Are the obtuse marginal 1 (OM1), obtuse marginal 2 (OM2), posterior descending artery (PDA), and left anterior descending artery (LAD) all considered inferior arteries?

Coronary Artery Anatomy: Classification of Inferior Arteries

No, the obtuse marginal 1 (OM1), obtuse marginal 2 (OM2), posterior descending artery (PDA), and left anterior descending artery (LAD) are not all considered inferior arteries. Only the posterior descending artery (PDA) supplies the inferior portion of the heart.

Coronary Artery Anatomical Classification

The coronary arteries can be classified based on their anatomical location and the territories they supply:

Left Coronary System

1. Left Main Coronary Artery (LMCA)

   • Originates from the left coronary sinus
   • Bifurcates into LAD and LCX

2. Left Anterior Descending (LAD)

   • Supplies the anterior wall and anterior portion of the septum
   • Runs in the anterior interventricular groove
   • Not an inferior artery but rather supplies the anterior and anterolateral portions of the left ventricle 1

3. Left Circumflex (LCX)

   • Courses in the left atrioventricular groove
   • Gives rise to:
     • Obtuse Marginal 1 (OM1) - supplies the lateral wall of the left ventricle
     • Obtuse Marginal 2 (OM2) - supplies the lateral wall of the left ventricle
   • These branches supply the lateral wall, not the inferior wall 1

Right Coronary System

1. Right Coronary Artery (RCA)
   • Originates from the right coronary sinus
   • Has proximal, middle, and distal segments
   • In right-dominant circulation (most common), gives rise to:
     • Posterior Descending Artery (PDA) - This is the only true inferior artery among those mentioned, running in the posterior interventricular groove and supplying the inferior wall of the heart 1
     • Posterolateral branches - supply the inferior and posterior walls

Anatomical Significance and Imaging

The distinction between these arteries is important for:

1. Echocardiographic Assessment:

   • Different imaging planes are required to visualize each artery
   • The PDA is visualized using:
     • Apical 4-chamber (inferior view)
     • Subcostal atrial long axis (inferior view)
     • Precordial long axis (inferior tangential) imaging
     • Posterior interventricular groove 1

2. Clinical Relevance:

   • In coronary artery disease, the location of stenosis determines the territory at risk
   • Proximal LAD stenosis is considered high-risk due to the large amount of myocardium supplied 1
   • PDA occlusion typically affects the inferior wall of the heart

Coronary Dominance Patterns

The coronary artery that gives rise to the PDA determines the dominance pattern:

• Right dominance (most common): PDA arises from the RCA
• Left dominance: PDA arises from the LCX
• Co-dominance: PDA contributions from both RCA and LCX

Common Pitfalls in Coronary Anatomy

1. Misclassification: Confusing the OM branches with inferior arteries when they actually supply the lateral wall
2. Dominance Variation: Not accounting for left dominance patterns where the PDA may arise from the LCX
3. Terminology Confusion: The term "inferior" refers to the anatomical location (bottom surface of the heart), not to clinical importance

Understanding the correct anatomical classification is crucial for proper interpretation of coronary angiography, echocardiography, and management of coronary artery disease.