Impedance cardiography during exercise in patients with coronary heart disease

Impedance cardiography may be a simple way of assessing left ventricular performance during exercise. Measurements were therefore made during exercise testing in 102 consecutive male patients with suspected coronary disease prior to cardiac catheterization. These were subsequently divided into four groups: group A, normal; group B, 1-or 2-vessel disease; group C, 3-vessel disease (groups A, B, and C, left ventricular ejection fraction (LVEF) > 55%); and group D, 3-vessel disease with LVEF < 55%. Immediately after peak exercise several impedance measures were significantly correlated with resting LVEF, especially dZ/dtmax (R = 0.41, P < 0.001) and Heather index (R = 0.46, P < 0.001). Heather index was the best discriminator between the disease groups with mean values (95% confidence intervals) of 25.7 (22.2–29.2) (group A), 21.9 (20.6–23.2) (group B), 18.4 (16.2–20.6) (group C), and 15.3 (10.3–20.3) Ωs−2 (group D) but there was considerable overlap between groups (risk ratios 1.17 and 3.15 for any and triple-vessel coronary disease respectively). Measurements were therefore of little diagnostic value. The majority of patients with abnormal responses could be identified more simply by their poor exercise tolerance or abnormal blood pressure response.