Typical vasovagal syncope as a "defense mechanism" for the heart by contrasting sympathetic overactivity

Normal baseline cardiac autonomic function and increased pupillary parasympathetic tone in patients with vasovagal syncope

It is controversial whether people with vasovagal syncope (VVS) have abnormal autonomic responses at baseline and whether specific diagnostic manoeuvres have a diagnostic value. We investigated whether the pupillary light reflex and cardiac autonomic tests can be used to identify autonomic dysfunction in volunteers with a medical history of VVS. The study groups included 128 healthy volunteers, of whom 31 reported a history of typical VVS. The right pupil was evaluated using an automated, commercial infra-red pupillometer under strict conditions. In addition to miosis and mydriasis kinetics, pupil diameters were measured. Heart rate variability at rest and heart rate changes to standing were quantified with high-resolution electrocardiography and designated software. The demographic and clinical characteristics of both groups were statistically similar. Average constriction velocity (ACV) was significantly higher in VVS patients following a univariate analysis (3.83 ± 0.59 vs. 3.56 ± 0.73 mm/s, p = 0.042) and after correcting for potential confounders (p = 0.049). All other pupillometric and heart rate indices were comparable between groups. Patients with a history of VVS depict pupillary parasympathetic overactivity in response to light stimuli, manifested as increased ACV. The prognostic implications of this finding and the significance of using this simple clinical tool to identify patients who are at risk for developing frequent episodes of VVS or physical injuries following a syncope merits further study.

Prevalence and clinical predictors of vasodepressor syncope during head up tilt test

INTRODUCTION

The aim of our study was to evaluate the prevalence and clinical predictors of vasodepressor (VD) response during head-up tilt test (HUTT) in patients with history of syncope admitted to a tertiary referral syncope unit.

MATERIAL AND METHODS

We retrospectively evaluated all consecutive patients who underwent HUTT for suspected or established reflex syncope at our institution from March 1st, 2017, to June 1st, 2023. VD response was defined when syncope occurred during hypotension along with no or slight (< 10% bpm) decrease of heart rate. Univariate and multivariate analyses were performed to test the association of VD response to HUTT with a set of clinical covariates.

RESULTS

1780 patients (40 ± 19.9 years; 49.3% male) were included; among them, 1132 (63 %) showed a positive response to HUTT and 124 (7.0%) had a VD response. The prevalence of VD response showed a peak after 69 years (11.52% vs 6.18%; P = 0.0016), mainly driven by male patients (13.7% vs 4.9%; P < 0.0001). At multivariate analysis, age (OR: 1.15; P = 0.0026) was independently associated to HUTT-induced VD syncope; in contrast, smoking (OR: 0.33: P = 0.0009) and non-classical presentation of syncope (OR: 0.55; P = 0.0029) inversely correlated with VD syncope.

CONCLUSIONS

VD response represents the less frequent responses among those induced by HUTT, accounting up to 7% of overall responses. A gender and age-related distribution has been shown. Advanced age was the only independent predictor of VD syncope; conversely, smoking and non-classical presentation of syncope reduced the probability of VD response to HUTT.

Under-Recognized Life-Threatening Vasovagal Reflex During Chest Tube Insertion

Chest tube insertion is a common and relatively safe procedure in an emergency setting. However, a potentially fatal complication, vasovagal reflex, may be under-recognized due to its generally mild severity. We present a case of pulseless electrical activity (PEA) requiring chest compression due to vasovagal reflex during chest tube insertion for spontaneous pneumothorax. A 23-year-old male who had a history of spontaneous pneumothorax presented with left chest pain to our emergency department. Based on point-of-care ultrasonography and chest radiography, we made a diagnosis of recurrent pneumothorax. Although he had stable vital signs and received adequate pain control, during chest tube insertion, he developed severe sinus bradycardia with a six-second pause, leading to PEA requiring chest compressions. After a few compressions, his heart rate increased and he regained consciousness. He underwent video-assisted thoracoscopic surgery for pneumothorax and was discharged without complications. Vasovagal reflex during chest tube insertion in young patients with spontaneous pneumothorax may cause severe bradycardia and cardiac arrest. Physicians should be aware of this rare but potentially fatal complication and be prepared with appropriate measures, such as pre-administration of atropine, before chest tube insertion.

