Culprit Vessel in Septal Myocardial Infarction
The left anterior descending (LAD) coronary artery is the culprit vessel in septal myocardial infarction, specifically through its septal perforator branches which supply the interventricular septum. 1
Anatomical Basis
- The interventricular septum receives its blood supply primarily from septal perforator branches of the LAD, which originate from the proximal and mid portions of this vessel 1
- These septal perforator branches penetrate the myocardium to supply the anterior two-thirds of the interventricular septum 1
- The first septal perforator is typically the largest and most important branch supplying the proximal ventricular septum 2
Clinical Evidence
- In alcohol septal ablation procedures for hypertrophic cardiomyopathy, ethanol is deliberately injected into a septal perforator branch of the LAD to produce a controlled myocardial infarction of the proximal ventricular septum 1
- This technique relies on the anatomical fact that septal perforators from the LAD are the vessels supplying the interventricular septum 1
- During these procedures, myocardial contrast echocardiography is used to confirm that the selected septal perforator supplies the target septal area before alcohol injection 1
Diagnostic Considerations
- Electrocardiographic findings in septal infarction may include ST-segment elevation in anterior leads (V1-V4) due to the anterior location of the septum 2
- Proximal LAD occlusions that affect the first septal perforator are associated with worse clinical outcomes compared to more distal occlusions, partly due to the larger area of myocardium at risk 3
- A greater degree of ST-segment depression in lead III than ST-segment elevation in lead aVL has been identified as a predictor of proximal LAD occlusion in anterior myocardial infarction, with 85% sensitivity and 95% specificity 2
Clinical Implications
- Septal infarctions can lead to conduction abnormalities including bundle branch blocks and heart blocks due to the septum's role in the cardiac conduction system 1
- Proximal LAD lesions (which affect septal perforators) are associated with higher in-hospital mortality (6.7%) compared to mid (3.2%) or distal (2.5%) lesions 3
- The proximity of the culprit lesion to the LAD ostium is independently associated with adverse outcomes even after adjustment for coronary blood flow and other covariates 3
Management Considerations
- Revascularization of the culprit artery (LAD) is appropriate in patients with ST-elevation myocardial infarction affecting the septum 1
- Prompt identification of LAD occlusion is critical as proximal occlusions subtend a larger area of myocardium and are associated with higher mortality and morbidity 3, 4
- In patients with high-risk features for short-term risk of death or recurrent myocardial infarction, revascularization of the presumed culprit artery (LAD in septal infarction) receives an appropriateness score of 9 (highly appropriate) 1
In conclusion, septal myocardial infarction is primarily caused by occlusion of the LAD coronary artery or its septal perforator branches, with the first septal perforator being particularly important for blood supply to the proximal interventricular septum.