Werner classification of collaterals

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Werner Classification of Coronary Collaterals (angiographic classification, widely used in interventional cardiology):

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Werner Collateral Connection (CC) Classification

Grade	Description	Angiographic Finding
CC0	No continuous connection	Collateral channels not visible between donor and recipient arteries
CC1	Thread-like connection	Thin, thread-like continuous connection between donor and recipient artery, but not large enough for wire passage
CC2	Side branch-like connection	Large, side branch-like continuous connection between donor and recipient artery, usually sufficient for guidewire passage

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✅ Clinical Use:

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• Werner classification is often used in chronic total occlusion (CTO) interventions to assess the feasibility of crossing collateral channels with guidewires.
• CC2 collaterals are usually the most useful for retrograde CTO PCI.

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Werner Classification of Coronary Collaterals

Grade	Description	Angiographic Finding
CC0	No continuous connection	No visible collateral channel between donor and recipient artery
CC1	Thread-like connection	Thin, thread-like collateral channel; usually not large enough for guidewire passage
CC2	Side branch-like connection	Large, side branch-like collateral channel; usually sufficient for guidewire passage

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Short Questions & Answers – Werner Classification

Question	Answer
What does Werner classification assess?	The quality of coronary collateral channels in chronic total occlusion (CTO).
What is CC0?	No continuous collateral channel is visible between donor and recipient arteries.
What is CC1?	A thin, thread-like collateral connection that usually does not allow guidewire passage.
What is CC2?	A large, side branch-like collateral channel, often usable for retrograde CTO PCI.
Which Werner grade is most useful for PCI?	CC2.
Does Werner classification measure functional flow?	No, it only grades anatomical collateral channels.
Which classification is more detailed: Rentrop or Werner?	Rentrop has 4 grades (0–3), Werner has 3 (CC0–CC2).
Is Werner classification commonly used in CTO interventions?	Yes, especially to plan retrograde PCI strategies.
What is the main limitation of Werner classification?	It does not reflect collateral flow capacity, only channel size/appearance.
Who introduced this classification?	Werner et al., for grading collaterals in CTO angiography.

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20 Important Facts – Werner Classification of Coronary Collaterals

#	Fact
1	Werner classification is used to grade coronary collateral connections in chronic total occlusion (CTO).
2	It has three grades: CC0, CC1, and CC2.
3	CC0 = no continuous connection between donor and recipient arteries.
4	CC1 = thread-like connection; not usually suitable for guidewire passage.
5	CC2 = side branch-like connection; usually allows guidewire passage.
6	The classification focuses on anatomical channel morphology, not flow capacity.
7	It is especially relevant in planning retrograde PCI approaches in CTO cases.
8	CC2 collaterals are the most favorable for intervention.
9	CC0 indicates very poor collateralization, often requiring antegrade strategies.
10	Unlike Rentrop, Werner classification does not measure myocardial filling but only channel connection.
11	CC1 collaterals appear thin, thread-like, and rarely used for wire passage.
12	CC2 collaterals resemble normal coronary side branches on angiography.
13	A higher Werner grade often correlates with easier CTO crossing success.
14	CC0 suggests absence of meaningful collateral circulation.
15	Werner classification is widely used in interventional cardiology literature.
16	It helps operators decide whether to attempt a retrograde approach.
17	Werner grading is simple and reproducible during coronary angiography.
18	CC2 collaterals significantly increase retrograde PCI success rates.
19	CC1 collaterals may be supportive but usually insufficient for catheter techniques.
20	Overall, Werner classification is complementary to Rentrop for assessing coronary collateral circulation.

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