Asystole on loop recorder in patients with unexplained syncope and negative tilt testing: age distribution and clinical predictors

BACKGROUND

Approximately 50% of patients with unexplained syncope and negative head-up tilt test (HUTT) who have an electrocardiogram (ECG) documentation of spontaneous syncope during implantable loop recorder (ILR) show an asystolic pause at the time of the event.

OBJECTIVE

The aim of the study was to evaluate the age distribution and clinical predictors of asystolic syncope detected by ILR in patients with unexplained syncope and negative HUTT.

METHODS

This research employed a retrospective, single-center study of consecutive patients. The ILR-documented spontaneous syncope was classified according to the International Study on Syncope of Uncertain Etiology (ISSUE) classification.

RESULTS

Among 113 patients (54.0 ± 19.6 years; 46% male), 49 had an ECG-documented recurrence of syncope during the observation period and 28 of these later (24.8%, corresponding to 57.1% of the patients with a diagnostic event) had a diagnosis of asystolic syncope at ILR: type 1A was present in 24 (85.7%), type 1B in 1 (3.6%), and type 1C in 3 (10.7%) patients. The age distribution of asystolic syncope was bimodal, with a peak at age < 19 years and a second peak at the age of 60-79 years. At Cox multivariable analysis, syncope without prodromes (OR 3.7; p = 0.0008) and use of beta blockers (OR 3.2; p = 0.002) were independently associated to ILR-detected asystole.

CONCLUSIONS

In patients with unexplained syncope and negative HUTT, the age distribution of asystolic syncope detected by ILR is bimodal, suggesting a different mechanism responsible for asystole in both younger and older patients. The absence of prodromes and the use of beta blockers are independent predictors of ILR-detected asystole.

The Rate of Asystolic Reflex Syncope Is Not Influenced by Age

BACKGROUND

The head-up tilt test (HUT) and other evidence suggest that the vagal effect on the heart decreases with age.

OBJECTIVES

The main aim of the study was to assess whether this age effect also affects the rate of asystole in spontaneous reflex syncope (RS).

METHOD

We performed an analysis of pooled individual data from 4 studies that recruited patients ≥40 years of age affected by certain or suspected RS who received an implantable loop recorder (ILR) and reported follow-up data on syncope recurrence. We assessed the presence of asystolic syncope of >3 seconds or nonsyncopal asystole of >6 seconds recorded by ILR and compared the findings to tilt test results on the same patients.

RESULTS

A total of 1,046 patients received ILR because of unexplained syncope. Of these, 201 (19.2%) had a documentation of an asystolic event of 10-second (Q1-Q3: 6- to 15-second) duration. They were subdivided in 3 age tertiles: ≤60 years (n = 64), 61 to 72 years (n = 72), and ≥73 years (n = 65). The rate of asystolic events was similar in the 3 subgroups (50.1%, 50.1%, and 49.2%, respectively; P = 0.99). Conversely, the rate of asystolic syncope induced during HUT (performed in 169 of 201) was greatly age dependent (31.0%, 12.1%, and 11.1% in increasing age tertiles, respectively; P = 0.009).

CONCLUSIONS

The rate of the spontaneous asystolic form of RS documented by ILR is constant at any age >40 years. Conversely, the rate of asystolic syncope induced by HUT is higher in younger patients and decreases with age. The contrasting results between spontaneous and tilt-induced events cast doubt on the concept that asystole in RS is less common in older patients.

Left atrial function evaluation by 2D speckle-tracking echocardiography in patients with vasovagal syncope

OBJECTIVES

Evidence indicates left atrial (LA) involvement in vasovagal syncope (VVS). The LA regulates left ventricular filling during the cardiac cycle. We aimed to assess LA function in patients with VVS by 2D speckle-tracking echocardiography.

METHODS

Sixty-nine consecutive patients with VVS were recruited. Based on the head-up tilt test (HUTT) results, the study population was divided into two groups: HUTT+ (n = 45) and HUTT- (n = 24). Fifty-one consecutive subjects were enrolled as the control group. LA myocardial deformation parameters were measured by 2D speckle-tracking echocardiography to evaluate LA function.

