The benefit of closed loop stimulation in patients with cardioinhibitory vasovagal syncope confirmed by head-up tilt table testing: a systematic review and meta-analysis

Atomoxetine for suppression of vasovagal syncope

OBJECTIVE

Vasovagal syncope (VVS) is a common clinical condition with few effective medical therapies. The study aimed to evaluate the effectiveness of atomoxetine in suppressing syncope in patients with recurrent VVS.

METHODS

This was a retrospective, open-label, observational case series of 12 patients taking atomoxetine for suppression of recurrent vasovagal syncope. We compared syncope frequency in the 1 year before atomoxetine and while subjects were taking atomoxetine. We used novel applications of the Poisson distribution to describe the results as a collection of n = 1 studies.

RESULTS

There were 12 subjects, eight female, with a mean age 47 ± 22 years and a mean Calgary Syncope Symptom Score of 2 (diagnostic of vasovagal syncope). The patients received a mean dose of atomoxetine of 66 ± 16 mg (1.06 ± 0.21 mg/kg). The mean follow-up period was 1.21 ± 1.01 years. While taking atomoxetine, 11/12 patients appeared to improve and 7/12 had no syncope in follow-up (p = 0.0046). The annualized syncope frequency decreased from a median 5.5 (IQR 4, 6.75) syncope per year to 0 (IQR 0, 0.88) syncope per year (p = 0.002, Wilcoxon rank-sum test). According to the Poisson distribution, 7/12 subjects significantly improved with p values of < 0.0001 to 0.0235, 3/12 did not faint but had too brief follow-up times to detect significance, and 2/12 did not improve significantly.

CONCLUSIONS

In this case series, atomoxetine was a promising oral agent for the prevention of vasovagal syncope. The Poisson distribution permits individual patient-level assessment of improvement and detects insufficient follow-up despite apparent improvement.

Current approach to the treatment of vasovagal syncope in adults

Vasovagal syncope (VVS) is the most common cause of transient loss of consciousness. Although not associated with mortality, it causes injuries, reduces quality of life, and is associated with anxiety and depression. The European and North American cardiac societies recently published syncope clinical practice guidelines. Most patients with VVS do well after specialist evaluation, reassurance and education. Adequate hydration, increased salt intake when not contraindicated, and careful withdrawal of diuretics and specific hypotension-inducing drugs are a reasonable initial strategy. Physical counterpressure maneuvers might be helpful but can be of limited efficacy in older patients and those with short or no prodromes. Orthostatic training lacks long term efficacy and is troubled by non-compliance. Yoga might be helpful, although the biomedical mechanism is unknown. Almost a third of VVS patients continue to faint despite these conservative measures. Metoprolol was not helpful in a pivotal randomized clinical trial. Fludrocortisone and midodrine significantly reduce syncope recurrences with tolerable side effects, when titrated to target doses. Pacing therapy with specialized sensors appears promising in carefully selected population who have not responded conservative measures. Cardioneuroablation may be helpful but has not been studied in a formal clinical trial.

Permanent pacing for recurrent vasovagal syncope: New answers or just more questions?

Vasovagal syncope (VVS) is a clinical condition related to bradycardia (cardioinhibitory response) and/or hypotension (vasodepressor response), likely mediated by parasympathetic overactivity and sympathetic withdrawal. Although clinical presentation is usually related to a self-limited event, frequent episodes or events without prodrome might be debilitating. There are limited medical therapies proven effective in randomized clinical trials. In patients not responsive to standard therapy, permanent pacemaker therapy may be suggested. However, the role of cardiac pacing for the prevention of syncope recurrences remains controversial due to difficulties to exclude potential role of the vasodepressor component during the episode.

Pacing Therapies for Vasovagal Syncope

Vasovagal Syncope (VVS) is mediated by a cardiac autonomic reflex with resultant bradycardia and hypotension, precipitating syncope. While benign and mostly well controlled, recurrent VVS can be debilitating and warrants intervention. Non-pharmacological management of VVS have had variable success. In patients with recurrent cardioinhibitory VVS, permanent pacing can be effective. The utility of pacing to preempt the syncopal depends on the prominent temporal role of bradycardia during the vasovagal reflex. Current guidelines recommend pacing as a therapy to consider in older patients with recurrent VVS. Although younger patients can benefit, one should be cautious given the long-term risk of complications. Available data appears to favor a dual chamber pacemaker with closed loop stimulation algorithm to prevent recurrent cardioinhibitory VVS. Several aspects, including mechanistic understanding of VVS and appropriate patient selection, remain unclear, and require further study.

Novel Methods for Quantification of Vasodepression and Cardioinhibition During Tilt-Induced Vasovagal Syncope

Rationale:

Assessing the relative contributions of cardioinhibition and vasodepression to the blood pressure (BP) decrease in tilt-induced vasovagal syncope requires methods that reflect BP physiology accurately.

Objective:

To assess the relative contributions of cardioinhibition and vasodepression to tilt-induced vasovagal syncope using novel methods.

