Sick sinus syndrome in the elderly
Introduction
Introduction to sick sinus syndrome in the elderly Sick sinus syndrome (SSS) refers to lesions in the sinus node and its adjacent tissues. Pacing and/or impulsive efferent disturbances lead to a series of arrhythmias, causing dizziness, darkness, and transient consciousness. Barriers and syncope, including a series of clinical manifestations of the whole body, nerves, and heart, are more common in the elderly. basic knowledge The proportion of the disease: the incidence rate of the elderly over 60 years old is about 0.04% - 0.07% Susceptible people: the elderly Mode of infection: non-infectious Complications: syncope, sinus arrest, sudden death
Cause
The cause of sick sinus syndrome in the elderly
(1) Causes of the disease
1. The most common is idiopathic degenerative changes that cause the conduction system to proliferate.
2. Coronary heart disease, acute myocardial infarction (may be transient).
3. Hypertensive heart disease, myocarditis, cardiomyopathy.
4. Sinus atherosclerotic occlusion.
(two) pathogenesis
Anatomical and physiological characteristics of sinus node
Sinus node anatomy
Sinus node is a kind of special differentiated myocardial tissue. Its shape is flat and long. It is generally divided into three parts of the head and tail. It is located at the upper end of the right atrial superior vena cava entrance. The head end is 1mm below the epicardium. Endocardium, size (15 ~ 20) mm × 5mm × 2mm, the structure of the sinus node is not uniform, the cells of its composition can be roughly divided into two categories, one is called pacemaker cells (P cells), more Gathering together to form a cluster of multiple pacemaker cells, the cell diastolic phase is very fast, which is the basic sinus rhythm pacemaker of the heart, and another type of cells are distributed around the entire pacemaker cell cluster, called transitional cells. The conduction function is better, there are connective tissue and interstitial cells between cells, and with the increase of age, the number of cells decreases, and the fibrous connective tissue can increase.
The sinus node is rich in blood supply and is supplied by the sinus node artery running through it. About 55% to 60% of the artery is from the right anterior anterior artery of the right coronary artery, and 40% to 45% is from the left of the left coronary artery circumflex artery. The blood supply to the anterior chamber of the anterior chamber is 8 times the area of the diameter of the small arteries adjacent to the atrial wall, and the blood supply is 15 times that of the nearby atrial muscle.
Sinus node is rich in autonomic innervation, especially cholinergic nerve fibers are extremely abundant, and the number of adrenal nerve fibers is small. Therefore, the vagus nerve has a greater influence on sinus node function.
2. Physiological characteristics of sinus node
Sinus node is the pacemaker of normal sinus rhythm of the heart. It is a slow-reacting cell. Its transmembrane potential and action potential are very different from those of ventricular intrinsic myocardial fast-reacting cells. It is opened by calcium channels, closed, and calcium influx. According to the characteristics, the maximum diastolic membrane potential level is -60 ~ -70mV, the fourth phase potential is not fixed, the threshold potential is about -60mV, the 0 phase rises slowly, and the action potential curve 1, 2, 3 phase shifts, distinguish Not obvious, the action potential amplitude is low, about 60mV. Because this type of cell has a faster spontaneous depolarization of the 4 phases, it has higher self-discipline than other parts of the pacemaker cells.
The pacing function and sinus conduction of the sinoatrial node are determined by the intrinsic physiological functions of the cells, but they are also obviously affected by the autonomic nerve. The vagus nerve is excited and can be released by acetylcholine, which makes the phase depolarization slower and the heart rate is slow. Slowing, prolonged intraductal and sinus conduction time, effective refractory period and relative refractory period of sinus node, and sympathetic excitation, can release norepinephrine, so that the 4 phase depolarization slows down, sinus node The self-discipline is accelerated and the sinus conduction time is shortened.
3. Etiology and pathophysiology
Pacemakers and conductive cells in the aged cardiac conduction system decline with age, replaced by elastic, increased reticular and collagenous fibrous tissue, and fatty infiltration and calcification, which can be part of the conduction system. Or all, this is the pathological basis of sinus syndrome in the elderly, the disease is mainly the sinus node P cells and surrounding fiber lesions, sometimes more extensive, involving the atrial or atrioventricular junction, the latter also known as double knot Lesion.
