Kembara Xtra - Medicine- Carotid Sinus Hypersensitivity
Introduction The baroreceptors in the carotid sinus are sensitive to changes in artery pressure and are found close to where the internal and external carotid arteries split. The carotid sinuses are crucial to maintaining the balance of blood pressure (BP). In carotid sinus hypersensitivity (CSH), stimulation of one or both carotid sinuses, such as mechanical forces with turning neck), causes an exaggerated baroreceptor response that can slow the heart rate and raise blood pressure. An endogenous increase in BP or external pressure applied to a carotid sinus increases the baroreceptor firing rate, activates vagal efferents, and/or inhibits the sympathetic discharge to the heart and blood ● There are three ways to define CSH: Standard criteria include a 3 second halt in heart rate in response to carotid sinus massage (CSM) and/or a vasodepression of a systolic blood pressure drop of at least 50 mm Hg. – Krediet criteria: a heart rate halt lasting six seconds in response to CSM and/or a drop in blood pressure to 60 millimeters of mercury for six seconds. CSH is typically divided into three subtypes based on response to CSM: a pause in heart rate in response to CSM >95th percentile of the population response (7.3 seconds asystole), and/or vasodepression in response to CSM >95th percentile of the population response (>77 mm Hg fall in systolic BP), or both. - Cardioinhibitory (70–75%): at least three seconds of asystole - Vasodepressive (5-10%): systolic blood pressure falls by at least 50 mm Hg. - Mixed (20–25%): the first two categories together. Carotid sinus syndrome (CSS) is a term that is frequently (though not always) used to describe CSH with syncope and can be categorized as: Syncope caused by unintentional mechanical manipulation (trigger) of the carotid sinuses, such as shaving, wearing a tight collar, or tumors, is known as spontaneous CSS. - Induced CSS: CSM diagnoses syncope despite the absence of a mechanical stimulus. Prevalence and incidence of disease Age-related disease that most frequently affects men over 65. Correlated with a history of hypertension (HTN) and coronary artery disease (CAD), with right CSH prevalence being higher than left CSH Using accepted diagnostic criteria, CSH was discovered in 39% of randomly chosen adults over the age of 65 in 2006. This finding was compared to a 2019 evaluation of prevalence statistics. 30% of older adults with unexplained syncope may have CSH at the root of their symptoms. Pathophysiology and Etiology It is still unclear what specific defect in persons with CSH produces the hypersensitive reaction. This condition may result from modifications to any component of the reflex arc or the target organs, or it may be a symptom of a systemic autonomic illness linked to autonomic dysregulation. Linked to elevated baroreflex sensitivity and resting sympathetic overactivity Bradycardia and asystole are thought to be mediated by vagal efferents in the cardioinhibitory and mixed CSH subtypes, whereas vasodilation and arterial hypotension are thought to be caused by a reduction in sympathetic tone in the vasodepressor and mixed subtypes. Cerebral autoregulation has been linked to symptoms of CSH, and it has been discovered to be normal in asymptomatic CSH. CSH is typically idiopathic but can be brought on by: - Carotid body tumors - Increased afferent impulse traffic in the baroreflex pathway as a result of atherosclerosis. - Neck lymph nodes that are inflammatory and cancerous - Significant scarring around the carotid sinus from earlier neck surgeries - Metastatic cancer Risk factors include advanced age, being a man, and CAD, HTN, and DM. Vasovagal syncope, sick sinus syndrome, atrioventricular block, coronary artery disease, hypertension in the lower extremities, Alzheimer disease, Parkinson illness Introducing History Unexplained falls: Evidence of a causal association between falls and the cardiac inhibitory subtype is proposed. Recurrent syncope: typically sudden, unexplained, of short duration, appearing spontaneous, and with complete recovery. Dizziness is more commonly associated with vasodepressor and mixed subtypes, and presents as momentary light-headedness or presyncope rather than real vertigo. Syncope and prodrome or retrograde amnesia may occur together. Any CSM-like action, such as shaving, donning a tight collar, or turning one's head forcefully, are exacerbating or causative factors. Neck trauma, radical neck resection, severe scarring in the neck from radiation fibrosis, and neck malignancies - There are some drugs that can make CSH symptoms worse: Digoxin or beta-blockers, particularly those of the cardioinhibitory subtype Methacholine, morphine, and physostigmine all increase vagal sensitivity and may put someone at risk for the cardiac inhibitory subtype of CSH. clinical assessment Unless the carotid baroreceptor is activated, which causes bradycardia, hypotension, pallor, and diaphoresis, everything is OK. Differential Diagnosis: Neurocardiogenic Syncope, Postural Hypotension, Situational Syncope, Postural Tachycardia Syndrome (POTS), Primary Autonomic Deficiency, Hypovolemia, Dysrhythmias, Sick Sinus Syndrome, Cerebrovascular Deficiency, Other Causes of Syncope (e.g., Metabolic, Psychogenic), and ECG that may show sinus pauses or atrial-ventricular block. Carotid duplex scan to exclude carotid stenosis if there is a bruit (see the one after this one) Diagnostic tests and laboratory results Other/Diagnostic Procedures After a negative initial evaluation, CSM is recommended for patients >40 years old with syncope of unknown