Anterior MI

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

• 

  A typical example of an acute anterior wall infarction.

• 

  Acute MI with proximal LAD occlusion

• 

  Large acute MI with LAD occlusion

• 

  Acute MI with LAD occlusion

• 

  A 2 weeks old anterior infarction with Q waves in V2-V4 and persisting ST elevation, a sign of formation of a cardiac aneurysm.

• 

  cute MI with LAD occlusion

• 

  A 2 days old anterior infarction with Q waves in V1-V4 with persisting ST elevation, a sign of formation of a cardiac aneurysm.

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 |
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 |
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. DOI:10.1016/s0735-1097(99)00197-7 |