Cabrera's sign and the diagnosis of old MI in LBBB

In a recent blog we looked at the use of the Sgarbossa criteria in the diagnosis of acute myocardial infarction in the setting of pre-existing left bundle branch block.

In this blog we're going to take a look at another useful diagnostic clue: Cabrera's sign, which can be used in the diagnosis of an old myocardial infarction in LBBB.

Cabrera's sign refers to a notch that occurs within the first 40 msec in the ascending portion of the S wave in lead V3 or V4:

Cabrera's sign (arrowed)

This ECG sign was first described by Cabrera & Friedland in 1953.

Although Cabrera's sign has a high specificity for the diagnosis of an old myocardial infarction in LBBB, it has a poor sensitivity.

More details about the original paper by Cabrera and Friedland can be found here:

Cabrera E, Friedland C. La onda de activacion ventricular en el bloqueo de rama izquierda con infarto: un nuevo signo electrocardiografico. Arch Inst Cardiol Mex 1953; 23: 441–460.