Vagal cardiovascular reflexes in young persons with syncope
Article Abstract:
High vagal tone may predispose young people to syncope, or fainting, at times of emotional stress. The vagus nerves control the functioning of many areas of the body. Vagal tone decreases as people age, which may explain why fainting occurs less frequently in older people. Lightheadedness often precedes syncope, which is caused by a temporary lack of oxygen flow to the brain. A study compared 60 people between the ages of 15 and 17 years old who had a history of fainting with 40 volunteers who did not have a history of fainting. Differences between the two groups were found in cardiac responses stimulated by the vagus nerves. Vasodepressor syncope is characterized by lowering of blood pressure. This decrease should be countered by an increase in heart rate stimulated by a lowered vagal nerve tone. In patients with high vagal tone, stimulation to increase the heart rate may not occur.
Publication Name: Annals of Internal Medicine
Subject: Health
ISSN: 0003-4819
Year: 1993
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Syncope mediated by posturally induced ventricular tachycardia
Article Abstract:
An irregular heartbeat triggered by body position may be responsible for repeated fainting spells even in patients with no history of heart disease. Doctors evaluated a 66-year-old patient with no history of heart disease who began having chest pain, fainting and near-fainting spells, and trouble breathing during mild exercise. They identified an irregular heartbeat that became progressively worse as the patient moved from lying down to a sitting position. This patient's heartbeat returned to normal with two doses of radiofrequency energy directly administered to the origin of the irregular heartbeat in this patient's heart. The patient remained free of chest pain, had no trouble breathing with mild exercise, experienced no fainting spells, and had a normal heartbeat at one year following treatment.
Publication Name: Annals of Internal Medicine
Subject: Health
ISSN: 0003-4819
Year: 1995
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Transcranial Doppler ultrasonography during head-upright tilt-table testing
Article Abstract:
Loss of consciousness during tilt-table testing may not always be accompanied by a drop in blood pressure or heart rate. A 23-year-old woman underwent tilt-table testing to determine why she had fainted four times in a recent 11-day period. Fainting spells occurred after she stood up from sitting or lying down. Tilt-table tests are used to determine whether fainting spells are caused by the effect of the vagus nerve on blood vessels (vasovagal). Normally, people with vasovagal fainting spells experience drops in blood pressure and heart rate. This patient experienced increases in heart rate and no change in blood pressure when fainting was induced. The blood flow to her brain slowed markedly, as measured by transcranial Doppler ultrasonography.
Publication Name: Annals of Internal Medicine
Subject: Health
ISSN: 0003-4819
Year: 1995
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