Image Diagnosis: aVR, the Forgotten Lead

Tweet

Perm J 2015 Winter; 19(1):e101-e102 [Full Citation]

https://doi.org/10.7812/TPP/14-099

The 12-lead electrocardiogram has been referred to as an "11-lead study" on the basis of the false assumption that lead aVR yields only limited information. As this area is already covered by other leads (I, aVL, V5, V6), aVR was only used to confirm correct arm lead placement and was assumed to reflect only reciprocal changes from the lateral portion of the heart. As a result, the unpaired lead aVR has been largely ignored and has been coined the "forgotten lead."¹ In reality, aVR is an informative lead that also reflects the right ventricular outflow tract and the basal portion of the interventricular septum. Analysis of aVR's individual waveforms should be performed in concert with all other leads because it can provide critical information in the management of a number of medical conditions.

The ST segment in lead aVR is used in the assessment of narrow complex tachyarrhythmia. Ho et al² reported the presence of ST elevation in aVR has a 71% sensitivity and a 70% specificity of distinguishing atrial ventricular reciprocating tachycardia (such as Wolff-Parkinson-White) from atrial ventricular nodal reentrant tachycardia. In addition, aVR morphology can also be used to distinguish wide complex supraventricular tachycardia from ventricular tachycardia. For example, in 2008 Vereckei et al³ reported a 98% sensitivity in differentiating wide complex supraventricular tachycardia from ventricular tachycardia based solely on the analysis of aVR morphology (Figure 1).

The presence of a prominent R wave in aVR is a critical finding in sodium channel blocker poisonings, such as with tricyclic antidepressants.⁴ Liebelt et al⁴ concluded that an R wave amplitude > 3.0 mm is more sensitive than QRS interval as a predictor of seizures and ventricular dysrhythmias (Figure 2).

Finally, aVR is a valuable lead in the management of acute coronary ischemia.  Although aVR ST-segment elevation may be an abnormal variant in supraventricular tachycardia, bundle branch blocks, left ventricular hypertrophy, or right ventricular hypertrophy, in the presence of other ischemic changes aVR ST-segment elevation is a sensitive indicator of left main, left anterior descending, or triple vessel disease.^5-9 Barrabés et al⁶ and Kosuge et al⁷ have reported aVR ST-segment elevation to be an independent risk factor for increased morbidity and mortality. Therefore, the presence of aVR ST-segment elevation, in conjunction with other ischemic changes, should be considered an ST-segment elevation myocardial infarction equivalent and warrants immediate interventional reperfusion^6,7,10 (Figure 3).

Disclosure Statement

The author(s) have no conflicts of interest to disclose.

References

   1.  George A, Arumugham PS, Figueredo VM. aVR—the forgotten lead. Exp Clin Cardiol 2010 Summer;15(2):e36-44.

   2.  Ho YL, Lin LY, Lin JL, Chen MF, Chen WJ, Lee YT. Usefulness of ST-segment elevation in lead aVR during tachycardia for determining the mechanism of narrow QRS complex tachycardia. Am J Cardiol 2003 Dec 15;92(12):1424-8. DOI: https://doi.org/10.1016/j.amjcard.2003.08.051.

   3.  Vereckei A, Duray G, Szénási G, Altemose GT, Miller JM. New algorithm using only lead aVR for differential diagnosis of wide QRS complex tachycardia. Heart Rhythm 2008 Jan;5(1):89-98. DOI: https://doi.org/10.1016/j.hrthm.2007.09.020.

   4.  Liebelt EL, Francis PD, Woolf AD. ECG lead aVR versus QRS interval in predicting seizures and arrhythmias in acute tricylcic antidepressant toxicity. Ann Emerg Med 1995 Aug;26(2):195-201. DOI: https://doi.org/10.1016/S0196-0644(95)70151-6.

   5.  Williamson K, Mattu A, Plautz CU, Binder A, Brady WJ. Electrocardiographic applications of lead aVR. Am J Emerg Med 2006 Nov;24(7):864-74. DOI: https://doi.org/10.1016/j.ajem.2006.05.013.

   6.  Barrabés JA, Figueras J, Moure C, Cortadellas J, Soler-Soler J. Prognostic value of lead AVR in patients with a first non-ST-segment elevation acute myocardial infarction. Circulation 2003 Aug 19;108(7):814-9. DOI: https://doi.org/10.1161/01.CIR.0000084553.92734.83.

   7.  Kosuge M, Minura K, Ishikawa T. Combined prognostic utility of ST segment in lead aVR and troponin T on admission in non-ST-segment elevation acute coronary syndromes. Am J Cardiol 2006 Feb 1;97(3):334-9. DOI: https://doi.org/10.1016/j.amjcard.2005.08.049.

   8.  Hennings JR, Fesmire FM. A new electrocardiographic criteria for emergent reperfusion therapy. Am J Emerg Med 2012 Jun;30(6):994-1000. DOI: https://doi.org/10.1016/j.ajem.2011.04.025.

   9.  Aygul N, Ozdemir K, Tokac M, et al. Value of lead aVR in predicting acute occlusion of proximal left anterior descending coronary artery and in-hospital outcome in ST-elevation myocardial infarction: an electrocardiographic predictor of poor prognosis. J Electrocardiol 2008 Jul-Aug;41(4):335-8. DOI: https://doi.org/10.1016/j.jelectrocard.2008.02.025.

  10.  Rokos IC, French WJ, Mattu A, et al. Appropriate cardiac cath lab activation: optimizing electrocardiogram interpretation and clinical decision-making for acute ST-elevation myocardial infarction. Am Heart J 2010 Dec;160(6):995-1003. DOI: https://doi.org/10.1016/j.ahj.2010.08.011.