At the heart of the arterial baroreflex: a physiological basis for a new classification of carotid sinus hypersensitivity

Carotid sinus massage in clinical practice: the Six-Step-Method

Carotid sinus massage (CSM) as integral part of cardiovascular autonomic testing is indicated in all patients > 40 years with syncope of unknown origin and suspected reflex mechanism. However, large practice variation exists in performing CSM that inevitably affects the positivity rate of the test and may result in an inaccurate diagnosis in patients with unexplained syncope. Even though CSM was introduced into medical practice more than 100 years ago, the method of performing CSM is still largely operator- and centre-dependent, while in many places, the test has been entirely abandoned. Here, we describe a standardized protocol on how to perform CSM, which basic monitoring equipment is necessary and why CSM is a safe procedure to perform. Our aim is to create a uniform approach to perform CSM. The new proposed algorithm, the Six-Step-Method, includes: (i) check history for exclusion CSM; (ii) turn head slightly contralaterally and posterior (see also explanatory video and poster provided as Supplementary material; (iii) palpation to identify carotid sinus location; (iv) massage for 10 s; (v) monitoring of blood pressure and heart rate to assess of the haemodynamic response type; and (vi) include time intervals between subsequent massages. Carotid sinus massage should be performed on both the left and right and in the supine and upright position. The recommended equipment to perform CSM consists of: (i) a tilt table in order to perform CSM in supine and standing position, (ii) a continuous blood pressure monitor or cardiac monitor, and (iii) at least two persons.

The impact of cardiovascular diagnostics and treatments on fall risk in older adults: a scoping review and evidence map

BACKGROUND

We aimed to summarize the published evidence on the fall risk reducing potential of cardiovascular diagnostics and treatments in older adults.

METHODS

Design: scoping review and evidence map.

DATA SOURCES

Medline and Embase.

ELIGIBILITY CRITERIA

all available published evidence; Key search concepts: "older adults," "cardiovascular evaluation," "cardiovascular intervention," and "falls." Studies reporting on fall risk reducing effect of the diagnostic/treatment were included in the evidence map. Studies that investigated cardiovascular diagnostics or treatments within the context of falls, but without reporting a fall-related outcome, were included in the scoping review for qualitative synthesis.

RESULTS

Two articles on cardiovascular diagnostics and eight articles on cardiovascular treatments were included in the evidence map. Six out of ten studies concerned pacemaker intervention of which one meta-analyses that included randomized controlled trials with contradictory results. A combined cardiovascular assessment/evaluation (one study) and pharmacotherapy in orthostatic hypotension (one study) showed fall reducing potential. The scoping review contained 40 articles on cardiovascular diagnostics and one on cardiovascular treatments. It provides an extensive overview of several diagnostics (e.g., orthostatic blood pressure measurements, heart rhythm assessment) useful in fall prevention. Also, diagnostics were identified, that could potentially provide added value in fall prevention (e.g., blood pressure variability and head turning).

CONCLUSION

Although the majority of studies showed a reduction in falls after the intervention, the total amount of evidence regarding the effect of cardiovascular diagnostics/treatments on falls is small. Our findings can be used to optimize fall prevention strategies and develop an evidence-based fall prevention care pathway. Adhering to the World guidelines on fall prevention recommendations, it is crucial to undertake a standardized assessment of cardiovascular risk factors, followed by supplementary testing and corresponding interventions, as effective components of fall prevention strategies. In addition, accompanying diagnostics such as blood pressure variability and head turning can be of added value.

Extracorporeal Membrane Oxygenation (ECMO) Cannula Stimulation of the Carotid Sinus Causing Bradycardic Pauses in a Patient With COVID-19

Veno-venous extracorporeal membrane oxygenation (VV-ECMO) cannulation is a potential cause of episodic bradycardia during an intensive care course because of the proximal cannula insertion site being in the vicinity of the carotid sinus. Herein, we report the case of episodic bradycardia throughout a multi-week intensive care stay of a VV-ECMO recipient due to a severe coronavirus disease 2019 (COVID-19) infection that did not emerge for the rest of the patient's hospitalization after decannulation.

