Report:

AV sequential pacemaker rhythm 78/min 4

Atrial capture in alternate cycles 3

Sinus ? atrial bigeminy in alternate cycles 3

Comment:

Nobody would have looked hard at the atrial activity were the alternans not observed on the pressure display. Sustained pulsus alternans due to myocardial failure is rarely seen nowadays; atrial transport alternation, once looked for, was the obvious explanation. This was verified by abolishing ventricular component of the pacemaker for four cycles (below). The atrial trigeminy is perpetuated by pacemaker captures and sinus escapes32.

The above configuration does not preclude atrial contribution in all the cycles; it merely happens at different PR intervals and with different atrial activation sequence in alternate cycles. Alternans due to atrial electromechanical dissociation in alternate cycles has also been described33.

Fig 52a. Atrial activity exposed by turning off the ventricular lead (note the reduced spike amplitude just before switch-off).

Fig 53. 72 year old man with mitral annular calcification in the XR Department, unconscious following removal (by a surgeon) of the temporary pacemaker and some delay in connecting the permanent one.