Cardiovascular Autonomic Neuropathy Testing: 7 Essentials for Physicians

Cardiovascular autonomic neuropathy testing is a group of noninvasive assessments that evaluate how well the autonomic nervous system regulates the heart and blood vessels. For physicians, cardiovascular autonomic neuropathy testing combines heart rate variability (HRV) analysis with cardiovascular autonomic reflex tests — the heart rate and blood pressure responses to deep breathing, the Valsalva maneuver, and standing — to identify autonomic dysfunction that often develops silently in patients with diabetes and other chronic conditions.

Because cardiovascular autonomic neuropathy (CAN) is often clinically silent in its early stages, structured cardiovascular autonomic neuropathy testing gives clinicians an objective way to detect early changes and support cardiovascular risk stratification.

This guide explains what the testing involves, which patients to consider, the relevant CPT codes, and how the FDA-cleared TM-Flow system from HealthWright Technologies brings autonomic assessment into the office. It is written for independent physicians and practice teams evaluating whether to add this capability.

What Is Cardiovascular Autonomic Neuropathy?

Cardiovascular autonomic neuropathy is damage to the autonomic nerve fibers that control heart rate, cardiac output, and vascular tone. It is one of the most clinically significant forms of diabetic autonomic neuropathy, though it can occur in other conditions as well.

In its early stages CAN is frequently subclinical, producing no obvious symptoms. As it advances, patients may develop resting tachycardia, reduced exercise tolerance, orthostatic intolerance, or blunted heart rate variability. Because these findings are nonspecific and easily attributed to other causes, cardiovascular autonomic neuropathy testing is often the only reliable way to recognize the condition before it contributes to adverse cardiovascular events.

What Are the Early Signs of Cardiovascular Autonomic Neuropathy?

One of the challenges of CAN is that it tends to develop in stages, beginning silently. In the earliest, subclinical stage there may be no symptoms at all, and the only detectable change is reduced heart rate variability on objective measurement.

As the condition progresses, patients may begin to notice a persistently elevated resting heart rate, lightheadedness on standing, reduced tolerance for exercise, or a heart rate that fails to respond normally to activity. In more advanced disease, orthostatic hypotension and a blunted cardiovascular response to physical or postural stress can appear.

Why Objective Measurement Matters

Because the early stage produces no clear warning signs, clinicians cannot rely on symptoms alone to identify autonomic dysfunction. Objective measurement is what distinguishes a normal autonomic response from an abnormal one, which is why a structured testing protocol is so valuable for at-risk patients.

Recognizing the condition while it is still subclinical gives the care team the longest possible window to address modifiable cardiovascular risk factors and to monitor the patient over time. It also creates a documented baseline that later assessments can be compared against, which is useful when tracking how a patient’s autonomic status changes year to year.

What Does Cardiovascular Autonomic Neuropathy Testing Involve?

Cardiovascular autonomic neuropathy testing centers on a battery of cardiovascular autonomic reflex tests (CARTs), historically known as the Ewing battery, supported by heart rate variability analysis. Each component measures a different branch of autonomic control:

• Heart rate response to deep breathing: paced breathing assesses parasympathetic (cardiovagal) function through the expiration-to-inspiration ratio.
• Valsalva ratio: the heart rate response to a forced expiratory effort reflects both parasympathetic and sympathetic pathways.
• Postural change (standing): heart rate and blood pressure responses on standing evaluate adrenergic and baroreflex function.
• Heart rate variability (HRV): beat-to-beat variation quantifies cardiovagal tone and is a sensitive early marker of autonomic dysfunction.

Together, these noninvasive measures form the foundation of cardiovascular autonomic neuropathy testing. Reviewing them as a set — rather than relying on any single result — gives a more complete picture of how the autonomic nervous system is regulating the cardiovascular system.

Grading the Results

Clinicians often interpret the battery using a staged framework based on how many of the reflex tests fall outside the normal range. A single borderline result may indicate early or subclinical involvement, while several clearly abnormal responses point to more definite or advanced autonomic dysfunction.

