Pacing for neurally-mediated syncope: How to decide?

Neurally-mediated syncope has a broad clinical spectrum which ranges from typical vasovagal syncope on one hand, to those situations in which reflex syncope occurs with uncertain, or even apparently absent, triggers or prodromes, on the other hand. Overlap of clinical features is frequent in clinical practice and makes any classification difficult to apply when selecting patients for cardiac pacing. Typically, the reflex is both hypotensive and cardio-inhibitory. The rationale for efficacy of cardiac pacing is that the cardio-inhibitory reflex is dominant, since there is no role for pacing in preventing vasodilatation and hypotension. Establishing a relationship between symptoms and cardio-inhibitory reflex should be the goal of the clinical evaluation before embarking on permanent pacing. Similar efficacy has been observed in patients affected by dominant cardio-inhibitory reflex irrespective of the clinical form. In general, cardiac pacing should be considered last choice applied only in highly selected patients, i.e. those ≥ 40 years of age, affected by severe forms of reflex syncope with recurrences associated with frequent injury, often due to the lack of prodromes. Recurrence of syncope may still occur despite cardiac pacing in a minority of patients

Management of transient loss of consciousness in emergency department: what’s new from 2018 European Society of Cardiology guidelines?

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A very prolonged asystolic vasovagal syncope is suspended but not aborted by counterpressure manoeuvre

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Additional diagnostic value of implantable loop recorder in patients with initial diagnosis of real or apparent transient loss of consciousness of uncertain origin

Aims Non-syncopal transient loss of consciousness (T-LOC) encompasses disorders that sometimes resemble syncope, and the differential diagnosis with true syncope may be challenging. The implantable loop recorder (ILR) is potentially useful, but has never been systematically assessed. The aim of the study is to evaluate the diagnostic value of ILR in distinguishing syncope from non-syncopal forms of T-LOC. Methods and results We implanted an ILR in 58 patients (mean age 71 ± 17 years, 25 males) who had had 4.6 ± 2.3 episodes of real or apparent T-LOC, in order to distinguishing epilepsy from syncope (#28), unexplained fall from syncope (#29), or functional pseudo-syncope from syncope (#1). During 20 ± 13 months of follow-up, 33 patients (57%) had a spontaneous event documented by ILR. A diagnosis of syncope was established by ILR documentation of an arrhythmia in 15 (26%) patients: an asystole of 6 s (IQR 4–10 s) duration was documented at the time of the spontaneous event in seven patients with initial suspicion of epilepsy and in five patients with unexplained fall; atrial tachyarrhythmia was documented at the time of the spontaneous event in 1 and 1 patient, respectively, and ventricular tachycardia in 1 patient with unexplained fall. Conversely, in another 18 patients, ILR monitoring documented no significant rhythm abnormalities at the time of T-LOC recurrence, thus excluding an arrhythmic syncope. Finally, ILR was unable to document any syncopal episode in 25 (43%) patients. Among the 15 patients with an established diagnosis of arrhythmic syncope, syncope recurred during follow-up in 2 of 11 patients who were on pacemaker therapy and in 3 of 4 patients who were on other therapies. Conclusion Implantable loop recorder monitoring provides additional diagnostic value in 'difficult' patients with an initial diagnosis of non-syncopal real or apparent T-LOC

The Higgs mass as a function of the compactification scale

We calculate to a few percent precision the Higgs potential in a model with supersymmetry broken by boundary conditions on an extra-dimension, compactified to a segment of length $L$, and a top quark quasi-localized on one of the two boundaries. 1/L alone, in the range 2-4 TeV, determines the Higgs mass, in the range 110-125 GeV, and the spectrum of gauginos, higgsinos and of the third-generation squarks. Lower values of 1/L cannot be excluded, with a progressive delocalization of the top quark.Comment: 22 pages, 6 figure

