Cardioneuro ablation (CNA) for cardioinhibitory syncope

31 May 26 | Dr Boon Lim and Mohamed Zuhair

What is CardioNeuro Ablation (CNA)

Cardioneuroablation (CNA) is a minimally invasive catheter procedure designed to reduce excessive vagal signals reaching the heart.

In some people with cardioinhibitory vasovagal syncope, the body’s nervous system sends powerful signals through the vagus nerve that can suddenly slow the heart or even cause it to stop briefly. CNA aims to reduce these abnormal reflexes.

The procedure works by targeting small clusters of nerve cells called ganglionated plexi (GPs) that sit on the surface of the heart. These nerve clusters act as communication stations between the brain, the vagus nerve and the heart.

Think of the vagus nerve as a telephone cable and the ganglionated plexi as telephone exchange boxes. In some patients, these exchange boxes send excessively strong slowing signals to the heart. Cardioneuroablation modifies these signals, helping to prevent the dramatic slowing of the heart that can lead to fainting.

The procedure is performed using thin tubes called catheters, which are inserted through veins in the leg and guided into the heart. Radiofrequency energy is then delivered to carefully selected areas containing these nerve clusters.

Unlike a pacemaker, CNA does not involve leaving a permanent device inside the body. Instead, it aims to treat the underlying reflex responsible for the fainting episodes.

Current research suggests that CNA may be particularly useful in younger patients with recurrent cardioinhibitory vasovagal syncope who continue to experience symptoms despite lifestyle measures and medical treatment. While results from many studies have been encouraging, ongoing research is helping doctors better understand which patients are most likely to benefit and how best to perform the procedure.

For carefully selected patients, Cardioneuroablation offers a promising new approach to reducing or preventing recurrent fainting episodes and improving quality of life.

Cardioneuroablation (CNA) - a patient journey through his catheter laboratory procedure

This patient, Rob is a healthy 38-year-old professional whose heart scans, echocardiogram and cardiac MRI were all completely normal. Despite this, he experienced frequent episodes of dizziness, near-fainting and blackouts caused by sudden pauses in his heartbeat. These episodes occurred almost daily, affecting his confidence, work and quality of life. Like many patients with cardioinhibitory vasovagal syncope, he was frustrated by being told that his heart was “normal” while continuing to experience disabling symptoms.

After careful consideration, he decided that he did not want to have a pacemaker implanted for the heart pauses, and instead, was considered for a CNA procedure

In the video below, Dr Lim explains the cardioneuroablation to Rob before he undergoes the CNA ablation procedure

The video below provides an anatomical illustration of the nervous system which supplies the heart, and the target for CNA

CNA live case study

Cardioneuroablation (CNA): A Live Case Demonstration (see video below)

Watching the Vagus Nerve Control the Heart in Real Time

One of the most fascinating aspects of Cardioneuroablation (CNA) is that doctors can often see the abnormal vagal response causing symptoms during the procedure itself.

In this live case, Rob had recurrent episodes caused by excessive vagal activity affecting both his natural pacemaker (the sinus node) and the electrical connection between the upper and lower chambers of the heart (the AV node).

The aim of CNA was to reduce this excessive vagal influence and prevent future pauses.

Step 1: Testing the Vagus Nerve

At the start of the procedure, catheters were placed in the veins of the groin and special stimulation catheters were positioned in the neck.

The vagus nerve travels through the neck before reaching the heart. By delivering brief electrical stimulation in the neck, we can temporarily activate the vagus nerve and observe its effects on the heart.

Before any ablation was performed, stimulation of Rob’s left vagus nerve produced a pause of approximately three seconds. His heart slowed dramatically and his blood pressure fell.

This demonstrated that excessive vagal activation was capable of reproducing the physiological problem responsible for his symptoms.

Step 2: Targeting the AV Node Pathway

The first stage of ablation targeted areas within the left atrium that contain nerve fibres supplying the AV node.

These nerve clusters, known as ganglionated plexi (GPs), act as relay stations between the vagus nerve and the heart.

Following ablation, the neck stimulation test was repeated.

