2:1 & Advanced 2o AV Block

Report:

Sinus tachycardia 125/min

Left atrial abnormality (LAA)

Second degree AV block, 2:1 & advanced

First degree AV block (PR 0.28”) in conducted beats

VEB (ventricular escape beat)

Left anterior hemiblock

Right bundle branch block, atypical

Left ventricular hypertrophy with ST/T changes

Comment:

The broad S wave in V1 makes one consider superimposition of a P-terminal force of a P wave, but this is not the case: the real P waves are in their expected positions. The complex looks bizarre in all the right precordial leads, suggesting more than a pure conduction system disease. This is confirmed by the ST/T changes in Lead 1 and aVL, or V4-5.

A 2o AV block is advanced if there is less than 50% conduction of the supraventricular impulses occurring at a reasonable rate. This patient’s rate is reasonable (defined as what one thinks is reasonable!) but, even here, a slower rate may result in 1:1 conduction. There is only one instance of advanced block here, with two consecutive blocked P waves. There may have been more, but the escape beat prevents the potential conduction ratio from being revealed. We are not to know whether the P wave following the two nonconducted ones would have been conducted, were it not for the VEB.

I am not sure whether 2:1 block should be called advanced. Marriott opposes this69 and this is good enough for me. There is certainly nothing wrong calling the 2:1 block what it actually is: 2:1 block!

The QRS has lost its septal r and terminal S wave in lead 1 and looks like LBBB rather than RBBB: it’s on the way to becoming standard masquerading BBB when aVL loses its q wave too.