Tilt table testing is used to evaluate syncope in
Tilt table testing produces maximal venous pooling, which can trigger vasovagal (neurocardiogenic) syncope and reproduce the symptoms and signs that accompany it (nausea, light-headedness, pallor, hypotension, bradycardia).
After an overnight fast, a patient is placed on a motorized table with a foot board at one end and is held in place by straps over the body; an IV line is inserted. After the patient remains supine for 15 minutes, the table is tilted nearly upright to 60 to 80° for 45 minutes during which symptoms and vital signs are monitored.
If vasovagal symptoms develop, vasovagal syncope is confirmed. If symptoms do not occur, a drug (eg, isoproterenol) may be given to induce them. (NOTE: Isoproterenol should not be used in patients with hypertrophic cardiomyopathy or severe coronary artery disease.) Sensitivity varies from 30 to 80% depending on the protocol used. The false-positive rate is 10 to 15%.
With vasovagal syncope, heart rate and blood pressure (BP) usually decrease. Some patients have only a decrease in heart rate (cardioinhibitory); others have only a decrease in BP (vasodepressor). Other responses that suggest alternative diagnoses include a gradual decrease in systolic and diastolic BP with little change in heart rate (dysautonomic pattern), significant increase in heart rate (> 30 beats/minute) with little change in BP (postural orthostatic tachycardia syndrome), and report of syncope with no hemodynamic changes (psychogenic syncope).
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