Presyncope and Syncope - Josh Corwin



Presyncope and Syncope

I. Syncope is a sudden, transient loss of consciousness associated with inability to maintain postural tone and with spontaneous recovery. Presyncope: premonition of syncope without the loss of consciousness

II. Epidemiology: 3% of patient each year and 1% get admitted

a. The elderly population has the highest incidence and is at increased risk for morbidity from syncopal episodes. Aging causes blood vessel to become calcified and less compliant, leading to decrease flow rates (S4 sound) Left ventricle becomes less compliant, resulting in increased diastolic filling pressures and dependence on atrial kick”. There is a general decrease in adrenergic receptor responsiveness of both the heart and the peripheral blood vessels. Chronic pathological processes contribute to decrease cerebral perfusion: atherosclerosis, DM, HTN, valvular heart disease, medication

b. Pregnancy is associated with numerous physiologic changes including increased HR, decreased peripheral resistance, and increased stroke volume.

i. Late pregnancy, uterus becomes very large and compresses the inferior vena cava when they lay on the right or supine and have syncope. Any cardiac dysrhythmia can cause syncope

ii. Premature ventricular contractions are higher in women and cause syncope

III. Pathophysiology and etiology

a. The final common pathway of syncope is a lack of vital nutrient delivery to the brainstem reticular activating system, leading to loss of consciousness and postural tone. Most commonly an inciting event causes a drop in cardiac output, which, unless corrected rapidly, decreases oxygen and substrate delivery to the brain. Less commonly, vasospasm or other alterations in flow singularly reduce CNS blood flow.

b. The reclined posture of syncope and response of autonomic autoregulatory centers reestablish cerebral perfusion, leading to a spontaneous return of consciousness. (When you syncopize, you fall then return back

c. The most common causes are:

i. Orthostatic hypotension

ii. Vasovagal (reflex mediated)

iii. Cardiac dysrhythmia

IV. Reflex mediated: vasovagal, situational, cough, micturition, defecation, swallowing, pain, carotid sinus hypersensitivity, orthostatic hypotension

a. Normally, physical or emotional stress leads to increased sympathetic outflow and subsequent increase in HR, BP, and cardiac output. In reflex-mediated syncope, stimulus produces an abnormal autonomic NS reflex. Most commonly, an initial increase in sympathetic outflow is inappropriately withdrawn and replaced by increased vagal tone. Hypotension with or without bradycardia follows, leading to decreased cerebral perfusion and syncope. Less commonly, stimulus leads directly to vagal hyperactivity and symptoms.

b. Prodromal symptoms are varied: light headed, dizzy, sweating, nausea, blurred vision or loss of vision from periphery in, feel hot

c. Vasovagal syncope is incited by a noxious stimulus (pain, fear) or a characteristic setting: vertical, standing position and the attacks are aborted or resolve after reclining (blood perfuses to brain)

d. Vasovagal syncope is typically preceded by warning symptoms, which may last several minutes. This diagnosis should not be made without the typical prodromal symptoms. Dx: upright tilt table testing

e. Carotid sinus hypersensitivity: carotid body, located at the carotid bifurcation, is a pressure-sensitive organ. The stimulation of an abnormally sensitive carotid body by external pressure may lead to:

i. Most commonly, abnormal vagal response with bradycardia and asystole of greater than 3s

ii. Less commonly, vasodepressor response leading to a decreased BP of >50mmHg

f. It is more common in: men, elderly, patients with hypertension, ischemic heart disease, certain head/neck malignancies

g. Dx: Carotid sinus massage; unless it results in syncope or recurrence of prodromal symptoms and is associated with an inciting event (shaving or turning of head), it cannot be definitely diagnosed. Can be done at the bedside in the ED with continuous EKG and BP monitoring after informed consent has been obtained. Each carotid body is separately massaged for 5 to 10s. The test is considered positive if symptoms are reproduced in the presence of asystole greater than 3s or fall in systolic blood pressure of >50mmHg. Contraindicated: presence of bruits (carotid stenosis), history of CVA or MI

h. Situational syncope: abnormal or hypersensitive autonomic reflex response to a specific physical stimulus; may be a component of increased intracranial or intrathoracic pressure leading to decreased cerebral perfusion. The physical stimulus may be associated with another underlying disease process: swallowing- achalasia, esophageal stricture

