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Nuclear stress testing remains the most common non-invasive means to assess for obstructive coronary artery disease (CAD). Despite the prognostic utility of the test, equivocal results are common. The significance of ischemic electrocardiographic changes in the presence of normal myocardial perfusion imaging (MPI) is not well established.
Data from 3,723 exercise nuclear stress tests performed at our institution between January 2013 and December 2015 were analyzed. We identified those patients whose results revealed normal SPECT MPI but had ischemic changes on their electrocardiogram (ECG). Ischemic changes were defined as 1 mm horizontal or downsloping or 1.5 mm upsloping ST segment depressions. Only patients with a follow-up anatomical coronary assessment [invasive coronary angiography or multidetector cardiac CT angiography (CTA)] were included. We then correlated the results of the nuclear stress test and the coronary angiogram/CTA to identify the significance of an abnormal ECG in the presence of normal MPI.
We identified 229 patients that had normal MPI but had ischemic changes on ECG. Of these 229 patients, 47 patients (21%) had a coronary angiogram or CTA following the nuclear stress test and were included in the study. Only 12 out of 47 patients (25.5 %) had completely normal coronary arteries. Despite normal MPI, the majority of patients [35/47 patients (74.5 %)] had some degree of CAD. Twenty out of forty seven (42.6%) patients had severe (>70%) obstruction in at least one major epicardial coronary artery. Fifteen out of forty seven (31.9%) patients had non-obstructive CAD. Male patients with normal MPI/abnormal ECG were far more likely (65% vs. 35%) to have at least one severe lesion (>70% stenosis) compared to females.
The presence of ischemic ECG changes during exercise stress test is associated with the presence of CAD despite normal MPI. The discrepancy between electrocardiographic findings and MPI should not be ignored, and further testing should be considered, particularly in male patients.
IMAGING: Imaging: Non-Invasive