RESULTS

Maximal, minimal, and pre-P LA volumes were lower in patients with VVS. Strain and strain rate during reservoir, conduit, and contraction phases in VVS patients with HUTT+ or HUTT- were not statistically significantly different from those in the control group. Additionally, the volumetric parameters of LA function showed no difference in statistical significance between the three study groups.

CONCLUSIONS

While LA phasic function was not different between the two groups of VVS patients with HUTT+ or HUTT- and the control group, LA size during the three LA phases was smaller in patients with VVS.

An ethologically based view into human fear

The quality of the defensive response to a threat depends on the elements that trigger the fear response. The current classification system of phobias does not account for this. Here, we analyze the fear-eliciting elements and discern the different types of fears that originate from them. We propose Pain, Disgust, Vasovagal response, Visual-vestibular and postural interactions, Movement and Speed, Distance and Size, Low and mid-level visual features, Smell, and Territory and social status. We subdivide phobias according to the fear-eliciting elements most frequently triggered by them and their impact on behavior. We discuss the implications of a clinical conceptualization of phobias in humans by reconsidering the current nosology. This conceptualization will facilitate finding etiological factors in defensive behavior expression, fine-tuning exposure techniques, and challenging preconceived notions of preparedness. This approach to phobias leads to surprising discoveries and shows how specific responses bear little relation to the interpretation we might later give to them. Dividing fears into their potentially fear-eliciting elements can also help in applying the research principles formulated by the Research Domain Criteria initiative.

Beyond fear: A longitudinal investigation of emotions and risk of a vasovagal reaction in first-time whole-blood donors

BACKGROUND

Fear is a recognized predictor of vasovagal reactions (VVRs) in blood donors. However, less is known about the role of other emotions, including positive emotions, that donors might experience. The aim of this study was to identify the emotions experienced in center that predict onsite VVRs, and to determine at what point during the donation appointment, the experience of these emotions is most influential.

STUDY DESIGN AND METHODS

A sample of 442 first-time whole-blood donors (57.7% female; mean ± SD age 30.7 ± 11.7 years) completed a survey in the waiting area and before venepuncture in the donation chair to assess their current emotional experience. The survey data were matched with routinely-collected demographic, donation, and donor adverse event information. A generalized estimating equations model was used to identify emotions associated with the occurrence of a VVR.

RESULTS

A total of 56 (12.7%) participants experienced a VVR. The occurrence of a VVR was significantly associated with lower love/closeness/trust (OR: 0.53, 95%CI: 0.34-0.82) and higher scared/fearful/afraid (OR: 1.96, 95%CI: 1.18-3.25) states. Significant interaction effects suggested that the effect of scared/fearful/afraid decreased while stressed/nervous/overwhelmed increased from the waiting area to before venepuncture on the likelihood of a VVR.

DISCUSSION

To effectively reduce donor VVR risk, blood collection agencies need to address a broader range of emotions at different points during the donation process.

The blood-brain barrier disruption after syncope: a dynamic contrast-enhanced magnetic resonance imaging study: A case report

RATIONALE

Using dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI), we demonstrated blood-brain barrier (BBB) disruption following syncope.

PATIENT CONCERNS

A 45-year-old man experienced syncope with a chief complaint of syncope (duration: 1 minutes), 1 day before visiting a university hospital for examination. He had no history of medical problems and was not taking any medications. This episode was the first in his lifetime.

DIAGNOSES

After syncope, the patient did not have any illnesses or symptoms, such as headache, cognitive deficits, or somnolence.

INTERVENTIONS

Cardiac evaluation did not reveal any abnormal findings. In addition, in conventional brain and chest computed tomography and brain MRI, no abnormal lesions were observed.

OUTCOMES

DCE-MRI of the patient showed bright blue colored lines within the sulci throughout the cerebral cortex. The regions of interest, including bright blue colored lines, had significantly higher Ktrans values (6.86 times higher) than those in healthy control participants. These findings are indicative of BBB disruption of the vessels in the sulci.

