The correct answer is number 3. Initially, the pacemaker works in AAI mode with first-degree atrioventricular block (AVB) (asterisk) until a blocked atrial event occurs (star). Subsequently, a paced ventricular event is assured after loss of atrioventricular (AV) conduction (cross). Afterwards, an absent second ventricular event presents (star) with a switch to DDD mode and reduction of the paced AV delay to 220 ms (hash). This is all part of the managed ventricular pacing mode1 of the patient's pacemaker device (Medtronic Ensura) (Figure).
This is not a ventricular sensing failure, as the pacemaker is able to correctly sense appropriate ventricular events (answer 1, correct). Likewise, it is not programming of a variable 400 ms paced AV delay, as this cannot be programmed (answer 2, incorrect). Finally, the blocked atrial activity is not derived from progressively longer AV intervals, as would be required with Wenckebach AVB (answer 4, incorrect).
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