Tilt testing potentiated with sublingual nitroglycerin in children with unexplained syncope

We read with great interest the article by Foglia-Manzillo et al.1 on head-up tilt testing (HUT) with sublingual nitroglycerin in children with unexplained syncope. The authors concluded that nitroglycerin challenge greatly increased the positive rate of passive tilt with a small decrease in specificity. In our early studies with passive HUT, we observed that sensitivities of a test were 60% in children and 26% in adults.2 However, we noticed that the specificity of HUT in children is lower than in young adults (100 vs. 68%, respectively).3 ‘The Italian Protocol’ is generally accepted as an investigation tool of unexplained syncope in adults.4 The question remains whether we should accept the same doses of nitroglycerin for adults and children (even those <8 years of age). The anthropometric characteristics (weight, height, and body mass index) or/and activity in sports should be factored into clinical investigation. Both body mass index and activity in sports may influence the tilt test results.5 Moreover, the optimal testing of a control group would demand longer follow-up to predict potential future syncope in up to 18 years. However, we realize that this may be very difficult in practice. Recently, the paper by Vlahos et al.6 questions the routine use of nitroglycerin in the evaluation of syncope in children. However, it is impossible to compare the results of those studies due to different inclusion criteria and different HUT protocols. Finally, we believe that the discussed largest study of HUT on children with NTG may have resulted in better diagnostics of unexplained syncope. However, further researches are needed to confirm the utility of this procedure.