Are angiograms (angiography) being overutilized in clinical practice?

Overutilization of Coronary Angiography in Clinical Practice

Yes, coronary angiography is being significantly overutilized in clinical practice, with approximately 45% of elective cardiac catheterizations not detecting clinically significant coronary stenoses. 1

Current Utilization Patterns and Evidence of Overuse

The evidence clearly demonstrates patterns of coronary angiography overuse:

• In the American College of Cardiology's National Cardiovascular Data Registry, approximately 45% of elective cardiac catheterizations performed did not detect clinically significant stenoses (defined as >50% luminal diameter), with rates varying dramatically between hospitals (range 0% to 77%) 1

• Even among patients with positive noninvasive tests, only 41% were found to have significant coronary artery disease (CAD) on angiography 1

• Within the Veterans Health Administration, 21% of patients undergoing elective catheterization had "normal" coronary arteries (defined as having no lesions ≥20%) 1

• Hospitals with lower rates of significant CAD findings were more likely to have performed angiography on:

  • Younger patients
  • Those with no symptoms or atypical symptoms
  • Those with negative, equivocal, or unperformed functional status assessment 1

Appropriate Indications for Coronary Angiography

According to guidelines, coronary angiography should be reserved for specific clinical scenarios:

1. High-risk patients with:

   • Survived sudden cardiac death or life-threatening ventricular arrhythmias 1
   • Development of heart failure symptoms and signs 1
   • Clinical characteristics indicating high likelihood of severe ischemic heart disease (IHD) 1

2. After noninvasive testing when:

   • Results indicate high likelihood of severe IHD and benefits exceed risks 1
   • Revascularization is being considered for known coronary stenosis of unclear physiologic significance 1

When Coronary Angiography Should NOT Be Used

Guidelines explicitly recommend against coronary angiography in several scenarios:

• Patients who elect not to undergo revascularization or are not candidates for revascularization 1
• Patients with preserved left ventricular function (ejection fraction >50%) and low-risk criteria on noninvasive testing 1
• Patients at low risk based on clinical criteria who have not undergone noninvasive risk testing 1
• Asymptomatic patients with no evidence of ischemia on noninvasive testing 1
• Patients with stable IHD who are able to exercise adequately and have an interpretable ECG (pharmacologic stress imaging should be used instead) 1

Appropriate Testing Sequence and Ratios

The evidence suggests an optimal ratio of myocardial perfusion scintigraphy (MPS) to angiography to revascularization of approximately 4:2:1 1. However, actual practice in the UK showed a ratio of 1,200:2,600:1,161, indicating significant underutilization of noninvasive testing before angiography 1.

Factors Contributing to Overutilization

Several factors contribute to the overutilization of coronary angiography:

• Variation in patient selection criteria across hospitals 1
• Performing angiography without adequate prior functional testing 1
• Geographic variations in practice patterns 1
• Performing angiography in patients with atypical symptoms or negative functional tests 1
• Combining diagnostic angiography with angioplasty as a single procedure, which has become common practice in many institutions 2

Clinical Implications and Recommendations

To address the overutilization of coronary angiography:

1. Adhere to a stepwise diagnostic approach:

   • Begin with appropriate noninvasive functional testing in stable patients
   • Reserve angiography for patients with high-risk features on noninvasive testing or specific high-risk clinical scenarios

2. Implement appropriateness criteria:

   • Patient-specific appropriateness criteria have demonstrated prognostic validity and can help identify which patients might benefit from coronary angiography 3
   • These criteria can help standardize practice and reduce unnecessary procedures

3. Consider occult coronary abnormalities:

   • In patients with angina but no obstructive CAD, comprehensive invasive assessment may still be warranted, as studies show the majority have occult coronary abnormalities including endothelial dysfunction (44%), microvascular impairment (21%), or myocardial bridging (58%) 4

4. Balance risks and benefits:

   • While outpatient angiography is relatively safe with low significant complication rates (1.5%) 5, the risks must be weighed against potential benefits
   • Unnecessary procedures expose patients to risks without clear benefit

By following evidence-based guidelines and appropriateness criteria, clinicians can ensure coronary angiography is used judiciously, improving patient outcomes while reducing healthcare costs associated with unnecessary invasive procedures.