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Ventricular Arrhythmias
1
Amara H. Estrada, DVM, DACVIM (Cardiology) and Romain Pariaut, DVM, DACVIM (Cardiology),
DECVIM-CA (Cardiology) 2
1 Department of Small Animal Clinical Sciences, University of Florida, Gainesville, FL, USA
2 Department of Clinical Sciences, College of Veterinary Medicine, Cornell University, Ithaca, NY, USA

Etiology/Pathophysiology appears that in dogs and cats with VPCs and no underlying
heart disease, the number of VPCs is not predictive of the
Ventricular arrhythmias (VA) such as single ventricular risk of sudden death, which in this setting is typically low.
premature depolarizations (contractions) (VPCs) can be When there is underlying myocardial disease, the presence
seen in normal animals in low numbers (less than 50 per of VPCs may indicate an increased risk of sudden death or
24‐hour period on a Holter monitor). They are very com- simply be a marker for the severity of the disease (for exam-
monly seen in association with noncardiac disease, pos- ple, Doberman pinschers with dilated cardiomyopathy or
sibly due to myocardial ischemia, electrolyte abnormalities cats with hypertrophic cardiomyopathy). The presence of
or other factors surrounding the underlying disease. For VPCs in boxers with familial ventricular arrhythmias may
example, VPCs can be seen following vehicular trauma indicate an increased risk of sudden death.
(traumatic myocarditis), surgery, gastric dilation and vol-
vulus, splenic disease, immune‐mediated hemolytic ane- Signalment
mia and/or polycythemia, hypoxia, the use of anesthetic
agents (especially thiobarbiturates), pancreatitis, prosta- Certain breeds with specific underlying cardiac diseases are
titis, and neurologic disease. Thus, ventricular arrhyth- predisposed to malignant VA. Doberman pinschers with
mias are relatively common to any number of different dilated cardiomyopathy, boxers with arrhythmogenic right
systemic diseases. They may also be associated with ventricular cardiomyopathy, dogs with severe subaortic ste-
primary underlying myocardial diseases such as dilated nosis, young German shepherds with inherited ventricular
cardiomyopathy in Doberman pinschers and arrhythmo- arrhythmias, dogs and cats with myocarditis and cats with
genic right ventricular cardiomyopathy in boxers. They hypertrophic cardiomyopathy represent situations where a
can also be idiopathic in origin, meaning that no underly- VA may signal increased risk for clinical signs or sudden
ing systemic or cardiac disorder can be identified. death. Other than the specific patient groups and underly-
The most important clinical considerations with VPCs ing type of cardiac diseases mentioned above, there is no
are whether there is an underlying systemic or cardiac other specific age, breed or sex predilection
cause of the VPCs and whether there is the need to treat
the VA. Decisions to treat VA should be based on hemody-
namic consequences and the risk of degeneration of the VA History and Clinical Signs
into an unstable rhythm such as ventricular fibrillation.
Single VPCs do not cause clinical signs as they are transient Dogs with VA secondary to systemic disease often do not
and hemodynamically not significant. What is more need the VA to be treated as the arrhythmia tends to be
important is attempting to identify malignant characteris- self‐limiting if the underlying disease is addressed. For
tics of VPCs or patient groups that might be more suscep- example, a patient with VPCs and gastric dilation‐volvu-
tible to the development of an unstable rhythm that can lus does not necessarily require antiarrhythmic therapy
lead to sudden death. However, our ability to predict the for the VPCs, and instead needs relief of the dilation and
likelihood of sudden death associated with VPCs is poor. It volvulus. This will in turn lead to resolution of the

Clinical Small Animal Internal Medicine Volume I, First Edition. Edited by David S. Bruyette.
© 2020 John Wiley & Sons, Inc. Published 2020 by John Wiley & Sons, Inc.
Companion website: www.wiley.com/go/bruyette/clinical