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Drug-refractory, rapid atrial fibrillation can be treated by atrioventricular junction (AVJ) catheter ablation with use of an existing or newly implanted pacemaker. This is proven to be a relatively safe method that potentially improves quality of life. Increased risk of sudden cardiac death related to ventricular fibrillation or polymorphic ventricular tachycardia (PMVT) has been described in the early period following ablation, especially in patients with structural heart disease.
Bradycardia dependent QT prolongation and ventricular fibrillation following catheter ablation with the atrioventricular junction with radiofrequency energy.
Malignant ventricular arrhythmias are reduced by increasing the basal pacing rate for several weeks after ablation and are supported by the current guidelines.
We report a case of nocturnal PMVT storm due to the sleep function feature in an implantable cardioverter-defibrillator (ICD) being inadvertently programmed on following AVJ ablation.
Case report
A 68-year-old male patient with a history of severe nonischemic cardiomyopathy (being evaluated for heart transplant), primary prevention biventricular ICD since 2018, permanent atrial fibrillation, hypertension, chronic obstructive pulmonary disease, chronic kidney disease, acute COVID-19 infection, and recent AVJ ablation 2 weeks prior to admission presented with ventricular tachycardia (VT) storm and 21 ICD shocks. No prior significant burden of VT or nonsustained VT were noted on prior device interrogations.
His medications at the time of presentation were allopurinol 300 mg daily, apixaban 5 mg twice daily, aspirin 81 mg daily, budesonide-formoterol 2 puffs twice daily, bumetanide 2 mg twice daily, carvedilol 12.5 mg twice daily, hydralazine 100 mg thrice daily, isosorbide dinitrate 40 mg thrice daily, and melatonin 5 mg nightly.
On examination, he was in no acute distress. Despite his active COVID-19 infection, lung fields were clear bilaterally. He had mild jugular vein distention and trace bilateral lower extremity edema. Admission labs were unremarkable aside from potassium being slightly low at 3.6 mmol/L.
A device interrogation showed normal function and programming (VVIR 90). He was started on intravenous amiodarone for arrhythmia suppression. However, the patient continued to experience PMVT overnight and intravenous lidocaine was added. During the daytime hours he was ectopy free, but the following night he again experienced PMVT with appropriate device therapy (Figure 1). Elective intubation was being considered to help avoid further events.
With further scrutiny, the VT appeared to be premature ventricular contraction and bradycardia initiated and exclusively occurring at night. The ICD was interrogated again and a sleep rate was noted to be programmed on at 50 beats per minute (bpm) starting at 10 PM every night. The device was reprogrammed with the sleep rate feature turned off. He was monitored over an additional 24 hours and no further VT was noted after these programming changes. Antiarrhythmic drips were subsequently discontinued and he was discharged home.
Discussion
PMVT following AVJ ablation has been well described. The current guidelines support an initial increased basal pacing rate for several weeks following this type of ablation to protect from PMVT and ventricular fibrillation. Programming the lower rate of the device between 90 and 100 bpm at the time of AVJ ablation and then gradually tapering over the following months is recommended.
In this case, although the basal pacing was programmed VVIR 90 following AVJ ablation, the sleep function was inadvertently left on at 50 bpm in the overnight hours. The sleep function operates by suspending the programmed lower rate and replaces it with a sleep rate that is lower than the device’s lower rate during a specified sleep period. This feature is intended to reduce pacing during sleep. However, in this case, it contributed to repetitive VT storm.
Conclusion
This case illustrates the real risk of bradycardia-dependent PMVT following AVJ ablation and highlights the importance of pacemaker programming and the adverse events that may arise from overlooking different pacing modes and features. With the myriad programming features and options in contemporary pacing devices, it is important to be vigilant in assessing adjunctive bradycardia features and to program sleep and hysteresis options off after AVJ ablation.
References
Peter R.H.
Wever E.F.
Hauer R.N.
Wittkampf F.H.
Robles de Medina E.O.
Bradycardia dependent QT prolongation and ventricular fibrillation following catheter ablation with the atrioventricular junction with radiofrequency energy.
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