Tilt-table study in vasovagal syncope. The diagnostic gain from isoprenaline administration

The cause of syncope remains unclear in half of the cases, even after extensive neurological and cardiological examination. A study was, therefore, undertaken to determine the number of patients with the suspected diagnosis of vasovagal syncope that were confirmed by the tilting table test and how often it required the additional administration of isoprenaline to do so. A tilting table test was performed on 75 patients (49 men, 26 women; mean age 41 [17-80] years) with syncopes of uncertain cause, previous examinations having failed to discover any neurological or cardiological cause. The test was done with a head-up angle of 60 degrees for 30 min. ECG and arterial blood pressure by indwelling catheter were recorded continuously. If the test was negative, isoprenaline was given intravenously at a rate of 5 micrograms/min during a five-minute period in the horizontal position, followed by 10 minutes at 60 degrees head-up position. Vasovagal syncope or presyncope was induced in 49 of the 75 patients during the tilting table test, a sensitivity of 65%. But 45% of the tests were positive only with the administration of isoprenaline, i.e. an increase in sensitivity to 81.5%. In 96% of the patients with a positive test there was conformity of symptoms between the induced and the spontaneously occurring syncopes. The tilting table test is a valuable means of investigating cases of syncope. More than half of the cases of syncope of uncertain cause can be correctly diagnosed classified in this way. The additional use of isoprenaline infusion greatly increases the sensitivity of the method.