What does T wave inversion in inferior leads indicate?

T Wave Inversion in Inferior Leads: Clinical Significance

T wave inversion in the inferior leads (II, III, aVF) may indicate unstable angina/NSTEMI, particularly when the inversions are marked (≥2 mm deep) and symmetric, though nonspecific inversions (≤2 mm) are less diagnostically helpful and require clinical correlation. 1

Primary Diagnostic Considerations

Acute Coronary Syndrome

• Marked T wave inversions (≥2 mm or ≥0.2 mV) in inferior leads suggest acute myocardial ischemia, particularly involving the right coronary artery (RCA) or left circumflex artery (LCx). 1
• These inversions carry prognostic significance: patients with isolated T wave inversion have lower mortality risk compared to those with ST-segment deviation, but higher risk than those with normal ECGs. 1
• T wave inversions in inferior leads may represent an early warning sign of impending myocardial infarction (termed "inferior Wellens sign"), particularly when associated with critical stenosis of the RCA or LCx. 2

Nonspecific Changes

• T wave inversions ≤2 mm (≤0.2 mV) are considered nonspecific and are less diagnostically helpful for acute ischemia. 1
• Isolated Q waves in lead III may be normal, especially without accompanying repolarization abnormalities in other inferior leads. 1

Critical Clinical Context

When to Suspect Prior Infarction

• When T wave inversions accompany Q waves in the same inferior lead group, the likelihood of prior myocardial infarction increases significantly. 1
• Minor Q waves (0.02-0.03 seconds, ≥0.1 mV deep) become suggestive of prior infarction when accompanied by inverted T waves in the same leads. 1

Pseudo-Normalization Warning

• During acute chest pain, previously inverted T waves that become upright ("pseudo-normalization") may indicate acute myocardial ischemia and should prompt immediate evaluation. 1

Important Differential Diagnoses

Non-Ischemic Causes to Exclude

• Central nervous system events (particularly intracranial hemorrhage) can cause deep T wave inversions. 1
• Tricyclic antidepressants or phenothiazines may produce deep T wave inversions. 1
• Cardiac memory following resolution of bundle branch block or ventricular pacing can produce persistent T wave inversions that mimic ischemia. 3, 4
• Respiratory variation may cause T wave inversions in inferior leads that normalize with breath-holding, suggesting non-cardiac chest pain. 5
• Other considerations include pericarditis, myocarditis, pulmonary embolism, electrolyte abnormalities, and left ventricular hypertrophy. 1

Clinical Action Algorithm

Immediate Assessment

• Compare with prior ECGs when available—this significantly improves diagnostic accuracy. 1
• Assess the clinical context: presence of chest pain, timing of symptoms relative to ECG changes, and cardiovascular risk factors. 1
• Measure cardiac biomarkers serially to distinguish between unstable angina and NSTEMI. 1

Risk Stratification

• Marked symmetric T wave inversions (≥2 mm) in inferior leads warrant high suspicion for critical coronary stenosis, particularly if accompanied by symptoms. 1
• Consider coronary angiography for patients with marked inferior T wave inversions and clinical evidence of acute coronary syndrome. 1, 2

Common Pitfalls to Avoid

• Do not dismiss T wave inversions as benign without clinical correlation—even nonspecific changes can represent acute coronary syndrome in 1-6% of cases. 1
• Always obtain serial ECGs during symptomatic episodes, as transient changes strongly suggest acute ischemia. 1
• Be aware that confounding patterns (bundle branch block, paced rhythm, LV hypertrophy) carry the highest mortality risk and require careful evaluation. 1