Common causes are:
1 coronary heart disease: the most common cause of sinus syndrome in the elderly, sinus node blood supply from the central sinus node artery, the arterial blood supply 55% from the right coronary artery, 45% from the left coronary artery circumflex, due to sinus node Only one artery supplies blood, so when coronary atherosclerosis involves the artery, the sinus node will have ischemic changes. In acute myocardial infarction, especially in the inferior wall infarction, more than half of the patients may have bradycardia. Caused by poor coronary blood supply, it is often a chronic process, progressive progressive, but some studies have found that patients with sinus syndrome with coronary atherosclerosis often have no sinus node disease, sick sinus syndrome Clinically, there are no more than 25% of patients with coronary heart disease. In addition to acute inferior wall and lateral wall infarction, it is uncommon and often temporary, so there may be other more important factors involved. The pathogenesis of this disease is currently considered to be the most common underlying disease in the elderly due to the degenerative changes and hardening of the sinoatrial node and its adjacent tissues.
2 Myocarditis and cardiomyopathy: It is also another common cause of sick sinus in China, such as rheumatic and viral myocarditis, systemic lupus erythematosus, cardiomyopathy caused by amyloidosis and primary cardiomyopathy.
3 trauma, cardiac surgery and radiation therapy and other damage to the sinus node or affect the sinus node blood supply can cause sinus node dysfunction.
4 hypertension, hyperthyroidism, muscular dystrophy, hemochromatosis, Friedreiech hereditary ataxia, congenital and rheumatic heart disease, drug poisoning, electrolyte balance disorder and some such as digitalis, beta-adrenergic resistance Drugs such as stagnation drugs, calcium channel antagonists, antiarrhythmic drugs and lithium carbonate can aggravate sinus node dysfunction.
Although the sinoatrial node and its surrounding cells are easily damaged, the sinus node artery has abundant branches. The area of the small arterial tube diameter is much larger than that of the adjacent atrial wall arteries. At the same time, the sinus node is extensive. The distribution of the nerves, therefore, the occurrence of sick sinus syndrome also reflects the blood supply disorder or necrotic lesions of the sinus node, and the inflammatory damage has reached a rather serious stage.
Prevention
Prevention of sick sinus syndrome in the elderly
The decline of sinus node function is actually the process of aging of the sinus node itself, and is not the inevitable result of the development of some kind of organic heart disease. Therefore, it is believed that the SSS treatment of the elderly should still be implanted on the basis of improving myocardial ischemia. Pacemaker treatment.
Complication
Complications of elderly patients with sick sinus syndrome Complications, syncope, sinus arrest, sudden death
Common complications include senile syncope, sinus arrest, ventricular fibrillation, and sudden death.
Symptom
Symptoms of sick sinus syndrome in the elderly Common symptoms Weak bradycardia, chest tightness, memory disorder, arrhythmia, chest pain, chest tightness, palpitations, dizziness, chest pain, or emotional excitement... palpitations with fatigue, pale
The progression of sinus node failure is generally slow, and it usually takes 5 to 10 years or more to completely lose function. Therefore, most patients have insidious onset, long history, slow progression, and no other discomfort in early patients. At the time of physical examination, it was found that the general symptoms were mainly due to insufficient blood supply to the brain, heart, kidney and other organs caused by slow heart rate, especially the lack of blood supply to the brain.
Brain performance
Symptoms vary in severity, manifestations vary, can be intermittent, mild fatigue, dizziness, vertigo, insomnia, intermittent memory loss, slow response or irritability, language ambiguity, contempt, judgment error, Short-term loss of consciousness, dizziness and approximate syncope. The most common and serious symptoms of severe cases are syncope and darkness, which are often the main reason for the treatment. During tachycardia, there are fewer obvious brain symptoms, about 10 % of patients may have sudden death, and some undiagnosed patients who died suddenly after physical activity or after sports may be a manifestation of this disease.