Resuscitative Endovascular Balloon Occlusion of the Aorta (REBOA) in Non-Traumatic Cardiac Arrest: A Narrative Review of Known and Potential Physiological Effects

Resuscitative endovascular balloon occlusion of the aorta (REBOA) is widely used in acute trauma care worldwide and has recently been proposed as an adjunct to standard treatments during cardiopulmonary resuscitation in patients with non-traumatic cardiac arrest (NTCA). Several case series have been published highlighting promising results, and further trials are starting. REBOA during CPR increases cerebral and coronary perfusion pressure by increasing the afterload of the left ventricle, thus improving the chances of ROSC and decreasing hypoperfusion to the brain. In addition, it may facilitate the termination of malignant arrhythmias by stimulating baroreceptor reflex. Aortic occlusion could mitigate the detrimental neurological effects of adrenaline, not only by increasing cerebral perfusion but also reducing the blood dilution of the drug, allowing the use of lower doses. Finally, the use of a catheter could allow more precise hemodynamic monitoring during CPR and a faster transition to ECPR. In conclusion, REBOA in NTCA is a feasible technique also in the prehospital setting, and its use deserves further studies, especially in terms of survival and good neurological outcome, particularly in resource-limited settings.

Systemic and cerebral circulatory adjustment within the first 60 s after active standing: An integrative physiological view

Transient cardiovascular and cerebrovascular responses within the first minute of active standing provide the means to assess autonomic, cardiovascular and cerebrovascular regulation using a real-world everyday stimulus. Traditionally, these responses have been used to detect autonomic dysfunction, and to identify the hemodynamic correlates of patient symptoms and attributable causes of (pre)syncope and falls. This review addresses the physiology of systemic and cerebrovascular adjustment within the first 60 s after active standing. Mechanical factors induced by standing up cause a temporal mismatch between cardiac output and vascular conductance which leads to an initial blood pressure drops with a nadir around 10 s. The arterial baroreflex counteracts these initial blood pressure drops, but needs 2-3 s to be initiated with a maximal effect occurring at 10 s after standing while, in parallel, cerebral autoregulation buffers these changes within 10 s to maintain adequate cerebral perfusion. Interestingly, both the magnitude of the initial drop and these compensatory mechanisms are thought to be quite well-preserved in healthy aging. It is hoped that the present review serves as a reference for future pathophysiological investigations and epidemiological studies. Further experimental research is needed to unravel the causal mechanisms underlying the emergence of symptoms and relationship with aging and adverse outcomes in variants of orthostatic hypotension.

Afferent Baroreflex Dysfunction: Decreased or Excessive Signaling Results in Distinct Phenotypes

Head and neck tumors can affect afferent baroreceptor neurons and either interrupt or intermittently increase their signaling, causing blood pressure to become erratic. When the afferent fibers of the baroreflex are injured by surgery or radiotherapy or fail to develop as in familial dysautonomia, their sensory information is no longer present to regulate arterial blood pressure, resulting in afferent baroreflex failure. When the baroreflex afferents are abnormally activated, such as by paragangliomas in the neck, presumably by direct compression, they trigger acute hypotension and bradycardia and frequently syncope, by a mechanism similar to the carotid sinus syndrome. We describe our observations in a large series of 23 patients with afferent baroreflex dysfunction and the cardiovascular autonomic features that arise when the sensory baroreceptor neurons are injured or compressed. The management of afferent baroreceptor dysfunction is limited, but pharmacological strategies can mitigate blood pressure swings, improve symptoms, and may reduce hypertensive organ damage. Although rare, the prevalence of afferent baroreflex dysfunction appears to be increasing in middle-aged men due to human papillomavirus related oropharyngeal cancer.

