Carotid sinus syndrome is a decrease in cerebral perfusion that occurs when the sensitivity of the carotid sinus baroreceptors to mechanical stimulation increases. In elderly patients, reflex cardiac arrhythmia and /or vasodilation can lead to a sharp loss of consciousness without previous prodromal symptoms or manifest only dizziness. The diagnosis is confirmed when performing a massage of the sinocarotid region. Complex therapy, which includes general recommendations, medical and surgical correction, helps to reduce the risk of negative consequences.
ICD 10
G90.0 Idiopathic peripheral autonomic neuropathy
General information
The true prevalence of carotid sinus syndrome (synocarotid syncope, Charcot-Weiss-Baker syndrome) is not easy to assess, since it is not always manifested by loss of consciousness. The incidence rate is 35-40 new cases per 1 million population per year, but it can be much higher. This diagnosis is established by 0.5–9.0% of patients with recurrent fainting. Pathology affects mainly elderly people – from 26 to 60% of unexplained syncope over the age of 75 is due to increased sensitivity of carotid receptors. The gender structure of the disease is dominated by men, their prevalence rate is 2-3 times higher compared to women.
Causes
Carotid sinus syndrome is associated with stimulation of sensitive receptors in the bifurcation zone of the common carotid artery. It is often provoked by turns and tilting the head back (when looking at objects in the sky, washing the head in a barber shop). It is important to wear stiff collars, tie a tie tightly, stretch the skin when shaving, squeeze the artery with your fingers when determining the pulse. Syncopal state is provoked by massage of the sinocarotid zone, separate diagnostic procedures (gastroscopy, bronchoscopy), sometimes occurs during meals.
The sensitivity of the carotid artery receptors increases with age, especially in the presence of concomitant cardiovascular pathology. Risk factors include ischemic disease, arterial hypertension, atherosclerosis. Pathology can occur with tumors of the thyroid gland and lymph nodes, due to scarring after radical surgery, neck injuries, radiation therapy. The syndrome is associated with Alzheimer’s and Parkinson’s diseases, provoked by taking certain medications (cardiac glycosides, beta blockers, methyldophy).
Pathogenesis
The carotid reflex is an important element of maintaining the constancy of blood pressure. Baroreceptors perceive changes in wall stretching and transmural tension, transmitting afferent impulses along the lingual and vagus nerves to the brain stem. Efferent stimuli go to the heart and blood vessels, controlling the frequency of contractions and vasomotor reactions. In sinocarotid syncope, mechanical deformation of the vessel wall leads to an excessive reflex response with bradycardia and vasodilation, which is accompanied by hypotension and loss of consciousness.
Hemodynamic shifts after stimulation of the carotid artery do not depend on the position of the body. Usually they have clear temporal patterns: first, due to bradycardia, cardiac output drops, later peripheral vascular resistance decreases. Carotid sinus syndrome is part of generalized autonomic dysfunction. Hypersensitivity of baroreceptors is reported to be associated with degenerative processes caused by the accumulation of synuclein protein in the brain substance, which leads to a violation of the central regulation of reflex reactions.
According to one hypothesis, the syndrome is the result of a compensatory increase in the number of postsynaptic alpha-2-adrenergic receptors of the brain stem, due to a decrease in afferent stimulation due to an age-related decrease in vascular compliance. But, despite the ongoing research, the exact mechanism of abnormal sensitivity of the sinocarotid region and its role in the development of syncope is not fully understood. An overreaction can be provoked by changes in any part of the reflex arc or the target organs themselves.
Classification
Carotid sinus syndrome occupies a separate place in the structure of neurocardiogenic syncopations. Like other fainting spells, it goes through three periods – pre-syncopal (prodromal), immediate loss of consciousness, post-syncopal (restorative). The combination of pathophysiological and clinical signs induced by massage of the carotid sinus allows us to distinguish 3 variants of pathology:
- Cardioinhibitory. It is 70-75% of cases. Suppression of the heart rhythm prevails, which is manifested by sinus bradycardia, atrioventricular blockade or asystole lasting from 6 s. Under the influence of atropine, the heart rate is restored.
- Vasodepressor. It is detected in 5-10% of patients. Vasodilation dominates without changing the heart rate. The drop in blood pressure is more than 50 mm Hg or less than 30 mm Hg with fainting, in the absence of asystole or its duration up to 3 s. Symptoms are insensitive to atropine.
- Mixed. It accounts for 20-25% of cases. It is characterized by a simultaneous decrease in heart rate and vascular tone. Ventricular asystole lasts 3-6 s. Atropine normalizes the heart rate, but weak symptoms due to a drop in blood pressure persist.
Some authors suggest considering all synocarotid syncope exclusively as mixed, others supplement the existing classification with new criteria. It introduced the terms spontaneous and induced syndrome, characterized by the presence of clinical manifestations in the anamnesis. In the latter case, a hypersensitive response is formed only with targeted massage of the carotid artery.