LESSONS

Using DCE-MRI, we demonstrated BBB disruption following syncope. DCE-MRI is a useful tool for the detection of BBB disruption following syncope.

The pathophysiology of vasovagal syncope: Novel insights

The pathophysiology of vasovagal syncope (VVS) is reviewed, focusing on hemodynamic aspects. Much more is known about orthostatic than about emotional VVS, probably because the former can be studied using a tilt table test (TTT). Recent advances made it possible to quantify the relative contributions of the three factors that control blood pressure: heart rate (HR), stroke volume (SV) and total peripheral resistance (TPR). Orthostatic VVS starts with venous pooling, reflected in a decrease of SV. This is followed by cardioinhibition (CI), which is a decrease of HR that accelerates the ongoing decrease of BP, making the start of CI a literal as well as fundamental turning point. The role of hormonal and other humoral factors, respiration and of psychological influences is reviewed in short, leading to the conclusion that a multidisciplinary approach to the study of the pathophysiology of VVS may yield new insights.

Underlying hemodynamic differences are associated with responses to tilt testing

Aim of this study was to explore whether differences in resting hemodynamic parameters may be associated with tilt test results in unexplained syncope. We analyzed age, gender, systolic (SBP), diastolic blood pressure (DBP) and heart rate (HR) by merging three large databases of patients considered likely to be of vasovagal reflex etiology, comparing patients who had tilt-induced reflex response with those who did not. Tilt-induced reflex response was defined as spontaneous symptom reproduction with characteristic hypotension and bradycardia. Relationship of demographics and baseline supine BP to tilt-test were assessed using logistic regression models. Individual records of 5236 patients (45% males; mean age: 60 ± 22 years; 32% prescribed antihypertensive therapy) were analyzed. Tilt-positive (n = 3129, 60%) vs tilt-negative patients had lower SBP (127.2 ± 17.9 vs 129.7 ± 18.0 mmHg, p < 0.001), DBP (76.2 ± 11.5 vs 77.7 ± 11.7 mmHg, p < 0.001) and HR (68.0 ± 11.5 vs 70.5 ± 12.5 bpm, p < 0.001). In multivariable analyses, tilt-test positivity was independently associated with younger age (Odds ratio (OR) per 10 years:1.04; 95% confidence interval (CI), 1.01–1.07, p = 0.014), SBP ≤ 128 mmHg (OR:1.27; 95%CI, 1.11–1.44, p < 0.001), HR ≤ 69 bpm (OR:1.32; 95%CI, 1.17–1.50, p < 0.001), and absence of hypertension (OR:1.58; 95%CI, 1.38–1.81, p < 0.001). In conclusion, among patients with suspected reflex syncope, younger age, lower blood pressure and lower heart rate are associated with positive tilt-test result.

Repolarization disparity as a predictor of response to Head up Tilt-table Test in pediatric syncope

BACKGROUND

Head up Tilt-table Test (HUTT) is a practical examination of the most common type of pediatrics syncope. The electrocardiographic (ECG) changes during this test, show the autonomic defects that cause neuraly-mediated syncope in response to tilting process.

METHODS

All pediatric syncope patients referred to our center in a 1-year period, were included in the study. HUTT was performed and patients were classified into two groups of Negative and Positive HUTT results, and the latter group was subclassified as three subgroups of "vasodepressor", "cardioinhibitory" and "mixed type" responses to HUTT. QT and corrected QT (QTc) dispersion was measured by the baseline standard 12-lead ECG obtained before HUTT.

RESULTS

Eighty-six patients with a mean age of 12.19 ± 5.34 were included. Patients with positive HUTT were significantly younger and male gender was more prevalent in this group. Mean QT dispersion was significantly higher in patients with positive HUTT result and also in patients with mixed response to HUTT compared to isolated vasodepressor response. Duration of QTc interval did not change between different study groups. Reciever-Operating-Characteristic (ROC) analysis showed that QT dispersion higher than 32 ms is a significant predictor of positive HUTT result (with 92% sensitivity and 98% specificity) and values higher than 40 ms can predict the mixed type of response to HUTT (with 84% sensitivity and 63% specificity).

