Postural tachycardia during head-up tilt test predicts persistent orthostatic intolerance in young adults
2013
Background: Head-up tilt (HUT) test is an important
tool in establishing the cause of past syncope.
As postural tachycardia is associated with
orthostatic intolerance, we hypothesise that heart
rate (HR) increase during the early phase of
HUT can be used as a surrogate test outcome to
predict future orthostatic intolerance in an individual
patient.
Methods: Patients aged 18 to 40 years who had
undergone HUT test at our centre were included
in the cross-sectional study. Telephone interviews
about orthostatic symptoms and recurrent
syncope were performed 9 to 12 months after
HUT with 73 consecutive patients in the exploratory
and 67 consecutive patients in the confirmatory
cohort. Data from interviews were related to
past HUT test results.
Results: Orthostatic intolerance was reported
by 52 (71 %) patients in the exploratory and 41
(61 %) in the confirmatory cohort. Positive predictive
value (PPV) of HR increase ≥ 30 bpm for
orthostatic intolerance in confirmatory cohort
was 0.88 (only one patient had this level of tachycardia
in the exploratory cohort). HR increase
≥ 23 bpm was established as cut-off value
with high specificity for orthostatic intolerance,
its PPV was 0.89 in exploratory and 0.87 in confirmatory
cohort. PPVs of HUT test outcome
for orthostatic intolerance were 0.84 and 0.62,
respectively. Both prominent HR increase and
HUT test outcome had low PPV for recurrent
syncope.
Conclusions: In young adults referred for HUT
test postural tachycardia in the early phase of
HUT predicts orthostatic intolerance a year after
testing independently of test outcome.
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