What is the clinical evidence from this study?

Population: Arrhythmia. Intervention: Tetrodotoxin (TTX) and ranolazine vs. E-4031 alone. Primary outcome: MAPD90, TDR, BVR, and Tpeak-Tend (p=<0.01).

What does this research mean for the field?

Inhibition of endogenous late Na+ current with TTX or ranolazine shortens MAPD90, decreases repolarization dispersion, and abolishes torsade de pointes in hearts with reduced repolarization reserve. Novelty: ClaimNovelty.INCREMENTAL. Consensus alignment: ConsensusAlignment.NEUTRAL.

What question did this study set out to answer?

This study aims to investigate how reducing repolarization reserve affects the proarrhythmic actions of late sodium current.

July 11, 2009AJP Heart and Circulatory Physiology

Reduction of repolarization reserve unmasks the proarrhythmic role of endogenous late Na⁺current in the heart

Q: What are the key findings of this study?

Inhibition of endogenous late Na+ current with TTX or ranolazine shortened MAPD90, decreased repolarization dispersion, and abolished torsade de pointes in hearts with reduced repolarization reserve.

Q: What does this research mean for the field?

Inhibition of endogenous late Na+ current with TTX or ranolazine shortens MAPD90, decreases repolarization dispersion, and abolishes torsade de pointes in hearts with reduced repolarization reserve. Novelty: ClaimNovelty.INCREMENTAL. Consensus alignment: ConsensusAlignment.NEUTRAL.

Q: What question did this study set out to answer?

This study aims to investigate how reducing repolarization reserve affects the proarrhythmic actions of late sodium current.

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Key result

Inhibition of endogenous late Na+ current with TTX or ranolazine shortened MAPD90, decreased repolarization dispersion, and abolished torsade de pointes in hearts with reduced repolarization reserve.

Why the study?

Does inhibition of late Na+ current with TTX or ranolazine prevent arrhythmogenesis in isolated rabbit hearts with reduced repolarization reserve?

Key Points

This study aims to investigate how reducing repolarization reserve affects the proarrhythmic actions of late sodium current.
Monophasic action potentials and electrocardiograms were recorded from female rabbit isolated hearts.
I(K) was inhibited using E-4031, 4-aminopyridine, and BaCl(2) to decrease repolarization reserve.
Endogenous late I(Na) was blocked using tetrodotoxin (TTX) and ranolazine.
E-4031 prolonged MAPD(90) and increased TDR, leading to spontaneous TdP events.
Inhibition of late I(Na) with TTX and ranolazine shortened MAPD(90) and abolished TdP episodes.
Ranolazine's effects were due to inhibiting late I(Na) rather than reversing the HERG-blocking action of E-4031.

Structured PICO

Does inhibition of late Na+ current with TTX or ranolazine prevent arrhythmogenesis in isolated rabbit hearts with reduced repolarization reserve?

Population

Female rabbit isolated hearts

Intervention

Tetrodotoxin (TTX) (0.6-3 μM) or ranolazine (5-10 μM) to block endogenous late INa

Comparator

Hearts treated with IK blockers (E-4031, 4-aminopyridine, BaCl2) alone

Outcome

Monophasic action potential duration (MAPD90), T wave duration (Tpeak-Tend), transmural dispersion of repolarization (TDR), beat-to-beat variability (BVR) of MAPD90, and episodes of torsade de pointes (TdP)surrogate

Main Result

p-value: p=<0.01

Inhibition of endogenous late Na+ current with ranolazine or TTX reverses action potential prolongation and abolishes torsade de pointes in rabbit hearts with reduced repolarization reserve.

Discussion

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Implication

Supports late Na+ inhibition for TdP suppression in repolarization-impaired models; hypothesis-generating for clinical translation.

Cite This Study

Wu et al. (2009) studied Arrhythmia. Tetrodotoxin (TTX) and ranolazine vs. E-4031 alone was evaluated on MAPD90, TDR, BVR, and Tpeak-Tend (p=<0.01). Inhibition of endogenous late Na+ current with TTX or ranolazine shortened MAPD90, decreased repolarization dispersion, and abolished torsade de pointes in hearts with reduced repolarization reserve.

synapsesocial.com/papers/6a1c73434d97451bbd2fc039 https://doi.org/10.1152/ajpheart.00467.2009

Topics

Ventricular arrhythmias

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Reduction of repolarization reserve unmasks the proarrhythmic role of endogenous late Na⁺current in the heart

Key Points

Structured PICO

Main Result

Discussion

Implication

Cite This Study

Topics

Reduction of repolarization reserve unmasks the proarrhythmic role of endogenous late Na⁺current in the heart

Key Points

Structured PICO

Main Result

Discussion

Implication

Cite This Study

Also Consider

Topics

Also Consider