[False diagnosis of myocardial infarction due to inversion of the electrocardiographic leads in the right limbs (author's transl)]. / Infarto de miocardio: falso diagnóstico por inversión de los electrodos del electrocardiógrafo en las extremidades derechas.

An abnormal ECG suggested the diagnosis of myocardial infarction in a 65-year-old man who had suffered a transient chest pain. When the patient was admitted to the Hospital a new ECG and biochemical enzymes were normal, but and identical pathologic ECG was registered following inversion of the electrocardiographic leads in the right superior and inferior extremities. A prospective study of 160 adult patients has demonstrated that inversion of the leads in the right limbs frequently causes the appearance of pathologic Q waves (37.14 percent) and ischemic T waves (51.22 percent), especially in lead I and aVL. Number of pathologic Q and T waves may vary when they are present in the basal register, but we never observed their disappearance in all the precordial lead series. A constant finding was the marked low voltage of P, QRS and T in lead II due to the "distance" of the electrocardiographic leads right leg-left leg. Technical recognition may be difficult because P waves and QRS complex are frequently negative or isoelectric in aVR.