PAT with Block: Pacemaker Lead

Report:

Atrial tachycardia 138/min

Second degree AV block, Möbitz 1; 2:1 & 3:2 block

Right atrial electrode recording (bottom strips)

Comment:

The question is a "trick" one, designed to implicate the spurious change in the heart rate in the patient's progressive hypotension. The tachycardia is in fact virtually unchanged throughout, as is the degree of AV block and the consequent ventricular rate. The relative size of the atrial and ventricular complexes is reversed in the atrial (pacemaker) lead.

The tachycardia shown is an autonomous one, not abolished by atrial pacing (the presence of AV block alone is usually sufficient evidence against a reentry mechanism). The atrial pacemaker was inserted for episodes of junctional bradycardia observed on admission. The patient was later given temporary AV sequential pacing (Fig 15a). It did not work as such during the PAT with block and later the patient did not need any pacing at all.

The real reason for “progressive hypotension” should be familiar to all those working in critical care areas: the patient was given extra sedation for the procedure! It should rarely be necessary, but…