This patient's exercise electrocardiographic (ECG) stress testing results indicate that he has coronary artery disease (CAD), and his Duke treadmill score (−11.5) indicates the presence of high-risk disease. He should undergo cardiac catheterization for diagnosis and possibly revascularization.

Exercise ECG stress testing can be used for the diagnosis of CAD (as in this patient), to evaluate adequacy of medical therapy in patients with known CAD, and to evaluate functional status. When used to evaluate chest pain, the test is considered diagnostic of obstructive CAD (>70% obstruction) if there is greater than 1-mm ST-segment depression with exercise in two contiguous leads. The findings in this patient are consistent with occlusive coronary disease as the cause of his exertional chest pain.

In addition to diagnosis, a positive treadmill study can be used to further risk stratify obstructive CAD. The Duke treadmill score is one method and is calculated as follows: Exercise time in minutes − (5 × ST-segment depression) − (4 × angina score). (Angina score: 0 = asymptomatic; 1 = nonlimiting angina; 2 = exercise-limiting angina.) Scores below −11 are high risk, and those above 5 are low risk. Patients with high-risk scores are likely to have left main or proximal left anterior descending (LAD) artery disease. Other markers of a high-risk exercise study that would be suggestive of proximal LAD artery disease or multi-vessel disease would include a drop in blood pressure with exercise or severe ST-segment depression. Based on his high-risk Duke treadmill score, this patient should be further evaluated with coronary arteriography.

Although this patient should be treated with medical therapy including aspirin, a β-blocker, and a statin, he should also undergo cardiac catheterization because of the high likelihood of severe obstructive CAD.

The use of imaging, such as stress echocardiography or myocardial perfusion imaging, can localize ischemia to a vascular territory and can be helpful to determine affected vascular territory prior to revascularization. Stress testing with imaging can also be helpful in making the diagnosis of CAD in patients with equivocal exercise stress tests or those in whom there is a higher likelihood of a false-positive exercise stress test. However, because of this patient's high-risk ECG stress test, he should undergo catheterization for a definitive diagnosis and possible revascularization. There would be no benefit to a noninvasive imaging test prior to or instead of that intervention.