Is a q wave formation with t wave inversion in lead aVL (augmented limb lead), trace upsloping ST elevation in inferior leads, and a prolonged QT segment in lead I indicative of a posterior-lateral myocardial infarction?

ECG Findings Suggestive of Lateral Wall Ischemia with Possible Inferior Involvement

The ECG pattern you describe—Q wave with T wave inversion in aVL, trace upsloping ST elevation in inferior leads, and prolonged QT in lead I—is most consistent with lateral wall ischemia/infarction, potentially with concomitant inferior involvement, rather than a classic posterior-lateral infarction. This patient requires urgent evaluation and coronary angiography given the high-risk ECG features.

Interpretation of Lead aVL Changes

• Q waves with T wave inversion in lead aVL indicate lateral wall myocardial infarction or ischemia 1.
• Lead aVL reflects the high lateral wall of the left ventricle, and abnormal Q waves in this lead (but not V6) actually indicate mid-anterior wall MI according to newer cardiac MRI correlation studies 1.
• Isolated T wave inversion in aVL alone can precede an inferior myocardial infarction and should raise concern even without other changes 2.

Inferior Lead ST Elevation Pattern

• When left circumflex (LCx) artery is occluded, the ST segment spatial vector is directed leftward, causing ST elevation that may be greater in lead II than lead III, and can show isoelectric or elevated ST segments in leads I and aVL 1.
• This pattern differs from right coronary artery (RCA) occlusion, where ST elevation is typically greater in lead III than lead II 1.
• The trace upsloping ST elevation you describe in inferior leads, combined with the aVL changes, suggests possible LCx involvement affecting both lateral and inferior territories.

Regarding True Posterior Infarction

• Classic posterior MI presents with ST depression in leads V1-V3 with tall R waves and upright T waves—not the pattern you describe 3, 2.
• The AHA/ACCF guidelines note that what was traditionally called "posterior" MI actually represents lateral wall involvement based on cardiac MRI studies 1.
• Posterior chest leads (V7-V9) should be obtained if LCx occlusion is suspected, as approximately 4% of acute MIs show ST elevation isolated to these posterior leads that are "hidden" from standard 12-lead ECG 1.

Critical High-Risk Pattern to Consider

• The prolonged QT segment you mention is concerning: deeply inverted T waves with QT prolongation in precordial leads (particularly V2-V4) indicate severe stenosis of the proximal left anterior descending artery and represent a pre-infarction state (Wellens syndrome) 1, 4.
• This pattern requires urgent intervention as 75% of untreated patients develop extensive anterior wall infarction within weeks 5, 4.
• Patients with this ECG pattern should be considered high-risk NSTE-ACS requiring urgent coronary angiography and revascularization 4.

Clinical Action Algorithm

1. Obtain posterior leads (V7-V9) immediately to assess for hidden ST elevation from LCx occlusion 1.

2. Perform serial ECGs at 15-30 minute intervals or continuous 12-lead monitoring, as dynamic changes are common and a single ECG provides only a snapshot 1, 4.

3. Initiate immediate management:

   • Aspirin 162-325 mg if no contraindications 4
   • ECG monitoring for arrhythmias 4
   • Nitroglycerin for symptom relief if present 4

4. Urgent cardiology consultation and coronary angiography within 120 minutes 4.

5. Check cardiac biomarkers (troponin), though ECG changes alone warrant urgent intervention in this high-risk pattern 1.

Important Pitfalls to Avoid

• Do not dismiss subtle ECG findings: misinterpretation occurs in 20-40% of missed myocardial infarctions 2.
• The 4:1 block you mention is a confounding pattern that places this patient at highest risk for death, even higher than those with ST-segment deviation alone 1.
• Do not wait for symptom recurrence—the presence of high-risk ECG features (Q waves in aVL, QT prolongation) mandates urgent evaluation even if currently asymptomatic 4, 5.
• Comparing to a prior ECG is valuable: an unchanged ECG reduces risk, but new changes significantly increase risk 1.

Vessel Localization

Based on your ECG description, the most likely culprit is the left circumflex artery 1, given:

• Lateral wall involvement (aVL changes)
• Inferior ST elevation with leftward vector orientation
• LCx occlusions frequently present with non-diagnostic standard 12-lead ECGs, requiring posterior leads for diagnosis 1