The impact of intravenous atropine bolus on eye pupil diameter in patients undergoing cardioneuroablation

Pupil diameter (PD) assessment is an essential component of neurological evaluation and sometimes needs to be assessed during electrophysiological procedures. Cardioneuroablation (CNA) with radiofrequency energy is a promising treatment method for a spectrum of cardiac rhythm disorders associated with increased parasympathetic tone. A crucial part of pre-procedural evaluation is the diagnostic administration of atropine aimed at determining the future effect of parasympathetic denervation. However, atropine administration may affect pupil diameter in patients undergoing CNA. The impact of intravenously administered atropine on pupil diameter in the CNA population has not been determined yet.

Consecutive patients undergoing CNA were included in the study. A 2mg intravenous atropine test was performed in the setting of electrophysiology laboratory. Pupil diameter measurements of both eyes were conducted using a slit lamp directly before, immediately after, and at 3 and 16 hours post-atropine administration.

Seventeen consecutive patients underwent pre-CNA evaluation (age 45±19, 10 females). Primary indications for the atropine test were: atrioventricular block (8), mixed-type vasovagal syncope (4), symptomatic sinus bradycardia (2), cardioinhibitory vasovagal syncope (1), vagally mediated atrial fibrillation (1), and long QT syndrome (1). Compared to baseline values, atropine administration caused statistically significant dilation of pupils immediately post-bolus (4.38±0.35 vs 4.84±0.47; p<0.0001); at 3 hours post-administration (4.38±0.35 vs 5.04±0.43; p<0.0001); and at 16 hours post-administration (4.38±0.35 vs 4.82±0.36; p<0.0001). Atropine administration significantly reduced deceleration capacity (DC) (7.7±4.4 vs 1.1±0.9ms; p<0.0001) and simultaneously increased heart rate (HR) (67±19bpm vs 112±27bpm, p<0.0001) in the study group. There were no statistically significant differences in DC (7.7±4.4ms vs 6.9±3.9ms; p=0.6) or HR (67±19 vs 68±18bpm; p=0.9) when baseline values were compared with measurements performed 16 hours post-administration.

Intravenous administration of atropine significantly affects pupil diameter in patients undergoing CNA, and this effect persists in a 16-hour observation. However, 16 hours post-atropine administration, atropine influence on HR and DC is minimal. These findings should impact timing of CNA following the atropine test.