The test library
Cardiac Autonomic Reflex Tests
The standardized challenge maneuvers used to assess whether the nerves controlling the heart and blood pressure are still responding normally.
For patients
What you will be asked to do
- Breathe deeply in time with a prompt — usually six breaths a minute, for one minute. Your heart rate should speed up as you breathe in and slow as you breathe out; how much it does is the measurement.
- Stand up from lying down and remain still while your heart rate and blood pressure are recorded for a few minutes. A normal response is a brisk rise in heart rate that then settles, with blood pressure holding steady.
- Blow gently against resistance for around fifteen seconds, then relax. This produces a characteristic sequence of heart rate and blood pressure changes that is quite specific when it is normal, and quite specific when it is not.
None of these is uncomfortable. Doing them properly matters, so you will be coached through each one and given a practice attempt.
Why the coaching matters
If a maneuver is performed badly — breathing at the wrong rate, standing too slowly, blowing too hard or letting go early — the recording looks exactly like an abnormal result. This is the most common reason a test has to be repeated, and it is why the person running the study will be particular about technique.
What it shows
Together these maneuvers describe whether the parasympathetic and sympathetic branches are both responding, and in what proportion. Persistent abnormality across several of them is a much stronger signal than one abnormal value. Autonomic symptoms.
For physicians
The battery
| Maneuver | Branch assessed | Primary index |
|---|---|---|
| Deep metronomic breathing, six per minute | Cardiovagal (parasympathetic) | Expiration-to-inspiration ratio and heart rate range |
| Active standing or head-up tilt | Sympathetic adrenergic and cardiovagal | Heart rate response ratio and positional blood pressure change |
| Valsalva maneuver | Both branches, sequentially | Valsalva ratio and the phase structure of the blood pressure response |
Acquisition
Photoplethysmographic acquisition correlates closely with electrocardiographic interval measurement, which permits the battery to be run with optical rather than electrode-based instrumentation in an office setting. Positional blood pressure is measured separately and is not derived.
Failure modes that produce false abnormality
- Uncoached or inconsistent respiratory cadence during timed breathing.
- A Valsalva performed at the wrong pressure or released early — use a manometer, not instruction alone.
- Standing performed too slowly, which blunts the expected transient.
- An inadequate rest period before baseline acquisition.
- Beta-blockade, which blunts the heart rate responses across the whole battery and must be recorded rather than discovered afterwards.
Where it fits
Part of autonomic testing; read together with heart rate variability and, where the presentation is unsteadiness, with balance testing. Interpreting the report.
Evidence and limitations
Written for a reader who wants the literature rather than the summary. Where the evidence is thin we say so and give both sides, and where a claim is mechanistic rather than demonstrated we label it as such.
Mechanism
Each maneuver in the battery perturbs the cardiovascular system in a defined way and measures the corrective response. Deep metronomic breathing entrains respiratory sinus arrhythmia and probes cardiovagal function. Active standing displaces roughly half a liter of blood to the lower body and probes the sympathetic adrenergic response that defends blood pressure, alongside the vagal heart rate transient. The Valsalva maneuver drives both branches through a stereotyped four-phase sequence. Because each maneuver isolates a different limb of the reflex arc, abnormalities across several of them carry far more information than one.
What the evidence shows
The Toronto Consensus criteria are built on precisely this logic: one abnormal cardiovagal result identifies possible or early cardiovascular autonomic neuropathy, at least two are required for definite or confirmed disease, and orthostatic hypotension in addition to abnormal heart rate results identifies severe or advanced disease, with progressively worse prognosis by stage.
Prognostically, the composite carries a pooled relative risk of 3.16 (95% CI 2.42 to 4.13) for future cardiovascular events and 3.17 (95% CI 2.11 to 4.78) for all-cause mortality across 26 synthesized studies, with a stronger association for definite than for possible disease.
In a 2024 cohort of 211 patients with type 2 diabetes and overweight or obesity, Ewing test scores remained significantly associated with calculated cardiovascular risk on multiple linear regression, alongside sudomotor scores.
Limitations of that evidence
- Operator dependence is the dominant source of error. An uncoached respiratory cadence, a Valsalva released early or performed at the wrong pressure, or a slow stand all produce traces that mimic autonomic failure.
- Age-stratified normative data is essential and not uniform between laboratories.
- Medication effects are large and are inconsistently reported in the source cohorts.
- Contraindications limit the battery. Valsalva is avoided or modified in proliferative retinopathy, recent eye surgery and some cardiac conditions, so a complete battery is not available in every patient.
- The outcome literature is largely diabetic. Applying the pooled risk estimates outside diabetes is not supported.
What remains uncertain
The unresolved question is the same one that runs through this whole field: staging autonomic function reliably identifies a higher-risk group, and no trial has yet shown that acting on the stage — as opposed to acting on the glycemic and vascular risk factors that produced it — independently improves outcomes. The Toronto Consensus said as much, noting that apart from intensive glycemic control in type 1 diabetes, recommendations could not be made for most therapeutic approaches. That is an argument for using the battery to characterize and to direct conventional risk-factor treatment, which is how it is used here.
Talk to someone about testing
Tell us what you are trying to find out and we will explain which Measura assessments answer that question, what each one involves, and how the results are reviewed with a clinician.
4477 Woodson Rd, Suite 201, St. Louis, MO 63134. Monday to Friday, 9:00 a.m. to 5:00 p.m. Please do not send symptoms, diagnoses or images through a web form — a website form is not a secure medical channel. Call us with clinical detail.
Common questions
What if I cannot do the breathing properly?
You will be coached and given a practice attempt; a badly performed maneuver is repeated rather than reported. What the appointment feels like.
Is the Valsalva maneuver safe?
It is a brief, low-pressure exhale performed under supervision, and it is omitted where there is a reason to avoid it. Tell us about eye surgery, retinal disease or recent cardiac events when you book. What to tell us in advance.
Why does one abnormal result not settle it?
Because coaching, medication and acquisition conditions all produce the same appearance. Persistent abnormality across maneuvers is the signal. What a result can and cannot tell you.
References
- Spallone V, Ziegler D, Freeman R, et al. Cardiovascular autonomic neuropathy in diabetes: clinical impact, assessment, diagnosis, and management. Toronto Consensus Panel on Diabetic Neuropathy. Diabetes/Metabolism Research and Reviews. 2011;27(7):639–653. doi:10.1002/dmrr.1239
- Chowdhury M, Nevitt S, Eleftheriadou A, et al. Cardiac autonomic neuropathy and risk of cardiovascular disease and mortality in type 1 and type 2 diabetes: a meta-analysis. BMJ Open Diabetes Research & Care. 2021;9(2):e002480. doi:10.1136/bmjdrc-2021-002480
- Nica AE, Rusu E, Dobjanschi C, et al. The relationship between the Ewing test, Sudoscan cardiovascular autonomic neuropathy score and cardiovascular risk score calculated with SCORE2-Diabetes. Medicina (Kaunas). 2024;60(5):828. doi:10.3390/medicina60050828
Medically reviewed by Dr. Gurpreet Singh Padda, MD, MBA, MHP, medical director of Measura. Last reviewed .