (CAP dP/dt) could be recorded during moderate exercise. To establish that the CAP (dP/dt)/P is a noninvasive substitute for the left ventricular (LV) value, LV (dP/dt)/P, an index of cardiac contractility, we studied CAP (dP/dt)/P under various states of activity in the autonomic nervous system in 12 healthy male subjects. Increased sympathetic nerve activities yielded by passive tilting, emotional load, or cold stress increased CAP (dP/dt)/P significantly (P < 0.05). Increased parasympathetic nerve activity by ocular compression, however, did not significantly affect the value. Moderate exercise at a heart rate of approximately 150 beats.min-1 increased it significantly from 16.7 to 25.2.s-1 in a supine position (P < 0.001) and from 16.6 to 24.8.s-1 in an upright position (P < 0.001). It increased monotonically as heart rate increased, but the slope was steeper when the heart rate was greater than approximately 100 beats.min-1 than it was when the rate was less than 100 beats.min-1. In conclusion, the present study indicated that CAP (dP/dt)/P can be used as a noninvasive index of cardiac contractility even in moderate exercise.