This ECG demonstrates the classical pattern of left main coronary artery (LMCA) occlusion:
- Widespread horizontal ST depression, most prominent in leads I, II and V4-6
- ST elevation in aVR ≥ 1mm
- ST elevation in aVR ≥ V1
However, ST elevation in aVR is not entirely specific to LMCA occlusion. It may also be seen with:
- Proximal left anterior descending artery (LAD) occlusion
- Severe triple-vessel disease (3VD)
Mechanism of STE in aVR
- Lead aVR is electrically opposite to the left-sided leads I, II, aVL and V4-6; therefore ST depression in these leads will produce reciprocal ST elevation in aVR.
- Lead aVR also directly records electrical activity from the right upper portion of the heart, including the right ventricular outflow tract and the basal portion of the interventricular septum; infarction in this area could theoretically produce ST elevation in aVR.
ST elevation is aVR is thought to result from two possible mechanisms:
- Diffuse subendocardial ischaemia (producing reciprocal change in aVR)
- Transmural ischaemia / infarction of the basal interventricular septum (e.g. due to a proximal occlusion within the left coronary system)
NB. The basal septum is supplied by the first septal perforator artery (a very proximal branch of the LAD), so ischaemia/infarction of the basal septum would imply involvement of the proximal LAD or LMCA.
Predictive Value of STE in aVR
In the context of widespread ST depression + symptoms of myocardial ischaemia:
- STE in aVR ≥ 1mm indicates proximal LAD / LMCA occlusion or severe 3VD
- STE in aVR ≥ 1mm predicts the need for CABG
- STE in aVR ≥ V1 differentiates LMCA from proximal LAD occlusion
- Absence of ST elevation in aVR almost entirely excludes a significant LMCA lesion
In the context of anterior STEMI:
- STE in aVR ≥ 1mm is highly specific for LAD occlusion proximal to the first septal branch
In patients undergoing exercise stress testing:
- STE of ≥ 1mm in aVR during exercise stress testing predicts LMCA or ostial LAD stenosis
Magnitude of ST elevation in aVR is correlated with mortality in patients with acute coronary syndromes:
- STE in aVR ≥ 0.5mm was associated with a 4-fold increase in mortality
- STE in aVR ≥ 1mm was associated with a 6- to 7-fold increase in mortality
- STE in aVR ≥ 1.5mm has been associated with mortalities ranging from 20-75%
A Brief Review of the Literature
Over the past 18 years, multiple studies have examined the utility of ST elevation in aVR for predicting severe coronary artery disease (proximal LAD/LMCA/3VD) and mortality in patients with acute coronary syndromes and those undergoing exercise stress testing. Some of the important studies are summarised below…
- 113 patients with unstable angina, including 20 patients with LMCA stenosis and 24 patients with 3VD.
- Patients with LMCA or 3VD frequently demonstrated ST-segment depression in multiple leads (typically I, II and V4-V6) plus ST-segment elevation in lead aVR during attacks of angina.
- 100 patients with anterior STEMI.
- STE in aVR of any magnitude was 43% sensitive and 95% specific for LAD occlusion proximal to the first septal branch.
- 16 patients with acute LMCA occlusion, 46 patients with acute LAD occlusion and 24 patients with acute RCA occlusion.
- STE in aVR (≥ 0.5mm) occurred with a significantly higher incidence in the LMCA group (88%) than in the LAD (43%) or RCA (8%) groups.
- Magnitude of STE in aVR was significantly greater in the LMCA group (1.6 ± 1.3 mm) than the LAD group (0.4 ± 1.0 mm).
- In contrast, magnitude of STE in V1 was less in the LMCA group (0.0 ± 2.1 mm) than in the LAD group (1.4 ± 1.1 mm).
- STE in aVR ≥ V1 distinguished the LMCA group from the LAD group with 81% sensitivity, 80% specificity and 81% accuracy.
- 775 patients with first presentation of acute NSTEMI.
- Two-thirds of patients with STE in aVR ≥ 1 mm had either LMCA occlusion or severe 3VD.
- Degree of STE in aVR was an independent predictor of mortality: STE of ≥ 1 mm was associated with a six- to seven-fold increase in in-hospital mortality (odds ratio of death = 6.6).
- Magnitude of STE in aVR was also closely associated with rates of recurrent ischemic events and heart failure.
- STE in aVR predicted the need for CABG – coronary grafting was required in 22% of patients with aVR STE > 1mm compared to 5% of those without.
- 150 patients with acute coronary syndromes – 46 with LMCA obstruction, 104 with occlusion of a different vessel.
- STE in aVR was twice as common in patients with LMCA occlusion as those without (69.6% vs 34.6%).
- 310 patients with non-ST-elevation acute coronary syndromes.
- STE in aVR ≥ 0.5 mm was the strongest predictor of LMCA or 3VD (78% sensitivity, 86% specificity, 57% PPV and 95% NPV).
- STE in aVR was superior to the presence of ST depression in other leads for predicting LMCA/3VD.
