What is the most appropriate next step in evaluating a patient with chest pain on exertion, relieved by rest, normal resting electrocardiogram (ECG) and cardiac enzymes, and a history of osteoarthritis (degenerative joint disease) of the knee?

Exercise Stress ECG is the Most Appropriate Next Step

For this patient with exertional chest pain relieved by rest, normal resting ECG and cardiac enzymes, and a history of knee osteoarthritis, exercise stress ECG (Option A) is the most appropriate initial diagnostic test. 1, 2

Rationale for Exercise Stress ECG

The American College of Cardiology/American Heart Association guidelines explicitly recommend that exercise ECG testing should be used as the first-line noninvasive stress test for ambulatory patients when the resting ECG is normal and the patient is not on digoxin therapy. 1, 2 This patient meets all key criteria:

• Normal resting ECG - no ST-segment abnormalities, bundle branch blocks, or confounding findings that would interfere with interpretation 1, 2
• Ability to exercise - despite knee osteoarthritis, the patient can ambulate (presenting to clinic suggests functional mobility) 2
• Intermediate-risk presentation - exertional chest pain with normal initial workup places this patient in the intermediate-risk category requiring further evaluation 1
• Classic anginal pattern - chest pain on exertion relieved by rest is the hallmark presentation for stable coronary artery disease 2

Why Not the Other Options?

Echocardiogram (Option B) is not indicated as the next step because:

• Resting echocardiography is reserved for patients with pathological Q waves, signs of heart failure, complex arrhythmias, or heart murmurs - none of which are present here 2
• While echocardiography provides structural information, it does not assess for inducible ischemia in this stable presentation 1

CT Coronary Angiography (Option C) is a reasonable alternative but not preferred because:

• While CCTA is useful for intermediate-risk patients with acute chest pain, it is preferentially recommended for younger patients (<65 years) not on optimal preventive therapies 2
• Exercise stress ECG provides both diagnostic and prognostic information at lower cost and without radiation exposure 1, 3
• The 2021 ACC/AHA guidelines list both exercise ECG and CCTA as Class 1 recommendations for intermediate-risk patients, but exercise ECG remains first-line when patients can exercise and have normal resting ECGs 1

Dobutamine Stress Echocardiography (Option D) is inappropriate because:

• Pharmacologic stress testing is specifically reserved for patients unable to exercise adequately (cannot achieve ≥5 METs) or who are unsafe to exercise 2, 4
• This patient's knee osteoarthritis does not automatically preclude exercise testing - modified protocols (Naughton, ACIP, or Balke) can accommodate patients with deconditioning or orthopedic limitations 1
• Dobutamine stress echo would only be considered if the patient truly cannot perform any exercise 2, 5

Clinical Implementation

The exercise stress test should be:

• Symptom-limited maximum testing rather than predetermined heart rate or workload endpoints 1
• Modified protocol if needed - use lower work rate increments (ramp, Naughton, or Balke protocols) to accommodate the knee osteoarthritis rather than the standard Bruce protocol 1
• Supervised appropriately - can be performed by trained personnel with physician immediately available, given the intermediate-risk presentation 1

Test interpretation should consider:

• Tests failing to achieve ≥6 METs or 85% age-predicted maximum heart rate should be considered inconclusive and require further evaluation 1
• Exercise stress ECG has excellent negative predictive value (>95%) in intermediate-risk populations, with 5-year mortality rates of 1.2% and combined event rates of 3.8% when negative 6
• Positive tests warrant consideration of invasive coronary angiography, particularly if moderate-to-severe ischemia is demonstrated 1, 7

Safety Considerations

Exercise stress ECG is exceptionally safe in this population:

• Symptom-limited maximum exercise testing has a very low incidence of adverse events when performed after appropriate risk stratification 1, 2
• The patient's normal cardiac enzymes and resting ECG exclude acute coronary syndrome, making immediate exercise testing safe 1