In certain patients, usually those with recurrent syncope, subcutaneous implanted recorders may be used to maintain ECG data for long-term evaluation of rare events commonly missed by short-term monitoring and data assessment. A continuous-loop event monitor is sometimes worn intermittently for a period of 30 days to continuously record data however, data are recorded only when the device is prompted by the patient when experiencing symptoms of palpitations or syncope. This device records data without patient activation. A Holter monitor may also be used for 24 to 48 hours to continuously monitor and assess the rhythm and rate of the heart. 10,12Įlectrocardiograms (ECGs) and electroencephalograms may be used upon initial presentation postsyncope in order to exclude cardiac and neurologic causes (i.e., arrhythmias and seizures). However, it is believed that 50% to 66% of these patients actually experience neurocardiogenic syncope. In most cases (up to 50%), patients who experience syncope have no exact cause despite comprehensive evaluation. Thorough histories and physical examinations are necessary to rule out any cardiac, neurologic, or other etiologies. Prompt identification of the underlying cause of a syncopal episode is essential in determining prognosis and management strategies. Other proposed mechanisms of vasovagal syncope involve serotonin, vasopressin, endorphin, and epinephrine pathways. 11,15,16 Transient hypotension results from the peripheral vasodilatation and bradycardia, yielding a reduction in cerebral blood flow and loss of consciousness, which usually lasts for seconds and is followed by recovery with no memory loss or sensory disturbances. Stimulation of the vagal efferent fibers ultimately occurs causing a vasodepressor and/or cardioinhibitory response, in addition to sympathetic withdrawal. 15,16 Excessive peripheral venous pooling (mainly in the lower extremities) leads to a sudden decrease in peripheral venous return. Although the exact mechanism of this type of syncope is not fully understood, it is believed to occur as a result of reflex-mediated changes in vascular tone and/or heart rate. ![]() It is often precipitated by emotional situations, pain, blood loss, dehydration, or standing for prolonged periods of time. Vasovagal syncope is responsible for the majority of neurocardiogenic cases therefore, it is commonly used synonymously with the term neurocardiogenic syncope. Carotid sinus syncope is defined as syncope due to the manipulation of the carotid sinuses (i.e., rotation/turning of the head or pressure placed on the carotid sinuses) that may be reproduced by carotid sinus massage. Situational syncope refers to neurally mediated syncope commonly associated with cough, micturition, and defecation. Further classifications of this particular type of syncope include situational, carotid sinus, and vasovagal syncope. Neurocardiogenic syncope is a self-limiting condition caused by an abnormal or exaggerated autonomic response to certain stimuli. 13,14 It is usually characterized by a presyncopal warning period of warmth, weakness, diaphoresis, nausea, lightheadedness, dizziness, and/or visual disturbances. Neurocardiogenic syncope is the most common type of syncope among children and adults, accounting for up to 50% of cases. 12 Therefore, timely identification of the underlying cause(s) of this disorder is important for appropriate management and evaluation of sudden cardiac death risk. Noncardiac causes of syncope are associated with a mortality of 5% to 10%, while cardiac causes have an annual mortality of 20% to 30%. 2,11 Prognosis is highly dependent on etiology. 1,10 Patients frequently report a prodromal state of lightheadedness, headache, nausea, warmth, sweating, weakness, and/or visual disturbances. In addition, numerous cardiac, neurologic, psychiatric, metabolic, and pulmonary disorders can contribute to a syncopal episode. 6,9 The loss of consciousness experienced is frequently precipitated by factors such as pain, exercise, stressors, sudden changes in body position, micturition, defecation, heat, dehydration, sweating, and exhaustion. 8 Its overall incidence is estimated to be 3.3% in younger adults and is reported to increase with age, up to 6% in long-term health care institutions. ![]() Syncope accounts for 1% to 6% of hospital admissions and 3% of emergency departments visits. 4,5 In 30% of patients, recurrent syncopal episodes have been reported, which may lead to increased morbidity (i.e., lacerations, contusions, fractures, and organ damage due to trauma). 1-3 It is a common and potentially disabling incident that may be associated with a risk of sudden death. Onset is sudden, rapid, and usually followed by a prompt and complete spontaneous recovery. Syncope is a transient loss of consciousness associated with a loss of postural tone due to decreased cerebral perfusion.
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