Cerrone et al reported that the mechanism of

Cerrone et al. reported that the mechanism of CPVT was due to delayed afterdepolarization‐induced triggered activity in a focal Purkinje network in a knock-in (RyR2) mouse [36]. In addition, chemical ablation of the RV endocardial cavity with Lugol׳s solution, which selectively destroys the Purkinje network, could convert bidirectional VT into monomorphic VT in a CPVT model of anesthetized mice. Therefore, the Purkinje network is considered to be a critical contributor to arrhythmogenic triggers in CPVT and may be a promising therapeutic target for catheter ablation. Our group presented the first case report of the successful catheter ablation of bidirectional VPCs triggering VF in patients with CPVT [37]. This case was of a 38-year-old woman who had often experienced syncope since childhood. The patient׳s daughter also had similar episodes of syncope and developed VF during treadmill exercise testing, which was successfully defibrillated with an electric shock. Witnessing this situation, the patient also lost consciousness, with documented VF which was converted to sinus rhythm by cardiopulmonary resuscitation. There were no significant abnormalities in her resting 12-lead ECG, echocardiography, or coronary angiography. Genetic analysis revealed that she and her daughter had same missense mutation (c.1259G>A, p.R420Q) in RyR2, and both were diagnosed as having CPVT. During the patient׳s epinephrine stress test (Fig. 1), multifocal VPCs (VPC #1, RBBB, and superior axis; VPC #2, RBBB, and inferior axis, the same VPC configuration as that induced during the treadmill exercise testing; and VPC #3, LBBB, and inferior axis) appeared, and VPC #1 following VPC #2 subsequently induced VF. We performed catheter ablation targeting the catecholamine-induced VPCs (Fig. 2). VPC #1 was recorded at the left ventricular inferoseptal area near the posteromedial papillary muscle, where a presystolic Purkinje potential preceded VPC #1 by 18ms. RF fexofenadine hydrochloride application to this site accelerated the VPCs, and additional applications around the target site subsequently eliminated VPC #1. After the procedure, VPC #2 continued to occur, and a local bipolar electrogram recorded on the left coronary cusp showed a discrete prepotential that preceded the onset of VPC #2 by 65ms. RF energy application to the left coronary cusp abolished VPC #2. After ablation at both sites, neither the VPCs nor VF was inducible, even with an infusion of epinephrine at up to 1.2g/kg per min. The patient underwent ICD implantation and was discharged from the hospital on bisoprolol. During a 16-month follow-up after ablation, no episodes of syncope or ICD therapy occurred. Thus, catheter ablation of the bidirectional VPCs triggering VF may become an adjunctive therapeutic option for CPVT.
Conclusions
Conflict of Interest
Acknowledgements
Introduction
Cardiac alternans Cardiac alternans are beat-to-beat oscillations in either arterial pulse or electrocardiographic QRS and T waves. Of these, T-wave alternans (TWAs) have been associated with re-entrant arrhythmogenesis and identified as a good predictor of sudden cardiac death [1]. They are due to alternations in repolarisation time courses (measured as action potential durations, APDs) at the cellular level, which increase in amplitude with faster heart rates. TWAs have been observed in a number of conditions, including electrolyte abnormalities, hypothermia, coronary artery disease, post-myocardial infarction, long QT and Brugada syndromes, vasospastic angina, dilated, hypertrophic, and Takotsubo cardiomyopathies, and end-stage heart failure.
Spatially concordant and discordant alternans APD alternans can be either spatially concordant or discordant (Table 2). As the pacing rate is increased, spatially concordant alternans are observed, in which APD is long throughout the cardiac tissue on one beat and short on the next beat, i.e., APDs in different regions alternate in phase with each other. When the pacing rate is increased further, spatially discordant alternans are produced, in which APD is long in one region but short in an adjacent region, and changes phase on the next beat; i.e., APD in different regions alternate out of phase with each other. A number of mechanisms have been identified as being responsible for the production of spatially discordant APD alternans. These can involve pre-existing heterogeneities, which often interact with dynamic factors to produce them. However, pre-existing tissue heterogeneities may not be necessary; the presence of dynamic factors alone may be sufficient for producing spatially discordant alternans [23].