Preliminary observations on the use of closed-loop cardiac pacing in patients with refractory neurocardiogenic syncope
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In many patients with recurrent neurocardiogenic syncope (NCS), a significant fall in blood pressure precedes any appreciable decline in heart rate. Closed-loop pacing (CLS) employs a sensing system that measures myocardial contractility, thereby providing a potential way to detect the onset of NCS at a much earlier point in time than that provided by standard pacing systems.
Patients were included in the study if they suffered from recurrent NCS and met all of the following criteria: (1) They had suffered at least two syncopal episodes in the preceding 6 months. (2) Patients were refractory to (or intolerant of) all conventional, non-pharmacological, or pharmacological treatments. (3) They had evidence of asystole (>10 s) or severe bradycardia (heart rate <30 bpm) on implantable loop recorder or during head-up tilt test (HUTT).
Thirty five patients meeting the above criterion received 44 devices. Twelve patients received a standard unit (with rate drop or rate hysterisis response) and 32 patients received a CLS unit (Cylos, Biotronik). The pacemaker implantation was termed successful if there was no recurrence of syncope, if the syncope burden decreased by ≥50%, if only presyncope occurred, or if the syncope occurred but with significant warning symptoms. Thirty-five patients, 29 females and six males, age 41 ± 11, with refractory NCS underwent pacemaker implantation. Mean follow-up was 9 ± 3 months. Out of 32 patients who received CLS, nine had a conventional pacemaker implanted in the past. Recurrence (59% vs 83%), reduction in syncope burden and pacemaker success (84% vs 25%, P = 0.002), and occurrence prodrome/warning signs (40% vs 16%) were much better in the closed-loop group.
These preliminary observations suggest that dual-chamber CLS pacing may be promising therapy for refractory NCS. Further randomized trials will be needed to better determine the role of this therapy in refractory NCS.
KeywordsClosed-loop pacing Neurocardiogenic Syncope Pacemaker
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