What is the next step in managing an adult patient with possible cardiovascular risk factors and baseline scattered nonspecific ST (electrocardiogram) changes that became prominent with a treadmill stress test?

Management of Prominent ST Changes During Treadmill Stress Testing

Yes, further testing with stress imaging (exercise echocardiography or myocardial perfusion imaging) is strongly recommended when baseline nonspecific ST changes become prominent during treadmill stress testing, as baseline ST abnormalities interfere with accurate interpretation of exercise-induced ischemic changes. 1, 2

Why Standard Treadmill Testing Alone Is Inadequate

Baseline ST segment abnormalities fundamentally compromise the diagnostic accuracy of standard exercise ECG testing. The primary diagnostic markers during treadmill testing are exercise-induced ST segment changes, but when abnormalities already exist at baseline, it becomes impossible to reliably distinguish true ischemic changes from baseline artifacts 2, 3. This creates both false-positive and false-negative results that can lead to inappropriate management decisions 2.

The 2024 ESC guidelines explicitly state that exercise ECG has no diagnostic value in patients with ECG abnormalities at rest that prevent interpretation of ST-segment changes during stress, including ≥0.1 mV ST-segment depression on resting ECG 1. The 2013 ESC guidelines similarly emphasize that false-positive results are more frequent in patients with abnormal resting ECG 1.

Recommended Next Steps: Stress Imaging

The appropriate next step is stress testing with an imaging modality rather than proceeding directly to invasive coronary angiography or stopping the diagnostic workup 1.

Imaging Options for Patients Who Can Exercise:

• Exercise echocardiography 1
• Exercise myocardial perfusion imaging (SPECT or PET) 1

Both modalities provide superior diagnostic accuracy compared to ECG changes alone when baseline abnormalities are present 1.

If Patient Cannot Exercise Adequately:

• Pharmacologic stress testing with imaging (adenosine, dipyridamole, or dobutamine) should be used 1

Risk Stratification Determines Urgency

The Duke Treadmill Score should still be calculated to guide the urgency and type of further testing, even though the ST changes themselves are not reliably interpretable 1, 4.

Duke Treadmill Score Formula:

Exercise time (minutes) - (5 × ST deviation in mm) - (4 × angina index) 4

Risk Categories:

• Low risk (score ≥5): These patients have excellent prognosis and may not require immediate imaging if asymptomatic, though the presence of prominent ST changes warrants consideration of imaging for definitive evaluation 1
• Intermediate risk (score -10 to +4): Exercise myocardial perfusion imaging or exercise echocardiography should be performed 1
• High risk (score ≤-11): Exercise myocardial perfusion imaging or exercise echocardiography should be performed, with consideration for direct coronary angiography if high-risk features are present 1

Additional Prognostic Markers Beyond ST Changes

Even when ST segments are uninterpretable, other treadmill parameters provide valuable prognostic information and should be carefully evaluated 1:

• Exercise capacity: <5 METs or inability to achieve 85% maximum predicted heart rate indicates higher risk 1, 3, 4
• Blood pressure response: Decrease in systolic BP >10 mmHg from rest to peak exercise indicates high risk 4
• Symptoms during exercise: Development of typical angina, especially at low workload 1
• Arrhythmias: Ventricular arrhythmias during exercise 1

When to Proceed Directly to Coronary Angiography

Coronary angiography should be considered without intermediate stress imaging in specific high-risk scenarios 1:

• Recurrent symptoms despite adequate medical therapy
• Heart failure or serious ventricular arrhythmias
• Markedly elevated cardiac biomarkers (if acute coronary syndrome suspected)
• High-risk Duke Treadmill Score (≤-11) with limiting symptoms 1
• Previous PCI or CABG with recurrent symptoms 1

Common Pitfalls to Avoid

Do not dismiss prominent ST changes during exercise as "false positive" simply because baseline abnormalities exist 2. While baseline ST changes reduce specificity, the development of additional or worsening ST changes during exercise may still represent true ischemia that requires evaluation with imaging 5.

Do not repeat standard treadmill testing without imaging in an attempt to clarify results—this will yield the same interpretive limitations 2, 3.

Do not assume the patient is low-risk based solely on achieving adequate heart rate if prominent ST changes developed, as the ST changes themselves cannot be reliably interpreted for ischemia 2, 6.

Evidence Quality Considerations

The recommendations for stress imaging in patients with baseline ST abnormalities are based primarily on expert consensus (Level C evidence) from major cardiology societies 1. However, these recommendations are consistently endorsed across multiple guidelines from the American College of Physicians, European Society of Cardiology, and American Heart Association 1. The 2024 ESC guidelines represent the most current guidance and emphasize that exercise ECG has low sensitivity (58%) and specificity (62%) for obstructive CAD even in ideal circumstances, making imaging essential when baseline abnormalities exist 1.