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.

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.