What is the significance of upright vs inverted T waves on an electrocardiogram (EKG)?

Significance of T Wave Direction on ECG

The direction of T waves on an electrocardiogram (ECG) has significant clinical implications, with inverted T waves often indicating abnormal cardiac repolarization that may represent underlying pathology requiring further evaluation.

Normal T Wave Patterns

• In adults 20+ years, normal T waves are 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 1
• T wave amplitude is normally most positive in lead V2 or V3, with upper normal thresholds of 1.0-1.4 mV in men and 0.7-1.0 mV in women 1
• The T wave corresponds to the phase of rapid ventricular repolarization (phase 3) of the ventricular action potential 1
• Normal repolarization proceeds from epicardium to endocardium, opposite to the direction of ventricular depolarization 1

Inverted T Wave Significance

• T wave inversions can be quantitatively described as:

  • Inverted: T-wave amplitude from -0.1 to -0.5 mV
  • Deep negative: T-wave amplitude from -0.5 to -1.0 mV
  • Giant negative: T-wave amplitude less than -1.0 mV 1

• T wave negativity in lateral chest leads V5 and V6 is clinically particularly important and concerning 1, 2

• Inverted T waves produced by myocardial ischemia are classically narrow and symmetric, often described as "coronary T waves" or "coved T waves" 3

• Ischemic T-wave inversion typically shows an isoelectric ST segment that is usually bowed upward (concave) followed by a sharp symmetric downstroke 3

Clinical Significance of Abnormal T Waves

• Inverted T waves may indicate:

  • Myocardial ischemia or infarction 3, 4
  • Pulmonary embolism (especially in precordial leads) 5
  • Left ventricular hypertrophy 3
  • Acute myocarditis 3
  • Wolff-Parkinson-White syndrome 3
  • Cerebrovascular accident 3, 4
  • Bundle branch block 3
  • Later stages of pericarditis 3
  • Cardiomyopathy 2

• Deep T wave inversion in V2-V4 may indicate severe stenosis of the proximal left anterior descending coronary artery 2

• T wave inversion with elevated troponin but no chest pain may represent myocarditis 2

U Wave Considerations

• The U wave is a low-amplitude, low-frequency deflection that occurs after the T wave, most evident in leads V2 and V3 6
• Normal U wave amplitude is approximately 0.33 mV or 11% of the T wave 6
• An inverted U wave in leads V2 through V5 is abnormal and may appear during acute ischemia or hypertension 6
• Increased U-wave amplitude may occur with hypokalemia or cardioactive drugs with quinidine-like effects 6

Diagnostic Approach to T Wave Abnormalities

• Assess for concerning patterns: T wave inversions in lateral or inferior leads are more concerning than anterior leads 2
• Evaluate depth of T wave inversions: deeper inversions generally indicate more severe pathology 2
• Check for associated ECG findings such as QT prolongation 2
• Consider cardiac biomarkers to rule out acute myocardial injury 2
• Echocardiography should be performed to exclude structural heart disease 2

Common Pitfalls in Interpretation

• Misinterpreting normal variant T wave inversions as pathological (especially in athletes or young adults) 2
• Failure to recognize that isolated T-wave abnormalities can be difficult to interpret and may lead to inappropriate diagnoses of myocardial ischemia and infarction 1
• Overlooking that T-wave abnormalities may be the initial manifestation of underlying cardiomyopathy, even before detectable structural changes appear on cardiac imaging 2
• Not recognizing that T-wave changes can be caused by non-cardiac pathology such as cerebrovascular events 4