Relation Between Ambulatory Electrocardiographic Monitoring and Myocardial Perfusion Imaging to Detect Coronary Artery Disease and Myocardial Ischemia: An ACIP Ancillary Study

Objectives. This study sought to explore the relation between markers of ischemi detected by ambulatory electrocardiographic (AECG) monitoring and stress myocardial perfusion single-photon emission computed tomography (SPECT). Background. Stress myocardial SPECT and AECG monitoring are both utilized in evaluating patients with coronary artery disease. However, information is limited regarding the relation between the presence and extent of ischemi as detected by these two modalities. Methods. This was an ancillary study of the Asymptomatic Cardiac Ischemi Pilot (ACIP) trial. One hundred six patients with previous coronary angiography underwent AECG monitoring and stress SPECT within close temporal time period. The frequency and duration of ischemi as assessed by AECG monitoring and the total and ischemic stress-induced myocardial perfusion defect sizes as assessed by SPECT were quantified in separate core laboratories. Multivariate logistic regression and linear regression analysis were used to determine associations between AECG and SPECT abnormalities with regard to angiographic, demographic and treadmill exercise variables. Results. Seventy-four percent of patients with significant (≥50%) coronary artery stenosis had SPECT abnormalities, whereas 61% had ischemi by AECG monitoring. The most important predictors of SPECT abnormalities were severity (p < 0.001) of coronary artery stenosis, followed by total exercise duration (p = 0.016) and patient age (p = 0.04). The only predictor of AECG abnormalities was the presence of ST segment depression on the initial exercise treadmill test (p = 0.021). Only 50% concordance for normalcy or abnormalcy was observed between the SPECT and AECG results, and no relation was observed between the frequency or duration of AECG ischemi and the quantified total or ischemic myocardial perfusion defect size as assessed by SPECT. Conclusions. Ischemi as detected by AECG monitoring does not correlate with the presence and extent of ischemi as quantified by stress SPECT. Because these techniques appear to detect different pathophysiologic manifestations of ischemia, they may be complementary in more fully defining the functional significance of coronary artery disease and, in particular, which patients are at highest risk for adverse cardiac events.