2. Cardiopulmonary performance
In addition to slow heart rate or slow and rapid heart rhythm in the early stage, there may be no other manifestations of the heart. As the disease progresses, the clinical manifestations are palpitations, discomfort in the anterior region, chest tightness, etc., regardless of the rate of heart rate for coronary blood supply. Influence, and senile sickle sinus syndrome is often accompanied by atherosclerotic heart disease, so it can be associated with angina pectoris. Periodically sudden onset of pulmonary edema is a feature of sick sinus syndrome, combined with sick sinus synthesis in acute myocardial infarction At the time of enrollment, congestive heart failure and even shock may occur. In patients with severe sinus syndrome, persistent cardiac arrest or ventricular fibrillation may occur and death may occur. Generally, when the body is examined, the heart rate is slow, and when the tachyarrhythmia is combined The heart rate can suddenly reach 100 times/min or more, and the duration is different. After the tachycardia is stopped, there may be a ventricular suspension with or without syncope.
3. Other performance
Various non-specific clinical manifestations such as oliguria and gastrointestinal discomfort are not uncommon, but these manifestations are usually caused by insufficient perfusion of the organs due to the heart itself.
Sick sinus syndrome currently lacks a unified diagnostic criteria, and the sinus node function test is a comprehensive dynamic analysis. The main clinical diagnosis is arrhythmia, combined with clinical manifestations for suspected sick sinus syndrome with sinus bradycardia. The main manifestations should be differentiated from sinus bradycardia caused by other causes. If the diagnosis is difficult, the clinical use of long-term follow-up observation, if necessary, use various monitoring systems for long-term monitoring, to ensure accurate diagnosis and prevent one-sidedness .
Examine
Examination of sick sinus syndrome in the elderly
Blood routine: generally normal.
Electrocardiogram
According to the performance of electrocardiogram and dynamic electrocardiogram, it can be divided into the following types: type I: persistent and severe sinus bradycardia, heart rate <60 times/min, sometimes as low as 40 times/min or lower. Type II: sinus bradycardia with sinus arrest or sinus block, type III: bradycardia tachy cardia syndrome (BTS) or fast-slow syndrome, ie Bradycardia-based, with paroxysmal atrial tachycardia, atrial flutter or atrial fibrillation, type IV: double-junction lesions, manifested by the combination of the above-mentioned types of atrioventricular junctions and Or) conduction dysfunction, mostly delayed atrioventricular junctional escape, slowed atrioventricular junction escape rhythm (easy stroke period > 1.5s) or atrioventricular block, V: can eventually develop into Chronic atrial fibrillation (>6 months), but the rate of ventricular rate is slow, the order of this type basically represents the development process of sick sinus syndrome, the latter three types are late performance, which means that the lesion range has been extensive, sinus Both the knot and the atrioventricular node have been affected.
2. Dynamic electrocardiogram (DEG)
Some patients have intermittent episodes, the duration of episodes is short, and various arrhythmia occur at night. Conventional electrocardiogram is not easy to obtain positive results. At this time, dynamic electrocardiogram is very helpful, and more than double-junction lesions can be found compared with conventional electrocardiogram. Caused by arrhythmia, can assess the severity of sick sinus, easy to find intermittent sinus, and can be used as a cause of syncope, dizziness and other differential diagnosis, cardiogenic syncope often due to bradycardia, sinus pause or severe arrhythmia Caused by DEG to confirm, rather than cardiogenic syncope or dizziness, such as transient ischemic attack, vasomotor disorder or otogenic vertigo, etc., there is often no corresponding arrhythmia change in DEG, but pay attention Some healthy elderly people also have sinus bradycardia at night.
3. Determination of sinus node function
Sinus node function tests included: sinus node recovery time (SNRT), corrected sinus node recovery time (CSNRT), sinus conduction time (SACT), and sinus node effective refractory period (SNERP), where SNRT and CSNRT has good sensitivity and specificity for diagnosing sick sinus.
(1) Intrinsic heart rate (IHR): refers to the frequency of self-rhythm of sinus node in the absence of autonomic nerves (blocking vagus and sympathetic nerves to temporarily detach the sinus node from neurohumoral regulation) In general, it slows down with age.
METHODS: After 10 minutes of supine, intravenous atropine 0.04 mg/kg and propranolol 0.1 mg/kg were administered intravenously within 3 min. The heart rate measured by 5 to 7 min was IHR. Jose suggested propranolol 0.2 mg/kg. Minute 1 mg was intravenously injected to block the sympathetic nerves. After 10 minutes, atropine was administered intravenously at 0.04 mg/kg. After 2 minutes, the vagus nerve was blocked. The heart rate measured after 3 to 5 minutes was IHR, which was maintained for 30 minutes.
