aVR: la derivada olvidada

aVR lead is a frequently forgotten derivative when interpreting an electrocardiogram. This may be largely explained by the fact that it does not provide specific information on the left ventricle. However, it is very useful in terms of both, diagnosis and prognosis, of different clinical entities such as acute coronary syndrome, pericarditis, aortic dissection, tricyclic antidepressants intoxication, arrhythmias and multiple cardiac conduction disorders. The main purpose of this article is to highlight the clinical importance of aVR lead and thus encourage its use in clinical practice.