Page 26 - Rapid Review of ECG Interpretation in Small Animal Practice, 2nd Edition

Evaluation of the Electrocardiogram

VetBooks.ir 10 mm/mV Average heart rate = 12 beats/6 s = 12 x 10 = 120 bpm
25 mm/s
150 mm (30 large squares) = 6 s

Fig. 2.3 Calculation of heart rate when rhythm is irregular.

aVF–
II– –90° III–
–120° –60°

aVR+ aVL+
–150° –30°

I– +/–180° 0° I+

aVL– +150° +30° aVR–

+120° +60°
III+ +90° II+
aVF+

Fig. 2.4 The 6-lead ECG system.

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