Are there other types of collaterals besides epicardial and septal collaterals in patients with coronary artery disease (CAD)?

Types of Coronary Collaterals in Coronary Artery Disease

Yes, there are several types of collaterals beyond epicardial and septal collaterals in patients with coronary artery disease, including coronary bypass grafts, veno-venous collaterals, and aortic collaterals. 1, 2

Main Types of Coronary Collaterals

1. Septal Collaterals

• Typically straighter and less tortuous than epicardial collaterals
• Lower risk of perforation during interventional procedures
• Can be safely dilated with small balloons to facilitate microcatheter passage
• Preferred for retrograde approaches during chronic total occlusion (CTO) interventions 1, 2

2. Epicardial Collaterals

• More tortuous and challenging to navigate
• Higher risk of complications during intervention
• Cannot be safely dilated with balloons like septal collaterals
• Require careful assessment before intervention 1

3. Coronary Bypass Grafts

• Both patent and occluded bypass grafts can serve as retrograde conduits
• Represent ideal retrograde pathways due to:
  • Absence of side branches
  • Predictable course
  • Large caliber 1
• Important consideration: Access via mammary artery grafts supplying the LAD increases risk of global ischemia and should be avoided when possible 1, 2

4. Additional Collateral Types

• Veno-venous collaterals: Found in 20-33% of patients with single ventricle physiology 1
• Aortic collaterals: Develop from existing vessels such as intercostal and mammary arteries to bypass aortic obstructions 1

Classification and Assessment of Collaterals

Werner Classification System

Used to grade collateral size:

• CC0: No continuous connection
• CC1: Threadlike connection
• CC2: Side branch-like connection 1, 2

Important Factors in Collateral Assessment

When evaluating collateral channels for intervention, consider:

• Size
• Tortuosity
• Presence of bifurcations
• Angle of entry to and exit from the collateral
• Distance from collateral exit to distal cap 1, 2

Clinical Significance

• Well-developed coronary collaterals mitigate myocardial infarct size and improve survival in CAD patients 3
• Collateral flow sufficient to prevent myocardial ischemia during coronary occlusion amounts to approximately 20-25% of normal flow through an open vessel 3
• In patients without CAD, preformed collateral arteries can prevent myocardial ischemia during brief vascular occlusion in 20-25% of individuals 3
• Among CAD patients, collateral arteries sufficient to prevent ischemia during brief occlusion are present in approximately one-third of individuals 3

Interventional Considerations

• Septal collaterals are typically safer and easier to navigate using soft-tip, polymer-jacketed guidewires compared to epicardial collaterals 1
• Previously visualized collaterals that disappear at the time of procedure may still be crossable ("shifting collaterals") 1
• Careful review of collaterals before procedures can reduce contrast and radiation dose, and decrease procedure duration 1
• In cases with unfavorable noninterventional epicardial collaterals providing dominant blood flow to the CTO, balloon occlusion of the epicardial collateral for 2-4 minutes may help recruit more favorable interventional collaterals 1

Understanding the various types of coronary collaterals and their characteristics is essential for optimal management of patients with coronary artery disease, particularly when planning interventional procedures for chronic total occlusions.