Syncope: Pathophysiology, Diagnosis, and Pharmacotherapy

Abstract

Syncope is a common disorder with many different etiologies. The patient's history and physical examination are extremely important in making the diagnosis. The recent availability of head-upright tilt testing and electrophysiologic studies of the myocardium have helped define the etiology in many patients in whom an etiology would not have been found in the past. When the cause of syncope has been diagnosed, the appropriate therapy to prevent future attacks will be defined in many instances. One form of syncope, known as neurocardiogenic syncope, can be difficult to treat. Recent trials have suggests the use of beta-blockers, fludrocortisone, disopyramide, or selective serotonin reuptake inhibitors may be helpful in some patients.

A Review of Pathophysiology and Therapy of Patients with Vasovagal Syncope

“…18 In most cases, vasovagal syncope begins with an exaggerated response to blood volume displacement on standing or greater displacement of blood volume than normal. 11 During diagnostic head-up tilt testing, these patients have an exaggerated myocardial inotropic effect compared with controls. 19 The hypercontractility of the ventricles, in the face of relative volume depletion, is detected by mechanoreceptors and transmitted to the medulla by way of the afferent vagus nerve.…”

“…Assumption of the upright position places the brain above the level of the heart, with downward displacement of 300-800 ml of blood. 11 Most of this blood is stored in compliant capacitance veins. 10 The resulting loss of preload reduces cardiac output, an important component of blood pressure, by way of the Frank-Starling mechanism and diminishes the stretch of baroreceptors located in the aortic arch and carotid sinus.…”

“…Patients usually compensate on becoming upright for several minutes before their blood pressure suddenly drops and they become bradycardic. 11 Bradycardia can vary from relative to temporary heart block or sinus arrest. It is in the face of these decompensatory effects that syncope occurs.…”

“…It is in the face of these decompensatory effects that syncope occurs. 11 Bradycardia is vagally mediated, and atropine can reverse the negative chronotropic effects. However, it is seldom the only mechanism of syncope, as reversal of bradycardia may not fully compensate for the hypotension.…”

Selective ablation of atrial ganglionated plexus as a therapeutic option for vasovagal syncope

“…Patients experiencing refractory syncopal episodes have poor quality of life and high risk of syncope‐related physical injuries . VVS begins with an exaggerated response to blood volume displacement on standing or greater displacement of blood volume than normal . During diagnostic head‐up tilt testing, these patients have an exaggerated myocardial inotropic effect compared with controls .…”