Syncope Information - symptom, cause, treatment of Syncope
Syncope, defined as a transient loss of consciousness and postural tone due to inadequate cerebral blood flow with prompt recovery without resuscitative measures, is a common clinical problem, especially in the elderly. Thirty percent of the adult population will experience at least one episode, and syncope accounts for approximately 3% of emergency room visits. Causes include cardiac abnormalities (either disturbances of rhythm or hemodynamics), vascular disorders, or neurologic processes. A specific cause is identified in about 50% of cases during the initial evaluation. The prognosis is relatively benign except when accompanying cardiac disease is present. Syncope is more likely to occur in patients with known heart disease, older men, and young women (who are prone to vasovagal episodes). Syncope is characteristically abrupt in onset, often resulting in injury, transient (lasting for seconds to a few minutes), and followed by prompt recovery of full consciousness.
Orthostatic (postural) hypotension is another common cause of vasomotor syncope, especially in the elderly, in diabetics or other patients with autonomic neuropathy, in patients with blood loss or hypovolemia, and in patients taking vasodilators, diuretics, and adrenergic blocking drugs. In addition, a syndrome of chronic idiopathic orthostatic hypotension exists primarily in older men. In most of these conditions, the normal vasoconstrictive response to assuming upright posture, which compensates for the abrupt decrease in venous return, is impaired. A greater than normal decline (20 mm Hg) in blood pressure immediately upon arising from the supine to the standing position is observed, with or without tachycardia depending on the status of autonomic (baroreceptor) function. Studying patients with a tilt table can establish the diagnosis with more certainty. Autonomic function can be assessed by observing blood pressure and heart rate responses to Valsalva's maneuver and by tilt testing. In older patients, vasoconstrictor abnormalities and autonomic insufficiency are perhaps the most common causes of syncope. Thus, tilt testing should be employed before proceeding to invasive studies unless clinical and ambulatory electrocardiographic evaluation suggests a cardiac abnormality.
The evaluation for syncope depends on findings from the history and physical examination (especially orthostatic blood pressure evaluation, examination of carotid and other arteries, cardiac examination, and, if appropriate, carotid sinus massage). The resting ECG may reveal arrhythmias, evidence of accessory pathways, prolonged QT interval, and other signs of heart disease (such as infarction or hypertrophy). If the history is consistent with syncope, ambulatory electrocardiographic monitoring is essential. This may need to be repeated several times, since yields increase with longer periods of monitoring, at least up to 3 days. Event recorder and transtelephone electrocardiographic monitoring may be helpful in patients with intermittent presyncopal episodes. Electrophysiologic studies to assess sinus node function and atrioventricular conduction and to induce supraventricular or ventricular tachycardia are indicated in patients with recurrent episodes and nondiagnostic ambulatory ECGs. They reveal an arrhythmic cause in 20–50% of patients, depending on the study criteria, and are most often diagnostic when the patient has had multiple episodes and has identifiable cardiac abnormalities.
Neuro Cardiogenic Syncope