Intra- and interindividual reproducibility of heart rate variations in the tilt-table test

Various methods are used for the routine diagnosis of autonomic regulation disorders. The evaluation of blood pressure and heart rate response during active orthostasis together with assessment of the 30/15-ratio (Ewing's ratio) was proven to be a valid method. One main disadvantage of these tests is their dependence on the active cooperation of the patient. In contrast, passive orthostasis using the tilt-table may also be carried out in bed-ridden patients. The test comprises a manual tilting manoeuvre of the patient lying on the tilt-table, with continuous assessment of heart rate and blood pressure. Until now, the main advantages of the tilt-table test were considered to be its better standardisation and good reproducibility, especially with regard to the diagnosis of vasovagal syncope. Several authors have postulated a specific pattern of initial heart rate response in healthy patients, showing characteristic changes in cases of underlying autonomic neuropathy. However, the diagnostic relevance of these tests is dependent on the reproducibility of the course of initial heart rate response. The objective of our study was to assess the intra- and interindividual reproducibility of initial heart rate response in the tilt-table test in healthy subjects. The tilt-table test was repeated 10 times in all 40 subjects under standardised conditions, and heart rate and blood pressure response were presented in a diagram. Reproducible courses of initial heart rate response were not seen, neither on intra- nor on interindividual comparison. After an initial rise, most subjects showed a rather horizontal course of heart rate, whereas others presented a heart rate response similar to that in the Ewing test, with an initial rise of heart rate around the 15th beat, followed by a decrease, and a maximum around the 30th beat. However, all subjects showed considerable variations in heart rate response within the 10 tilting manoeuvres. A reliable quotient comparable with the 30/15 ratio (Ewing's ratio) in active orthostasis was not seen. Based on these results, we conclude that the initial heart rate response in the tilt-table test is not suitable for routine diagnosis of autonomic regulation disorders, since it is not sufficiently reproducible in healthy individuals.