QT Interval in the Guinea Pig Model

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Recent publications detail a probabilistic method of correcting QT interval in canine and NHP using intensive telemetry interrogation. Our objective was to interrogate whether QTcH is appropriate for …

Recent publications detail a probabilistic method of correcting QT interval in canine and NHP using intensive telemetry interrogation. Our objective was to interrogate whether QTcH is appropriate for small animals, specifically the guinea pig.

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  • 1. Rat  Dual  Pressure  Telemetry   1   Ultra  High  Fidelity  QT  Interval  in   Conscious  Guinea  Pigs        
  • 2. - 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
  • 3. y  =  0.179x  +  248.1 R²  =  0.155 250 260 270 280 290 300 310 100 150 200 250 300 350 400 QTc  [Bazett's]  interval  (msec) RR  interval  (msec) y  =  0.320x  +  152.9 R²  =  0.502 180 190 200 210 220 230 240 250 260 100 150 200 250 300 350 400 QTc  [Fridericia's]  interval   (msec) RR  interval  (msec) y  =  0.002x  +  124.1 R²  =  0.000 80 90 100 110 120 130 140 150 160 100 150 200 250 300 350 400 QTc  [Holzgrefe'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.