Anterior MI

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This is part of: Myocardial Infarction

ECG-characteristics:[1]

  • ST-elevation in leads V1-V6, I and aVL. Maximum elevation in V3, maximal depression in III
  • later: pathological Q-wave in the precordial leads V2 to V4-V5.
Anterolateral infarct caused by occlusion of the LAD.
The Left Anterior Descending (LAD) coronary artery is the most important coronary artery. On this mercatorprojection of the heart, the grey area is supplied by blood by the LAD and is at risk if this artery occludes.

Anterior MI can involve the anterior part of the heart and a part of the ventricular septum. Is supplied by blood by the LAD. Can lead to a cardiac aneurysm if not treated timely.

Proximal or distal occlusion of the LAD can be differentiated when looking at the ST elevation V1-V3 [2]

Characteristics of proximal LAD occlusion
  • ST-segment elevation in V1 (>2.5 mm) or RBBB with a pathologic Q wave or both (sens 12%, spec 100%)
  • ST-segment depression (>1 mm) in II, III and aVF (sens 34%, spec 98%)
Characteristics of distal LAD occlusion
  • Little ST-segment depression (<= 1 mm) or elevation in II, III, and aVF (sens 66%, spec 73%)

Another way to look at this is by assessing the axis of the ST vector. If it points upwards (with ST depression in II, III, and AVF) the proximal LAD is occluded. If it points downwards (with little ST depression or even elevation in II, III, and AVF) the distal LAD is occluded. An ECG that does not show any ST depression sugggests an occlusion after the origin of the first diagonal branch.

A more precise determination of the location of the occlusion can be made with below table.

ECG criteria to determine site of LAD occlusion [3]
Criterion Occlusion site Sensitivity Specificity PPV NPV
RBBB Proximal to S1 14 100 100 62
ST elevation in V1 > 2.5mm Proximal to S1 12 100 100 61
ST elevation in AVR Proximal to S1 43 95 86 70
ST depression in V5 Proximal to S1 17 98 88 62
Q AVL Proximal to D1 44 85 67 69
ST depression in II > 1.0 mm Proximal to D1/S1 34 98 93 68
Q in V5 Distal to S1 24 93 71 53
ST depression in AVL Distal to D1 22 95 87 46
Absence of ST depression in III Distal to S1/D1 41 95 92 53


Examples

References

  1. Wung SF and Kahn DY. A quantitative evaluation of ST-segment changes on the 18-lead electrocardiogram during acute coronary occlusions. J Electrocardiol 2006 Jul; 39(3) 275-81. doi:10.1016/j.jelectrocard.2005.10.007 pmid:16777513. PubMed
  2. Zimetbaum PJ and Josephson ME. Use of the electrocardiogram in acute myocardial infarction. N Engl J Med 2003 Mar 6; 348(10) 933-40. doi:10.1056/NEJMra022700 pmid:12621138. PubMed
  3. Engelen DJ, Gorgels AP, Cheriex EC, De Muinck ED, Ophuis AJ, Dassen WR, Vainer J, van Ommen VG, and Wellens HJ. Value of the electrocardiogram in localizing the occlusion site in the left anterior descending coronary artery in acute anterior myocardial infarction. J Am Coll Cardiol 1999 Aug; 34(2) 389-95. pmid:10440150. PubMed