Early Post-stress Decrease in Cardiac Performance by Impedance Cardiography and its Relation to the Severity and Extent of Ischemia by Myocardial Perfusion Imaging

Background: In certain patients single photon emission computed tomography (SPECT) myocardial perfusion imaging (MPI) is unable to detect the presence of or underestimates the extent of ischemia. The Non-Invasive Cardiac System (NICaS, NI Medical, Israel) is a whole-body bio-impedance device which measures various hemodynamic parameters. Noninvasive detection of an early post-stress decrease in cardiac performance may be a potential marker for the presence of significant ischemia.

Objectives: To test for an early post-stress change in several hemodynamic parameters by impedance cardiography and its relation to the severity and extent of myocardial ischemia in patients undergoing exercise stress MPI.

Methods: We prospectively enrolled patients referred to the Nuclear Cardiology Center at the Sheba Medical Center for an exercise stress MPI study. Patients underwent testing using the NICaS before exercise and immediately after exercise. The differences between rest and stress hemodynamic parameters were compared with the severity and extent of myocardial ischemia by MPI.

Results: The study population included 198 patients; mean age was 62 years, 26% were women, 54% had hypertension, and 29% diabetes mellitus. 188 patients had ≤10% of ischemic myocardium and 10 patients had >10% of ischemic myocardium. In the first group, compared to rest, there was a significantly greater increase in post-exercise stroke index, stroke work index, cardiac index and cardiac power index (19.2%, 29.1%, 90.5% and 107%, respectively) when compared to the second group (-2.7%, 3.8%, 43.7% and 53.5%, respectively) as well as a significantly greater decrease in total peripheral resistance index (-38.7%) when compared to the second group (-16.3%), with corresponding p values of 0.015, 0.017, 0.040, 0.016, and <0.001, respectively.

Conclusions: The immediate post-stress changes in several hemodynamic parameters as detected by the NIcAS may be used as an important adjunct to SPECT MPI for the early detection of myocardial ischemia.