ECG technique in dogs and cats: positioning and calibration
You are about to record a six-lead ECG on a calm dog to investigate an irregular rhythm and measure wave and interval durations.
Which statement about the standard technique is correct?
chevron_right Show answer and explanation
A. Left lateral recumbency, because the heart lies closer to the electrodes
Reference values for amplitude and axis were established in right lateral recumbency; changing position alters amplitudes and axis, so measurements are no longer comparable.
B. Right lateral recumbency with the limbs perpendicular to the body, 50 mm/s and 10 mm/mV
Correct. This is the position in which reference values were obtained. At 50 mm/s each 1 mm small box equals 0.02 s, which allows P, PR, QRS and QT to be measured; at 10 mm/mV, each vertical millimetre equals 0.1 mV.
C. Record at 25 mm/s to measure intervals more accurately
At 25 mm/s each millimetre is 0.04 s and the complexes are compressed, so intervals are measured less accurately. That speed is useful for assessing rhythm on long strips, not for measuring.
D. At 10 mm/mV, an R wave 15 mm tall corresponds to 0.15 mV
This is a common calculation error: at 10 mm/mV, 15 mm equals 1.5 mV. Getting the scale wrong leads to missing (or overdiagnosing) increased voltage.
lightbulb Key takeaway
To measure, record in right lateral recumbency at 50 mm/s and 10 mm/mV; for rhythm, a long strip in whatever position keeps the animal calmest is enough. Quick heart rate: at 50 mm/s, count the QRS complexes in 15 cm (3 s) and multiply by 20. Use gel rather than alcohol if defibrillation may be needed.
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Updated: October 31, 2026 · Educational content for veterinary professionals. It does not replace current clinical guidelines or the judgement of the attending veterinarian.