Catecholaminergic polymorphic ventricular tachycardia: risk modulators in patients treated with beta-blockers

Background

Due to the catecholaminergic nature of arrhythmias that define the Catecholaminergic Polymorphic Ventricular Tachycardia (CPVT), beta-blockers (BBs) represent the first line therapy for this severe arrhythmogenic syndrome. Despite optimal BB therapy, a proportion of patients continue to suffer breakthrough life-threatening arrhythmias (LAE).

Purpose

To evaluate the role different classes of BBs (β1-selective vs. non-selective) in LAE reduction and to identify risk factors for breakthrough LAE while on BB monotherapy.

Methods

We studied 238 consecutive patients with CPVT and treated with BB monotherapy followed-up prospectively. CPVT was diagnosed according to the 2015 European Society of Cardiology Guidelines. The endpoint was the occurrence of the first LAE (sudden cardiac death, aborted cardiac arrest, or hemodynamically non-tolerated ventricular tachycardia) in BB monotherapy. The follow-up for each patient was calculated from BB therapy start to the occurrence of the endpoint, death from non-arrhythmic cause, the date of last visit, or the initiation of other treatments (i.e.: other antiarrhythmics or left cardiac sympathetic denervation [LCSD]), whichever occurred first.

Multivariable Cox proportional hazards model was used to evaluate the effects of history of LAE before diagnosis of CPVT, occurrence of unexplained syncope before diagnosis of CPVT, genotype, and type of BB therapy, as a time-dependent variable, on the risk of experiencing an LAE during BB monotherapy.

Results

We enrolled 238 CPVT patients (135 probands, 135 females): 226 with typical CPVT (n=216 RYR2; n=10 CASQ2) and 12 with atypical CPVT (n=5 RYR2-Loss-of-Function, n=4 TRDN and n=3 TECRL).

Prior to BB monotherapy, 48/238 (20%) patients had survived an LAE, and 110/238 (46%) patients had experienced an unexplained syncope.

During 1,629 person-years of follow-up during BB monotherapy, 35 patients experienced an LAE (annual LAE rate 2.1%, 95% CI: 1.5%–3.0%; Figure A). Five-year cumulative probability of experiencing an LAE during BB monotherapy was 11.9% (95% CI: 7.0%-16.6%). In this population, multivariable analysis showed that history of LAE before diagnosis (HR 3.6; 95% CI: 1.6–8.1; p=0.002) and syncope before diagnosis (HR 6.1; 95% CI: 2.5–14.9; p<0.001) were clinical risk factors for LAE occurrence. Patients with TRDN mutations were significantly more likely to suffer LAE (HR 20.9; 95% CI: 2.2–196.3; p=0.008). Using nadolol as the gold standard, the use of β1-selective BBs (HR 3.4; 95% CI: 1.4–8.6; p=0.009), but not propranolol (HR: 0.9; 95% CI: 0.2–3.8; p=0.887), was associated with poorer outcome during BB monotherapy (Figure B).

Conclusions

In patients with CPVT, selective BBs are associated with a higher risk of LAE as compared to nadolol. Patients who have survived an LAE and/or experienced an unexplained syncope prior to diagnosis, as well as carriers of TRDN mutations are at high risk of BB failure.

Funding Acknowledgement

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Ricerca Corrente Funding scheme of the Italian Ministry of Health and Italian Ministry of Research and University Dipartimenti di Eccellenza 2018–2022 grant to the Molecular Medicine Department (University of Pavia).

Natural History of Patients with Typical and Atypical Catecholaminergic Polymorphic Ventricular Tachycardia

Background

Recently, a novel genetic-based classification for Catecholaminergic Polymorphic Ventricular Tachycardia (CPVT) has been proposed to distinguish “typical” (RYR2 and CASQ2 genes) and “atypical” (TRDN, TECRL, CALM1–3, RYR2 loss-of-function [RYR2-LoF]) CPVT variants. Although some genetic forms were reported as malignant forms of CPVT, natural history data comparing typical and atypical CPVT variants are lacking.

Purpose

We compared the natural history of “typical” and “atypical” forms of CPVT in a large cohort of patients with genetically confirmed CPVT.

Methods

CPVT was diagnosed according to the criteria defined in the 2015 European Society of Cardiology Guidelines. Based on the genetic background, we classified the patients in two groups: 1) “Typical” CPVT (i.e., carriers of pathogenic or likely pathogenic mutations in RYR2 and CASQ2 genes); 2) “Atypical” CPVT (i.e., carriers of pathogenic or likely pathogenic mutations in TRDN, TECRL, CALM1–3 and RYR2-LoF). Patients with mutations in the CALM1, CALM2 or CALM3 were not identified in our cohort. The outcome was the occurrence of a life-threatening arrhythmic event (LAE), defined as: sudden cardiac death, aborted cardiac arrest or hemodynamically non-tolerated ventricular tachycardia. The Kaplan-Meier life-table method was used to determine the cumulative probability of experiencing a first LAE before the age of 40 years and in the absence of treatment. Outcomes in two groups were compared using the log-rank test.

Results

The study cohort included 238 patients (56% females, median age at diagnosis 14 years [IQR: 9–28 years]), of whom 226/238 (95%) patients with “typical” CPVT (216 RYR2, 10 CASQ2), and 12/238 (5%) patients with “atypical” CPVT (5 RYR2-LoF, 4 TRDN, 3 TECRL). In the entire population, the cumulative probability of experiencing a first LAE between birth and the diagnosis of CPVT was 2.3%, 21.2 and 40.8% at 5, 20, and 40 years, respectively. At any given age, the probability of a first LAE in the absence of therapy was significantly higher in patients with atypical CPVT (25%, 36%, and 100% at 5, 20, and 40 years, respectively), as compared to patients with typical CPVT (1%, 20%, and 39% at 5, 20, and 40 years, respectively; p=0.003, Figure 1). Patients with atypical CPVT suffered LAEs in early childhood (i.e., by the age of 5 years) significantly more often than patients with typical CPVT (3/5 patients [60%] in atypical CPVT vs. 2/43 patients [5%] in typical CPVT, p<0.001; Figure 2).

Conclusions

The natural history of CPVT is modulated by the genetic cause. Atypical CPVT variants are rare but are characterized by a worse outcome and a greater likelihood of experiencing an LAE since the early childhood, as compared to typical CPVT.

Funding Acknowledgement

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Ricerca Corrente funding scheme of the Italian Ministry of Health