Background: Significance of electrocardiographic (ECG) changes during vasodilator stress myocardial perfusion imaging (MPI) is controversial. We examined the diagnostic and prognostic significance of ECG changes during vasodilator single photon emission computerized tomography (SPECT) MPI.
Methods: We studied consecutive patients who underwent vasodilator SPECT MPI from 1995 to 2009. Patients with baseline ECG abnormalities, previous history of coronary artery bypass graft surgery or myocardial infarction (MI) were excluded. Significant coronary artery disease (CAD) was defined as >70% stenosis of any vessel or ≥50% stenosis of left main. Mean follow-up was 2.4 ± 1.5 years for cardiac events (cardiac death and non-fatal MI).
Results: Of patients in the diagnostic cohort, ST depression was associated with increased incidence of CAD with abnormal (P = .020 and P <.001) but not in those with normal perfusion (P = .342). Of 3,566 patients with follow-up in the prognostic cohort, including 130 (5.0%) with ST depression and normal perfusion, the presence of ST depression ≥1 mm did not affect the outcomes in any summed stress score category.
Conclusions: ST depression ≥1 mm during vasodilator SPECT MPI is associated with CAD in patients with abnormal perfusion, but provides no additional risk stratification beyond concomitant perfusion imaging, including those with normal studies.