Lateral Wall Myocardial Infarction

Like other acute myocardial infarctions, isolated lateral wall myocardial infarction (LMI) arises from acute atherosclerotic plaque rupture with subsequent thrombus formation in the left circumflex (LCx) coronary artery or one of its branches. Myocardial infarctions more commonly result from extensive anterolateral wall involvement due to blockage of the left anterior descending (LAD) coronary artery. LMI is less common than anterior or inferior myocardial infarction, with the LCx involved in approximately 15% to 20% of all myocardial infarctions. LMI presents like other types of myocardial infarction. The condition is often detected through lateral electrocardiogram (ECG) lead changes; acute treatment includes immediate reperfusion.

Myocardial infarctions are classified based on presenting ECG findings and the location of ischemia. Branches of the LAD and LCx supply the left ventricular lateral wall. Isolated lateral wall involvement is uncommon and typically occurs as part of multiterritorial infarctions, including anterolateral, posterolateral, and inferolateral myocardial infarctions (see Image. Anterolateral Myocardial Infarction on Electrocardiography). Occlusion of the obtuse LCx marginal branch or the diagonal LAD branch can cause isolated LMI.

The 2018 collaborative expert consensus from the European Society of Cardiology, American College of Cardiology, American Heart Association, and World Heart Federation issued the fourth universal definition of myocardial infarction, defining type I myocardial infarction as a rise or fall in cardiac troponin, with at least 1 value exceeding the ninety-ninth percentile and accompanied by at least 1 of the following factors:

1. Symptoms of acute myocardial infarction

2. New signs of ischemia on ECG

3. The occurrence of pathological Q waves

4. New wall motion abnormality or loss of viable myocardium, as evident on imaging

5. Coronary thrombus identification on angiography