How to diagnose ST-Elevation Myocardial Infarction (STEMI) on an electrocardiogram (ECG) in patients with Left Ventricular Hypertrophy (LVH)?

Diagnosing STEMI in Patients with Left Ventricular Hypertrophy

In patients with LVH, diagnose STEMI by applying a proportional ST elevation criterion: ST elevation ≥25% of the R-S wave amplitude in the same lead, particularly for anterior territory changes, rather than relying on absolute ST elevation thresholds alone. 1

The Core Problem

LVH creates baseline ST segment elevation (especially in V1-V3) and T wave inversions in lateral leads that mimic or obscure acute STEMI patterns. 2 The standard STEMI criteria (≥2 mm in V2-V3 for men ≥40 years, ≥1 mm in other leads) were explicitly defined for patients without LVH or LBBB, making direct application problematic. 3

Recommended Diagnostic Approach

Step 1: Recognize the Baseline LVH Pattern

• LVH typically shows ST elevation in V1-V3 with ST depression and T wave inversion in lateral leads (I, aVL, V5-V6) 2
• These changes are secondary repolarization abnormalities and may vary over time without representing acute ischemia 2
• Compare with prior ECGs whenever available—this is extremely valuable in LVH patients 3

Step 2: Apply the Proportional Criterion

For anterior territory ST elevation (V1-V4): Use ST elevation ≥25% of the total R-S wave amplitude in the same lead as your threshold for STEMI. 1 This criterion achieved a c-statistic of 0.82 with net reclassification improvement of 37% in identifying true culprit lesions. 1

Calculation example: If lead V2 shows an R wave of 20 mm and S wave of 20 mm (total R-S amplitude = 40 mm), then ST elevation ≥10 mm (25% of 40 mm) suggests acute STEMI rather than baseline LVH changes.

Step 3: Look for Additional Discriminating Features

Patients with true STEMI in the setting of LVH demonstrate:

• Greater magnitude of ST elevation (mean 3.0 mm vs 1.9 mm in false positives) 1
• More leads with ST elevation (mean 3.1 vs 2.0 leads) 1
• Concordant ST elevation (ST elevation in leads with positive QRS deflections) if LBBB is also present 3
• Dynamic ST changes on serial ECGs during ongoing symptoms 3

Step 4: Extend the ECG When Needed

• For suspected inferior/posterior MI: Record right-sided leads (V3R, V4R) and posterior leads (V7-V9) 3, 4
• ST elevation ≥0.5 mm in V7-V9 confirms posterior MI even when anterior leads show only ST depression 3, 4
• This is critical because LCx occlusions are frequently missed—standard STEMI criteria detect only 35% of LCx occlusions 5

Step 5: Integrate Clinical Context

• Prolonged chest pain (>20 minutes) not responding to nitroglycerin strongly supports acute MI regardless of ECG ambiguity 3
• Radiation to neck, jaw, or left arm increases likelihood 3
• Point-of-care troponin at 1-2 hours can help decide on emergency angiography when ECG is equivocal 3

Critical Pitfalls to Avoid

Do not dismiss patients with LVH and chest pain based on "expected" ST changes. Only 26% of patients with ECG-LVH presenting with chest pain actually have acute ischemia, but their short-term mortality (7.5%) approaches that of patients with primary ST-T abnormalities (10.6%). 6

Do not wait for biomarkers to initiate reperfusion. If clinical suspicion is high and proportional ST criteria are met, proceed directly to emergency angiography. 3

Recognize that physicians frequently misidentify LVH. In one study, only 22% of LVH cases were correctly identified, with secondary ST-T changes misread as primary ischemic changes in >70% of cases. 6 When uncertain, transthoracic echocardiography can identify focal wall motion abnormalities to guide triage. 3

When Guidelines Conflict

The 2012 ESC and 2013 ACCF/AHA guidelines both state that standard STEMI criteria apply only "in the absence of LVH or LBBB" but provide no specific thresholds for patients with LVH. 3 The proportional criterion (ST/R-S ratio ≥25%) fills this evidence gap with the strongest available data. 1

Algorithm Summary

1. Obtain 12-lead ECG within 10 minutes of presentation 3
2. Compare with prior ECG if available 3
3. Calculate ST/R-S ratio in leads with ST elevation (target ≥25% for anterior changes) 1
4. Record V7-V9 and right-sided leads if inferior/posterior MI suspected 3, 4
5. Obtain serial ECGs at 15-30 minute intervals if initial ECG non-diagnostic 3
6. If proportional criteria met + ongoing symptoms: Proceed to emergency angiography without waiting for biomarkers 3, 1
7. If ECG remains equivocal: Use point-of-care troponin and/or echocardiography to guide decision 3