Key result
Isoprenaline-challenged RyR2-R2474S/+ mice showed a significantly increased incidence of ventricular arrhythmias accompanied by abnormal regional calcium transients compared to wild-type mice.
Why the study?
The mechanisms underlying abnormal regional variations in electrical and calcium homeostasis properties in CPVT had not been well explored in intact hearts.
Does the RyR2-R2474S mutation alter regional voltage and calcium signals leading to arrhythmias during adrenergic stress in intact murine hearts?
Does the RyR2-R2474S mutation alter regional voltage and calcium signals leading to arrhythmias during adrenergic stress in intact murine hearts?
In a murine model of CPVT, the RyR2-R2474S mutation causes delayed regional calcium transient recovery and altered voltage-calcium coupling during adrenergic stress, driving localized calcium alternans and ventricular arrhythmias.
Answers are grounded in this paper and cite their sources.
Regional Ca²⁺/Vm heterogeneity in RyR2-mutant hearts merits mechanistic follow-up; leaves open relevance to human CPVT.
Abnormal regional variations in electrical and calcium homeostasis properties have been implicated in catecholaminergic polymorphic ventricular tachycardias (CPVT) attributable to abnormal RyR2-mediated store Ca 2+ release, but their underlying mechanism have not been well explored in intact hearts. We performed in vivo and ex vivo studies including high throughput mapping of Ca 2+ transients (CaT) and transmembrane voltage (V m ) in murine wild-type (WT) and heterozygous RyR2 -R2474S/+ hearts, before and during isoprenaline (ISO) challenge. ISO-challenged RyR2 -R2474S/+ showed increased incidence of arrhythmia accompanied by abnormal Ca 2+ transients compared to WT. CaT duration (CaTD) in the LV apex amongst regions studied both before and during ISO challenge in both WT and RyR2 -R2474S/+ ventricles. RyR2 -R2474S/+ ventricles showed prolonged CaTD, both before and during isoprenaline (ISO) challenge. Conversely, action potential durations (APD) were the same in WT and RyR2-R2474S/+ ventricles and identically reduced by ISO challenge. RyR2 -R2474S/+ showed V m -CaT latencies at time to half decay, but not rise time to peak, which were significantly prolonged compared to WT in all ventricular regions examined with ISO challenge. Following burst pacing, ventricular localized concordant alternans in CaT and APD were readily observed in RyR2 -R2474S/+ but not in WT mice. Such CaT and APD alternans occurred mostly semiannually in specific regions of the ventricular pre-occurrence of VT. The pro-arrhythmic RyR2 -R2474S/+ phenotype in intact hearts thus directly parallels delayed regional CaT recovery properties and alteration of V m -CaT latencies. Studies suggest that discordant localized calcium alternans are mechanistically responsible for action potential duration alternans and occurrence of VT in RyR2 -R2474S/+ mice. • Clarified the electrophysiological mechanisms in the RyR2-R2474S model using dual-dye optical mapping. • Defined the disrupted coupling dynamics between transmembrane voltage and intracellular calcium based on C-clock and M-clock. • Determined the role of variable CaT alternans in the susceptibility to ventricular arrhythmias in a CPVT mouse model
No takes yet. Share an insight, caveat, or question.
Li et al. (2024) studied Catecholaminergic polymorphic ventricular tachycardia (CPVT) (n=32). RyR2-R2474S mutation and Isoprenaline challenge vs. Wild-type mice was evaluated on Incidence of cardiac arrhythmia during Isoprenaline challenge (p=<0.05). Isoprenaline-challenged RyR2-R2474S/+ mice showed a significantly increased incidence of ventricular arrhythmias accompanied by abnormal regional calcium transients compared to wild-type mice.
Synapse has enriched 10 related papers. Consider them for comparative context: