Validation of the new index of baroreflex function to identify neurogenic orthostatic hypotension

According to expert opinion, orthostatic hypotension (OH) associated to a change in heart rate (ΔHR) less than 15 bpm suggests neurogenic OH (NOH). Recently, the ratio between HR and systolic blood pressure changes at 3 min of tilt test (ΔHR/ΔSBP) has been proposed as a better index than the ΔHR cut-off of 17 bpm. Our aim was to validate these indexes based on HR in an independent cohort of patients who performed cardiovascular reflex tests according to standardized procedures at our Institution.

We applied the HR indexes to all cardiovascular reflex tests that fulfilled the following criteria: (1) presence of classical OH at tilt test, (2) reliable Valsalva manoeuvre (VM), (3) absence of heart disease. We classified OH according to VM (absence of overshoot = NOH), and verified how many were correctly identified by ΔHR/ΔSBP (≤0.49 neurogenic) and ΔHR (≤17 and ≤15 neurogenic).

We identified 369 tests with OH. Based on VM, 335 were NOH. The ΔHR/ΔSBP ≤ 0.49 identified NOH with a sensitivity of 91% and a specificity of 59%, the ΔHR ≤ 17 bpm with 88% sensitivity and 38% specificity, and the ΔHR ≤ 15 bpm with 84% sensitivity and 50% specificity.

In our cohort, the ΔHR/ΔSBP ratio had a good sensitivity but a limited specificity to identify NOH. This easily applicable test may represent a valuable screening tool in a clinical setting to identify patients who need further detailed autonomic testing to confirm the neurogenic origin of OH.