CONCLUSIONS

Baseline myocardial repolarization disparity significantly correlates with susceptibility to symptomatic vasovagal syncope. This pathology seems to play its role mainly via excessive vagotonic response to sympathetic activation during HUTT process (known as cardioinhibitory response).

Considering Needle Phobia among Adult Patients During Mass COVID-19 Vaccinations

As mass vaccination is underway to combat the COVID-19 pandemic and achieve herd immunity, healthcare professionals need to recognize the fear and phobia of needles among their patients. Approximately 11.5 to 66 million U.S. adults may suffer from this condition. This population often avoids seeking medical care including vaccinations. The exact number of people suffering from this phobia is unknown, and the potential years of life lost in the American health care system cannot be estimated accurately. The resistance to vaccinations among this population may delay achieving herd immunity to end this current pandemic. An overview of needle phobia, vaccinations, and current treatments are explored. The use of telemedicine could prove critical for reaching this population as well as those who are hesitant about vaccinations. Providing education to healthcare providers to identify and manage these patients during the pandemic is necessary.

Impact of Yoga on Cardiac Autonomic Function and Arrhythmias

With the expanding integration of complementary and alternative medicine (CAM) practices in conjunction with modern medicine, yoga has quickly risen to being one of the most common CAM practices across the world. Despite widespread use of yoga, limited studies are available, particularly in the setting of dysrhythmia. Preliminary studies demonstrate promising results from integration of yoga as an adjunct to medical therapy for management of dysrhythmias. In this review, we discuss the role of autonomic nervous system in cardiac arrhythmia,interaction of yoga with autonomic tone and its subsequent impact on these disease states. The role of yoga in specific disease states, and potential future direction for studies assessing the role of yoga in dysrhythmia.

Postural Tachycardia Syndrome and Neurally Mediated Syncope

PURPOSE OF REVIEW

This article reviews the diagnosis and management of the most common disorders of orthostatic intolerance: postural tachycardia syndrome (POTS) and neurally mediated syncope.

RECENT FINDINGS

POTS is a heterogeneous syndrome caused by several pathophysiologic mechanisms that may coexist (limited autonomic neuropathy, hyperadrenergic state, hypovolemia, venous pooling, joint hypermobility, deconditioning). Neurally mediated syncope occurs despite intact autonomic reflexes. Management of orthostatic intolerance aims to increase functional capacity, including standing time, performance of daily activities, and exercise tolerance. Nonpharmacologic strategies (fluid and salt loading, physical countermaneuvers, compression garments, exercise training) are fundamental for patients with POTS, occasionally complemented by medications to raise blood pressure or slow heart rate. Neurally mediated syncope is best managed by recognition and avoidance of triggers.

SUMMARY

Significant negative effects on quality of life occur in patients with POTS and in patients with recurrent neurally mediated syncope, which can be mitigated through targeted evaluation and thoughtful management.

Focusing attention on biological markers of acute stressor intensity: Empirical evidence and limitations

ARMARIO, A, J. Labad and R. Nadal. Focusing attention on biological markers of acute stressor intensity: empirical evidence and limitations. NEUROSCIENCE AND BIOBEHAVIORAL REVIEWS. The availability of biological markers that objectively quantify stress is a highly relevant issue. However, experimental evidence suggests that most physiological changes elicited by emotional stressors do not reflect their intensity and are not useful for this purpose. Thus, we review experimental evidence in animals and humans about the putative validity of neuroendocrine and sympathetic/parasympathetic variables to measure stress. Plasma levels of some hormones (e.g. ACTH, glucocorticoids, prolactin and catecholamines) have been found to reflect, at least under certain conditions, the intensity of emotional stressors in animals and probably in humans. However, the temporal resolution of hormone changes is insufficient to reflect the very dynamic psychological processes taking place while experiencing stressors. Cardiovascular parameters (e.g. heart rate and blood pressure) have much better temporal resolution but their validity as markers of stressor intensity either in animals or humans is problematic. Skin conductance and pupil dilation appear to be promising. Additional and more systematic studies are needed to demonstrate the actual validity of stress-induced physiological changes to quantify stress.

