What is a type C coronary lesion?

Type C Coronary Lesion Definition

A Type C coronary lesion is a high-risk, complex coronary stenosis characterized by at least one of the following features: diffuse disease (>20mm length), chronic total occlusion (>3 months old), extreme angulation (>90°), inability to protect major side branches, or degenerated vein grafts with friable lesions. 1

Historical Classification System

The original ACC/AHA lesion classification system, established in 1988, stratified coronary lesions into three categories based on anticipated procedural success and complication rates during balloon angioplasty 1:

• Type A lesions: High success (>95%), low risk - discrete (<10mm), concentric, readily accessible, minimal calcification 1
• Type B lesions: Moderate success (60-85%), moderate risk - tubular (10-20mm), moderate calcification, some thrombus 1
• Type C lesions: Low success (<60%), high risk - characterized by the most complex anatomic features 1

Specific Type C Characteristics

Type C lesions are defined by the presence of any one of these features 1:

• Diffuse disease: Lesion length >20mm (some definitions use >2cm) 1
• Chronic total occlusion: Complete vessel closure >3 months duration 1
• Extreme angulation: Vessel segment angulation >90° 1
• Inability to protect major side branches: Lesions where major branches cannot be protected during intervention 1
• Degenerated vein grafts: Saphenous vein graft lesions with friable, atherosclerotic material 1

Evolution in the Stent Era

The classification system underwent significant revision with the advent of coronary stenting 1:

• The 2005 ACC/AHA/SCAI guidelines simplified the system to distinguish between "high-risk" (at least one Type C characteristic) versus "non-high-risk" (no Type C characteristics) lesions 1
• This modification reflected that stents could manage many acute complications (dissection, abrupt closure) that previously made Type B lesions high-risk 1
• Complex coronary lesions (Type C characteristics) remain predictive of adverse events after PCI even in the contemporary stent era 1

Clinical Significance and Outcomes

Type C lesions continue to portend worse outcomes despite modern interventional techniques 2, 3, 4:

• Restenosis rates: 32.6-33.2% for Type C lesions versus 21.7-24.9% for Type A lesions after stenting 3
• 30-day outcomes: Higher rates of mortality (1.2% vs 0.6%), myocardial infarction (9.2% vs 6.3%), and unplanned revascularization (4.3% vs 3.1%) compared to non-Type C lesions 2
• Procedural success: 82.7-90% for Type C lesions versus 99.6% for Type A lesions in contemporary practice 5, 4
• One-year event-free survival: 75.2-75.6% for Type C lesions versus 85.2% for Type A lesions 3

Important Clinical Caveats

Chronic total occlusions represent a unique subset within Type C lesions 1:

• While restenosis and technical failure rates remain high, the risk of acute complications is not increased compared to other lesion types 1
• This distinguishes them from other Type C characteristics where both acute and long-term risks are elevated 1

The presence of Type C characteristics independently predicts adverse outcomes after multivariate adjustment for other clinical and angiographic factors 2, 3:

• Type C lesions are independently associated with myocardial infarction (OR 1.37,95% CI 1.04-1.80) and composite ischemia (OR 1.49,95% CI 1.17-1.88) at 30 days 2
• This prognostic value persists across different antithrombotic regimens without significant interaction 2

Contemporary Relevance

The ACC/AHA lesion classification remains clinically relevant in the modern PCI era 4:

• Increasing lesion complexity correlates with lower procedural success and worse medium-term clinical outcomes 4
• The classification should be calculated preprocedure to predict acute PCI success and clinical outcomes 4
• Type C lesions more frequently require adjunctive devices such as rotational atherectomy, drug-eluting stents, and longer stent lengths 4