Ventricular pacing failure

These tracings highlight a loss of permanent or intermittent ventricular capture in patients implanted with a dual-chamber pacemaker. Consequences vary according to the underlying rhythm of the patient. In the first pacemaker-dependent patient with complete atrioventricular block, an intermittent loss of capture (rise in threshold in a dialyzed patient) is associated with the occurrence of syncope and a high risk of sudden death. In the second patient with preserved atrioventricular conduction (implanted for sinus dysfunction), a permanent loss of capture does not cause symptoms. Finally, in the last patient with paroxysmal second-degree atrioventricular block, the loss of ventricular capture is associated with the occurrence of 1- to 2-second pauses due to blocked P wave and responsible for the described lipothymias.

In the presence of a rise in threshold, the question of whether to program the automatic adjustment of pacing output arises. It is therefore important to be completely familiar with the operation of this algorithm and in particular the maximum amplitude that can be delivered in this setting. Indeed, there is a delivered upper limit that does not correspond to the maximum capacities of the device so as to avoid a premature wear of the batteries in the event of algorithm dysfunction. The programming of the automatic amplitude adjustment is therefore not adjusted when the threshold is very high.