Coronary Artery Anomalies

Coronary artery anomalies (CAAs) are congenital variations in the origin, course, or termination of the coronary arteries. While most are benign, some carry a risk of myocardial ischemia, arrhythmia, or sudden cardiac death.

Epidemiology

Classification

Classification by Hemodynamic Significance

Benign anomalies (80-90%):

• No hemodynamic effect
• Usually incidental findings
• No treatment required

Potentially malignant anomalies (10-15%):

• Risk of myocardial ischemia
• Risk of arrhythmia
• Risk of sudden cardiac death

Significant hemodynamic anomalies (1-3%):

• Congenital coronary fistula
• Anomalous origin from pulmonary artery
• Myocardial bridging (controversial)

Anatomic Classification

Anomalous Origin from the Opposite Sinus

This is the most clinically important group, associated with sudden cardiac death during exercise.

Anomalous RCA from the Left Sinus

• RCA originates from the left coronary sinus
• Most common malignant anomaly
• The RCA courses between the aorta and pulmonary trunk (interarterial)

Types of course:

• Interarterial (between aorta and PA): Highest risk (malignant)
• Retroaortic (behind aorta): Benign
• Septal (within the septum): Generally benign
• Pre-pulmonic (anterior to PA): Benign

Anomalous LCA from the Right Sinus

• LMCA originates from the right coronary sinus
• Less common but higher risk
• The LMCA typically courses between the aorta and pulmonary trunk

Risk factors for ischemia:

• Acute angle takeoff (slit-like ostium)
• Intramural course within the aortic wall
• Compression between great vessels during exercise
• Kinking at the origin

Anomalous LCx from the Right Sinus

• LCx originates from the right sinus or proximal RCA
• Most common single coronary anomaly
• Course: Retroaortic (behind the aorta)
• Generally benign, no increased risk of sudden death

Clinical Presentation

Mechanism of Ischemia:

• Slit-like ostium at the acute angle origin
• Compression between the aorta and pulmonary trunk during exercise
• Intramural course within the aortic wall
• Kinking of the vessel at the origin

Diagnosis

Risk Stratification

High-risk features:

• Interarterial course
• Intramural course
• Slit-like ostium
• Acute angle takeoff (< 30 degrees)
• Length of intramural segment > 5 mm

Treatment

Anomalous Origin from the Pulmonary Artery

ALCAPA (Anomalous Left Coronary Artery from the Pulmonary Artery)

Also known as Bland-White-Garland syndrome.

Incidence: 1 in 300,000 live births

Pathophysiology:

• LCA arises from the pulmonary trunk
• In infancy, pulmonary vascular resistance drops
• Flow reverses in the LCA (from LAD to pulmonary artery)
• Myocardial ischemia and infarction develop
• Collaterals from the RCA develop but create a coronary steal

Presentation:

• Infancy: Crying, diaphoresis, feeding difficulty (angina equivalent)
• Heart failure: Dilated cardiomyopathy
• Mitral regurgitation (papillary muscle ischemia)
• Survival to adulthood rare without surgery

ECG:

• Q waves in I, aVL, V5, V6 (anterolateral infarction)
• Left ventricular hypertrophy

Treatment:

• Surgical reimplantation of the LCA into the aorta
• Takeuchi procedure (creation of aortopulmonary tunnel)
• Ligation of the LCA at the pulmonary origin + bypass grafting

ARCAPA (Anomalous Right Coronary Artery from the Pulmonary Artery)

• Much rarer than ALCAPA
• Often less symptomatic (RCA supplies smaller territory)
• May present in adulthood with right ventricular ischemia
• Treated with reimplantation or bypass grafting

Coronary Artery Fistulas

Definition

Abnormal direct communication between a coronary artery and a cardiac chamber or great vessel.

Types

Most common origin: RCA (50-60%)

Pathophysiology

• Left-to-right shunt (coronary to right heart)
• Coronary steal (blood diverted from myocardium)
• Volume overload of the receiving chamber

Presentation

Treatment

• Small fistulas with no shunt: Observation
• Large fistulas or symptoms: Closure
• Transcatheter closure: Coils, plugs, or covered stents
• Surgical ligation: For large or complex fistulas

Myocardial Bridging

Definition

A segment of a coronary artery that courses intramyocardially (within the myocardium) rather than epicardially.

Incidence

• Angiography: 1-5%
• Autopsy: 15-30%
• CT coronary angiography: 20-30%

Most Common Location

Mid-segment of the LAD (70-80%)

Anatomy

• The myocardial bridge (tunneled segment) is covered by muscle (tunneled artery)
• The proximal segment often has atherosclerosis
• Systolic compression of the bridged segment
• Diastolic relaxation allows normal flow

Hemodynamic Significance

Clinical Presentation

• Most patients are asymptomatic
• Angina (especially with tachycardia, when diastole shortens)
• Myocardial infarction (rare, usually with plaque proximal to bridge)
• Stress-induced arrhythmias
• Syncope

Diagnosis

• Angiography: Milking effect with systolic compression and delayed diastolic relaxation (the half-moon sign)
• IVUS: Echolucent half-moon sign around tunneled segment
• FFR: Abnormal during tachycardia (Doppler flow velocity assessment)

Treatment

Stenting is contraindicated due to high risk of stent fracture, perforation, and restenosis.

Other Coronary Anomalies

Duplication of Coronary Arteries

• Duplication of the LAD: Type I-IV classification
• Duplication of the RCA: Uncommon
• Usually benign

Hypoplasia or Atresia

• Coronary hypoplasia: Underdeveloped coronary artery
• Coronary atresia: Absent coronary ostium
• Usually associated with other congenital heart disease
• Collateral circulation determines viability

Separate Ostia of LAD and LCx

• LAD and LCx arise independently from the left sinus
• Present in approximately 1% of population
• Usually benign

High Takeoff

• Coronary ostium located above the sinotubular junction
• Can complicate coronary angiography
• May cause ostial stenosis

Single Coronary Artery

• One coronary artery supplies the entire heart
• Several types (Lipton classification L, R, I, II, III)
• The anomalous vessel must course around the heart to supply the other side
• Risk depends on the course (interarterial = high risk)