Does T wave inversion in lead V4R (fourth right precordial lead) indicate right ventricular (RV) wall extension even if V3R (third right precordial lead) is not involved?

T-Wave Inversion in V4R Without V3R Involvement in Right Ventricular Infarction

T-wave inversion in V4R alone, without V3R involvement, does not reliably indicate right ventricular wall extension in the context of inferior myocardial infarction—ST-segment elevation in V4R is the validated diagnostic criterion, not T-wave inversion. 1

The Gold Standard for RV Involvement

The AHA/ACCF/HRS guidelines explicitly state that ST-segment elevation >0.05 mV in lead V4R (>0.1 mV in men <30 years old) provides the diagnostic criteria for right ventricular infarction in the setting of inferior wall MI. 1 This is the established marker, not T-wave inversion patterns.

• The guidelines recommend recording right-sided chest leads V3R and V4R in all patients presenting with ECG evidence of acute inferior wall ischemia/infarction (ST elevation >0.1 mV in leads II, III, and aVF). 1
• ST elevation in V4R is specifically associated with proximal right coronary artery occlusion causing right ventricular ischemia/infarction. 1
• Critically, ST elevation in right-sided leads persists for a much shorter period than inferior lead changes—these leads must be recorded rapidly after chest pain onset. 1

Why T-Wave Inversion Patterns Are Not the Diagnostic Criterion

T-wave inversions in right precordial leads have entirely different clinical significance:

• In the context of right ventricular pathology, T-wave inversion in V1-V3 (and extending to V4R) is characteristic of arrhythmogenic right ventricular cardiomyopathy (ARVC), not acute RV infarction. 1, 2
• T-wave inversion in V1-V3 has 47% sensitivity and 96% specificity for ARVC when evaluating ventricular tachycardia of RV origin. 2
• Deep negative T waves in right-sided precordial leads (V3R, V4R) are the most common ECG finding in chronic RV systolic dysfunction (90% prevalence), not acute RV infarction. 3

The Critical Distinction: Acute vs. Chronic RV Pathology

The pattern you're describing—T-wave inversion without ST elevation—suggests chronic RV pathology or post-ischemic changes, not acute RV wall extension:

• Post-ischemic T-wave changes occur after ST-segment elevation has resolved, representing a later phase of infarction evolution. 1
• In acute inferior MI with RV involvement, you should see ST elevation in V4R during the acute phase, which may later evolve to T-wave inversion as a chronic finding. 1
• The absence of V3R involvement while V4R shows changes is not a recognized pattern for acute RV extension—the guidelines emphasize ST elevation in V4R as the key finding. 1

Important Clinical Pitfall

Do not confuse chronic RV dysfunction patterns with acute RV infarction extension. 3 If you're evaluating for acute RV involvement in inferior MI:

• Look for ST elevation in V4R, not T-wave inversion. 1
• The presence of posterior wall involvement (ST depression in V1-V3 or ST elevation in V7-V9) can attenuate the sensitivity of ST elevation in V4R for detecting RV involvement (sensitivity drops from 96% to 34%). 4
• T-wave inversion in isolation, particularly if V3R is spared, more likely represents either a normal variant, chronic RV pathology, or post-infarction changes rather than acute RV extension. 3, 2

Practical Algorithm for Assessment

When evaluating suspected RV involvement in inferior MI:

• Obtain V3R and V4R leads immediately upon presentation with inferior ST elevation. 1
• Measure ST-segment elevation (not T-wave morphology) in V4R: ≥0.5 mm elevation indicates RV involvement. 1
• Check for posterior wall involvement (ST depression V1-V3 or obtain V7-V9) as this affects diagnostic accuracy. 4
• If only T-wave inversion is present without prior ST elevation, consider alternative diagnoses including ARVC, chronic RV dysfunction, or post-ischemic changes. 3, 2