CONTENTS
ECG features of anterior OMI
key features of anterior OMI
- 🔑 Hyperacute T-waves (bulky, +/- terminal QRS distortion).
- 🔑 STE in anterior leads, especially if:
- STE >5 mm.
- Convex, coved STE.
- 🔑 Q-waves and/or loss of R-wave voltage (Q in V1 can be normal, but it shouldn't extend further).
- 🔑 Reciprocal changes may occur with anteroseptal or high lateral MI (involving inferior leads and/or V5-V6).
(1) hyperacute T-waves
- Hyperacute T-waves occur initially (often preceding ST elevation).
- Terminal QRS distortion in V2-V3 may occur (it results from the development of broad, malignant T-waves that invade the QRS complex).
(2) STE in anterior leads (+/- aVL)
- Anterior STE:
- The most frequent lead with STE is V2.
- STE >5 mm often favors the diagnosis of OMI.
- Convex, coved ST segments favor ischemia. However, about half of anterior OMI may have upwardly concave ST segments in V2-V5. (16798159)
- STE in aVL may be seen, and this supports the diagnosis.
(3) reciprocal changes may occur
- Reciprocal inferior ST depression/flattening:
- Anterior OMI often doesn't have reciprocal STD, so this may be absent. (29304992)
- If present, STD anywhere other than aVR or V1 favors OMI.
- These can be subtle (e.g., flattening of the ST segment in inferior leads).
- Reciprocal TWI in Lead III (mirroring hyperacute T-waves in aVL). 🌊
- Reciprocal STD in V5-V6 may occur in proximal LAD occlusion.
(4) voltage loss in precordial leads
- Loss of normal R-wave progression:
- R-wave amplitude which increases and then decreases (e.g., RV4 > RV3) may suggest MI, especially if this is new.
- Loss of R-wave amplitude compared to prior ECG.
- Q-waves may emerge rapidly:
- It can appear in about half of patients within the first hour!
- Q-waves are not a contraindication to cardiac catheterization. (7897120)
differential diagnosis: mimics of anterior OMI
proximal LAD
- Proximal to first septal perforator (“anteroseptal MI”):
- New RBBB (often with qR in V1).
- STE in V1 > 2.5 mm.
- STE in aVR.
- STD in V5.
- Proximal to first diagonal artery (“anterolateral MI”):
- STE in aVL.
- STD in inferior leads >1 mm.
mid LAD (distal to main septal perforators)
- No STE in aVR.
- Usually no/slight STE in V1.
- STE in ~V2-V6 or V3-V6.
distal LAD occlusion
- STD in aVR.
- STE in lateral precordial leads.
- Inferior leads: frequently no reciprocal STD.
high lateral MI (usually 1st diag off the LAD)
- STE in V2 (but no other precordial leads), aVL, and Lead I.
- Discussed further in the chapter on lateral MI here: 📖
wraparound LAD (anterior & inferior MI)
- STE with positive T-waves seen in III
- This is a much-feared mimic pericarditis (diffuse STE without reciprocal STD).
- Differential diagnosis: Causes of diffuse STE with STD in aVR. 📖
left main coronary occlusion
- Summation of:
- Proximal LAD occlusion (causing STE in V2-V6, I, aVL)
- LCX occlusion (posterolateral OMI with STE in aVL, STD in V1-V4)
- Result:
- STE is seen in precordial leads (but may not be dramatic due to cancellation).
- Dramatic STE in aVL (summation of LAD and LCX ischemia). 🌊
- Anterior MI may cause Mobitz II or a 3rd-degree block.
- This will generally cause cardiogenic shock and require emergent transvenous pacing.
- The initial episode of AV block may be transient and then recur later. Consider placement of a pacemaker even if the heart block subsides.
Shark fin patterns are generated by combining a wide-complex QRS plus dramatic ST elevation with hyperacute T waves. The net result is a bizarre ECG that resembles a shark's fin in some leads (this is similar to the more classic “tombstone” appearance of occlusive MI, but the bundle branch block creates a more gradual upslope). Diagnosis is challenging because it can be nearly impossible to tell where the end of the QRS lies. (33353817)
Anterior shark fin: Often proximal anterior MI causing RBBB and LAHB
- (1) RBBB, as defined by:
- QRS >120 ms.
- V1 with RSR' or qR.
- Prolonged terminal S-wave in I and V6.
- (2) LAHB causing leftward axis (-30 to -90 degrees) of the first half of the QRS complex:
- qR in aVL.
- rS complexes in inferior leads.
- (3) Proximal LAD occlusion:
- STE in V1-V3, aVR, and aVL.
- STD may occur in inferior leads, V5-V6.
- This may be very difficult to recognize since the QRS complex blends directly into the ST segment, obscuring the J-point.
- Clinically, this is associated with a massive MI due to occlusion of the proximal LAD or left main coronary artery. Conduction system involvement often leads to third-degree heart block.
Inferior shark fin: Often inferior MI plus RBBB and left posterior hemiblock
- This seems to be less common than the anterior shark fin pattern.
- Anterior WMA may be observed on the short-axis view
- Apical WMA seen on long-axis or four-chamber view
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References
- 07960274 Sclarovsky S, Birnbaum Y, Solodky A, Zafrir N, Wurzel M, Rechavia E. Isolated mid-anterior myocardial infarction: a special electrocardiographic sub-type of acute myocardial infarction consisting of ST-elevation in non-consecutive leads and two different morphologic types of ST-depression. Int J Cardiol. 1994;46(1):37-47. doi:10.1016/0167-5273(94)90115-5 [PubMed]
- 7897120 Raitt MH, Maynard C, Wagner GS, Cerqueira MD, Selvester RH, Weaver WD. Appearance of abnormal Q waves early in the course of acute myocardial infarction: implications for efficacy of thrombolytic therapy. J Am Coll Cardiol. 1995 Apr;25(5):1084-8. doi: 10.1016/0735-1097(94)00514-q [PubMed]
