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Carotid sinus syncope is due to pressure on the carotid sinus in the neck. [2] The underlying mechanism involves the nervous system slowing the heart rate and dilating blood vessels, resulting in low blood pressure and thus not enough blood flow to the brain. [2] Diagnosis is based on the symptoms after ruling out other possible causes. [3]
The sympathetic response causes peripheral vasoconstriction and increased heart rate. These together act to raise blood pressure back to baseline. [9] Apparently healthy individuals may experience minor symptoms ("lightheadedness", "greying-out") as they stand up if blood pressure is slow to respond to the stress of upright posture.
Orthostatic syncope refers to syncope resulting from a postural decrease in blood pressure, termed orthostatic hypotension. [1]Orthostatic hypotension occurs when there is a persistent reduction in blood pressure of at least 20mmHg systolic or 10mmHg diastolic within three minutes of standing or being upright to 60 degrees on the head-up tilt table.
Postural orthostatic tachycardia syndrome (POTS) is a condition characterized by an abnormally large increase in heart rate upon sitting up or standing. [1] POTS is a disorder of the autonomic nervous system that can lead to a variety of symptoms, [10] including lightheadedness, brain fog, blurred vision, weakness, fatigue, headaches, heart palpitations, exercise intolerance, nausea ...
This is complemented by gastro-coronary reflexes [12] whereby the coronary arteries constrict with "functional cardiovascular symptoms" similar to chest-pain on the left side and radiation to the left shoulder, dyspnea, sweating, up to angina pectoris-like attacks with extrasystoles, drop of blood pressure, and tachycardia (high heart rate) or ...
The vagovagal reflex is active during the receptive relaxation of the stomach in response to swallowing of food (prior to it reaching the stomach). When food enters the stomach a "vagovagal" reflex goes from the stomach to the brain, and then back again to the stomach causing active relaxation of the smooth muscle in the stomach wall.
Water will increase sympathetic nervous system activation, raising blood pressure and combating vasovagal response. [8] Certain physical maneuvers also have the capacity to temporarily boost blood pressure, alleviating symptoms of pre-syncope like lightheadedness by boosting blood flow to the brain.
Vasodilation works to decrease vascular resistance and blood pressure through relaxation of smooth muscle cells in the tunica media layer of large arteries and smaller arterioles. [17] When vasodilation causes systolic blood pressure to fall below 90 mmHg, circulatory shock is observed. [11]