What is the preferred initial diagnostic test for suspected coronary artery disease, stress test or catheterization?

Initial Diagnostic Testing for Suspected Coronary Artery Disease: Stress Test vs. Catheterization

For patients with suspected coronary artery disease (CAD), coronary computed tomography angiography (CCTA) is recommended as the preferred initial diagnostic test for patients with low to moderate (5-50%) pre-test likelihood of obstructive CAD, while functional imaging tests are preferred for those with moderate to high (15-85%) pre-test likelihood. 1

Diagnostic Testing Algorithm Based on Pre-test Likelihood

Low to Moderate Pre-test Likelihood (5-50%)

• First choice: Coronary CT Angiography (CCTA)
  • High negative predictive value makes it excellent for ruling out CAD
  • Provides visualization of non-obstructive CAD, which may trigger preventive measures
  • Supported by randomized trials showing equivalence or superiority to functional testing 1
  • Not recommended if patient has severe renal failure, extensive coronary calcification, irregular heart rate, or inability to cooperate with breath-hold 1

Moderate to High Pre-test Likelihood (15-85%)

• First choice: Functional Imaging Tests
  • Stress echocardiography
  • Single-photon emission computed tomography (SPECT)
  • Positron emission tomography (PET)
  • Cardiac magnetic resonance (CMR)
  • Better "rule-in" power compared to CCTA for this population 1

Very High Pre-test Likelihood (≥85%)

• First choice: Invasive Coronary Angiography (ICA)
  • Recommended for patients with:
    • Very high clinical likelihood of obstructive CAD
    • Symptoms unresponsive to medical therapy
    • Angina at low level of exercise
    • Clinical evaluation indicating high event risk 1
  • Should include invasive functional assessment (FFR/iFR) to evaluate stenosis severity 1

When to Choose Invasive Coronary Angiography First

Invasive coronary angiography (catheterization) is appropriate as the initial test in specific circumstances:

1. Very high pre-test likelihood (≥85%) of obstructive CAD 1
2. Severe symptoms refractory to medical therapy 1
3. Angina occurring at low exercise levels 1
4. High-risk findings on initial clinical evaluation:
   • Severe left ventricular dysfunction
   • Ventricular arrhythmias
   • Hypotension during exercise 1

Limitations and Considerations

CCTA Limitations

• Not recommended in patients with:
  • Severe renal failure (eGFR <30 mL/min/1.73 m²)
  • Decompensated heart failure
  • Extensive coronary calcification
  • Fast irregular heart rate
  • Severe obesity
  • Inability to cooperate with breath-hold commands 1

Stress Testing Considerations

• Exercise ECG can be considered when imaging is not available, but is less accurate 1
• Pharmacological stress testing should be used for patients unable to exercise adequately 2
• Stress imaging has higher diagnostic accuracy than standard exercise ECG testing 2

Avoiding Common Pitfalls

1. Inappropriate use of invasive angiography: Studies show that approximately 25% of diagnostic catheterizations for suspected CAD are rated as inappropriate, with most of these patients having no previous stress test 3

2. Overreliance on exercise ECG: Not recommended as a diagnostic tool in patients with ST-segment depression on resting ECG or those taking digitalis 1

3. Failure to use functional assessment during ICA: When ICA is performed, it is essential to have coronary pressure assessment available to evaluate the functional severity of intermediate stenoses 1

4. Ignoring patient-specific factors: Consider local expertise and availability, patient characteristics that affect test performance, and contraindications to specific tests 1

The diagnostic approach has evolved significantly, with CCTA now playing a more prominent role as an initial test for suspected CAD, particularly in patients with low to moderate pre-test likelihood. This represents a shift from the traditional paradigm that relied heavily on stress testing as the gatekeeper for invasive angiography 4, 5.