What is the difference between Percutaneous Coronary Intervention (PCI) and Coronary Angiography?

Differences Between Percutaneous Coronary Intervention (PCI) and Coronary Angiography

Coronary angiography is a diagnostic imaging procedure that visualizes coronary arteries, while PCI is a therapeutic intervention that treats coronary artery blockages by restoring blood flow through balloon dilation and typically stent placement.

Coronary Angiography: Diagnostic Procedure

Coronary angiography is a diagnostic imaging technique with the following characteristics:

• Purpose: Diagnostic visualization of coronary arteries to identify stenoses, occlusions, and anatomical variations
• Procedure:
  • Involves insertion of a catheter through peripheral artery (typically femoral or radial)
  • Injection of radiopaque contrast dye into coronary arteries
  • X-ray imaging to visualize the coronary vasculature
• Outcome: Produces a 2-dimensional lumenogram of the coronary arteries 1
• Limitations:
  • Limited ability to characterize plaque morphology
  • Cannot directly treat identified blockages
  • Provides only a "silhouette" view of the vessel lumen 1

Percutaneous Coronary Intervention (PCI): Therapeutic Procedure

PCI (formerly called PTCA) is a therapeutic intervention that follows diagnostic angiography when treatment is indicated:

• Purpose: Treatment of coronary artery stenoses or occlusions to restore blood flow
• Procedure:
  • Follows diagnostic angiography when a treatable lesion is identified
  • Involves advancing specialized catheters to the site of blockage
  • Balloon dilation of the narrowed segment
  • Usually includes placement of a stent (bare-metal or drug-eluting) to maintain vessel patency
• Components: Family of techniques including balloon angioplasty, stenting, and atheroablative technologies (atherectomy, thrombectomy, laser angioplasty) 1
• Current practice: Most modern PCIs (80-85%) involve both balloon dilation and coronary stenting 1

Key Differences

1. Function:

   • Angiography: Diagnostic only - identifies disease
   • PCI: Therapeutic - treats identified disease

2. Mechanism of action:

   • Angiography: Visualizes blockages without modifying them
   • PCI: Physically opens blockages and restores blood flow

3. Timing:

   • Angiography: Performed first to identify lesions
   • PCI: May be performed immediately after angiography ("ad hoc PCI") or in a separate session ("delayed PCI") 2

4. Equipment:

   • Angiography: Uses diagnostic catheters and contrast dye
   • PCI: Requires specialized guiding catheters, guidewires, balloons, and typically stents

5. Outcome:

   • Angiography: Produces images for diagnosis
   • PCI: Results in improved coronary blood flow and symptom relief

Clinical Applications and Considerations

When PCI Follows Angiography

PCI is commonly performed in the following scenarios after diagnostic angiography:

• Acute coronary syndromes: Primary PCI is the preferred reperfusion strategy for STEMI when available within appropriate timeframes 1
• Stable coronary artery disease: When significant ischemia is demonstrated and anatomy is suitable 1
• Left main coronary disease: Increasingly considered as an alternative to CABG in selected patients, particularly those with ostial or midshaft lesions 1

Ad Hoc vs. Delayed PCI

• Ad hoc PCI (same-session PCI) is now the dominant approach, accounting for approximately 83% of PCIs in stable CAD 3

• Benefits of ad hoc PCI include:

  • Patient convenience (single procedure)
  • Lower bleeding risk compared to staged procedures 3
  • Cost efficiency

• Delayed PCI may be preferable in:

  • Complex cases requiring multidisciplinary discussion
  • Chronic total occlusions
  • Patients with severe renal dysfunction
  • Cases requiring additional testing before intervention 3

Adjunctive Technologies

Modern coronary interventions increasingly utilize advanced imaging beyond basic angiography:

• Intravascular imaging technologies such as IVUS (intravascular ultrasound) and OCT (optical coherence tomography) complement angiography by:

  • Providing detailed plaque characterization
  • Guiding stent sizing and deployment
  • Assessing post-intervention results 1
  • Potentially reducing major adverse cardiac events in complex lesions

• Fractional Flow Reserve (FFR) provides functional assessment of lesion significance, improving decision-making about which lesions require intervention 1

Common Pitfalls

1. Relying solely on angiography for PCI decisions: Angiography has limitations in assessing the functional significance of lesions, potentially leading to unnecessary interventions. Functional assessment with FFR should be considered for intermediate lesions.

2. Inappropriate patient selection for angiography: Hospitals with higher rates of angiography in asymptomatic patients tend to have higher rates of inappropriate PCI 4, highlighting the importance of proper patient selection.

3. Assuming all visualized lesions require treatment: Not all angiographically visible stenoses cause ischemia or warrant intervention.

4. Overlooking the need for Heart Team discussion: Complex cases, particularly those involving left main or multivessel disease, benefit from multidisciplinary evaluation to determine the optimal revascularization strategy (PCI vs. CABG) 1.

By understanding these fundamental differences between diagnostic coronary angiography and therapeutic PCI, clinicians can better communicate these procedures to patients and make appropriate decisions regarding coronary revascularization strategies.