This time, despite activating the vagus nerve, the previous AV block could no longer be produced.

This showed that the pathway allowing the vagus nerve to excessively slow electrical conduction through the AV node had been successfully interrupted.

Step 3: Targeting the Sinus Node Pathway

The next stage focused on the nerve supply to the sinus node, the heart’s natural pacemaker.

Before ablation, Rob’s resting heart rate was approximately 65–70 beats per minute.

As ablation was delivered at a key ganglionated plexus site, his heart rate increased immediately from around 70 beats per minute to almost 90 beats per minute.

This increase is often a very encouraging sign. It suggests that excessive vagal influence over the sinus node has been reduced and that the heart’s own pacemaker can now function more freely.

Step 4: Re-testing the Vagus Nerve

One of the most important principles of CNA is that treatment can be tested immediately.

After both the AV node and sinus node pathways had been targeted, stimulation was again delivered from the neck.

Before ablation, this stimulation caused pauses and significant slowing of the heart.

After ablation, the same stimulation no longer produced these effects.

The vagus nerve could no longer trigger the dangerous slowing that had been present at the beginning of the procedure.

This is one of the unique features of CNA: we can often demonstrate success during the procedure itself rather than waiting weeks or months for a result.

Step 5: The Atropine Test

At the end of the procedure, a medication called atropine was given.

Atropine temporarily blocks the effects of the vagus nerve. Normally, if a person still has significant vagal influence on their heart, atropine causes the heart rate to rise substantially.

Rob’s heart rate increased by only a few beats per minute.

This suggested that most of the excessive vagal influence had already been removed by the ablation itself.

For many operators, a minimal atropine response is another reassuring sign that adequate denervation has been achieved.

Why This Matters

Many patients with cardioinhibitory vasovagal syncope experience pauses because the vagus nerve becomes overactive.

This can result in:

Sinus arrest (the heart’s natural pacemaker temporarily stops)
AV block (electrical signals fail to pass from the atria to the ventricles)
Significant slowing of the heart rate
Reduced blood pressure
Dizziness, blackouts and fainting

Cardioneuroablation aims to reduce this excessive vagal influence while leaving the heart’s normal electrical system intact.

Rather than implanting a pacemaker, CNA seeks to address the underlying neural pathway responsible for the pauses.

Key Takeaway

This live case demonstrates the fundamental principle of Cardioneuroablation:

If stimulation of the vagus nerve can produce a pause before ablation, and the same stimulation can no longer produce a pause after ablation, then the abnormal pathway causing the symptoms has been successfully interrupted.

While long-term follow-up remains important, seeing these physiological changes in real time provides powerful evidence that the procedure has achieved its intended effect.

IS Cardioneuroablation suitable for everyone?

No. While Cardioneuroablation (CNA) can be highly effective in carefully selected patients, it is not appropriate for everyone who experiences fainting or slow heart rhythms.

The best candidates are typically younger patients with recurrent cardioinhibitory vasovagal syncope, where there is clear evidence that excessive vagal activity is causing significant slowing of the heart, sinus arrest, or AV block.

Before considering CNA, it is important to exclude other causes of blackouts and slow heart rhythms. Some patients may have disease of the heart’s electrical system rather than excessive vagal activity. In these cases, CNA may not be effective and a pacemaker may be a more appropriate treatment.

Other factors that influence suitability include the patient’s age, symptoms, frequency of episodes, severity of injury risk, underlying medical conditions, and the results of investigations such as ECG monitoring, implantable loop recorders, tilt-table testing, and electrophysiology studies.

At StopFainting.com, we believe that patient selection is one of the most important aspects of CNA. The procedure should not be viewed as a treatment for all fainting conditions, but rather as a specialised therapy for a specific group of patients in whom excessive vagal activity has been clearly demonstrated on ambulatory clinical grade ECG monitoring such as a Holter monitor or implantable loop recorder.

For this reason, every patient should undergo a detailed assessment by a specialist with experience in both vasovagal syncope and Cardioneuroablation before deciding whether CNA is the right option.