Long-Term Mortality in Cardioinhibitory Carotid Sinus Hypersensitivity Patient Cohort

Background

Cardioinhibitory carotid sinus hypersensitivity (CICSH) is defined as ventricular asystole ≥ 3 seconds in response to 5-10 seconds of carotid sinus massage (CSM). There is a common concern that a prolonged asystole episode could lead to death directly from bradycardia or as a consequence of serious trauma, brain injury or pause-dependent ventricular arrhythmias.

Objective

To describe total mortality, cardiovascular mortality and trauma-related mortality of a cohort of CICSH patients, and to compare those mortalities with those found in a non-CICSH patient cohort.

Methods

In 2006, 502 patients ≥ 50 years of age were submitted to CSM. Fifty-two patients (10,4%) were identified with CICSH. Survival of this cohort was compared with that of another cohort of 408 non-CICSH patients using Kaplan-Meier curves. Cox regression was used to examine the relation between CICSH and mortality. The level of statistical significance was set at 0.05.

Results

After a maximum follow-up of 11.6 years, 29 of the 52 CICSH patients (55.8%) were dead. Cardiovascular mortality, trauma-related mortality and the total mortality rate of this population were not statistically different from that found in 408 patients without CICSH. (Total mortality of CICSH patients 55.8% vs. 49,3% of non-CICSH patients; p: 0.38).

Conclusion

At the end of follow-up, the 52 CICSH patient cohort had total mortality, cardiovascular mortality and trauma-related mortality similar to that found in 408 patients without CICSH.

Small vessel disease pathological changes in neurodegenerative and vascular dementias concomitant with autonomic dysfunction

We performed a clinicopathological study to assess the burden of small vessel disease (SVD) type of pathological changes in elderly demented subjects, who had clinical evidence of autonomic dysfunction, either carotid sinus hypersensitivity or orthostatic hypotension or both or had exhibited unexpected repeated falls. Clinical and neuropathological diagnoses in 112 demented subjects comprised dementia with Lewy bodies (DLB), Parkinson's disease with dementia (PDD), Alzheimer's disease (AD), Mixed dementia (mostly AD-DLB) and vascular dementia (VaD). Of these, 12 DLB subjects had no recorded unexpected falls in life and therefore no evidence of concomitant autonomic dysfunction. A further 17 subjects were assessed as aging controls without significant pathology or signs of autonomic dysfunction. We quantified brain vascular pathological changes and determined severities of neurodegenerative lesions including α-synuclein pathology. We found moderate-severe vascular changes and high-vascular pathology scores (P < 0.01) in all neurodegenerative dementias and as expected in VaD compared to similar age controls. Arteriolosclerosis, perivascular spacing and microinfarcts were frequent in the basal ganglia and frontal white matter (WM) across all dementias, whereas small infarcts (<5 mm) were restricted to VaD. In a sub-set of demented subjects, we found that vascular pathology scores were correlated with WM hyperintensity volumes determined by MRI in life (P < 0.02). Sclerotic index values were increased by ~50% in both the WM and neocortex in all dementias compared to similar age controls. We found no evidence for increased α-synuclein deposition in subjects with autonomic dysfunction. Our findings suggest greater SVD pathological changes occur in the elderly diagnosed with neurodegenerative dementias including DLB and who develop autonomic dysfunction. SVD changes may not necessarily manifest in clinically overt symptoms but they likely confound motor or cognitive dysfunction. We propose dysautonomia promotes chronic cerebral hypoperfusion to impact upon aging-related neurodegenerative disorders and characterize their end-stage clinical syndromes.

Massage du sinus carotidien

Le massage du sinus carotidien (MSC) est un geste simple, utilisé en médecine d’urgence à visées diagnostique et/ou thérapeutique. Les indications principales au MSC sont l’évaluation des syncopes chez les patients de plus de 40 ans et le traitement de première ligne des tachycardies paroxystiques supraventriculaires bien tolérées hémodynamiquement. Les contre-indications incluent un antécédent d’accident vasculaire cérébral ou d’accident ischémique transitoire dans les trois mois qui précèdent ainsi que la présence d’une sténose carotidienne significative ou d’un souffle carotidien. Dans le bilan de la syncope, le MSC permet de diagnostiquer une hypersensibilité du sinus carotidien. Pour les tachycardies supraventriculaires, il permet de préciser le type de tachycardie et, dans certains cas, d’obtenir une restauration d’un rythme sinusal. Les rares complications sont liées au risque de provoquer une embolie cérébrale.

