Triple Hæmodynamic Handicap

Report:

Upper strip:

Dual pacemaker rhythm 89/min 1

Ventricular pacing, no atrial capture 1

1:1 retrograde (ventriculo-atrial) conduction 1

SVEB, blocked 3

Atrial capture by the atrial lead following the SVEB 1

Lower strip:

Dual pacemaker rhythm 89/min

Atrial pacing, possibly ventricular fusion beats 1

Loss of atrial capture in the penultimate cycle 1

Resumed ventricular pacing with retrograde conduction in the last cycle 1

Comment:

The upper strip is associated with significantly lower blood pressure (and, most likely, cardiac output as well) because (i) the paced ventricular complexes are broad, implying poorly synchronised contraction; (ii) they are followed by retrograde P waves, making the atria contract against closed AV valves and (iii) there is no atrial transport where expected, after the atrial spike.

The challenge here is not so much to be able to list the above mechanisms, but to account for the seemingly spontaneous changes in the pacing mode. Once seen, it is easy: the blocked SVEB in the upper strip prevents retrograde conduction and this in turn allows the atria to be captured. In the lower strip, this favourable state of affairs is overturned by the failure of the atrial lead to capture in the second last cycle: the broad QRS and the retrograde P wave reappear at once.