Page 246 - Clinical Small Animal Internal Medicine

214 Section 3 Cardiovascular Disease

I (a)
VetBooks.ir II

III

aVR

aVL

aVF

Speed: 50 mm/sec Limb: 5 mm/mV Chest: 5.0 mm/mV F 60~ 0.15–100 Hz
(b)
II

III

aVR

aVL

aVF

Figure 21.7 Six‐lead ECG of a dog with atrial fibrillation (speed: 50 mm/s). (a) Atrial fibrillation appears as an irregular and narrow QRS
complex tachycardia at a rate of 220 beats. Note that the eighty complex has a wide and “bizarre” morphology, suggesting it is a
ventricular premature contraction (VPC). (b) Following administration of rate‐control medications, atrial fibrillation is still present but the
heart rate has decreased to 140 bpm.

contractility and may cause hypotension when used in Prognosis
animals with severely depressed cardiac function.
Long‐term prognosis is good for dogs with “lone” AF.
However, in some breeds, in particular Irish wolfhounds,
Beta‐Blockers it may be considered an early sign of dilated cardiomyo­
The range of indications and side‐effects for beta‐block­ pathy. In AF dogs with heart disease, median survival has
ers is very similar to that of calcium channel blockers. been reported to be 32 months. However, it was only five
Beta‐1‐selective agents, such as atenolol, are preferred to months when congestive heart failure was present. In
nonselective agents that can cause bronchospasm. cats, treatment targeted at AF is rarely required as their