Judgment of results: In general, IHR 80 beats / min indicates dysfunction of the sinus node, but the older the age, the inherent heart rate decreases, so the normal value needs to be corrected by age, and Joses and Collison obtain the linear regression equation. The normal heart rate predicted by normal people (IHRp)=118.1-0.57×age, and the 95% confidence interval of 45 years old and above is IHRp±18%, ie, IHR<[118.1-(0.57×age)]×82% Determine the sinus node function is low.
The sensitivity of the diagnosis of sick sinus is 60% to 80%, and the specificity is about 70% to 80%. However, it should be noted that the elderly are accompanied by asthma, and prostate hypertrophy and glaucoma cannot be performed.
The relationship between IHR and resting heart rate (RHR) can also be used to determine whether autonomic function is positive or negative. The heart rate at rest depends on autonomic function to exert positive and negative effects on the sinus node. The net result of the two effects at the time of response can be calculated as the result of the direction and degree of autonomic control of the heart rate at the time of examination: autonomic nervous tension (%) = (RHR/IHR-1) × 100%, if the result is Negative, indicating that the autonomic nerve exerts a negative effect on the patient, and the vagus nerve is too strong or the sympathetic nerve is too weak. If the result is positive, the vagal tone is low or the compensated sympathetic function is hyperthyroidism. The result is a negative value.
(2) sinus node recovery time (SNRT): atrial pacing is mainly performed by atrial pacing with a higher frequency of pacing rate, and the sinus node is in a state of inhibition due to rapid frequency stimulation, and then Suddenly stop rapid atrial pacing, sinus node recovery after a period of "warm up" process to restore sinus rhythm, from the sudden stop pacing to restore sinus rhythm time, that is, sinus node recovery time, sinus node dysfunction recovery Sinus pacing takes longer.
Methods: 1 transesophageal atrial pacing method: the bipolar and quadrupole catheter electrodes were inserted into the esophagus from the nostrils or the oral cavity. The position of the electrodes was adjusted according to the P wave shape of the esophageal electrocardiogram, and the maximum bidirectional P wave or positive P wave was taken.
2 intravenous atrial pacing method: generally inserted into the right atrium wall through the right femoral vein inserted bipolar catheter electrode, for the intracardiac electrocardiogram or Histogram.
S1S1 grading stimulation method is usually adopted, that is, the stimulation frequency of each level is increased by 10-20 times/min, each stimulation is 60s, the interval is 2min, the maximum stimulation frequency is not more than 150 times/min, and the last stimulation pulse signal is measured to the next sinus beat. The starting point of the P wave is the recovery time of the sinus node, A1 represents the basal atrial wave, the atrial wave of the extra-stimulus is A2, and the atrial wave appearing later is A3.
Judgment of results: It is generally considered that the sinus node recovery time <1500ms is normal (normal value 800 ~ 1500ms), and its normal value is related to the original basal heart rate, such as the original heart rate is 70 ~ 80 times / min, SNRT is 800 ~ 900ms, heart rate 45 ~ 60 times / min, can be as long as 1200 ~ 1400ms, the elderly SNRT> 1600ms is abnormal, severe sinus syndrome can reach 6000ms, the following situation shows sinus node dysfunction, has a certain diagnostic significance :
1SNRT is extended by >2000ms.
2 The secondary SNRT is prolonged, that is, the second, third or even fifth cycle is abruptly extended after the pacing is stopped or the cycle length is extended for more than 3 cycles.
3 The recovery time of the junction area is prolonged. It is not the sinus rhythm but the junctional escape rhythm after stopping the pacing. The time interval between the last pulse signal and the borderline escape is >1500ms, and the corrected sinus node recovery. Time (CSNRT) is prolonged, and the recovery time of sinus node includes three parts, that is, the time from the atrial agitation to the sinus node at the pacing, the time of self-discipline recovery in the sinus node, and the excitement from the sinus node to the atrium. Time, and the recovery time of the sinus node depends on two factors, the basic sinus rhythm cycle (SCL, A1A1) and the degree of inhibition caused by overspeed pacing. The SNRT, including SCL, eliminates the basal sinus cardiac cycle by correction. The effect of sinus node recovery time is convenient for patients with different SCL to compare the effects of overspeed inhibition. There are currently three methods for measuring CSNRT: subtracting the original cardiac cycle A1A1 from SNRT, the corrected sinus node recovery time >550ms is abnormal, the sinus node recovery time index (SNRT/A1A1)>1.6; The period of the sex period (ms) is 1.3 times plus 101 ms, which is the upper limit of the normal SNRT.
