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Disorders of Vascular Tone or Blood Volume Disorders of vascular tone or blood volume that can cause syncope include the reflex syncopes and a number of conditions resulting in orthostatic intolerance. The reflex syncopes—including neurocardiogenic syncope, situational syncope, and carotid sinus hypersensitivity—share common autonomic nervous system pathophysiologic mechanisms: a cardioinhibitory component (e.g., bradycardia due to increased vagal activity), a vasodepressor component (e.g., inappropriate vasodilatation due to sympathetic withdrawal), or both. Neurocardiogenic (Vasovagal and Vasodepressor) Syncope The term neurocardiogenic is generally used to encompass both vasovagal and vasodepressor syncope. Strictly speaking, vasovagal syncope is associated with both sympathetic withdrawal (vasodilatation) and increased parasympathetic. | Chapter 021. Syncope Part 2 Disorders of Vascular Tone or Blood Volume Disorders of vascular tone or blood volume that can cause syncope include the reflex syncopes and a number of conditions resulting in orthostatic intolerance. The reflex syncopes including neurocardiogenic syncope situational syncope and carotid sinus hypersensitivity share common autonomic nervous system pathophysiologic mechanisms a cardioinhibitory component e.g. bradycardia due to increased vagal activity a vasodepressor component e.g. inappropriate vasodilatation due to sympathetic withdrawal or both. Neurocardiogenic Vasovagal and Vasodepressor Syncope The term neurocardiogenic is generally used to encompass both vasovagal and vasodepressor syncope. Strictly speaking vasovagal syncope is associated with both sympathetic withdrawal vasodilatation and increased parasympathetic activity bradycardia whereas vasodepressor syncope is associated with sympathetic withdrawal alone. These forms of syncope are the common faint that may be experienced by normal persons they account for approximately half of all episodes of syncope. Neurocardiogenic syncope is frequently recurrent and commonly precipitated by a hot or crowded environment alcohol extreme fatigue severe pain hunger prolonged standing and emotional or stressful situations. Episodes are often preceded by a presyncopal prodrome lasting seconds to minutes and rarely occur in the supine position. The individual is usually sitting or standing and experiences weakness nausea diaphoresis lightheadedness blurred vision and often a forceful heartbeat with tachycardia followed by cardiac slowing and decreasing blood pressure prior to loss of consciousness. The individual appears pale or ashen in dark-skinned individuals the pallor may only be notable in the conjunctivae and lips. Patients with a gradual onset of presyncopal symptoms have time to protect themselves against injury in others syncope occurs suddenly without warning. The depth and .
