Permanent cardiac pacing as primary therapy for neurocardiogenic (reflex) syncope

Closed-looped stimulation cardiac pacing for recurrent vasovagal syncope: A systematic review and meta-analysis

BACKGROUND

Vasovagal syncope (VVS) is defined by transient loss of consciousness with spontaneous rapid recovery. Recently, a closed-loop stimulation pacing system (CLS) has shown superior effectiveness to conventional pacing in refractory VVS. However, systematic review and meta-analysis has not been performed. We assessed the impact of CLS implantation and reduction in recurrent VVS events by a systematic review and a meta-analysis.

METHODS

We comprehensively searched the databases of MEDLINE and EMBASE from inception to September 2017. Included studies were published prospective or retrospective cohort, randomized controlled trial, and case-control studies that compared VVS events between recurrent, severe, or refractory cardioinhibitory VVS patient implanted with CLS and conventional pacing. Data from each study were combined using the random-effects, generic inverse variance method of DerSimonian and Laird to calculate odds ratios and 95% confidence intervals.

RESULTS

Six studies from November 2004 to October 2017 were included in this meta-analysis involving 224 recurrent, severe, or refractory cardioinhibitory VVS patients implanted with CLS and 163 recurrent, severe, or refractory VVS patients implanted with conventional pacing. CLS significantly reduced recurrent VVS events compared to conventional pacing (pooled odds ratio = 0.23, 95% confidence interval: 0.13-0.39, P = 0.000, I 2 = 36.5%) as well as subgroup of four randomized controlled trial studies (pooled odds ratio = 0.28, 95% confidence interval: 0.17-0.44, P = 0.000, I 2 = 39.2%).

CONCLUSION

Closed-loop stimulation significantly reduced recurrent VVS events up to 80% when compared to conventional pacing. Our study suggests that CLS is an effective tool for preventing syncope recurrences in patients with recurrent, severe, or refractory cardioinhibitory VVS.

Vasovagal syncope-role of closed loop stimulation pacing

The benefit of conventional pacing in vasovagal syncope remains controversial and is currently recommended for patients with recurrent syncope and documented asystole. In the last two decades, a growing body of evidence has emerged supporting the use of a new sensing technique called closed loop stimulation or CLS, to treat refractory vasovagal syncope. CLS uses a sensing algorithm that can detect variation in cardiac contractility and respond to drop in blood pressure by increasing the heart rate. Multiple observational and randomized studies have assessed its efficacy and showed its superiority to conventional pacing in reducing the burden of syncopal attacks in patients with cardio-inhibitory vasovagal syncope.

Renal nerve stimulation for treatment of neurocardiogenic syncope: a review from perspective of commercialization potential

A strong evidence of outcomes for vasovagal syncope is not easily identified. It would seem reasonable that the proposed Mayo Clinic technology would be reserved for cases with severe recurrent or refractory syncope. However, recurrence levels are relatively low, and while some predictive methods have been proposed, recurrence is also influenced by the interaction that occurs during screening and examinations, i.e. recurrence diminishes once an initial diagnosis has been made. Finally, a key factor in being able to identify suitable patients relates to understanding the relative significance of the vasodepression and cardioinhibitory components-the therapy is best suited to patients that have a significant level of both components. It is probably not needed in patients with mainly cardioinhibitory involvement-data from ISSUE 2 and ISSUE 3 studies suggest that this is a relatively large proportion, particularly with asystolic involvement. The challenge remains in having suitable screening tests to identify the best patients. Tilt table testing has questions concerning its ability to replicate clinical syncope-implantable loop recorders (ILRs) may provide more accurate data but their usage is not yet widely accepted given the costs and invasive nature of the monitor.

Does disgust increase parasympathetic activation in individuals with a history of fainting? A psychophysiological analysis of disgust stimuli with and without blood-injection-injury association

People with blood-injection-injury fear can faint when being confronted with blood, injections or injuries. Page (1994) holds that people with blood-injury phobia faint, because they are disgust sensitive and disgust facilitates fainting by eliciting parasympathetic activity. We tested the following two hypotheses: (1) Disgusting pictures elicit more disgust in blood-injection-injury-anxious people with a history of fainting than they do in controls. (2) Disgust causes parasympathetic activation. Subjects were 24 participants with high blood-injection-injury fear and a history of fainting in anxiety relevant situations and 24 subjects with average blood-injection-injury fear and no fainting history. We analyzed self-reported feelings of disgust, anxiety and faintness and reactions in heart rate, skin conductance, blood pressure and respiratory sinus arrhythmia during the confrontation with disgusting pictures with and without blood content. We did not find any evidence that the blood-injection-injury anxious subjects were more disgust sensitive than the control subjects and we also did not find any evidence that disgust elicits parasympathetic activation.

Blood-injury phobia with and without a history of fainting: disgust sensitivity does not explain the fainting response

OBJECTIVE

Individuals diagnosed with blood-injury phobia respond to venipuncture with strong psychophysiological responses. We investigated whether disgust sensitivity contributes to the fainting response and is associated with parasympathetic activation, as suggested by previous research.

METHODS

Twenty individuals diagnosed with blood-injury phobia (9 with a history of fainting to the sight of blood, 11 without such a fainting history) and 20 healthy controls were compared. Psychophysiological responses and self-report measures of anxiety, disgust, and embarrassment were monitored during rest, a paced breathing task, and venipuncture. In addition, trait disgust sensitivity and blood-injury fears were assessed.

RESULTS

Blood-injury phobics reported enhanced anxiety, disgust, and embarrassment during venipuncture. They also experienced heightened arousal, as indicated by heart rate, respiration rate, and minute ventilation. Blood-injury phobics without a fainting history tended toward higher anxiety and disgust scores. There was no evidence for increased parasympathetic activation in either blood-injury phobic subgroup or of an association of disgust and parasympathetic activation.

CONCLUSION

The tendency to faint when exposed to blood-injury stimuli may suffice as a conditioning event leading into phobia, without specific involvement of disgust sensitivity and parasympathetic activation.

Pathophysiology of syncope

Syncope or near-syncope is a not uncommon effect of gravitational or other stresses and it occurs when cerebral blood flow falls to below about half the normal value. It is not necessarily abnormal, and individuals who are usually asymptomatic show the same reaction if a stress is sufficiently great to result in hypotension. Blood pressure is regulated mainly by baroreceptor reflexes by their control of vascular resistance and heart rate. The ability to vasoconstrict powerfully is important in resisting syncope; heart rate responses are of much less physiological significance. The intriguing unanswered question is what suddenly changes vasoconstriction and tachycardia to vasodilatation and bradycardia. It is now known not to be due to stimulation of cardiac receptors and some cerebral signal is more probable. People are more likely to faint when upright, motionless, warm, following meals, dehydrated or emotionally stressed, and these factors may be involved in some reflex syncopes including micturition and defaecation syncopes. Plasma volume is of considerable importance and increasing this by interventions such as salt loading, exercise training, and even sleeping with the bed head raised can often be of clinical benefit.