Molecular dissection of cardiac repolarization by in vivo Kv4.3 gene transfer
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Key result
In vivo infection with a dominant-negative Kv4.3 construct suppressed peak Ito1 in rat ventriculocytes, significantly prolonged action potential duration, and prolonged the QT interval by about 30%.
Why the study?
Does in vivo gene transfer of Kv4.3 to overexpress or suppress Ito1 alter action potential duration and QT interval in guinea pigs and rats?
Population
Adult rats (Sprague-Dawley; 200–250 g) and adult guinea pigs (200–250 g)
Comparison
Intramyocardial injection of adenovirus vectors… vs Intramyocardial injection of receptor virus…
Design
Preclinical
Follow-up
72 hours
Authors
Discussion
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Implication
I(to1) modulation alters APD/QT in rodents; leaves open whether targeting this current modifies HF outcomes.
Structured PICO
Does in vivo gene transfer of Kv4.3 to overexpress or suppress Ito1 alter action potential duration and QT interval in guinea pigs and rats?
P
Population
Adult rats and guinea pigs used to study the electrophysiological effects of in vivo Kv4.3 gene transfer on cardiac repolarization.
I
Intervention
Intramyocardial injection of adenovirus vectors to overexpress (AdE8I-Kv4.3 in guinea pigs) or suppress (AdE8I-Kv4.3W362F in rats) Ito1, stimulated by intraperitoneal injection of an ecdysone analog (GS-E)
C
Comparator
Intramyocardial injection of receptor virus AdCGI-DBEcR alone or reporter virus AdCGI/AdEGI
O
Outcome
Action potential duration (APD), plateau potential, and QT interval on surface ECG at 72 hourssurrogate
Main Result
Effect estimate: 29.8% prolongation
Absolute Event Rate: 117.7% vs 90.5%
p-value: p=0.02
In vivo gene transfer demonstrates that Ito1 plays a crucial role in setting the plateau potential and overall action potential duration, providing a mechanism for the electrophysiological alterations seen in heart failure.
Limitations
- Small sample sizes for ECG recordings (n=3 per group)
- Incomplete suppression of Ito1 due to remaining competitive expression of wild-type channels
- Possible suppression of the maintained outward current component (Kv4.1)
Cite This Study
Hoppe et al. (2000) studied Cardiac repolarization (Animal Model). in vivo Kv4.3 gene transfer (dominant-negative Kv4.3-W362F) vs. Control adenovirus (AdEGI) was evaluated on QT interval (29.8% prolongation, p=0.02). In vivo infection with a dominant-negative Kv4.3 construct suppressed peak Ito1 in rat ventriculocytes, significantly prolonged action potential duration, and prolonged the QT interval by about 30%.
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