When is the aVR (augmented voltage right) lead positive?

When is aVR Lead Positive?

The aVR lead is typically positive during right ventricular involvement in myocardial infarction, specifically when there is proximal occlusion of the right coronary artery, causing the spatial vector of the ST-segment shift to be directed to the right, anteriorly, and inferiorly. 1

Normal aVR Lead Characteristics

Under normal conditions, the aVR lead is generally negative in all its components (P, QRS, T) because:

• aVR is an augmented unipolar lead that faces the right superior surface of the heart
• It has a unique perspective, looking from the right shoulder toward the apex of the heart
• Most cardiac electrical forces move away from this lead during normal depolarization and repolarization 2

Pathological Conditions Where aVR Becomes Positive

1. Myocardial Infarction Patterns

• Proximal Right Coronary Artery Occlusion:

  • ST elevation in aVR occurs with right ventricular involvement
  • Often accompanied by ST elevation in V1 and right-sided chest leads (V3R, V4R) 1, 3
  • The spatial vector of ST-segment shift is directed rightward, anteriorly, and inferiorly

• Left Main Coronary Artery Disease:

  • ST elevation in aVR greater than in V1 with concurrent ST depression in other leads
  • Represents extensive subendocardial ischemia 4, 2

2. Electrical Axis Abnormalities

• Extreme Right Axis Deviation:

  • Causes the QRS complex to become positive in aVR
  • May occur in severe right ventricular hypertrophy or right bundle branch block

• Dextrocardia:

  • P wave becomes upright in aVR due to reversed cardiac position 2

3. Right Ventricular Strain/Hypertrophy

• In patients with right ventricular loading (e.g., pulmonary hypertension, mitral stenosis):
  • Increased amplitude of R wave in aVR
  • R/Q ratio in aVR exceeds 1 5
  • Correlates with findings in right thoracic leads

4. Ectopic Rhythms

• Right Atrial Ectopic Rhythm:
  • Positive P wave in aVR is an important sign 5
  • Indicates abnormal atrial activation sequence

Clinical Significance of Positive aVR

Diagnostic Value

• Coronary Artery Localization:

  • ST elevation in aVR has high specificity (96%) for proximal LAD occlusion in anterior STEMI 4
  • Absence of ST elevation in aVR has high negative predictive value for left main stenosis in NSTEMI

• Anterior Wall Old MI:

  • Positive T wave in aVR correlates with:
    • Severely reduced cardiac function
    • Left anterior descending artery wrapping around the apex
    • Lower left ventricular ejection fraction 6

Prognostic Implications

• Positive T wave in aVR in anterior wall old MI is associated with:

  • Higher pulmonary arterial pressures
  • Higher left ventricular end-diastolic pressures
  • Lower cardiac index 6

• In acute pulmonary embolism, ST elevation in aVR indicates poor prognosis 2

Clinical Applications

The American Heart Association and American College of Cardiology recommend:

• Recording right-sided chest leads (V3R, V4R) when ST elevation occurs in leads II, III, and aVF to assess for right ventricular involvement 1, 3

• Using inverted aVR (–aVR) as an alternative presentation that aligns with the general axis of the left ventricle, positioned between leads I and II 1

• Considering the Cabrera sequence for frontal plane lead display, which incorporates inverted aVR in an anatomically logical sequence 1

Common Pitfalls

• Overlooking aVR: Historically neglected despite its diagnostic value 7, 2

• Misinterpreting ST elevation: ST elevation in aVR must be interpreted in context with other leads to distinguish between:

  • Right ventricular infarction
  • Left main disease
  • Other conditions like pericarditis or tricyclic antidepressant toxicity 2

• Isolated interpretation: The diagnostic value of aVR increases only when analyzed synchronically with other leads, especially precordial leads 5