1. Micturition- BPH, prostate cancer

2. Defecation- colon cancer, constipation

i. Orthostatic Syncope: When a person assumes an upright posture, blood is shifted to the lower part of the body and cardiac output drops. In a healthy individual, the autonomic NS responds with an increase in sympathetic output and a decrease in parasympathetic output, producing increase in heart rate and peripheral vascular resistance.

i. If patient remains upright and response is not efficient, we get decreased cerebral perfusion

ii. Patient will not syncopize from orthostatic hypotension unless standing for more than 3 minutes

j. Definition: A fall in systolic BP of >20mmHg upon assuming the upright posture

i. Caution in diagnosing orthostatic syncope based on orthostatic BP measurements alone, 5-50% of patients with other causes of syncope have orthostatic hypotension on physical exam.

ii. Consider autonomic dysfunction- failure of vasoconstriction during orthostatic stress due to primary disease, neuropathy, medications, volume depletion (GI losses, bleeding, diuresis)

1. Causes- diabetes Insipidus, alcohol, DM-MC)

V. Cardiac: structural cardiopulmonary disease, valvular heart disease, cardiomyopathy, pulmonary hypertension, pericardial disease, aortic dissection, pulmonary embolism, MI, dysrhythmias

a. Causes of cardiac syncope (heart can’t maintain adequate cardiac output to maintain cerebral perfusion) are divided into two categories:

i. Dysrhythmias- very common

ii. Structured cardiopulmonary disease

b. Both brady- and tachydysrhythmias may lead to transient cerebral hypoperfusion- there is no absolute high or low heart rate that will produce syncope. Symptoms depend on both the autonomic NS’s ability to compensate for decrease in cardiac output and the degree of Cerebrovascular atherosclerotic disease.

c. Dysrhythmias are most likely to occur in the setting of underlying structural heart disease, or primary electrolyte imbalance.

i. Syncope from dysrhythmias is typically sudden, with prodromal symptoms, if any, lasting less than 3s

d. Syncope caused by underlying structural cardiopulmonary disease often occurs in the setting of physical exertion, but also may be seen in response to vasodilation from medication or heat. A decrease in SVR is normally compensated by an increase in cardiac output is fixed, limiting compensation

e. Aortic stenosis should be excluded as a cause of syncope in the elderly. Classic presentation: Chest pain, DOE, Syncope

f. Hypertrophic cardiomyopathy is characterized by asymmetric left ventricular hypertrophy and occurs most commonly in the young.

g. Pulmonary outflow obstruction may also lead to syncope.

i. 13% of patients with acute pulmonary embolism develop syncope

h. Follow-up testing for cardiac cause includes: echocardiogram, electrophysiological testing, cardiac stress testing, Holter monitor, and event recorder

i. Patients in this category will often be admitted

VI. Neurological: transient ischemic attack, CVA, subclavian steal syndrome, migraine headache

a. Cerebrovascular disorders are rarely the primary cause of syncope, but must be considered in any patient with syncope and signs or symptoms indicating central nervous system pathology.

i. Brainstem ischemia may cause a decrease in blood flow to the reticular activating system, leading to sudden brief episodes of loss of consciousness. These episodes are typically associated with other signs and symptoms of posterior circulation ischemia: visual disturbances, tinnitus, vertigo

