A Mechanistic Clinical Trial Using ()- Versus )-Propafenone to Test RyR2 (Ryanodine Receptor) Inhibition for the Prevention of Atrial Fibrillation Induction.

BACKGROUND

Experimental data suggest ryanodine receptor-mediated intracellular calcium leak is a mechanism for atrial fibrillation (AF), but evidence in humans is still needed. Propafenone is composed of two enantiomers that are equally potent sodium-channel blockers; however, )-propafenone is an ryanodine receptor inhibitor whereas )-propafenone is not. This study tested the hypothesis that ryanodine receptor inhibition with )-propafenone prevents induction of AF compared to )-propafenone or placebo in patients referred for AF ablation.

METHODS

Participants were randomized 4:4:1 to a one-time intravenous dose of )-propafenone, )-propafenone, or placebo. The study drug was given at the start of the procedure and an AF induction protocol using rapid atrial pacing was performed before ablation. The primary endpoint was 30 s of AF or atrial flutter.

RESULTS

A total of 193 participants were enrolled and 165 (85%) completed the study protocol (median age: 63 years, 58% male, 95% paroxysmal AF). Sustained AF and/or atrial flutter was induced in 60 participants (84.5%) receiving )-propafenone, 60 (80.0%) receiving )-propafenone group, and 12 (63.2%) receiving placebo. Atrial flutter occurred significantly more often in the )-propafenone (N=23, 32.4%) and )-propafenone (N=26, 34.7%) groups compared to placebo (N=1, 5.3%, =0.029). There was no significant difference between )-propafenone and )-propafenone for the primary outcome of AF and/or atrial flutter induction in univariable (=0.522) or multivariable analysis (=0.199, adjusted for age and serum drug level).

CONCLUSIONS

There is no difference in AF inducibility between )-propafenone and )-propafenone at clinically relevant concentrations. These results are confounded by a high rate of inducible atrial flutter due to sodium-channel blockade.

REGISTRATION

https://clinicaltrials.gov; Unique Identifier: NCT02710669.