Risks of inappropriate use of an algorithm favouring intrinsic conduction

An 80-year-old woman received a dual chamber pacemaker (Boston Scientific Accolade MRI DR) for pre-syncopal episodes associated with transient II-degree atrioventricular block type 1 and 2:1, recorded in 24-h Holter monitoring. Due to residual AV conduction with I-degree AV block, the pacemaker was set with the RYTHMIQ® algorithm, in order to reduce inappropriate ventricular pacing. A month later the patient started to complain of severe asthenia and bradycardia (46-48 bpm). Telemetrysupported pacemaker control revealed III-degree AV block with junctional escape rhythm, unmaskingmissed switch of RYTHMIQ® algorithm.