In this video Dr. Singer discusses the use of tilt table testing as a part of the autonomic function screening including several tips for conducting a tilt table test.
That gets us to the tilt. What we do is we have the patient resting already during the rest of the battery, so the patient has really been laying there for about 35-40 minutes before we even start the baseline for the tilt recording. We record a baseline routinely of 5 for research purposes, 10 and 20 minutes depending, and during that time continue to record heart rate, blood pressure on a beat-to-beat basis and respiration. The patient is on a table where there’s an armrest that allows the arm to be at heart level, so where we sense the blood pressure, which is at the finger we want that at heart level before we tilt the patient up to make sure there’s not a hydrostatic pressure confounding our blood pressure reading. And we tilt the patient to 70 degrees, that is really a compromise. We want the tilt to be passive. If you go beyond 70 degrees, there is a chance the subjects will activate their muscle and you get the muscle pump effect and we want to avoid that that. That is closer to active standing. And once we have reached 60-70 degree of tilt, we have about 90% of gravity exposure already. So, you don’t really need to go higher than 70 degrees in order to get almost maximal gravity exposure.
We in our lab tilt typically 5-10 minutes depending on the indication. We don’t go longer than that. Our purpose is not to tilt the patient to syncope. We leave that to the cardiologist. We want to assess the autonomic nervous system. And in fact, we do have a cardiology department that does 45 minutes in drug-induced tilt etc. but that’s not the purpose of our autonomic lab.
Here’s an example of normal response, you can barely tell where the patient was tilted up, right? You see a little bit of an increase in heart rate, not much change in systolic blood pressure, maybe a little bit of an increase in diastolic blood pressure and then tilt back happens around here. My contrast to that, that’s a patient with POTS. Marked increase in heart rate with a relatively well-preserved blood pressure that did certainly not reach criteria of orthostatic hypotension, but there was a decline somewhat particularly in the beginning. The patient with orthostatic hypotension, significant drop in blood pressure. There is a heart rate rise that for a normal blood pressure would be more than adequate but considering this amount of blood pressure drop that heart rate response is relatively reduced. And here, the patient with vasovagal syncope, this patient is standing there, nothing happens really until suddenly there is a precipitous decline in both blood pressure and heart rate and the patient became presyncopal or syncopal. In fact, I had a talk to that technician because they kept the patient up too long. Right! I mean at this point you should have known there’s no way of return and you could have probably avoided syncope.