ECG Quick Reference
Normal Electrocardiographic Parameters in Dogs and Cats
PARAMETER
DOG
CAT
Adult 70 to 160
160 to 240
Gordon SG, Estrada AH.
The ABCDs of Small Animal Cardiology:
A Practical Manual. 1st ed.
Guelph, Canada: LifeLearn Inc.; 2013.
Heart Rate (bpm)
Toy breeds ≤180
Puppies ≤220
Rhythm
0.1 sec
Normal sinus
Normal sinus
Respiratory sinus arrhythmia
Sinus tachycardia
0.02 sec
R
Wandering atrial pacemaker
0.5 mv
Intervals (sec)
@ 25 mm/sec, 1 small box = 0.04 sec
@ 50 mm/sec, 1 small box = 0.02 sec
P
P
≤0.04
Baseline
≤0.04
PR
0.06 to 0.13
0.05 to 0.09
Q S
QRS
<20 kg: ≤0.05
≤0.04
QRS
PR
interval
≥20 kg: ≤0.06
Giant breed: ≤0.065
QT
0.15 to 0.25
T
0.1 mv
QT
interval
Paper speed 50 mm/sec; sensitivity 10 mm/mv
0.12 to 0.18
Amplitudes Lead II (mv)
-90°
≤0.4
≤0.2
R
<20 kg: ≤2.5
≤0.9
T
≤1/4 amplitude of R
S wave: Lead V3
<0.7
+
aVR
-150°
≥20 kg: ≤3.0
MEA
-180°
+180°
+40˚ to +100˚
-5˚ to +160˚
DOG
CAT
P Duration: Left Atrial
>0.04 sec
>0.04 sec
P Amplitude: Right Atrial
>0.04 mv
>0.2 mv
<20 kg: >2.5 mv
>0.9 mv
+
aVL
DO
GL
FT
HI
RV
LV
-30°
+
I
0°
0°
+30°
+150°
Criteria for Chamber Enlargement
R Amplitude Lead II:
Left Ventricle
-60°
XIS SHIFT
TA
EF
P
-120°
G RIGHT AXI
SS
DO
@ 5 mm/mv, 1 small box = 0.2 mv
@ 10 mm/mv, 1 small box = 0.1 mv (standard)
@ 20 mm/mv, 1 small box = 0.05 mv
+60°
+120°
+90°
+
III
+
II
+
aVF
≥20 kg: >3.0 mv
R
Right Ventricle
Note: Only 1 of 4 listed
criteria required
1. S wave in Lead I & II & III
2. MEA to RV (+100˚ to -90˚)
3. S wave in Lead V3 > V2 > V1
4. S wave > R wave in Lead V3
or S wave >0.7 mv
R
R
R
MEA to RV (+100˚ to -90˚)
Q
S
Q
S
A standard pen (with lid on) is 150 mm and so can be easily used as a 6-second ruler for rapid determination of
heart rate in ECGs that are run as 25 mm/sec (e.g., pen x 10).
0 mm
1 sec
25 mm
2 sec
50 mm
3 sec
75 mm
4 sec
100 mm
5 sec
125 mm
6 sec
150 mm
Q
S