4 The total recovery time (TRT) of sinus node is prolonged, from the last pacing pulse to the time to return to the length of the basic sinus cycle, that is, the total recovery time of sinus node, normal person <5s, or shorter than 4-6 recovery The sinus beat time is generally replaced by TRT after termination of pacing stimulation and the total length of 5 recovered sinus cycles, ie, PPC1~5 is the sum of the first five cardiac cycles after restoring sinus rhythm after sudden pacing > 5800ms is abnormal, or 5 times of the basic sinus cycle is corrected for CPPC1~5=PPC1~5-5 sinus cycles. If >1200ms is abnormal, the sensitivity of the method for diagnosing sick sinus is about 80%~95%. The specificity is about 90%, but it should be noted that the SNRT measurement value increases with the increase of the stimulation frequency. When the stimulation frequency increases to a certain value, the SNRT is the longest, and then the stimulation frequency is shortened, which is generally based on the longest SNRT. The correlation between SNRT and the duration of stimulation is not obvious in normal people, but the SNRT of patients with sick sinus can be prolonged with the prolongation of pacing time. Therefore, 60s pacing should be taken as the standard.
(3) Sinus atrial conduction time (SACT)
At present, the Narula method is mainly used, that is, the pulse frequency S1S1 which is 10 times faster than the heart rate is continuously pacing the atrium 8 times, so that it can capture the atrium without causing sinus node inhibition, but the pacing pulse will control and reconstruct the sinus The rhythm of the knot, the sinus escape cycle includes the sinus node self-period and the sinus, sinus time, and the period from the last pacing signal A2 to the sinus P wave A3 (A2 to A3) is measured. SACT=1/2[(A2A3)-(A1A1)], in order to avoid the influence of stimulation, it is proposed to change to SACT=1/2[(A2A3)-(A3A4)].
Judgment of results: Generally speaking, the sinus conduction time should be <150ms, >160ms has diagnostic significance; one room is enough to cause sinus arrest in patients with severe sinus conduction function; spontaneous metamorphosis is significantly extended after metastasis, also explained SACT is extended.
The sensitivity of this method is about 50% to 70%, and the specificity is 40% to 70%. Because of its influence on various factors such as sinus block and sinus arrhythmia, the repeatability is poor, and the diagnostic value for sick sinus is more than that of sinus. The recovery time of the house is small.
(4) effective refractory period of sinus node (SANERP): If the refractory period of sinoatrial node cells or sinus connective tissue is prolonged, the excitatory sinus node cells and the extra-atrial stimulation into the sinus node will be affected. Through the extra-atrial stimulation, the atrial fibrillation interval is further shortened after the I zone (reconstruction zone), and an insertional room early (III zone) occurs. This insertion occurs when the atrial activation is invaded. When the refractory period of the previous sinus agitation is reached, the refractory period of the sinus node can be indirectly measured by this method.
Generally, S1 stimulation is given 8 times faster than the basal heart rate 10 to 20 times/min, then S2 stimulation is given, S1S2 starts slightly shorter than the S1S1 interval, and the stimulation is successively decreased in 5 or 10 ms steps, when the S1S2 is decremented. When A1A2+A2A3=A1A1, it means that S2 enters zone III reaction, and A2 is inserted into the room early. At this time, the longest A1A2 interval is the effective refractory period of sinus node. Normally, it should be <400ms. If it is >600ms, it is abnormal. Its sensitivity to the diagnosis of sick sinus is about 33% to 60%, and the specificity is 85% to 94%.
4. Sinus node function stimulation test
(1) Exercise test: The purpose is to accelerate the metabolism of the body and speed up the heart rate. If the sinus node is in a pathological state, the exercise can not cause the heart rate to increase. At present, there is no certain amount of exercise or exercise for diagnosing the diseased sinus. 15 to 20 times inside, squat, two steps, flat and treadmill exercise, immediately record the heart rate within 10 ~ 15s, if the heart rate <90 times / min is positive, use 2 times or 3 times two step movement, The heart rate should not exceed the basal heart rate of 30 beats/min, or the junctional escape rhythm and the second degree sinus block should be positive.
