Objective: To assess the utility of stress electrocardiography (ECG) for identifying the presence and severity of obstructive coronary artery disease (CAD) defined by coronary computed tomographic angiography (CCTA) among patients with normal nuclear myocardial perfusion imaging (MPI).
Methods: The study population comprised 119 consecutive patients with normal MPI who also underwent CCTA (interval 3.5+/-3.8 months). Stress ECG was performed at the time of MPI. CCTA and MPI were interpreted using established scoring systems, and CCTA was used to define the presence and extent of CAD, which was quantified by a coronary artery jeopardy score.
Results: Within this population, 28 patients (24%) had obstructive CAD identified by CCTA. The most common CAD pattern was single-vessel CAD (61%), although proximal vessel involvement was present in 46% of patients. Patients with CAD were nearly three times more likely to have positive standard test responses (1 mm ST-segment deviation) than patients with patent coronary arteries (36 vs. 13%, P=0.007). In multivariate analysis, a positive ST-segment test response was an independent marker for CAD (odds ratio: 2.02, confidence interval: 1.09-3.78, P=0.03) even after adjustment for a composite of clinical cardiac risk factors (odds ratio: 1.85, confidence interval: 1.05-3.23, P=0.03). Despite uniformly normal MPI, mean coronary jeopardy score was three-fold higher among patients with positive compared to those with negative ST-segment response to exercise or dobutamine stress (1.9+/-2.7 vs. 0.5+/-1.4, P=0.03).
Conclusion: Stress-induced ST-segment deviation is an independent marker for obstructive CAD among patients with normal MPI. A positive stress ECG identifies patients with a greater anatomic extent of CAD as quantified by coronary jeopardy score.