What is the significance of an upright T wave in lead V1?

Significance of an Upright T Wave in Lead V1

Primary Clinical Significance

An upright T wave in lead V1 (≥0.15 mV) is most commonly associated with left circumflex coronary artery disease and serves as a marker for significant coronary artery disease, particularly when the rest of the ECG appears unremarkable. 1, 2

Diagnostic Implications

Association with Coronary Artery Disease

• Upright T wave in V1 increases the likelihood of significant coronary artery disease approximately 4-fold (OR 4.249,95% CI 1.594-11.328) in patients with otherwise unremarkable ECGs undergoing coronary angiography 2

• The prevalence of upright T wave in V1 correlates with disease severity:

  • 9% in patients without coronary artery disease 1
  • 20% in single-vessel disease 1
  • 27% in two-vessel disease 1
  • 35% in three-vessel disease 1

Specific Coronary Territory Involvement

• In single-vessel disease, upright T wave in V1 is most strongly associated with isolated left circumflex artery disease (p < 0.001), while being rare in isolated left anterior descending artery disease 1

• In two-vessel disease, upright T wave in V1 is more frequent when both the right coronary and left circumflex arteries are diseased (p < 0.005) 1

• Both left circumflex and left anterior descending coronary artery lesions occur more frequently in patients with upright T wave in V1 compared to those with inverted T wave 2

Context-Specific Interpretation

Posterior (Inferobasal) Myocardial Ischemia

• ST depression in leads V1-V3 with a positive terminal T wave (upright T wave) represents an ST elevation equivalent, suggesting posterior infarction, though this finding is non-specific 3

• This pattern indicates inferobasal myocardial ischemia and should prompt recording of posterior leads (V7-V9) at the fifth intercostal space 3

Acute Myocardial Infarction Detection

• In leads that normally have inverted T waves (III, aVR, V1), an upright T wave exceeding the 95th percentile provides useful diagnostic information for myocardial infarction 4

• Lead V1 specifically showed a positive likelihood ratio of 2.0 (95% CI 1.4-2.9) for myocardial infarction when T wave amplitude exceeded the 95th percentile 4

Normal Variants to Exclude

• A QS complex in lead V1 is normal, so the presence of an upright T wave must be interpreted in the context of the QRS morphology 3

• In right bundle branch block, ST-T abnormalities in leads V1-V3 are common and expected, making ischemia assessment difficult in these leads 3

Clinical Action Algorithm

When Upright T Wave in V1 is Identified:

1. Assess for posterior MI pattern: Look for ST depression in V1-V3 with the upright terminal T wave 3

   • If present with high clinical suspicion: Record posterior leads V7-V9 immediately 3
   • ST elevation ≥0.05 mV in V7-V9 confirms posterior MI 3

2. Evaluate for confounding conditions: Exclude right bundle branch block, right ventricular hypertrophy, or other QRS confounders 3

3. Risk stratification in stable patients:

   • Upright T wave in V1 with otherwise unremarkable ECG warrants consideration of stress testing or coronary angiography, particularly if left circumflex disease is suspected 1, 2
   • This finding has independent predictive value for significant coronary artery disease beyond traditional risk factors 2

Critical Pitfalls to Avoid

• Do not dismiss an upright T wave in V1 as a normal variant without considering the clinical context, especially in patients with chest pain or risk factors for coronary disease 5, 1, 2

• Failure to recognize the posterior MI pattern (ST depression V1-V3 with upright terminal T wave) can lead to missed ST-elevation equivalent requiring urgent revascularization 3

• In patients with prior myocardial infarction, upright T waves in lead aVR (not V1) independently predict cardiac death or heart failure hospitalization (HR 3.10), but this is a separate prognostic marker 6