Carotid Sinus Massage in Syncope Evaluation: A Nonspecific and Dubious Diagnostic Method

BACKGROUND

Carotid sinus hypersensitivity (CSH) is a frequent finding in the evaluation of syncope. However, its significance in the clinical setting is still dubious. A new criterion was proposed by Solari et al. with a symptomatic systolic blood pressure (SBP) cut-off value of ≤ 85 mmHg to refine the vasodepressor (VD) response diagnosis.

OBJECTIVE

To determine and compare the response to carotid sinus massage (CSM) in patients with and without syncope according to standard and proposed criteria.

METHODS

CSM was performed in 99 patients with and 66 patients without syncope. CSH was defined as cardioinhibitory (CI) for asystole ≥ 3 seconds, or as VD for SBP decrease ≥ 50 mmHg.

RESULTS

No differences in the hemodynamic responses were observed during CSM between the groups, with 24.2% and 25.8% CI, and 8.1% and 13.6% VD in the symptomatic and asymptomatic groups, respectively (p = 0.466). A p value < 0.050 was considered statistically significant. During the maneuvers, 45 (45.45%) and 34 (51.5%) patients in the symptomatic and asymptomatic groups achieved SBP below ≤ 85 mmHg. Symptoms were reported especially in those patients in whom CSM caused a SBP decrease to below 90 mmHg and/or asystole > 2.5 seconds, regardless of the pattern of response or the presence of previous syncope.

CONCLUSION

The response to CSM in patients with and without syncope was similar; therefore, CSH may be an unspecific condition. Clinical correlation and other methods of evaluation, such as long-lasting ECG monitoring, may be necessary to confirm CSH as the cause of syncope.

Usefulness of Tilt Testing and Carotid Sinus Massage for Evaluating Reflex Syncope

Thirty years ago Tilt Testing (TT) was described as a tool in the diagnostic work-up of vasovagal syncope; after its initial success, some flaws have become evident. The concept of hypotensive susceptibility has provided the test a new relevance, shifting from diagnosis only, to therapeutic management. Carotid Sinus Massage (CSM) was introduced at the beginning of the XX century; the technique has evolved over years, whereas the concept of carotid sinus syndrome (CSS) has remained unchanged and uncontested for more than half a century. Nowadays, CSS is a matter of debate, with new classifications and criteria coming on the scene. Recently, a common central etiological mechanism has been hypothesized for reflex syncope, manifesting as CSS, vasovagal syncope or both. In this context, TT and CSM acquire an important role in clinical practice, being essential for a complete diagnosis and treatment. Recalling their historical background, the present paper illustrates an actual interpretation of TT and CSM.

Use of Selective Serotonin Reuptake Inhibitor and Midodrine in a Patient With Autonomic Instability 2/2 Compressive Squamous Cell Carcinoma and Pain

A rare cause of reflex syncope is metastatic cancers involving the head and neck. These can irritate the glossopharyngeal nerve and lead to glossopharyngeal neuralgia with associated syncope. This type of syncope is difficult to treat since it commonly involves both a vasodepressor and cardioinhibitory response, and typically requires removal of the irritative focus. We report a case of a 52-year-old male who presented from home with syncope. He endorsed a 5-week history of progressively worsened positional headaches and dramatic 40-pound weight loss with night sweats over 6 months. In the emergency department, his heart rate was noted to drop into the 20s with associated hypotension 60/31 mm Hg. Heart rate and blood pressure increased with intravenous atropine. Physical examination revealed a large ulcerative lesion in the left tonsillar area. After biopsy of the lesion, a diagnosis of stage IV squamous cell carcinoma of the neck was made; computed tomography angiogram and positron emission tomography/computed tomography confirmed involvement in the posterior tongue extending to the left palatine tonsil in addition to the left jugular chain. The patient was started on cisplatin and radiation therapy, but continued to have episodes of syncope associated with bradycardia and hypotension. After a failed trial of benztropine, the patient was started on sertraline and midodrine with resolution of syncope. This could be a potential treatment option in those with compressive mixed syncope who are not candidates for surgery or chemotherapy or are awaiting definitive treatment.