(2) Atropine test: intravenous atropine 2mg or 0.02~0.03mg/kg, record II lead electrocardiogram before and after injection, 1, 3, 5, 10, 15, 20, 30min, record the fastest and slowest Heart rate, such as heart rate less than 90 times / min or instead induced arrhythmia such as sinus block, sinus arrest, junctional rhythm and atrial fibrillation, support the diagnosis of sick sinus syndrome, such as heart rate can not be in the original heart rate A 25% increase on the basis suggests that the sinus node function is poor.
(3) Isoproterenol test: generally for the elderly should first use isoproterenol 10mg mouth, if the heart rate increase is not obvious or no adverse reactions, then 0.2mg / 100ml concentration, 2 ~ 4ml per minute Intravenous infusion, also used 0.5mg into 250ml liquid intravenous input, 1 ~ 2g per minute, observed for 30min, if the heart rate <90 times / min is positive, can not exceed 25% of the original heart rate or borderline rhythm Also positive.
(4) Carotid sinus massage test: the right or left carotid sinus massage is not the same for cardiovascular inhibition. The right side of the massage mainly affects the sinus node and slows the sinus heart rate. Atrioventricular node, the PR interval is prolonged. Under the ECG monitoring, the carotid sinus massage is 5~10s. If there is an abnormality in the 3s stoppage interval, it may prompt the paroxysmal syncope caused by the carotid sinus hypersensitivity. Methods for patients with cerebral arteriosclerosis with caution.
As with the stimulation of the carotid sinus, the response to Valsalva's motion can be effectively used to confirm dysfunction of the sinus node. Valsalva action, in particular, can produce changes in the expected aortic pulse pressure, but with little or no change in pulse rate, and In contrast, physiologic bradycardia in the elderly manifests as an expected rate of heart rate acceleration during the stress phase (phase II), with the heart rate slowing during periods of high blood pressure (IV phase), but care must be taken that these operations It does not provide a direct diagnosis of sinus node disease, but only some clues about the sinus node function status.
Elderly people have constant heart, poor lung function, and many chronic heart and lung diseases such as coronary heart disease and hypertension. Care should be taken when conducting the above tests to induce acute myocardial infarction, heart failure, arrhythmia, etc., especially when using isoproterenol. It is easy to cause severe arrhythmia. Therefore, the indications should be strictly controlled and should be carried out under the condition of rescue to avoid accidents. In the elderly, the application of atropine has side effects such as urinary retention and glaucoma aggravation, so it is among the elderly. Use should be limited.
5. Sinus node electrogram
The sinus node is the primary pacing site of the heart. The surface electrocardiogram and the usual electrocardiogram cannot directly describe the electrical agonism, nor can it directly display its conduction and conduction functions, even the sinus node measured by the atrial pacing method described above. Recovery time and conduction time are also indirect judgments. The sinus node electrogram is to use the catheter technique to send the electrode to the vicinity of the sinus node at the junction of the upper right atrium and the superior vena cava to directly trace the electrical activity of the sinus node. From the starting point of the sinus node (ie, the fast rising wave) to the starting point of the atrial wave, it is the sinus node conduction time. If used in combination with the atrial pacing method, it can more accurately reflect the function of the sinus node.
Diagnosis
Diagnosis and diagnosis of sick sinus syndrome in the elderly
Diagnostic criteria
Anyone with one or more of the following may be considered as sick sinus syndrome:
1 persistent and severe sinus bradycardia, heart rate continued below 50 beats / min.
2 sinus arrest and no escape rhythm in the short term, or a short time after the stop is replaced by atrial or borderline rhythm, such as atrial or borderline paroxysmal tachycardia, atrial flutter and atrial fibrillation.
3 sinus arrest is persistent without new pacing points, or followed by ventricular arrhythmias.
4 Chronic atrial fibrillation caused by sinus arrest, slow ventricular rate (not caused by drugs) suggesting double knot lesions.
5 Atrial fibrillation can not restore sinus rhythm after a long time after electric shock.
6 non-drug caused sinus block.
7 sinus node function test showed sinus node dysfunction.
Differential diagnosis
Clinical should be differentiated from non-cardiac syncope or dizziness, such as transient ischemic attack, vasomotor disorder or otogenic vertigo.
