A study presented at the annual scientific sessions of the American College of Cardiology (ACC) (24–27 March, Chicago, USA) shows that active pacemaker therapy can reduce episodes of syncope in selected patients with neurally mediated syncope.
Lead investigator Michele Brignole, head of cardiology, Arrhythmologic Centre, Ospedali Tigullio, Lavagna, Genoa, presented the results of ISSUE 3 (International Study on Syncope of Uncertain Etiology 3) at the ACC conference. He explained that prior to the study, 511 patients who had a clinical history of neurally mediated syncope, who were aged ≥40 years and had had more than three episodes of syncope in the past two years received an implantable loop recorder (Reveal DX/XT, Medtronic) and were followed-up for two years. Of these patients, 89 were subsequently found to have syncope recurrence with asystole of 12±10s (72) or non-syncopal asystole of 10±6s (17). Seventy-seven patients (after 12 patients refused randomisation) then randomised to receive a pacemaker programmed on (38) or a pacemaker programmed off (39).
After 24 months, 25% of the patients in the “on” group had syncopal recurrence compared with 57% of patients in the “off” group (p=0.039). Procedure-related complications included right atrium lead dislodgement (two patients), right ventricular lead dislodgement (two patients), and subclavian vein thrombosis (one patient).
Brignole concluded that dual-chamber pacing was effective at reducing recurrence of syncope in patients aged ≥40 years with severe asystolic neurally mediated syncope. He added that the overall strategy of using an implantable loop recorder to determine the indication for pacing probably contributed to the study’s positive findings and explained the contrast with previous studies that have not shown pacing to be beneficial in patients with unselected neurally mediated syncope. Brignole said: “We estimate that approximately 40% of ISSUE-3-like patients receiving an implantable loop recorder will eventually be candidates for pacemaker therapy within four years.” However, he added: “The fact that pacing is effective does not mean that it is also always necessary. Cardiac pacing should be a last choice in highly selected patients affected by severe neurally mediated syncope.”