ST Elevation in Lead aVR: Left Main or Proximal LAD Occlusion
ST elevation in lead aVR most commonly indicates either left main coronary artery obstruction or proximal left anterior descending (LAD) artery occlusion above the first septal and diagonal branches, both representing high-risk coronary lesions requiring emergent cardiac catheterization. 1
Two Distinct Clinical Patterns
Pattern 1: Left Main or Multivessel Disease
The presence of ST depression >0.1 mV in eight or more surface leads, coupled with ST elevation in aVR and/or V1, suggests ischemia due to multivessel or left main coronary artery obstruction, particularly if the patient presents with hemodynamic compromise. 1, 2
- This pattern represents global subendocardial ischemia with the ST vector directed toward the ventricular cavity (aVR territory) 2
- Associated with 31% in-hospital mortality compared to 6.2% in STEMI without aVR elevation 3
- Critical caveat: Despite guideline endorsement, recent research shows only 10% of patients with this ECG pattern have an acutely occluded coronary artery requiring immediate reperfusion 3
- Most patients (59%) have severe coronary disease but with intact distal flow, while 40% have mild to moderate or no significant disease 3
- This means urgent (not emergent) catheterization is more appropriate than routine STEMI activation for immediate reperfusion 3
Pattern 2: Proximal LAD Occlusion (Anterobasal STEMI)
Occlusion of the proximal LAD above the first septal and first diagonal branches results in ST elevation in leads V1 through V4-6, I, aVL, and often aVR, with reciprocal ST depression in leads II, III, aVF, and often V5-6. 1, 4
- The ST-segment spatial vector is directed superiorly and to the left due to involvement of the basal left ventricle, anterior and lateral walls, and interventricular septum 1
- Typically, there will be more ST elevation in aVL than in aVR - this distinguishes proximal LAD from left main disease 1, 4
- More ST depression in lead III than in lead II because the ST vector is directed more leftward 1
- ST elevation ≥0.5 mm in aVR has 47% sensitivity but 96% specificity for proximal LAD occlusion (above first septal branch) in anterior STEMI 5
- This pattern represents true STEMI requiring immediate reperfusion therapy 1
Distinguishing Features
Compare the magnitude of ST elevation in aVR versus aVL and V1:
- aVR elevation > aVL elevation suggests left main disease 4
- aVL elevation > aVR elevation suggests proximal LAD occlusion 1, 4
- aVR elevation ≥ V1 elevation suggests left main disease 4
Clinical Management Algorithm
For hemodynamically unstable patients or those with ongoing chest pain despite medical therapy, proceed immediately to emergent cardiac catheterization regardless of the specific pattern. 1, 2
For hemodynamically stable patients with resolved symptoms:
- Perform urgent (not emergent) catheterization within hours 2, 3
- Obtain echocardiography to evaluate wall motion abnormalities and left ventricular function 2
- Serial troponin measurements 2
- Do not routinely activate the STEMI team for immediate reperfusion in the diffuse ST depression pattern, as most do not have acute thrombotic occlusion 3
Important Caveats
- The ECG should ideally be obtained during symptoms and compared with tracings when symptoms resolve 4
- Poor R wave progression in V3-V6 combined with ST elevation in aVR suggests anterior wall involvement from proximal LAD occlusion 4
- ST elevation in aVR with diffuse ST depression has multiple non-coronary causes including severe anemia, drug-induced vasospasm, and tachycardia - consider these before assuming coronary occlusion 6
- All patients with ST elevation in aVR and ST segment deviation have higher mortality risk regardless of the underlying cause 7, 3, 8