What additional testing is recommended for a patient with medium risk classification and equivocal electrocardiogram (ECG) results?

Recommended Additional Testing for Equivocal Stress ECG with Medium Risk

For this patient with an equivocal stress ECG (1 mm ST depression, artifact-limited interpretation) and medium Duke Treadmill Score risk, stress imaging with either radionuclide myocardial perfusion imaging or stress echocardiography is strongly recommended. 1

Rationale for Stress Imaging

The presence of equivocal ECG findings with significant artifact during stress testing makes the standard exercise ECG uninterpretable for definitive diagnosis. 1 When the resting ECG is interpretable but the stress ECG results are equivocal or uninterpretable (as in this case with artifact and non-specific ST changes), exercise stress with imaging is the appropriate next step. 1

Key Clinical Factors Supporting Imaging:

• Artifact-limited interpretation during stress testing renders the ECG findings unreliable for excluding ischemia 1
• Deep T wave inversions in V3, V5, V6 (even with artifact) combined with 1 mm horizontal ST depression in inferior leads during recovery constitute equivocal findings that warrant definitive evaluation 1
• Medium-risk Duke Treadmill Score (-1.88) places this patient in an intermediate-to-high risk category requiring more definitive testing 1

Specific Testing Recommendations

First-Line Options (Choose One):

Exercise stress echocardiography or exercise stress with radionuclide myocardial perfusion imaging (SPECT or PET) are both strongly recommended as equivalent first-line options. 1

• Exercise-based stress imaging is preferred over pharmacologic stress when the patient can exercise adequately, as it provides additional prognostic information from exercise capacity, hemodynamic response, and functional assessment 1
• If PET is available, it is reasonable to prefer PET over SPECT for improved diagnostic accuracy and reduced nondiagnostic results 1

When to Use Pharmacologic Stress:

Pharmacologic stress imaging should only be used if the patient cannot achieve adequate exercise capacity (≥5 METs or 85% age-predicted maximum heart rate). 1 For patients who can exercise, pharmacologic stress is specifically not recommended. 1

Important Clinical Caveats

Avoid These Common Pitfalls:

• Do not repeat standard exercise ECG testing in this patient—the artifact and equivocal findings make further ECG-only testing futile 1
• Do not use pharmacologic stress if the patient can exercise adequately—this is a Class III (no benefit) recommendation 1
• Do not order both stress imaging and coronary CTA simultaneously—this provides no additional benefit and increases cost and radiation exposure 1

Alternative Consideration:

Coronary CT angiography (CCTA) is reasonable after an inconclusive stress test in intermediate-risk patients, particularly if the patient is younger (<65 years) and not on optimal preventive therapies. 1 However, given the medium-risk classification and equivocal ischemic findings, stress imaging remains the preferred approach to directly assess for inducible ischemia and quantify ischemic burden. 1

Risk Stratification Implications

The 1 mm horizontal ST depression in inferior leads during recovery is a concerning finding that increases the likelihood of significant coronary disease, even with normal resting ECG. 1 ST segment changes during recovery (rather than just during exercise) can indicate higher-risk disease. 1

The Duke Treadmill Score of -1.88 (medium risk, 95% 5-year survival) indicates this patient requires definitive evaluation to guide management decisions regarding revascularization versus intensified medical therapy. 1

Prognostic Value of Imaging:

Stress imaging will provide critical information about:

• Extent and severity of inducible ischemia 1
• Left ventricular function during stress 1
• Risk stratification for major adverse cardiac events 1
• Guidance for revascularization decisions 1

Patients with positive ECG findings but normal stress imaging have been shown to have slightly increased cardiac event rates compared to those with entirely negative testing, emphasizing the importance of obtaining definitive imaging in equivocal cases. 2