A Houston Methodist doctor has shown that post-transplant heart block can be abolished with cardioneuroablation, a minimally invasive method that could eschew many of the risks that result when surgeons implant a pacemaker device.

The case — the first of its kind in the world — was written up in the Journal of the American College of Cardiology: Clinical Electrophysiology.

"The patient was discharged without further atrioventricular (AV) blocks and showed 100% ventricular sensing without pacing at three-month follow-up," said Dr. Miguel Valderrabano, a Houston Methodist electrophysiologist and author of the paper. "This is a conceptual breakthrough that suggests that cardioneuroablation could be an alternative mode of treatment to pacemakers in similar cases of orthotopic heart transplant."

Orthotopic heart transplant is the most common treatment for end-stage heart disease, but it often causes complications such as arrhythmias, sinus node dysfunction or heart block, a partial or complete disruption of the electrical impulses that control the beating of the organ. In such cases, a permanent pacemaker is implanted to accompany the new heart.

Pacemakers help control slower heart rates and long-term arrhythmias, but the implantation surgery comes with several risks, including infection, swelling, bruising, bleeding, blood clotting, damage to blood vessels or nerves as well as a collapsed lung.

Cardioneuroablation, on the other hand, is a simple 30-minute procedure performed using radiofrequency catheter ablation. It results in fewer complications.

Dr. Valderrabano's patient had a paroxysmal heart block, an ominous condition characterized by a sudden, complete AV block and no escape rhythm.

The 23-year-old had a history of multiple heart transplants for congenital dilated cardiomyopathy, first as a 1-year-old, then as a teenager for coronary vasculopathy, and again in 2022 because of rejection.

After his third transplant, the patient demonstrated a high-degree AV block while asleep and underwent a dual chamber pacemaker implantation because of the perceived high risk of sudden death owing to a bradyarrhythmia (abnormally slow resting heart rate). Interestingly, the patient's nerves were being activated autonomously, a novel finding in and of itself.

Dr. Valderrabano cautiously explored the avenue of cauterizing nerves in the newly transplanted heart, a technique that has been used to prevent fainting and improve outcomes in people with slow heart rates since its invention in the 1990s.

"We suspected a neurally mediated mechanism of his paroxysmal atrioventricular block because of the absence of graft dysfunction," Dr. Valderrabano explained. "If high-frequency stimulation of the intrinsic cardiac nerve could replicate the AV block, we reasoned that ablation would be therapeutic."

The case demonstrates the possibility that cardioneuroablation could potentially replace permanent pacemakers while offering improved outcomes for transplant recipients with heart blocks. A prospective clinical trial, even one with a small sample size, would help shed more light on the probability of success, Dr. Valderrabano said.

To learn more and see imaging from the case, check out the full story in Methodology, a publication from the Houston Methodist Academic Institute.