Methods and Results:

We studied the parameters determining BP, that is, stroke volume (SV), heart rate (HR), and total peripheral resistance (TPR), in 163 patients with tilt-induced vasovagal syncope documented by continuous ECG and video EEG monitoring. We defined the beginning of cardioinhibition as the start of an HR decrease (HR) before syncope and used logarithms of SV, HR, and TPR ratios to quantify the multiplicative relation BP=SV·HR·TPR. We defined 3 stages before syncope and 2 after it based on direction changes of these parameters. The earliest BP decrease occurred 9 minutes before syncope. Cardioinhibition was observed in 91% of patients at a median time of 58 seconds before syncope. At that time, SV had a strong negative effect on BP, TPR a lesser negative effect, while HR had increased (all P <0.001). At the onset of cardioinhibition, the median HR was at 98 bpm higher than baseline. Cardioinhibition thus initially only represented a reduction of the corrective HR increase but was nonetheless accompanied by an immediate acceleration of the ongoing BP decrease. At syncope, SV and HR contributed similarly to the BP decrease ( P <0.001), while TPR did not affect BP.

Conclusions:

The novel methods allowed the relative effects of SV, HR, and TPR on BP to be assessed separately, although all act together. The 2 major factors lowering BP in tilt-induced vasovagal syncope were reduced SV and cardioinhibition. We suggest that the term vasodepression in reflex syncope should not be limited to reduced arterial vasoconstriction, reflected in TPR, but should also encompass venous pooling, reflected in SV.

Pacing for Patients Suffering From Cardioinhibitory Vasovagal Syncope Using the Closed-Loop System

One in three vasovagal syncope (VVS) patients has syncopal recurrence after diagnosis, despite the standard recommendations for the avoidance of a recurrence, and one in five patients has more than one syncopal recurrence in the medium term. Given the high prevalence of VVS, there is a large population that continues to need effective treatment. There are numerous studies that use the implantable loop recorder (ILR) to document a cardioinhibitory response during VVS, with one study, ISSUE-3, demonstrating the efficacy of pacing using the rate-drop-response algorithm to trigger pacing and prevent syncopal recurrence in this population. There are more uncertainties in the studies that have used head-up tilt test (HUT) to select the population for pacing. We have recently performed the SPAIN randomized, controlled clinical trial using HUT to select the patients for pacing. The conclusion of the study was that, with the closed-loop system to introduce pacing, there was a significant reduction in the burden of syncope and a seven-fold increase in the time to first recurrence of syncope, which was greater than in the ISSUE-3 study. Since the completion of the SPAIN trial and its inclusion in the European guidelines, in our daily clinical practice, the use of this therapy is still recommended with caution in the context of the available literature, but it has increased our confidence in so doing. One in five patients with VVS needs treatment because of a high syncopal load. If an ILR is used to select the patients for pacing, the rate-drop-response algorithm can be recommended. In patients who have asystole on HUT, pacing with the closed-loop system has higher success and must now be considered as a tenable option for VVS patients.

Effective Pacing Intervention by Closed-loop Stimulation Using a Coronary Vein Lead in a Post-tricuspid Valve Replacement Patient

To avoid the negative effects associated with pacing, pacemakers are designed to achieve a pacing cadence as close to physiological pacing as possible. In closed-loop stimulation (CLS; a type of rate-responsive functionality used in pacemakers), the changes in impedance (which correlates with the contractility of the myocardium around the lead tip electrode) are tracked, and the paced heart rate is adjusted accordingly. We herein report a case in which we implanted a pacemaker in a post-tricuspid valve replacement patient. A ventricular lead positioned in the coronary vein exhibited good CLS functionality, and the patient's dizziness and heart failure improved.

Hemodynamic Response to the Head-Up Tilt Test in Patients With Syncope as a Predictor of the Test Outcome: A Meta-Analysis Approach

Aim: The paper presents a meta-analysis of studies comparing hemodynamic parameters: heart rate (HR), systolic blood pressure (sBP), diastolic blood pressure (dBP), and stroke volume (SV) measured during head-up tilt table test (HUTT) in patients with positive and negative HUT test outcome. Methods: Pubmed and Clinical Key databases were searched for English-only articles presenting results of biosignals measurements during tilt test in patients suffering from syncope. From 3,289 articles 13 articles published between 1997 and 2015 investigating 892 patients (467 with positive HUTT outcome and 401 with negative one) were selected. Results: There were not statistically significant differences observed between the parameters measured in supine position in patients with positive and negative test outcome [HR (p = 0.86), sBP (p = 0.32), dBP (p = 0.21), SV (p = 0.71)]. In tilt position the parameters HR and SV were significantly different when compared between the two groups of patients [HR (p = 0.02), sBP (p = 0.10), dBP (p = 0.59), SV (p = 0.0004)]. Conclusions: Changes in HR and SV parameters in response to tilt test turned out to be statistically significant. In supine position the differences between patients with positive and negative test outcome were not significant, hence tilt test can be considered as necessary in the diagnosis of vasovagal syndrome.