An abnormal neural reflex plays a role in causing syncope in sinus bradycardia

AbstractObjectives. This study Investigates the rote of an abnormal neural reflex in causing syncope in patients with sinus bradycardia.Background. Syncope is commonly considered an indication of severity in sinus bradycardia. However, the occurrence of syncope is unpredictable, and the prognosis appears to be similar in patients with and without syncope.Methods. Head-up tilt testing (60 ° for 60 min), carotid sinus massage in the supine and standing positions, 24-h Bolter ambulatory electrocardiographic (ECG) recording and etectrophysiologic study before and after pharmacologic autonomic blockade were performed in 25 patients with sinus bradycardia and syncope (group I, sinus rate <50 beats/min, age 71 ± 12 years) and 25 patients with sinus bradycardia and no neurologic symptoms (group II, sinus rate <50 beats/min, age 67 ± 16 years).Results. Clinical characteristics and ambulatory ECG monitoring data were similar in the two study groups. A positive response (induction of syncope or presyncope with hypotension and/or bradycardia) was obtained by head-up tilt testing in 15 group I (60%) and in 3 group II (12%) patients (p < 0.001) and by carotid sinus massage in 11 group I (44%) and 6 group II (24%) patients (p = NS). Results of at least one test (head-up tilt testing or carotid sinus massage, or both) were positive in 19 group I (76%) and 9 group II (36%) patients (p < 0.01). Basal and intrinsic corrected sinus node recovery time did not differ significantly between the two groups. An abnormal intrinsic heart rate was present in 66% of group I and 26% of group II patients (p < 0.01). The different percentage of positive findings on head-up tilt testing and carotid sinus massage in the two groups was independent of the presence of intrinsic sinus node dysfunction.Conclusions. These results indicate that an abnormal neural reflex plays a role in causing syncope in patients with sinus bradycardia. This reflex seems to be unrelated to the severity of sinus node dysfunction, even if the latter could enhance the cardioinhibitory response

Benefit of dual-chamber pacing with Closed Loop Stimulation in tilt-induced cardio-inhibitory reflex syncope (BIOSync trial): study protocol for a randomized controlled trial

Ritme cardíac; Síncope reflex neurològic; Prova de la taula d’inclinacióRitmo cardíaco; Síncope reflejo neuromediado; Prueba de la mesa inclinadaCardiac pacing; Neuro-mediated reflex syncope; Tilt-Table testBackground: The efficacy of dual-chamber cardiac pacing in neuro-mediated reflex syncope with a cardio-inhibitory response to the Tilt-Table test (TT) has not been definitively assessed so far. The lack of reproducibility of results from previous studies may be partially explained by discrepancies in subject selection and some weaknesses in design and methods. The European Society of Cardiology (ESC) has set a class IIb indication to pacemaker implantation in this population recommending further research. Methods/design: The BIOSync study is a multicenter, patient- and outcome-assessor-blind, randomized, parallel-arm, placebo-controlled trial with the objective of assessing the clinical benefit of cardiac pacing in patients with frequently recurrent reflex syncope, suspected (but not proven) to be triggered by asystolic pauses as showing a VASIS 2B response to the TT (>3-s pause regardless of blood pressure drop). The primary and secondary endpoints are time to first post-implantation recurrence of syncope or the combination of pre-syncope or syncope, respectively. One hundred and twenty-eight consenting patients will be 1:1 randomized to dual-chamber cardiac pacing 'on' or 'off' after pacemaker implantation, and followed up until the first adjudicated primary endpoint event for a maximum of 2 years. The so-called Closed Loop Stimulation function on top of dual-chamber pacing is the pacing mode selected in the study active arm. Participating patients are asked to self-report syncopal symptoms at least every 3 months with self-administered questionnaires addressed to an independent Adjudication Committee. Patients and members of the Adjudicating Committee are blinded to randomization. The study is designed to detect a 40% relative reduction in the 2-year incidence of syncopal recurrences with 80% statistical power. Discussion: The BIOSync study is designed to definitively assess the benefit of pacing against placebo in reflex syncope patients with a cardio-inhibitory response to the TT. The study will also provide important information on the efficiency of the TT in appropriately selecting reflex syncope patients for cardiac pacing.All study-related costs are being directly supported by the sponsor of the study (BIOTRONIK SE & Co. KG, Berlin, Germany). No further funding is provided

Cardiac Pacing in Cardioinhibitory Reflex Syncope: Clinical Use of Closed-loop Stimulation

Cardiac pacing has been studied extensively in patients with reflex syncope over the past two decades. The heterogeneity of the forms and clinical manifestations of reflex syncope explain the controversial results of older randomised clinical trials. New evidence from recent trials has changed medical practice, now leading to clear indications for pacing in patients with asystolic syncope documented during carotid sinus massage, implantable cardiac monitoring or tilt testing. Given that recent trials in reflex syncope have been performed using the closed-loop stimulation algorithm, the authors will briefly discuss this pacing mode, review hypotheses about the mechanisms underlying its activation during syncope and provide practical instructions for programming and troubleshooting