Purkinje-Related Ventricular Tachycardia Responsive to Ivabradine

The bradycardiac effect of ivabradine relies on selective inhibition of hyperpolarization-activated cyclic nucleotide-gated channel 4 within the sinoatrial node, which generates the funny pacemaker current (I_f). Previous animal studies have demonstrated that ivabradine can suppress Purkinje fiber automaticity, depending mainly on the I_f.¹

An 82-year-old man was admitted for heart failure (HF) with reduced ejection fraction. Catheter ablation for atrial fibrillation was performed, followed by cardiac resynchronization therapy implantation. One month after implantation, he was rehospitalized for HF. The biventricular pacing percentage was significantly decreased because of wide QRS tachycardia with right bundle branch block morphology and retrograde P’ waves without dissociation (Figure A), which was refractory to β-blockers. As the patient could not tolerate verapamil due to HF,² ivabradine (5.0 mg) was administered twice daily. Subsequently, the biventricular pacing percentage increased, and HF improved owing to tachyarrhythmia suppression immediately after ivabradine administration. Catheter ablation was performed as a curative treatment because both the adherence to and efficacy of ivabradine was unstable. Right ventricular overdrive pacing reproducibly suppressed tachycardia without fusion beats. Left ventricular endocardial mapping during tachyarrhythmia revealed a centrifugal pattern, with the earliest activation site at the distal left anterior fascicle, in which Purkinje potentials preceded local myocardial potentials in a 1-to-1 manner (Figure B). Hence, the patient was diagnosed with non-reentrant Purkinje-related VT, which was treated with radiofrequency application at the earliest activation site. The patient has remained free of VT for 8 months.

Figure.

(A) 12-lead electrogram of ventricular tachycardia and pacing trends of cardiac resynchronization therapy. (B) Left ventricular activation maps during atrial pacing and ventricular tachycardia.

This is the first documented case demonstrating the possible efficacy of ivabradine for Purkinje fiber automaticity.

Acknowledgments

This study was supported by JSPS KAKENHI (grant number: JP24K11205).

Disclosures

The authors declare no conflicts of interest.

Data Availability

N/A.

Supplementary Files

Please find supplementary file(s);

https://doi.org/10.1253/circj.CJ-25-0405

References

• 1.   Sosunov EA, Anyukhovsky EP. Differential effects of ivabradine and ryanodine on pacemaker activity in canine sinus node and Purkinje fibers. J Cardiovasc Electrophysiol 2012; 23: 650–655.
• 2.   Ono K, Iwasaki YK, Akao M, Ikeda T, Ishii K, Inden Y, et al. JCS/JHRS 2020 Guideline on pharmacotherapy of cardiac arrhythmias. Circ J 2022; 86: 1790–1924.