Anterior infarction

ECG 1A: Anteroseptal infarction with elevation in V1-V3; minimal elevation in aVR and aVL; reciprocal depression in V4-V6 and in the inferior leads; coronary angiography revealed an occlusion of the proximal LAD upstream of the first septal branch;

ECG 1B: 79-year-old man hospitalized for chest pain at H + 3; isolated ST-segment elevation in aVR; reciprocal depression in the inferior leads, lead I and from V2 to V5; coronary angiography showed a sub-occlusion of the left coronary trunk;

ECG 1C: 74-year-old man hospitalized for chest pain at H + 5; ST-segment elevation from V1 to V4 and in leads I, aVL; reciprocal depression in the inferior leads; necrosis Q-wave and poor R wave progression from V1 to V3; coronary angiography showed an occlusion of the LAD upstream of the first septal branch;

ECG 1D: 54-year-old man hospitalized for chest pain at H + 3; ST-segment elevation from V1 to V4, in leads I, aVL and aVR; reciprocal depression in the inferior leads and in V5-V6; taller elevation in aVL than in aVR; taller ST depression in lead III than in lead II; coronary angiography showed an occlusion of the LAD upstream of the first septal branch;

ECG 1E: 81-year-old man hospitalized for chest pain at H + 6; ST-segment elevation from V1 to V5 and in leads I, aVL; reciprocal depression in the inferior leads; necrosis Q-wave and poor R wave progression from V1 to V3; coronary angiography showed an occlusion of the LAD upstream of the first septal branch;

ECG 1F: 64-year-old patient, with no risk factors, hospitalized for chest pain; sinus rhythm, normal PR interval; discrete elevation in the upper lateral territory (leads I, aVL) with minimal mirror depression in leads III, aVR and V1; coronary angiography showed an occlusion of a first diagonal branch originating from the LAD;

ECG 1G: 67-year-old man, hypertensive, hospitalized for chest pain at H + 5; elevation from V2 to V5 of large amplitude from V2 to V4 with Q-wave in these leads; absence of reciprocal depression in the inferior leads; isoelectric ST-segment in leads I, aVL and aVR; the coronary angiography revealed an occlusion of the distal LAD (downstream of the first diagonal branch);

ECG 1H: 53-year-old man, hypertensive, smoker, overweight, hospitalized for chest pain at H + 8; elevation from V2 to V5 of large amplitude from V2 to V4 with long QT and biphasic T-waves (positive/negative); Q-waves in these leads; absence of reciprocal depression in the inferior leads; isoelectric ST-segment in leads I, aVL and aVR; coronary angiography revealed an occlusion of the distal LAD (downstream of the first diagonal branch);

Comments: Anterior infarctions include septal, apical and lateral infarctions in conjunction with an occlusion of the common trunk of the left coronary artery, of one of its branches (anterior interventricular or circumflex artery) or one of their divisions (septal, diagonal or marginal). The prognosis of an anterior infarction is more pejorative than that of an inferior infarction due to a larger infarcted area with increased mortality due to cardiac decompensation or ventricular arrhythmia.

The nomenclature is variable with different terms used to define the location of the infarction and a schematic division according to the leads presenting the elevation between septal (V1-V2), apical (V3-V4), inferolateral (V5-V6), upper lateral (leads I, aVL), extensive anterior (VI- V6), or extensive anterolateral (V1-V6, leads I, aVL) infarctions. There is, however, a weak correlation between the electrocardiographic estimation of the localization and the accurate determination by MRI or autopsy.

The severity and prognosis of the anterior infarction is dependent on the proximal or distal nature of the coronary occlusion and on the presence of a collateral network.

The proximal or distal localization of the LAD occlusion can be estimated from the analysis of the leads presenting the elevation by attempting to evaluate the presence of a thrombosis upstream or downstream of the first septal branch and of the first diagonal branch. The first septal branch supplies the basal portion of the interventricular septum, while the 2 conduction branches (leads aVR and V1) supply the first diagonal branch and the high lateral region (leads I, aVL). The electrical signs highly evocative of a proximal occlusion of the LAD are the presence of a ST-segment elevation in V1 > 2.5 mm, a right bundle branch block or a depression > 1 mm in the inferior leads. The electrical signs highly evocative of a distal occlusion of the LAD are the presence of a moderate depression in the inferior leads (< 1 mm) or even an elevation in these leads, the activation vector pointing downward.

• An occlusion of the common trunk of the left coronary artery usually results in the presence of a diffuse depression, an elevation > 1 mm in aVR and an elevation > 2.5 mm in V1; the elevation in aVR is a good sign of posterobasal ischemia and should lead, in an acute coronary syndrome, to performing an emergency coronary angiography (sign of severity);
• When a LAD occlusion occurs upstream of the first septal branch, there is a basal involvement of the anterior wall, of the lateral wall and of the interventricular septum; the electrocardiogram can show a ST-segment elevation from V1 to V4, in leads I and aVL and often in aVR with a reciprocal depression in the inferior leads and occasionally in V5; the elevation is generally taller in aVL than in aVR; the ST-segment depression is greater in lead III than in lead II; the presence of a right bundle branch block is common (sign of severity since attesting to an extensive impairment;
• When LAD occlusion occurs between the first septal branch and the first diagonal branch, the basal portion of the septum is spared (absence of elevation at V1); there is an elevation in leads I, aVL with inferior reciprocity (depression > 1 mm);
• When an occlusion occurs distant from the first diagonal branch, the basal portion is spared and the vector is oriented more downward; there is generally a lack of elevation in V1, aVR or aVL with little or no reciprocal depression in the inferior leads; presence of a ST-segment elevation from V3 to V6 (occasionally from V2 to V5);

Take-home message: The severity and prognosis of the anterior infarction is dependent on the proximal or distal nature of the coronary occlusion, which can be estimated from the surface electrocardiogram. The electrical pattern is dependent, however, on the anatomical characteristics of the patient and the presence of a collateral network.