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Rat Dual Pressure Telemetry 1
Ultra High Fidelity QT Interval in Conscious Guinea Pigs
- Recent publications detail a probabilistic method of correcting QT interval in dogs and NHP using intensive telemetry interrogation (Holzgrefe et al) - log QTc = log QTraw – (β * (log RRraw – log RRref)
- where β is slope of log QT/log RR regression line
- Our laboratories have confirmed the utility of this formula, QTcH, in dog and NHP, including via moxifloxacin administration.
- Our objective was to interrogate whether QTcH is appropriate for small animals, specifically guinea pig
- Six Dunkin-Hartley guinea pigs were instrumented with DSI implant C50-PXT for ECG and pressure.
- QT/RR pairs were acquired on a quasi beat to beat basis for 24h and plotted to obtain β as above.
- QTcH was then determined, and compared against QTcB, QTcF
y = 0.179x + 248.1R² = 0.155
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100 150 200 250 300 350 400QTc [Bazett's] interval (msec)
RR interval (msec)
y = 0.320x + 152.9R² = 0.502
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100 150 200 250 300 350 400
QTc [Frid
ericia's] interval
(msec)
RR interval (msec)
y = 0.002x + 124.1R² = 0.000
8090100110120130140150160
100 150 200 250 300 350 400
QTc [H
olzgrefe's] interval
(msec)
RR interval (msec)
- Slope of QTcH/RR regression is zero, Y-intercept of regression line is the uncorrected QT interval at the reference HR (- 0.5 ms)
- Commonly used QTcB and QTcF are flawed in the correction of guinea pig QT interval
- QTcH accurately corrects the guinea pig QT interval for changes in RR, and should be considered for telemetry studies in this species.