Background/case: A 27-year-old female presented electively for a dual-chamber pacemaker generator replacement as her existing generator was approaching elective replacement indicator (ERI). Her past medical history included Kearns–Sayre syndrome. Her original system was implanted in 2011 (at another centre) for acquired third-degree atrio-ventricular (AV) block (Medtronic 5076 52 cm and 45 cm leads, St Jude Identity ADx DR 5386 generator). The device was interrogated at the start of the case (Table 1). There had been no concerns regarding lead integrity. The battery voltage was 2.68 V (ERI 2.5 V), impedance 12.2 kΩ, magnet rate 94.8 bpm (ERI 86.3 bpm). The procedure was performed under local anaesthetic. Blunt dissection and diathermy were used. Short bursts of diathermy did not result in pacing inhibition. Further diathermy was used over the generator to incise the pocket and the device was gently manually manipulated in the pocket. At this point, loss of capture occurred for 30 seconds; the patient became syncopal and had a seizure. The device was re-interrogated, which confirmed that both leads remained in a bipolar pace/sense configuration. No noise was seen on either lead and noise reversion (to unipolar pacing) had not occurred. Further manual manipulation of the pocket, generator and leads did not result in further loss of capture. The remainder of the procedure was performed without incident and there were no lasting sequelae for the patient.
Discussion: Loss of capture likely resulted from a fault common to several models of St Jude (now Abbott) generators (Affinity, Entity, Integrity, Identity, Sustain, Frontier, Victory, Zephyr) whereby use of diathermy (as well as PlasmaBlade™) can cause the pacemaker to temporarily reduce pacing output. This was highlighted in a St Jude advisory in 2014. It was noted that the duration of this effect depends on several factors including battery status, proximity of diathermy to the generator and diathermy output. Any temporary change in function can last for “30 seconds or longer” after diathermy has ceased. Additionally, placement of a magnet to asynchronously pace will not terminate this phenomenon.
Future considerations: Given the unpredictability of this behaviour and the routine use of diathermy/PlasmaBlade™ there is significant concern for future procedures, particularly for pacing-dependent patients. This generation of St Jude devices are likely to reach ERI soon, so this issue will become more common. Consideration needs to be given to how to avoid a repeat of this case. Options include, avoiding use of diathermy/PlasmaBlade™ until the generator has been explanted, placement of a temporary pacing wire, or use of isoprenaline, which can help unmask a latent escape rhythm.1 ❑