Noninvasive beat-to-beat finger arterial pressure monitoring during orthostasis: a comprehensive review of normal and abnormal responses at different ages

Over the past 30 years, noninvasive beat-to-beat blood pressure (BP) monitoring has provided great insight into cardiovascular autonomic regulation during standing. Although traditional sphygmomanometric measurement of BP may be sufficient for detection of sustained orthostatic hypotension, it fails to capture the complexity of the underlying dynamic BP and heart rate responses. With the emerging use of noninvasive beat-to-beat BP monitoring for the assessment of orthostatic BP control in clinical and population studies, various definitions for abnormal orthostatic BP patterns have been used. Here, age-related changes in cardiovascular control in healthy subjects will be reviewed to define the spectrum of the most important abnormal orthostatic BP patterns within the first 180 s of standing. Abnormal orthostatic BP responses can be defined as initial orthostatic hypotension (a transient systolic BP fall of >40 mmHg within 15 s of standing), delayed BP recovery (an inability of systolic BP to recover to a value of >20 mmHg below baseline at 30 s after standing) and sustained orthostatic hypotension (a sustained decline in systolic BP of ≥20 mmHg occurring 60-180 s after standing). In the evaluation of patients with light-headedness, pre(syncope), (unexplained) falls or suspected autonomic dysfunction, it is essential to distinguish between normal cardiovascular autonomic regulation and these abnormal orthostatic BP responses. The prevalence, clinical relevance and underlying pathophysiological mechanisms of these patterns differ significantly across the lifespan. Initial orthostatic hypotension is important for identifying causes of syncope in younger adults, whereas delayed BP recovery and sustained orthostatic hypotension are essential for evaluating the risk of falls in older adults.

Carotid sinus syndrome

Carotid sinus hypersensitivity, first described less than 65 years ago, is an important and often undiagnosed cause of syncope in the elderly. Its pathophysiology is complex and certain aspects are not completely understood. The timely diagnosis and treatment of this condition can improve morbidity and prevent complications in the elderly. In this article, the prevalence, risk factors, pathophysiology, diagnosis, aspects of carotid sinus massage, and treatment options for the different kinds of carotid sinus hypersensitivity are discussed.

Neurologic state transitions in the eye and brain: kinetics of loss and recovery of vision and consciousness

Visual alterations, peripheral light loss (PLL) and blackout (BO), are components of acceleration (+Gz) induced loss of consciousness (LOC) and recovery of consciousness (ROC). The kinetics of loss of vision (LOV) and recovery of vision (ROV) were determined utilizing ocular pressure induced retinal ischemia and compared to the kinetics of LOC and ROC resulting from +Gz-induced cephalic nervous system (CPNS) ischemia. The time from self-induced retinal ischemia in completely healthy subjects (N = 104) to the onset of PLL and complete BO was measured. The time from release of ocular pressure, with return of normal retinal circulation, to the time for complete recovery of visual fields was also measured. The kinetics of pressure induced LOV and ROV was compared with previously developed kinetics of +Gz-induced LOC and ROC focusing on the rapid onset, vertical arm, of the +Gz-induced LOC and ROC curves. The time from onset of increased ocular pressure, immediately inducing retinal ischemia, to PLL was 5.04 s with the time to BO being 8.73 s. Complete recovery of the visual field from BO following release of ocular pressure, immediately abolishing retinal ischemia, was 2.74 s. These results confirm experimental findings that visual loss is frequently not experienced prior to LOC during exposure to rapid onset, high levels of +Gz-stress above tolerance. Offset of pressure induced retinal ischemia to ROV was 2.74 s, while the time from offset of +Gz-induced CPNS ischemia to ROC was 5.29 s. Recovery of retinal function would be predicted to be complete before consciousness is regained following +Gz-induced LOC. Ischemia onset time normalization in neurologic tissues permits comparison between different stress-induced times to altered function. The +Gz-time tolerance curves for LOV and LOC provide comparison and integration of neurologic state transition kinetics in the retina and CPNS.