cause. The steps in this technique are widely acknowledged as necessary for effective diagnosis. - For better diagnostic accuracy, the patient is placed in the supine position for 5 minutes while having their baseline blood pressure and electrocardiogram continuously monitored (on a footplate-style tilt table). – Apply firm longitudinal massage for 5 to 10 seconds over the right carotid sinus (between the angle of the mandible and the superior border of the thyroid) at the location of the greatest pulsation: Record symptoms, BP, and record ECG changes. Keep in mind that gentle pressure over the carotid sinus will not consistently result in a hypersensitive reaction. Stop if asystole is less than three seconds. – Apply pressure to the left carotid sinus while the patient is still supine if the initial test is nondiagnostic; if it is still nondiagnostic, repeat the test with a head-up tilt of 70 degrees (first to the right, then, if required, the left), giving the patient time to adjust hemodynamically to the head-up position. - Supporting data for the testing strategy First, the right side: 30% of CSM exams are found to be nondiagnostic in the supine position; the positive predictive value increases from 77% to 96% with a specificity of 93% by performing CSM in the 70-degree position. Up to 66% of CSH have positive response on the right; if a positive right response, there is no need to repeat the test on the left side. Absolute contraindications to CSM testing include the presence of a carotid bruit, which requires initial examination with carotid ultrasonography and Doppler. No testing if stenosis is greater than 70%, and supine-only testing if stenosis is between 50% and 70%. Myocardial infarction, transient ischemic attack, or stroke within the last three months. History of ventricular tachycardia or ventricular fibrillation is a relative contraindication to CSM testing, and elderly patients are more likely to have false-positive results. It is important to rule out any further syncope reasons. – There have been reports of neurological and cardiovascular problems during CSM. Cardiovascular issues, in particular arrhythmia, are relatively uncommon. Within 0.9% of individuals, transient neurologic symptoms and signs can be present. Following CSM, persistent neurologic impairments are relatively uncommon. CSM should be regarded as a risk-free, safe process when done properly (3)[C]. Interpretation of Tests Although the standard positive response criteria (asystole 3 seconds and/or a reduction in systolic blood pressure 50 mm Hg) are based on historical observations, a professional analysis of more current data suggests these criteria may be overly sensitive. If a patient's syncope is replicated during a test, the CSM approach becomes more specific. Management and Therapy In asymptomatic people, isolated CSH doesn't need to be treated. In patients with vasodepressor subtype and no other cardiovascular disease, high salt consumption and increased fluid intake may be useful to maintain intravascular volume. Assessment of driving restrictions The First Line of Medicine No one medication has proven to be consistently useful in treating recurrent and symptomatic CSH. Next Line In patients with vasodepressor subtype, fludrocortisone or midodrine may be used to alleviate orthostatic symptoms (FDA has not cleared this use). Fludrocortisone, however, promotes salt and water retention and should only be administered with caution in older heart disease patients. The fact that midodrine raises mean ambulatory BP is a side effect. Atropine may be administered to patients with the cardioinhibitory subtype of bradycardia in the acute context. There is some evidence that sertraline and fluoxetine help people who are not responsive to pacemakers. Surgical Techniques The 2017 ACC/AHA/HRS Guideline for the Evaluation and Management of Patients With Syncope states that the strength of the recommendations is low because the evidence is scarce. The evidence that is currently available does not support the use of pacing for reflex-mediated syncope in individuals other than those who have asystole and recurrent vasovagal syncope as verified by an implantable loop recorder. Permanent pacing may lessen the frequency of symptoms, but it may not be able to get rid of them entirely. Surgery for CSH patients due to the bulk effect of the tumor burden Due to the high likelihood of problems, carotid sinus denervation with surgery or radiation therapy is no longer advised. Steer clear of triggering actions (as mentioned above) that put strain on the neck, such as wearing a necktie or collar that is too tight. If you experience syncope, avoid driving or engaging in other potentially risky activities until your doctor gives the all-clear. Steer clear of drugs that can cause symptoms to recur, such as vasodilators. Teach the patient to lie down if prodromal symptoms or presyncope appear. Describe the diagnosis, offer assurance, and describe the possibility of a recurrence. Prognosis It has not been established that CSH confers a separate mortality risk. Patients with untreated CSS have a recurrent risk of syncope as high as 62% in just four years. In patients with cardiac inhibitory CSH who received pacemakers, the mean number of falls decreased significantly over a 1-year follow-up period, from 9.3 to 4.1. Complications Kerr criterion indicates a link between CSH and higher mortality. To predict future falls, syncope, and the capacity of criteria to identify patients who would benefit from pacing, more research is required.
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