Detection of impaired left ventricular function in coronary artery disease with acceleration index in the first derivative of the transthoracic impedance change

Abstract

In order to detect impaired left ventricular (LV) function in coronary artery disease (CAD) patients using acceleration index (Ac) of impedance cardiography (ICG), exercise ICG was performed in 29 patients with chest pain but without CAD (Group 1) and 21 patients with CAD (Group 2), and their resting values were compared with 30 healthy controls (Group 3). The acceleration index, which reflects indirectly aortic blood flow acceleration, was calculated as the ratio of dZ/dtmax to its accelerating time (AT). At rest, the values for Ac in Groups 1, 2, and 3 were 23±10, 15±6, and 36±13 Ω/s2, respectively. There were significant differences between Group 1 versus 3, 2 versus 3, and 1 versus 2 (all p<0.001). At maximal exercise, Ac showed the largest percent change among the various indices used in this study. An increase of 198% for Group 2 was markedly lower than that of 250% in Group 1 (40±14 vs. 68±24 Ω/s2, p<0.001). With a value of ≤40 Ω/s2, Ac can detect the CAD patients, with a sensitivity of 62% and specificity of 90%, superior to stress ECG using CM5 lead. It is concluded that: (1) Ac is the sole index capable of distinguishing not only between the normals and diseased groups, but also between CAD patients and suspected CAD cases at rest. (2) Ac is a remarkably sensitive index for detecting impaired LV function at maximal exercise. (3) Exercise ICG is useful for predicting CAD from the population predisposing to CAD. As an indicator of acceleration, Ac is the most valuable of its kind in exercise ICG. Copyright © 1988 Wiley Periodicals, Inc.