Atrial fibrillation (AF) is the most common arrhythmia, with a lifetime risk of 1 in 3-5. In cases of rapid ventricular rate, patients often experience low blood pressure, making standard rate and rhythm control medications contraindicated. While cardioversion may be necessary, it is often ineffective in long-standing AF and can lead to left ventricular stunning. This creates a vicious cycle, worsening heart failure and cardiogenic shock.

AV node ablation may be required, but it is irreversible and carries risks, including complications from long-term pacing. Therefore, temporary pacing may be a preferable option to allow for hemodynamic improvement and better ventricular filling.

Research suggests that parasympathetic fibers innervating the AV node can modulate conduction. Ablation in these fibers has shown promise for treating vagal-mediated syncope, and high-frequency pacing may provide chronic heart rate suppression. Intermittent pacing has also been effective in reducing ventricular rates in atrial fibrillation to prevent inappropriate ICD shock. This may be potentially beneficial for patients with uncontrolled fast AF.

In a proof-of-concept study with five patients, pacing at 30Hz and 10mA in the coronary sinus resulted in a dose-dependent prolongation of the ventricular cycle length during AF, with stable blood pressure and no discomfort reported. This suggests that pacing these fibers could achieve rate control without the need for medications or AV node ablation, with no complications observed.

This study aims to evaluate safety and efficacy of temporary cardio-neural pacing (CNP). This is a prospective cohort study involving patients with atrial fibrillation (AF) and rapid ventricular conduction who have failed or are contraindicated for rate control with antiarrhythmic medications. Enrolled patients will be followed up for 1 month.

During procedure, arterial line will be inserted for monitoring of blood pressure. A temporary ventricular lead will be first implanted, potentially to the left bundle area to preserve normal conduction physiology. A coronary sinus sheath (attain command or deflectable) will be delivered to RA septum, posterior to CS ostium, at the expected location of parasympathetic ganglion plexus. Pace mapping will be performed with a pacing lead (such as Select Secure 3830) at 30Hz. An electrophysiology catheter may be used where necessary for pace-mapping the response. At the site where lowest output can generate 30% prolongation of ventricular CL, the lead is fixed for 1-5mm depth. The output is tested again to achieve heart rate slowing to less than 80bpm. Fluoroscopic image will be collected with contrast injection at the sheath. Eventually, the implanted lead will be connected into a temporary pacemaker. The temporary leads will be removed when no longer clinically required, such as when the heart rate stabilized. Cardioneural pacing will be performed at lowest output at a frequency of 5-50Hz via the atrial lead (CNP lead). The ventricular lead will have pacing mode being set at 80bpm VVI.

Inclusion Criteria:

• Patients with atrial fibrillation or atrial flutter who are having rapid ventricular rate >100bpm
• Patient who cannot take rate control agents, or heart rate control remains unsatisfactory after rate control agents

Exclusion Criteria:

• Patients who cannot provide informed consent
• Patients < 18 years old
• Pregnant patients
• Illiterate patients