Anterolateral OMI

Patients with OMI are at risk for a number of complications, some of which will be discussed on the other OMI pages. Patients with large OMIs are more likely to develop cardiogenic shock. They do not always have hypotension. Frequently, patients will have mottling/poor capillary refill. Additionally, tachycardia is a sign of cardiogenic shock in the setting of OMI. Patients are also at a much higher risk of ventricular arrhythmias. LAD OMIs can be the most severe given the amount of myocardium affected compared to other sites.

Examples:

Tombstone pattern ST elevation

Predicting Site of LAD Occlusion

There are a number of branches off the LAD. A 'branch occlusion' is usually not as severe as an LAD occlusion as there is less myocardium involved. The first diagonal artery (D1) and the first septal branches (S1) can produce different patterns on an EKG. Occlusion proximal to these branches portends a larger LAD occlusion and worse prognosis ('proximal LAD occlusion').

S1 supplies the basal part of the interventricular septum (including the bundle branches. S1 correlates with V1 and aVR.

D1 supplies the high lateral region of the heart and correlates with I and aVL (has some overload with the left circumflex artery).

Occlusion Proximal to S1:

ST elevation in aVR
ST elevation in V1>2.5mm
complete RBBB
ST depression in V5

Occlusion Proximal to D1:

ST elevation in aVL
ST depression at least 1mm in the inferior leads

Signs of Proximal LAD Occlusion:

RBBB
ST elevation in aVL
>1mm ST depression in the inferior leads

In fact, another poor prognostic sign with OMI is a new block. New RBBB+LAFB indicates an even larger/more proximal territory and worse prognosis.

Lateral OMI

Most commonly, a lateral OMI is found as part of an anterolateral OMI from the LAD. Additionally, inferoposterolateral OMIs may occur and sometimes come from the RCA in a right dominant system, though also commonly is from an occluded left circumflex artery.

inferoposterolateral OMI from occluded left circumflex artery

An isolated lateral OMI is rare, but most commonly arises from the left circumflex artery or one of its branches (ie obtuse marginal); it is commonly referred to as a 'high lateral OMI'. High lateral OMIs are also commonly from the first diagonal (D1) branch of the LAD. The South African Flag sign is when there is ST elevation in I + aVL +/- V2 with ST depression in III; these produce the shape of the flag. Occasionally, the ST changes are more subtle and do not meet traditional STEMI criteria.

High Lateral OMI

South African Flag sign with overlay of EKG show STE in I+aVL+V2 and STD maximal around III

Subtle D1 OMI with South African Flag sign that does not meet STEMI criteria

Note that reperfusion does not develop Q waves when the T wave becomes inverted. Also note that the T wave inversion patterns are seen in a specific syndrome of reperfusion (Wellen's syndrome...).