A new diagnostic and treatment strategy provided an 80% reduction in the one-year recurrence rate and a 92% reduction of total burden of syncope in some forms of neurally-mediated syncope.
This strategy consisted of risk stratification based on simple initial evaluation, early application of an implantable electrocardiographic monitor (Implantable Loop Recorder – ILR), assessment of the exact mechanism of syncope by documenting a spontaneous episode and then prescribing mechanism-based specific therapy.
The previous strategy, in the absence of an electrocardiographic documentation of syncope, was principally guided by the results of tilt testing. Controlled trials of tilt-guided therapy, however, have often failed to show a benefit. In particular, the efficacy of pacemaker therapy was questioned after two recent controlled trials failed to prove superiority of cardiac pacing over placebo. This new research demonstrates that improved patient selection methods lead to significantly better therapy outcomes.
The International Study on Syncope of Uncertain Etiology 2 (ISSUE 2) was a multi-centre, prospective, observational study enrolling 442 patients from centres across Europe and in the US with a diagnosis of suspected neurally-mediated syncope (diagnosis made according to the criteria set by the Guidelines on Syncope of the European Society of Cardiology).
The ILR was placed subcutaneously under local anesthesia (Figure). High fidelity electrocardiographic recordings were captured through patient activation of the device or automatic activation using predefined arrhythmia triggers. The ILR carries an up-front cost of approximately €1.500. Previous studies showed that, when symptom-ECG correlation can be achieved in a substantial number of patients, analysis of the cost per symptom-ECG of the implanted device is more cost-effective than conventional diagnostic methods.
Four hundred and forty two patients with ?3 clinically severe syncopal episodes over two years with normal electrocardiograms and without significant electrocardiographic and cardiac abnormalities were included in the study. Patients with orthostatic hypotension and carotid sinus syncope were excluded. After ILR implantation, patients were followed until the first documented syncopal episode (Phase I). The mechanism of this episode was documented by ILR in 103 patients (mean time of 12±8 months) and guided subsequent therapy. Forty seven patients received a pacemaker because of asystole of a median 11.5 s duration, six patients had anti-tachyarrhythmia therapy (catheter ablation #4, implantable defibrillator #1, antiarrhythmic drug #1); the remaining 50 patients did not receive specific therapy. Following therapy, patients entered an observational period to determine syncope recurrence (Phase II). The table below summarizes recurrence results obtained in the two groups of patients.
The actuarial one-year recurrence rate in the subgroup of 47 patients who received pacemaker therapy was 5% (burden 0.05±0.15 episodes per patient/year), significantly lower than that observed in patients without asystole or bradycardia and of that observed in patients with asystole or bradycardia who did not receive a pacemaker.
The strategy was safe. Severe trauma secondary to syncopal relapse occurred in 2% and mild trauma in 4% of the patients. No patient died for syncope-related causes. In conclusion, this is the first study to demonstrate that a new strategy based on early application of ILR and therapy delayed after documentation of syncope allows a safe mechanism-based effective therapy
ISSUE 2 Steering Committee
Michele Brignole, MD (chairman), Italy
Richard Sutton, MD (co-chairman), UK
Carlo Menozzi, MD (co-chairman), Italy
Angel Moya, MD, Spain
Roberto Garcia-Civera, MD, Spain
David Benditt, MD, USA
Panos Vardas, MD, Greece
Wouter Wieling, MD, The Netherlands
Dietrich Andresen, MD, Germany
Roberta Migliorini, BSc, Italy
David Hollinworth, PhD, UK
European Heart Rhythm Association (EHRA) - formerly Working Group of Pacing of the European Society of Cardiology – a branch of the European Society of Cardiology.
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