1. Check for carotid bruits

ii. Subclavian steal syndrome is a rare cause of brainstem ischemia, characterized by an abnormal narrowing of the subclavian artery proximal to the origin of the vertebral artery such that with exercise of the ipsilateral arm, blood is shunted, or “stolen”, from the vertebrobasilar system to the subclavian artery supplying the arm muscles

1. More common in the left arm- occurs during weight lifting

2. Physical exam would show diminished pulses and BP in affected arm and arm claudication

b. Other causes of brainstem ischemia: Vertebrobasilar atherosclerotic disease, basilar artery migraines

c. Diagnostic work-up includes: CT scan brain, EEG, carotid Doppler

d. Drugs/medications: anti-hypertensives, B-blockers, cardiac glycosides, diuretics, anti-dysrhythmias, anti-psychotics, anti-depressants, nitrates, alcohol, cocaine

VII. Psychiatric: Psychiatric disorders are found in a modest percentage of patients with syncope; the most frequent psychiatric diagnoses were: generalized anxiety disorder and major depressive disorder

a. Hyperventilation is a provocative maneuver in diagnosing panic disorder and generalized anxiety disorders, and can lead to hypocarbia, cerebral vasoconstriction, and subsequent syncope

i. Presentation typically in a young female, with repeated episodes of syncope, multiple prodromal symptoms, and a generally positive review of symptoms. A psychiatric cause for syncope should be one of exclusion, assigned only after organic causes have been excluded.

ii. Patient must breath into a bag to reabsorb carbon dioxide

VIII. Miscellaneous: anemia, hypoglycemia

a. Diagnosis: Goal of evaluation is to identify those at increased risk for immediate decompensation as a result of an underlying disease process and for future risk of serious morbidity or sudden death.

b. History:

i. Clinical history should be obtained from patient and any witness of the event. Emphasis should be placed on events leading up to the LOC: including position, activity, environmental stimuli (pain, heat, and bad news), duration, premonitory symptoms (vasovagal), symptoms after recovery (seizures), and cardiopulmonary, neurological symptoms.

1. Symptoms associated with syncope that should raise concern of life-threatening diagnosis: headache (brainstem ischemia, stroke), chest pain (MI, aortic dissection, PE), AMS, abdominal/back pain (aortic aneurysm, ectopic pregnancy), any sudden event without warning and associated with exertion should increase suspicion of cardiac dysrhythmia or structural disease

ii. Any prior history of syncope should also be documented, as patient who have recurrent syncope with more than five episodes in 1 year are more likely to have vasovagal syncope or a psychiatric diagnosis than dysrhythmia as the cause.

iii. Aggressive dieting, vomiting, laxatives may cause electrolyte disturbances

IX. Differential:

a. Occasionally, underlying mechanisms that causes syncope may result in associated seizure (cerebral hypoperfusion). History is very important in differentiating syncope from seizure. A classic aura or postictal confusion and muscle pain indicate seizure while characteristic prodromal symptoms suggest reflex-mediated syncope. Witness information of the event may also be useful. (shaking, head turning, and abnormal posture)

b. Physical examination

i. Focus on cardiovascular and neurological systems

1. Subclavian steal, aortic dissection

ii. BP measurements should be taken in both arms

1. Orthostatic pressure

c. Electrocardiogram: should be evaluated of prior cardiopulmonary disease, acute ischemia, dysrhythmia, and heart block, prolonged QT interval. Patient should be monitored for abnormal cardiac activity until a cardiac origin has been reasonably excluded.

i. Studies fail to show any benefit from a CT, EEG, or lumbar puncture if the neurological exam is without findings

d. Laboratory testing: Complete blood count (CBC), urine pregnancy test, electrolyte panel

e. Consults: neurological, psychological

f. Disposition: Discharge vs. admittance of a patient with syncope in the absence of a diagnosis is directed by an assessment of subsequent risk of mortality for that patient.

i. Elderly patients or patients with neurological, heart, or lung disease should be admitted

ii. Young patients with no neurological history should not be admitted

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