The +Gz recovery of consciousness curve

Background

The limiting physiological envelope to extreme gravitational stress is defined by neurologic symptoms and signs that result from exceeding neurologic tolerance. The edge of the limiting envelope is defined by the complete incapacitation associated with acceleration (+Gz) induced loss of consciousness. Should + Gz-induced loss of consciousness occur in-flight, brisk recovery of conscious function is essential for aircraft recovery. If recovery does not occur, accident investigation aimed at preventing such accidents is enhanced by understanding the temporal aspects of the resulting incapacitation. The mechanistic basis of neurological reintegration leading to consciousness recovery is of broad medical and scientific interest.

Methods

Recovery of consciousness episodes from a prospectively developed +Gz-induced loss of consciousness repository of healthy individuals was analyzed to define variables influencing recovery of consciousness. The time from loss to recovery of consciousness as measured by observable signs, is defined as the absolute incapacitation period. The absolute incapacitation period from 760 episodes of loss and recovery of consciousness in healthy humans was analyzed to define +Gz-profile variables that determine the duration of functional neurologic compromise.

Results

Mean time from loss to return of consciousness for 760 episodes of consciousness recovery was 10.4 ± 5.1 s; minimum 1 s; maximum 38 s. Offset rate for the +Gz-exposure deceleration profiles varied from a minimum of 0.17 Gs⁻¹ to a maximum of 7.93 Gs⁻¹.The curve produced by plotting +G_z-offset rate (Gs⁻¹; y) versus absolute incapacitation period (s; x) described a hyperbolic relationship. The hyperbolic relationship indicates there is a minimum time (mean 8.29 ± 3.84 s) required for recovery of consciousness when complete loss of consciousness occurs.

Conclusions

Mean recovery time from +Gz-induced unconsciousness is dependent on the deceleration profile's offset rate from the point of loss of consciousness. This relationship is described by a curve plotting offset rate and time for recovery of consciousness. This curve predicts when conscious function should return following exposure to +Gz stress sufficient to cause unconsciousness. The maximum +Gz level of the recovery exposure profile was found to be inadequate for predicting variations in the time for recovery of consciousness.

Differential diagnosis between 'unexplained' fall and syncopal fall: a difficult or impossible task

Falls may be accidental (because of slipping, tripping or environmental hazards) or 'unexplained', when there is no apparent cause. Syncope is a transient loss of consciousness (LOC) and, if it occurs when the person is in the upright position, may lead to a fall. The differential diagnosis between 'unexplained' fall and syncopal fall can be difficult, if not impossible, because many patients have retrograde amnesia after syncope, that is they do not remember their prodromal symptoms. Based on the results of many randomized studies, the international guidelines on falls suggest multifactorial assessment and multifactorial treatment. Unfortunately, however, the vast majority of studies have been carried out on a mixed population of patients who have suffered accidental and 'unexplained' falls. As 'unexplained' falls account for a minority of cases, we really do not know the efficacy of multifactorial treatment in patients with this type of fall. Very recent data seem to prove that many older patients with 'unexplained' falls are actually affected by reflex syncope with retrograde amnesia, as they experience LOC during tilt testing or carotid sinus massage. Although these data make an important contribution to our knowledge of the mechanism of 'unexplained' falls, the therapeutic problems remain largely unsolved.