Anteroseptal Myocardial Infarction

Excerpt

Anteroseptal myocardial infarction (ASMI) is a historical nomenclature based on electrocardiographic (EKG) findings. EKG findings of Q waves or ST changes in the precordial leads V1-V2 define the presentation of anteroseptal myocardial infarction. The patients who had an MI with EKG changes in V1-V2 or to V3 or V4, the autopsy report found out that the infarction involved the majority of the basal anterior septum. This nomenclature was in use until recently. Based on more recent studies using echocardiography and cardiac magnetic resonance imaging in the MI patients with ECG changes on V1, V2, there is rarely involvement of the basal anterior septum, but rather apical and anteroapical myocardial segments are most likely involved.

The term anteroseptal is based on autopsy data. Multiple attempts have tried to differentiate the myocardial segments based on different imaging modalities. Echocardiogram segments myocardium into 16 segments while single-photon emission computed tomography myocardial perfusion imaging (SPECT-MPI) uses a 17-segment model. The 17 segment model is based on the long-axis of the heart from base to apex and short-axis through 360 degrees circumferential location dividing a circle into six 60 degrees segments into basal and mid locations, and 90 degrees segment in the apical location, dividing the heart into a total of 17 segments, a model which seems to be in more agreement to the autopsy studies.

The left ventricle divides into 17 segments:

1. Basal anterior

2. Basal anteroseptal

3. Basal inferoseptal

4. Basal inferior

5. Basal inferolateral

6. Basal anterolateral

7. Mid anterior

8. Mid anteroseptal

9. Mid inferoseptal

10. Mid inferior

11. Mid inferolateral

12. Mid anterolateral

13. Apical anterior

14. Apical septal

15. Apical inferior

16. Apical lateral

17. Apex/apical cap

Anteroseptum includes basal anteroseptal, mid anteroseptal, and apical septal segments. Isolated anteroseptal infarction is very uncommon.

The coronary artery supplying these segments is most commonly the left anterior descending artery and its septal branches, however, anatomical variation is sometimes a possibility.