Grading the findings this way helps standardize cardiovascular autonomic neuropathy testing across visits and clinicians, supports clearer documentation, and makes it easier to track whether a patient’s autonomic status is stable, improving, or progressing over time. The emphasis throughout remains on objective, reproducible measurement rather than on subjective impression, which is part of what makes a structured protocol valuable in day-to-day practice.

Why Is Early Cardiovascular Autonomic Neuropathy Testing Important?

Early cardiovascular autonomic neuropathy testing matters because CAN is independently associated with increased cardiovascular morbidity and mortality. It has been linked to silent myocardial ischemia, arrhythmia risk, exercise intolerance, and greater perioperative instability.

The National Institute of Diabetes and Digestive and Kidney Diseases recognizes autonomic neuropathy as a serious complication of diabetes that can affect the heart and circulation. Identifying autonomic dysfunction early does not by itself change a diagnosis, but it gives clinicians objective information to support risk stratification and more informed, individualized management decisions.

Which Patients Should Be Considered for Cardiovascular Autonomic Neuropathy Testing?

Professional guidance suggests considering cardiovascular autonomic neuropathy testing in patients at elevated risk for autonomic involvement. Common scenarios include:

• Patients with type 2 diabetes, and patients with type 1 diabetes of several years’ duration, as part of complication screening.
• Patients with diabetes who already have other microvascular complications, such as retinopathy or nephropathy.
• Patients with unexplained resting tachycardia, orthostatic symptoms, or reduced exercise tolerance.
• Patients in whom autonomic status would meaningfully inform cardiovascular risk assessment.

The decision to perform cardiovascular autonomic neuropathy testing always rests on clinical judgment and the individual patient’s history. The American Heart Association and other bodies emphasize comprehensive cardiovascular risk evaluation in people with diabetes, and autonomic assessment can be one objective input into that broader picture.

How Does the TM-Flow System Support Cardiovascular Autonomic Neuropathy Testing?

The TM-Flow system is an FDA-cleared device that performs cardiovascular autonomic neuropathy testing noninvasively at the point of care, typically as part of a brief in-office evaluation. It captures heart rate variability and cardiovagal (parasympathetic) reflex data, and it can be combined with sudomotor and vascular measurements such as the ankle-brachial and toe-brachial indices. In other words, it gathers several streams of autonomic nervous system testing data in a single workflow.

It is important to frame the technology correctly: the system measures autonomic function and supports the clinician’s assessment. It does not, on its own, diagnose diabetes, neuropathy, or any other disease — interpretation and diagnosis remain the responsibility of the treating physician. Used this way, cardiovascular autonomic neuropathy testing with TM-Flow becomes a structured, repeatable part of a practice’s diagnostic toolkit rather than a replacement for clinical reasoning.

In practice, the workflow is straightforward. A staff member places the sensors, the patient breathes and changes position according to simple prompts, and the system records the physiologic responses.

The output summarizes parasympathetic and sympathetic measures so the physician can review the autonomic profile alongside the patient’s history, examination, and other diagnostics. Because the test is quick and repeatable, it fits into a standard office visit and can be repeated at appropriate intervals to follow a patient over time.

Interpreting the results is where clinical judgment comes in. An abnormal pattern does not establish a diagnosis on its own, but it identifies patients who may benefit from closer cardiovascular follow-up and helps document the clinical rationale for that decision.

A normal result is also informative, offering reassurance and a baseline for future comparison. This balanced, evidence-supported approach is what makes structured autonomic assessment a practical addition to a modern practice.

What CPT Codes Apply to Cardiovascular Autonomic Neuropathy Testing?

Cardiovascular autonomic neuropathy testing is associated with the autonomic function study CPT family. The codes most relevant to cardiovascular assessment are:

• 95921 (cardiovagal, parasympathetic function)
• 95922 (vasomotor adrenergic, sympathetic function)
• 95924 (combined parasympathetic and sympathetic testing)

Code 95923 covers sudomotor testing, which is often performed alongside the cardiovascular components. TM-Flow’s cardiovagal HRV assessment aligns with the 95921 side of this family; tilt-dependent components reported under 95922 and 95924 require additional protocol and equipment.

