Comparison of Sensitivity and Specificity of Tilt Protocols with and without Isoproterenol in Children with Unexplained Syncope

Abstract

Head-up tilt testing with or without isoproterenol is extensively used in the evaluation of patients with unexplained syncope. However, sensitivity and specificity of tilt protocols with and without isoproterenol have not been clarified in children, due to lack of age matched control subjects. This study was designed to assess and to compare the sensitivity and specificity of tilting alone and tilting in conjunction with isoproterenol. Thirty children with unexplained syncope (group I) and 15 age-matched control subjects (control group I) underwent successive 60 degrees head-up tilts for 10 minutes during infusions of 0.02, 0.04, and 0.06 microgram/kg/min of isoproterenol, after a baseline tilt to 60 degrees for 25 minutes. Also, 35 children (group II) with unexplained syncope and 15 healthy control subjects (control group II) were evaluated by head-up tilt to 60 degrees for 45 minutes without an infusion of isoproterenol. In response to tilt protocol with graded isoproterenol, 23 (76.6%) of the patients in group I and 2 of the 15 (13.3%) control subjects developed syncope. Accordingly, the sensitivity of tilt testing with isoproterenol was 76.6%, and its specificity was 86.7%. Tilt testing without isoproterenol was positive in 17 (48.5%) of the patients in group II but in only 1 of the 15 (6.6%) control subjects. Thus, sensitivity and specificity of tilt testing without isoproterenol were 48.5% and 93.4%, respectively. The mean heart rate and systolic blood pressure decreased significantly (P < 0.001) in all tilt positive patients during syncope. In conclusion, the head-up tilt test is a valuable diagnostic test in the evaluation of children with unexplained syncope, and isoproterenol is likely to increase the sensitivity of the test without decreasing its specificity.

Provocation of Neurocardiogenic Syncope During Head-up Tilt Testing in Children: Comparison Between Isoproterenol and Nitroglycerin

“…We report almost equal sensitivity rates for isoproterenol-(78%) and for nitroglycerin-augmented (79%) tilt test. These values lie within the range reported for isoproterenol, 3,8,10,11 whereas the single previous study assessing nitrate-augmented tilt test in a pediatric population reported an almost identical sensitivity of 77.5%. 19 However, we found significantly lower specificity rates for nitroglycerin-compared with isoproterenol-augmented tilt test.…”

“…6,7 The specificity of tilt test is satisfactory, but concern has been raised with respect to its low sensitivity. 5,8,9 As a result, isoproterenol is now used as part of the tilt protocol in the majority of centers, 10,11 but its use requires venous cannulation, which may interfere with the diagnostic accuracy of the test. 12 Data in children, as well as clinical experience, indicate that such observations may apply to an even larger extent in pediatric patients.…”

Syncope in children: Diagnostic tests have a high cost and low yield

“…Reports on the specificity of tilt-testing in children range from 48% to 100%. [15][16][17][18][19][20] Thus, a positive tilttest may not reliably exclude other conditions. Furthermore, tilt-testing is rarely required to diagnose neurocardiogenic syncope.…”

Comparison of the active standing test and head-up tilt test for diagnosis of syncope in childhood and adolescence

“…It is also widely used in pediatric practice on the basis of adult studies. As Alehan reported, the average time for development of symptoms of syncope with HUT was about 20 minutes [2][3][4] and, therefore, 45min-HUT was recommended in syncopal children when isoproterenol is not used.…”

“…In order to increase positive response to HUT, invasive procedure (e. g. isoproterenol infusion) and long-time-load (60-minute HUT) are now applied in adults and children. Alehan reported that sensitivity of 10min-HUT for children with unexplained syncope increased to 76.6 % by infusion of isoproterenol while that of 45min-HUT was 48.5 % [3].…”