Carotid sinus syncope

Introduction Carotid sinus syncope, also known as carotid sinus syndrome, is a group of spontaneous clinical manifestations of sudden dizziness, fatigue, tinnitus and even syncope. When the primary brain type stimulates the carotid sinus, although there is no obvious heart rate and blood pressure changes, the patient has symptoms of syncope or syncope, often very short. Common in patients with obstructive lesions of the anterior carotid artery and vertebral-basal artery system. Symptoms often associated with autonomic dysfunction, usually caused by a sudden turn of the head or a tight collar.

Cause

The carotid sinus is located in the bifurcation of the internal carotid artery. This part is called the carotid sinus and has a baroreceptor. It is connected to the orbicular nucleus of the medulla and the dorsal nucleus of the vagus nerve. Stimulation of the carotid sinus can affect arterial blood pressure, heart rate, myocardial work, cardiac output, arterial resistance, and venous volume. The reflex pathway passes through the sinus nerve (branch of the vagus nerve) to the solitary tract nucleus, and then to the dorsal nucleus of the vagus nerve. The fibers are transmitted through the vagus nerve, resulting in slowing of heart rate and blood pressure. However, under normal circumstances, the heart rate is slowed down to 5 times/min, and the systolic blood pressure and diastolic blood pressure drop are all within 1.33 kPa (10 mmHg). In patients with carotid sinus syndrome, the sensitivity of carotid sinus to external stimuli is abnormally increased. When external stimuli are felt, the parasympathetic tone is significantly increased on the one hand, the sinus heart rate is significantly slowed down, the PR interval is prolonged, and the atrioventricular conduction is high. Blocking or a combination of the three, cardiac output is significantly reduced to cause cerebral ischemia, can occur syncope, on the other hand, secondary to decreased sympathetic activity, can cause systemic arterial relaxation, blood pressure significantly reduced and cause cerebral blood The perfusion pressure suddenly drops and syncope can occur. There are also some patients, although there is no obvious heart rate and blood pressure changes, but when the carotid sinus is stimulated, the cerebral vasoconstriction, causing cerebral ischemia, can also cause syncope.

an examination

Related inspection

Cerebrospinal fluid glucose and serum glucose ratio neck activity test jugular vein reflow test

Middle-aged and elderly patients often have syncope, especially when the syncope is suddenly turned, the head is turned or the tight collar is related to the cause of the disease, and the carotid sinus stimulation test is feasible.

Other auxiliary inspections:

1. Carotid sinus stimulation test is also called Czermak-Hering test. The method is to continuously massage the left and right carotid arteries with a medium pressure at the patient's bedside. The massage point is generally selected in the bifurcation of the common carotid artery (equivalent to 1/3 of the sternocleidomastoid muscle). Note that the left carotid sinus is lower than the right side. At the intersection of the transverse ligament and the sternocleidomastoid muscle, the upper point of Herping is the first point of Hering. When this point is pressed, the blood pressure drops and the pulse slows down. Take a point on the common carotid artery to Hering the second point (equivalent to the lower part of the carotid sinus). If this point is pressed, the carotid sinus pressure will decrease, and the opposite will cause the blood pressure to rise and the pulse to accelerate. Therefore, the first point of Hering should be selected for the diagnosis of carotid sinus syndrome. Generally, in the 2-4s of the massage, the heart rate slows down and the blood pressure drops, and the lowest value is reached in 5 to 50s. When a normal person massages the carotid sinus, the heart rate is slowed down 6-10 times. If it is slowed down by 10 times/min, the carotid artery stimulation test is considered to be positive. At this time, the electrocardiogram and heart rate changes should be closely observed, and the patient's systolic blood pressure should be monitored by cuff method to observe whether there is bradycardia and systolic blood pressure. Each massage time should not exceed 5s, the time interval between the left and right massage should be greater than 15s, and avoid double massage at the same time. To avoid excessive pressure, the examiner should simultaneously touch the strength of the ipsilateral carotid artery. It must be noted that elderly people with carotid atherosclerosis, carotid arthritis, and lymph nodes around the carotid artery should be used with caution to prevent cerebrovascular accidents. Carotid artery stimulation induces bradycardia and decreased blood pressure or syncope can often confirm the diagnosis.

2. Upright tilt test About 50% of patients with carotid sinus syndrome have positive in this test, so the value of the upright tilt test is not significant in the identification of vasopressive syncope.

Differential diagnosis

It is distinguished from reflex syncope, coughing syncope, swallowing syncope, and urinary syncope in vasopressive syncope.

Reflex syncope: common in simple syncope (vascular vagal syncope vasopressor syncope), carotid sinus syncope, orthostatic hypotonic syncope (post-position hypotension), urinary syncope, swallowing syncope, more common in Young men, in the urination or at the end of urination, lasted about 1 to 2 minutes, self-awaken, no sequelae. The mechanism may be comprehensive, including autonomic autonomic instability, sudden changes in body position (waking up at night), breath holding during urination, or decreased cardiac output, decreased blood pressure, and cerebral ischemia through vagal reflex.

Coughing syncope: seen in people with chronic lung disease, after a severe cough. The mechanism may be increased intrathoracic pressure during cough, blocked venous return, decreased cardiac output, decreased blood pressure, and cerebral ischemia. It is also thought that cerebrospinal fluid pressure rises rapidly during severe cough, causing shock to the brain. Middle-aged and elderly patients often have syncope, especially when the syncope is suddenly turned, the head is turned or the tight collar is related to the cause of the disease, and the carotid sinus stimulation test is feasible.

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