Symptoms
The clinical picture can vary quite widely, but its characteristic feature is the connection of manifestations with irritation of the sinocarotid region. Syncope is the most frequent and indicative sign of carotid sinus syndrome. If it is preceded by prodromal phenomena, then patients are able to recognize the impending condition. In the presyncopal period, shortness of breath, dizziness, and severe fear are noted, but in the older age group, symptoms are minimal or absent at all.
The duration of synocarotid syncope is usually 10-60 seconds, but loss of consciousness may not occur. Being in an upright position, patients fall, fainting is accompanied by pallor, sweating, a rare pulse and hypotension. Longer syncopal periods are manifested by convulsive muscle contractions, involuntary urination. In the recovery period, retrograde amnesia and weakness are noted.
In addition to disorders of consciousness, the pathological syndrome may be accompanied by speech disorders, involuntary lacrimation, loss of muscle tone that occur in the parasyncopal period. In old age, transient cognitive impairment is possible. In some patients with hypersensitivity syndrome of the carotid sinus, attacks of sharp weakness, loss of postural tone by the type of cataplexy without loss of consciousness are described. The pathological condition can be combined with other types of neurogenic syncope.
Complications
Half of the people who have experienced fainting due to carotid sinus syndrome report serious bodily injuries. The probability of adverse consequences increases in older people when syncopations occur suddenly in unforeseen situations. 25% of patients have hip fractures, intracranial hemorrhages, injuries of internal organs that require emergency and specialized therapy. Some cases are accompanied by episodes of focal neurological disorders, associated with atrioventricular blockade.
Diagnostics
In many cases, the pathological syndrome occurs without any trigger, sometimes there is even no indication of syncope in the past. Therefore, anamnesis and physical examination data may have low informative value. The only method that allows to confirm the hypersensitivity of the carotid artery baroreceptors is the massage of the carotid sinus. This diagnostic technique is indicated for all patients with syncope of unknown origin.
Massage is performed in the patient’s supine position with simultaneous continuous monitoring of ECG and blood pressure. The test is considered positive when an asystole occurs with a duration of more than 3 seconds, a decrease in blood pressure by more than 50 mm Hg. art. or a combination thereof. False positive results are possible with atherosclerosis of the carotid arteries – to exclude it, auscultation of this area for noise is carried out beforehand.
For elderly patients, massage of the sinocarotid zone has a special diagnostic value. Usually the procedure is safe, but there are reports of the development of neurological deficits, cardiac complications (atrial and ventricular tachycardia, blockades, coronary spasm) after it. Therefore, performing massage is contraindicated for people suffering from disorders of cerebral circulation, myocardial infarction, arrhythmias.
When making a diagnosis, a neurologist has to exclude other neurogenic syncopations (vasovagal, orthostatic, situational), cardiac pathology (sinus node weakness syndrome), metabolic disorders (hypoglycemia in diabetes mellitus), especially in conditions of comorbidity in the elderly. To do this, a passive orthostasis test (tilt test) is performed, round-the-clock ECG monitoring is performed, biochemical parameters of blood plasma (glucose level) are examined.
Treatment
Conservative therapy
When prescribing treatment, the frequency of symptoms, their severity, and the specifics of a particular case are taken into account. Against the background of therapy, patients need dynamic monitoring to monitor its results and possible side effects, which allows them to make appropriate adjustments in time. Conservative measures are of great importance for people suffering from carotid sinus syndrome:
- Lifestyle changes. The patient is advised to avoid sudden head movements, wearing clothes that squeeze the neck, he is trained to identify prodromal symptoms in order to take a horizontal position in time to prevent syncope. With vasodepressor variants of syncope and the absence of concomitant cardiac pathology, the intake of liquid (up to 2 liters) and table salt (up to 6 g) is increased.
- Pharmacotherapy. Treatment of recurrent sinocarotid syncope is carried out by medication. The effectiveness was demonstrated by drugs from the group of a1-agonists (midadrin), selective serotonin reuptake inhibitors (sertraline, fluoxetine), glucocorticoids (fludrocortisone). But in randomized trials, the long-term results of their use are not confirmed.
Surgical treatment
For the treatment of cardioinhibitory and mixed syncope without clear provoking factors, it is recommended to carry out constant pacing – atrial, ventricular or two-chamber. With asymptomatic hypersensitivity, it is not advisable to perform the procedure. Previously, surgical or radiological deneuration of the carotid sinus was used in operative neurology, but now the method is not used due to the high risk of complications. Tumors and scarring in the neck that irritate the receptor apparatus of the carotid artery are removed.
Prognosis and prevention
Injuries caused by sinocarotid syncope limit physical activity, reducing the quality of life. The risk of relapse is 62% for 4 years, but active therapy can reduce this indicator threefold. The worst prognosis is observed in people suffering from the vasodepressor variant of the syndrome. The recorded mortality rate is associated with old age and comorbidity. Primary prevention involves the elimination of factors irritating the carotid sinus, rational therapy of concomitant pathology.