Coding and coverage vary by payer and by the exact protocol performed, so always confirm which codes apply to your testing and verify coverage with your payer before billing. For a deeper breakdown, see our guides to autonomic function testing CPT codes and reimbursement considerations for the TM-Flow system.

How Is Cardiovascular Autonomic Neuropathy Testing Different From an ECG?

A standard electrocardiogram (ECG or EKG) records the heart’s electrical activity at a single point in time, which is valuable for detecting arrhythmias, conduction abnormalities, and signs of ischemia. Cardiovascular autonomic neuropathy testing answers a different question.

Rather than mapping the heart’s electrical signal, it measures how effectively the autonomic nervous system adjusts heart rate and blood pressure in response to controlled maneuvers such as paced breathing, the Valsalva maneuver, and a change in posture, together with heart rate variability over time. The two are complementary rather than interchangeable: a patient can have a normal ECG and still show measurable autonomic dysfunction.

For this reason, the TM-Flow system is not an ECG machine and does not replace one. Instead, cardiovascular autonomic neuropathy testing adds a distinct layer of autonomic information that an ECG alone cannot provide, which is why many practices use the two assessments side by side.

How Can Your Practice Add Cardiovascular Autonomic Neuropathy Testing?

Independent practices can add cardiovascular autonomic neuropathy testing through the CMAT Advantage program, which bundles the TM-Flow device with clinical training and billing support. The point-of-care test is noninvasive and typically takes only a few minutes, making it practical to integrate into existing visit workflows alongside other vascular screening services. Many practices position autonomic and vascular assessment together; our overview of the PAD-to-ANS testing workflow explains how these services complement one another clinically.

HealthWright Technologies works with independent physicians nationwide to implement cardiovascular autonomic neuropathy testing with full training, implementation, and billing guidance. To explore adding this capability, visit our partnership page or contact our team at contact@healthwrighttechnologies.com. HealthWright Technologies is located at 60 Bear Creek Marina Rd, Mansfield, GA 30055.

Frequently Asked Questions

What is cardiovascular autonomic neuropathy testing?

Cardiovascular autonomic neuropathy testing is a set of noninvasive assessments — heart rate variability analysis plus cardiovascular autonomic reflex tests such as deep breathing, the Valsalva maneuver, and postural change — that evaluate how the autonomic nervous system regulates the heart and blood vessels.

Is cardiovascular autonomic neuropathy testing invasive or painful?

No. Cardiovascular autonomic neuropathy testing is noninvasive and is typically completed in a few minutes in the office. It records physiologic responses such as heart rate and blood pressure changes and does not require needles or imaging dye.

Is the TM-Flow system FDA-approved?

The TM-Flow system is FDA-cleared, not FDA-approved. FDA clearance (the 510(k) pathway) and FDA approval are different regulatory processes for medical devices. TM-Flow measures autonomic and vascular function and supports clinical assessment; it does not by itself diagnose disease.

What CPT codes are used for cardiovascular autonomic neuropathy testing?

The autonomic function study codes 95921, 95922, and 95924 are most relevant to cardiovascular autonomic neuropathy testing, with 95923 covering sudomotor testing. The codes that apply depend on the components performed, so verify coverage and coding with your payer before billing.

Can cardiovascular autonomic neuropathy testing be performed in a primary care office?

Yes. With a point-of-care system such as TM-Flow, cardiovascular autonomic neuropathy testing can be performed in a primary care or specialty office as part of a routine visit, without referral to a separate testing facility.

This article is intended for healthcare professionals and is for general educational purposes only. It is not medical advice or a substitute for clinical judgment. CPT is a registered trademark of the American Medical Association; codes are provided for general reference and are not a guarantee of coverage or payment. Always verify coding and coverage with your payer.