Left ventricular performance during exercise: response of ear densitogram derivative.
The peak derivative of the ear densitogram (PD) has been shown to track left ventricular (LV) function during exercise. Measured as percent change in amplitude from resting control, PD in normal subjects slowly and consistently increased throughout exercise and to 2 minutes of recovery, followed by return to control level. In contrast, PD in patients with coronary artery disease rapidly increased only to 1 minute of exercise, with no significant subsequent increase. Expressed as a percent change from control, the response of normal subjects differs significantly from that of patients with coronary artery disease at 1 and 4 minutes of exercise, and 2 minutes of recovery. The PD increase in normal subjects from end-exercise to 2 minutes of recovery may be attributable to the heart rate decreasing faster than venous return, associated with LV ejection time, which is significantly shorter than heart rate-predicted values 2 minutes after exercise.