Cabrera sign is defined as the presence of a prominent, shelf-like or downward notching, of >0.04 second duration, at the ascending limb of the S wave.
Cabrera and Friedland in 1953 found that late notching of the up-slope of the S wave in leads V3–V5, is highly sensitive and specific for the diagnosis of old MI in LBBB. This electrocardiographic marker is a well-described sign of anteroseptal MI in the setting of LBBB and Wackers et al. estimated its sensitivity to 47% and a specificity to 87%. Hands et al. in 1989 determined the sensitivity and specificity of Cabrera’s sign to be 29% and 91% respectively. Furthermore, Barold et al. have reported that Cabrera’s sign, is the most useful single ECG criterion for the diagnosis of an old anterior, or anteroseptal MI during RV pacing with sensitivity 23–50% depending on the size of the MI, and specificity 97–100% if the notching is properly defined, findings, that are in accordance with many other studies.
- Specific Cabrera cariants:
- Small, narrow r wave deforming the terminal QRS
- Series of tiny notches giving a serrated appearance along the ascending S wave
- Series of late notches on QRS during epicardial pacing
- False Cabrera’s sign
- Slight notching of the ascending S wave in V leads is normal during RV apical pacing. It is usually confined to 1 lead, shows a sharp upward direction on the S wave and has a duration typically
- Ventricular fusion beats
- Early retrograde P waves deforming the late portion of the QRS complex masquerading as an intrinsic component of the QRS complex