Diagnostic and therapeutic approach to cardioinhibitory reflex syncope: A complex and controversial issue

Syncope is defined as a transient loss of consciousness due to global cerebral hypoperfusion and is one of the leading causes of emergency department admission. The initial approach should focus on excluding non-syncopal causes for loss of consciousness and risk stratification for cardiac cause, in order to ensure an appropriate etiological investigation and therapeutic approach. Vasovagal syncope (VVS), the most common type of syncope, should be assumed once other causes are excluded. Pathophysiologically, the vasovagal reflex is the result of a paradoxical autonomic response, leading to hypotension and/or bradycardia. VVS has not been shown to affect mortality, but morbidity may be considerable in those with recurrent syncopal episodes. The management of VVS includes both non-pharmacological and pharmacological measures that act on various levels of the reflex arc that triggers the syncopal episode. However, most are of uncertain benefit given the scarcity of high-quality supporting evidence. Pacemaker therapy may be considered in recurrent refractory cardioinhibitory reflex syncope, for which it is currently considered a robust intervention, as noted in the European guidelines. Non-randomized and unblinded studies have shown a potential benefit of pacing in recurrent VVS, but double-blinded randomized controlled trials have not consistently demonstrated positive results. We performed a comprehensive review of the current literature and recent advances in cardiac pacing and pacing algorithms in VVS, and discuss the diagnostic and therapeutic approach to the complex patient with recurrent VVS and reduced quality of life.

Hemodynamics of tonic immobility in the American alligator (Alligator mississippiensis) identified through Doppler ultrasonography

American alligators (Alligator mississippiensis) held inverted exhibit tonic immobility, combining unresponsiveness with flaccid paralysis. We hypothesize that inverting the alligator causes a gravitationally promoted increase in right aortic blood flowing through the foramen of Panizza, with a concurrent decrease in blood flow through the primary carotid, and thereby of cerebral perfusion. Inverting the alligator results in displacement of the liver, post-pulmonary septum, and the heart. EKG analysis revealed a significant decrease in heart rate following inversion; this decrease was maintained for approximately 45 s after inversion which is in general agreement with the total duration of tonic immobility in alligators (49 s). Doppler ultrasonography revealed that following inversion of the alligator, there was a reversal in direction of blood flow through the foramen of Panizza, and this blood flow had a significant increase in velocity (compared to the foraminal flow in the prone alligator). There was an associated significant decrease in the velocity of blood flow through the primary carotid artery once the alligator was held in the supine position. Tonic immobility in the alligator appears to be a form of vasovagal syncope which arises, in part, from the unique features of the crocodilian heart.

Alterations of brain network hubs in reflex syncope: Evidence from a graph theoretical analysis based on DTI

OBJECTIVE

We evaluated global topology and organization of regional hubs in the brain networks and microstructural abnormalities in the white matter of patients with reflex syncope.

METHODS

Twenty patients with reflex syncope and thirty healthy subjects were recruited, and they underwent diffusion tensor imaging (DTI) scans. Graph theory was applied to obtain network measures based on extracted DTI data, using DSI Studio. We then investigated differences in the network measures between the patients with reflex syncope and the healthy subjects. We also analyzed microstructural abnormalities of white matter using tract-based spatial statistics analysis (TBSS).

RESULTS

Measures of global topology were not different between patients with reflex syncope and healthy subjects. However, in reflex syncope patients, the strength measures of the right angular, left inferior frontal, left middle orbitofrontal, left superior medial frontal, and left middle temporal gyrus were lower than in healthy subjects. The betweenness centrality measures of the left middle orbitofrontal, left fusiform, and left lingual gyrus in patients were lower than those in healthy subjects. The PageRank centrality measures of the right angular, left middle orbitofrontal, and left superior medial frontal gyrus in patients were lower than those in healthy subjects. Regarding the analysis of the white matter microstructure, there were no differences in the fractional anisotropy and mean diffusivity values between the two groups.

CONCLUSIONS

We have identified a reorganization of network hubs in the brain network of patients with reflex syncope. These alterations in brain network may play a role in the pathophysiologic mechanism underlying reflex syncope.