Tragus Stimulation to Prevent Atrial Fibrillation After Cardiac Surgery

Tragus Stimulation to Prevent Atrial Fibrillation After Cardiac Surgery: The TraP-AF Study

Patients undergoing cardiac surgery, specifically a coronary artery bypass graft and/or heart valve replacement surgery, are at a higher risk for post-procedure atrial fibrillation (AF). AF is a condition in which the upper chambers of the heart do not contract normally and results in an irregular heartbeat. Recent studies have shown that tragus stimulation decreases the likelihood of AF in animals and humans. It has also been shown to reduce inflammation which may be related to post-procedure AF. Tragus stimulation involves stimulating a part of the outer ear, called the tragus, by sending a microcurrent through a small alligator clip. It is believed that tragus stimulation can affect the nervous system, which may reduce heart rate and lead to prevention of AF. The purpose of this study is to determine whether tragus stimulation in subjects undergoing cardiac surgery will lead to shorter occurrences, or even prevention, of AF.

This was a single-blind study where patients were randomized tragus stimulation versus sham procedure and remained blinded to their treatment allocation. Both treatment options utilized similar equipment, namely the use of alligator clips which will be placed on the tragus and earlobe of the right ear for patients.

Prior to cardiac surgery, the discomfort threshold of both left and right tragus stimulation was determined for all participating patients. Intermittent electrode signals, or microcurrents, were delivered at 20 Hz with100 µsec pulse width with variable microampere (mA) output. The discomfort threshold was defined as the stimulation intensity in mA at which point patients experience discomfort. The stimulation intensity used in the study was set below the sensation and discomfort threshold. The clip was placed on the patient's ear at the end of surgery. Stimulation then continued, one ear alternating with the other, every 4 hours for a total of 48 hours. If the patient showed any sign of discomfort from stimulation, the intensity of stimulation was reduced to a level at which signs of discomfort disappears.

Follow-up was performed with a 14-day event monitor at the time of discharge, as clinically indicated. Echocardiography were assessed prior to study initiation and when clinically available in follow-up.

Inclusion Criteria:

1. Patients ≥18 years of age, <90 years of age
2. Estimated life expectancy of at least 1 year at the time of enrollment
3. History of sinus rhythm or paroxysmal atrial fibrillation

Exclusion Criteria:

1. Patients ≥90 years of age, <18 years
2. Patients with known prior history of persistent or permanent AF
3. Atrial Fibrillation occurrence within the last 24 hours of procedure
4. Urgent or Emergency cases
5. Pregnant patients
6. Patients undergoing the following cardiac procedures: heart transplant, pulmonary thromboendarterectomy, isolated aortic arch procedures, congenital hear disease, ventricular assist device insertion, extracorporeal membrane oxygenation insertion, and surgical AF ablation
7. Antiarrhythmics prior to surgery (Class I and Class III)
8. High degree atrioventricular block requiring temporary pacing
9. Prior maze procedure for the treatment of AF