JORGENSEN J1010, Manual

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Arrythmias Originating in the Atrial Muscle
Atrial Premature Complexes
Atrial premature complexes arise from ectopic atrial foci. They are frequently caused by cardiac dis-
ease and may progress to atrial tachycardia or atrial fibrillation.
Atrial premature complexes are often caused by atrial enlargement from acquired chronic valvular
insufficiency, primary myocardial disease, right atrial hemangiosarcoma, hyperthyroidism, digitalis tox-
icity, general anesthesia, and various drug, chemical or noxious stimuli.
Figure 4-36 Atrial premature complexes (arrows) and P mitrale in a dog with congestive heart failure.
ECG: Usually normal heart rate, but the rhythm is irregular due to the premature P wave that dis-
rupts the normal sinus-initiated P wave rhythm.
Atrial Fibrillation
Atrial fibrillation is common in the dog and is usually associated with severe organic heart disease. it
is usually associated with chronic AV valvular insufficiency in small breeds, dilated cardiomyopathy
in large and giant breeds, and congenital heart defects.
ECG: Atrial and ventricular rates are rapid an totally irregular. Large oscillations waves replace the
normal sinus P waves.
Arrythmias Originating in the Ventricular Muscle
Ventricular Premature Complexes
Ventricular premature complexes (VPCs/PVCs) are impulses that arise from an ectopic ventricular
focus.
Cardiac causes of VPCs include congestive heart failure, myocardial infarction, neoplasia, pericardi-
tis, traumatic myocarditis, idiopathic myocarditis in boxers and Doberman pinschers, and bacterial
endomyocarditis. Secondary changes include changes in autonomic tone, hypoxia, anemia, uremia,
pyometra, gastric-volvolus, pancreatitis, and parvovirus. Drugs that can cause VPCs include digitalis,
epinephrine, anesthetic agents and atropine.
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