What causes inverted T waves on an electrocardiogram (ECG)?

Causes of Inverted T Waves on ECG

Inverted T waves on an electrocardiogram (ECG) can be caused by multiple cardiac and non-cardiac conditions, with myocardial ischemia being the most clinically significant cause requiring urgent evaluation and intervention. 1

Normal Variants of T Wave Inversion

• In children older than 1 month, T wave inversion is often normal in leads V1, V2, and V3 2
• In adolescents (12+ years) and young adults (<20 years), T waves may be slightly inverted in aVF and inverted in lead V2 2
• In adults 20+ years, the normal T wave is inverted in aVR; may be upright or inverted in leads aVL, III, and V1; and should be upright in leads I, II, and chest leads V3-V6 2
• T wave inversion can be a normal variant in asymptomatic adults, particularly when limited to inferior leads 3, 4

Pathological Causes of T Wave Inversion

Cardiac Causes

• Myocardial Ischemia/Infarction: Classically produces narrow and symmetric T wave inversions, particularly when affecting the left anterior descending coronary artery 1, 5

  • Marked symmetrical precordial T wave inversion (≥2 mm) strongly suggests acute myocardial ischemia 1
  • T wave inversion in lateral leads (V5-V6) is clinically particularly important and concerning 2

• Cardiomyopathy: T wave inversion may be the only sign of inherited heart muscle disease even before structural changes can be detected 1, 4

• Pericarditis: Later stages can present with widely splayed T wave inversions 5

Non-Cardiac Causes

• Central Nervous System Events: Cerebrovascular accidents and subarachnoid hemorrhage can cause deep T wave inversions 1, 6

  • These T waves are typically widely splayed rather than the narrow symmetric inversions seen in ischemia 6

• Pulmonary Embolism: Can cause T wave inversions, particularly in precordial leads, even in moderate-sized emboli 7

• Medications: Tricyclic antidepressants and phenothiazines can cause deep T wave inversion 1

• Electrolyte Abnormalities: Can affect repolarization and cause T wave changes 2

Diagnostic Approach to T Wave Inversion

• T wave inversion ≥2 mm in two or more adjacent leads requires further investigation to exclude underlying cardiac pathology 1

• The location of T wave inversion provides important diagnostic clues:

  • Anterior and lateral T wave inversions are independently associated with increased risk of coronary heart disease 3
  • Lateral T wave inversions are associated with increased mortality risk 3
  • Inferior T wave inversions alone are generally benign 3

• Morphology of the inverted T wave helps differentiate causes:

  • Ischemic T wave inversions: narrow, symmetric with isoelectric ST segment that is usually bowed upward (concave) 5
  • Non-ischemic T wave inversions: often deeply inverted and widely splayed 5

Clinical Implications

• Patients with acute coronary syndrome and T wave inversion are at lower risk for death compared to those with ST-segment deviation, but higher risk than those with normal ECGs 1

• When T wave inversion extends into the upper part of the precordium, precordial ECG mapping demonstrates excellent detection of coronary artery disease (sensitivity 88%, specificity 93%) 4

• T wave alternans (T wave amplitude variations that alternate every second beat) indicates latent instability of repolarization and may predict malignant arrhythmias 2

Common Pitfalls

• Misinterpreting normal variant T wave inversions as pathological, particularly in young patients 2
• Failing to recognize that T wave inversion may be the only sign of serious cardiac pathology 1
• Not considering non-cardiac causes of T wave inversion, such as neurological events or pulmonary embolism 6, 7
• Overlooking the prognostic significance of T wave inversion location (anterior and lateral being more concerning than inferior) 3