What is the management approach for a patient with concern about coronary artery supply to the atrioventricular node (AV node)?

Coronary Artery Supply to Leads I and aVL

The coronary artery territory corresponding to ECG leads I and aVL is the lateral wall of the left ventricle, supplied predominantly by the left circumflex artery (LCX) and its branches, particularly the obtuse marginal arteries.

Anatomical Correlation

Leads I and aVL reflect electrical activity from the high lateral wall of the left ventricle, which receives blood supply primarily from the left circumflex coronary artery system 1. The obtuse marginal branches of the LCX are the main vessels supplying this territory 1.

Key Anatomical Points:

• Primary supply: Left circumflex artery (LCX) and obtuse marginal branches supply the lateral wall territory corresponding to leads I and aVL 1
• Diagonal branches: In some patients, diagonal branches from the left anterior descending (LAD) artery may contribute to the high lateral wall supply 1
• Anatomic variation: The sinuatrial nodal artery originates from the LCX in approximately 27% of patients, traveling through the lateral atrial territory 1

Clinical Implications for Ischemia

ST-Segment Changes in Leads I and aVL:

• ST elevation in leads I and aVL indicates acute lateral wall myocardial infarction from LCX occlusion 2
• Reciprocal ST depression in leads I and aVL during inferior wall MI suggests concomitant lateral wall ischemia or extensive right coronary artery (RCA) territory involvement 2
• Isolated changes in these leads may represent high lateral wall ischemia from proximal LCX or first obtuse marginal occlusion 1

Conduction System Considerations:

The atrioventricular node receives dual blood supply in most patients, with the RCA supplying the AVN in 87% of cases and the LCX in 11% 1. When AV block occurs during inferior MI, there is a 91% likelihood of associated LAD obstruction, suggesting the importance of septal perforator supply to the proximal conduction system 2. The first septal perforating artery from the LAD contributes to AVN supply in 64% of cases 3, though recent imaging studies found no detectable connection 1.

Management Approach for Lateral Wall Ischemia

Patients presenting with ST-segment elevation in leads I and aVL require immediate coronary angiography and revascularization, as this represents acute lateral wall STEMI from LCX occlusion 4.

Revascularization Strategy:

• Acute presentation: Primary PCI of the culprit LCX lesion is the preferred strategy for lateral wall STEMI 4
• Multivessel disease: Careful assessment of risk/benefit profile is required when deciding between staged PCI versus complete revascularization 4
• Surgical candidates: CABG should be considered for patients with left main disease or three-vessel CAD with LV dysfunction 5

Common Pitfalls:

• Underestimating lateral wall ischemia: Isolated changes in leads I and aVL may be subtle but represent significant myocardium at risk 1
• Missing reciprocal changes: ST depression in leads I and aVL during inferior MI may indicate more extensive coronary disease requiring broader revascularization 2
• Delayed recognition: The LCX territory is sometimes called the "silent" artery because occlusions may not produce dramatic ECG changes in standard precordial leads 1