- 950 patients with STEMI (any type).
- STE in aVR ≥ 0.5 mm predicted proximal LAD or LMCA occlusion (with 50% sensitivity, 91% specificity, 55% PPV, 89% NPV).
- STE in aVR ≥ 0.5 mm was also an independent predictor of mortality (in-hospital mortality was 19% in those with ≥ 0.5 mm STE in aVR compared to only 5% in those without).
- Patients with STE in aVR also had higher heart rates, lower systolic BPs, lower ejection fractions and worse Killip class at the time of admission.
- 15, 315 patients with STEMI enrolled in the HERO-2 trial (heparin vs bivalirudin for acute MI).
- STE ≥1.5 mm in aVR was associated with a two-fold increase in 30-day mortality for both inferior and anterior STEMI, compared to the baseline mortality rate of 10.8%.
- 454 patients undergoing both exercise stress testing (standard Bruce protocol) and cardiac catheterization within 6 months, including 75 patients with LMCA or ostial LAD stenosis.
- STE of ≥ 1mm in aVR during stress testing predicted LMCA or ostial LAD stenosis with sensitivity 75%, specificity 81% and overall accuracy 80%.
- 572 patients with acute NSTEMI.
- Degree of STE in aVR was the strongest independent predictor of severe LMCA occlusion / 3VD requiring CABG (odds ratio 29.1), followed by positive troponin T level (odds ratio 1.27).
- STE ≥ 1.0 mm in aVR identified severe LMCA occlusion /3VD with 80% sensitivity, 93% specificity, 56% PPV, and 98% NPV.
More ECG Examples
Example 2 – LMCA occlusion
Another typical example of LMCA occlusion:
- Widespread ST depression, most prominent in the lateral leads (V4-6, I, aVL)
- ST elevation > 1mm in aVR
- ST elevation in aVR ≥ V1
Example 3 – LMCA occlusion
The ECG shows:
- Marked ST elevation in aVR >> V1
- ST depression in mulitple leads (V2-6, I, II, aVL, aVF), to some extent masked by a non-specific interventricular conduction delay
This patient presented to our ED recently with severe ischaemic chest pain, vomiting, syncope (due to runs of VT) and cardiogenic shock. He was taken for emergent angiography and found to have a complete ostial occlusion of his left main coronary artery.
Example 4 – Proximal LAD occlusion
This ECG shows:
- ST elevation in aVR and V1 of similar magnitude.
- Widespread ST depression (V3-6, I, II, III, aVF)
This patient had a severe ostial LAD thrombus that was close to the left main.
(This ECG is reproduced from Dr Smith’s ECG Blog – click here to see the ECG in its original context)
Example 5 – Severe Multi-Vessel Disease
This ECG shows:
- ST elevation in aVR and V1, of similar magnitude
- ST depression in multiple leads (V5-6, I, II, aVL, aVF)
- Evidence of anteroseptal STEMI – ST elevation with Q wave formation in V1-3
It would be reasonable to suspect a proximal LAD occlusion based on this ECG. However, this patient actually had severe multi-vessel disease. Angiography demonstrated a chronic total occlusion of his circumflex artery, with critical stenoses of his proximal LAD, RCA and ramus intermedius. Surprisingly, in this case the culprit vessel was thought to be the RCA, which had been collateralising his chronically occluded circumflex.
Implications for therapy in acute coronary syndromes
Given the ability of STE in aVR to predict critical coronary lesions and death, this ECG pattern is increasingly being recognised as a “STEMI equivalent” that requires emergent reperfusion therapy to prevent cardiogenic shock and death.
- Clopidogrel treatment ≤ 7 days before CABG is associated with an increase in major bleeding, haemorrhage-related complications, and transfusion requirements.
- Prasugrel is associated with even more bleeding than clopidogrel.
- If urgent CABG (within 7 days) is likely, then there is an argument for omitting thienopyridines during the initial management of an acute coronary syndrome (or at least using clopidogrel instead of prasugrel).
In the recent study by Kosuge et al. (2011)
- STE in aVR ≥ 1 mm was a strong predictor of severe LMCA / 3VD requiring CABG.
- Conversely, patients with < 1mm ST elevation in aVR had a negligible risk of severe LMCA / 3VD requiring CABG.
Based on this data:
- Patients with < 1mm STE in aVR may safely receive clopidogrel/prasugrel during the initial treatment of their ACS as they are unlikely to proceed to urgent CABG.
- Patients with ≥ 1 mm STE in aVR may potentially require early CABG; therefore these patients should ideally be discussed with the interventional cardiologist (± cardiac surgeon) before thienopyridines are given.
More on LMCA occlusion
- ECG BASICS – Waves, Intervals, Segments and Clinical Interpretation
- ECG CLINICAL CASES – Your favourite ECG’s placed in clinical context with a challenging Q&A approach
- ECG and Cardiology Eponymous Syndromes – Cheats guide to eponymous emancipation
- ECG Reference Sites on the WEB – the best of the rest
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