Page 81 - Feline Cardiology

78 Section B: Diagnostic Testing

I aVR V1 V4
QRS P T QRS QRS
P T P T P T
QRS V2 V5
Diagnostic Testing P T P QRS T P QRS T
aVL
II
QRS

III
P QRS T aVF P QRS V3 P QRS T V6

T
II QRS
P
T

Figure 9.1. Normal sinus rhythm in a cat. Ten-lead tracing with zoomed inserts for each lead identifying the components of the heart-
beat. The heart rate is 160 beats/minute and the mean electrical axis is +90°. 25 mm/sec, 1 cm = 1 mV.

I aVR V1 V4

QRS
II aVL V2 V5
P T

III aVF V3 V6

Figure 9.2. Advantage of multiple leads: the limb leads (I, II, III, aVR, aVL, aVF) are difficult to interpret due to severe motion artifact.
In this cat, the precordial leads are much clearer, especially lead V2 (P, QRS, T labeled). 25 mm/sec; 1 cm = 1 mV.

elegant and striking case report, the natural tendency of recumbency, an assistant holds all four limbs pointing
cats, when in lateral recumbency, to flex the elbows and away from himself/herself, toward the clinician record-
shoulders into a tucked, crouched posture changes the ing the tracing. Typically the assistant holds the fore-
position of the ECG electrodes, which in turn can dra- limbs in the right hand, with an index finger between
matically alter the amplitude of ECG deflections and the right and left paws for comfort, and the hindlimbs in the
resulting mean electrical axis (Bond 2005) (Figure 9.3). same manner in the left hand. The right wrist lies gently
Any recumbency will do if only the rhythm is being over the cat’s neck and the left forearm may rest over the
assessed, but if dimensions of waves and complexes are cat’s left lateral thigh. An Elizabethan collar is recom-
being measured in an attempt to infer cardiac size and mended for most cats as a precaution against the cat’s
structure, right lateral recumbency and proper restraint quick turning and biting the assistant’s wrist. The ECG
and positioning are required. An optimal tracing is most electrodes, which are typically alligator-type clips, should
likely to result when the cat is gently held recumbent on be of the minimally traumatic type (Figure 9.4), and
a comfortable, nonconductive surface (e.g., rubber- these are placed immediately distal to the right (RA) and
coated foam mat) in a quiet area. For right lateral left (LA) elbows and right (RL) and left (LL) stifles.