Page 50 - Rapid Review of ECG Interpretation in Small Animal Practice, 2nd Edition

Treatment of Arrhythmias

frequency or severity of the VA and to determine if of collapse, atenolol monotherapy may be recom-
mended.
treatment is having any proarrhythmic effects. The
VetBooks.ir goal is to reduce clinical signs, such as frequency of although its use is difficult because of the serious
For refractory VT, amiodarone is recommended,
syncope, and to eliminate or diminish runs of VT
and number of VPCs by more than 85% compared side effects reported in dogs (i.e., hepatoxicity,
with pre-treatment Holter. If the VA counts and neutropenia, thyroid dysfunction). However, in dogs
severity are not sufficiently lowered, the drug with life-threatening VT and poor contractility, it
dosage or regimen should be altered, and the Holter is a viable option as it does not affect contractility.
recording repeated 7–10 days later. Amiodarone can be combined with atenolol to
Sotalol is the most commonly prescribed oral enhance antiarrhythmic effects. Liver enzymes,
antiarrhythmic for treatment of VA in dogs and complete blood cell counts, and thyroid function
cats because of its ability to reduce clinical signs need to be monitored monthly for the first 3 months,
and the low incidence of side effects. Dogs with se- and bimonthly thereafter. Propafenone is also used
verely decreased systolic function may need to be occasionally for refractory VT at 5–8 mg/kg 3 times
started on lower doses and titrated to effect, while daily, but its efficacy in dogs is considered anecdotal
monitoring for signs of low output or congestion. at this time. No published studies are available for
In dogs with VA associated with repolarization ab- use of amiodarone or propafenone in cats with
normalities or aggravated by bradycardia, such as arrhythmias.
German Shepherds with inherited ventricular ar-
rhythmias and Boxers with bradycardia-associat- REFERENCES
ed syncope, sotalol is contraindicated as an initial Meurs KM, Weidman JA, Rosenthal SL, Lahmers
sole treatment. In cases of refractory VT on sotalol, KK, Friedenberg SG. Ventricular arrhythmias in
mexiletine, a sodium-channel blocker, can be com- Rhodesian Ridgebacks with a family history of
bined with sotalol. The combination of mexiletine sudden death and results of a pedigree analysis
and atenolol is also an effective therapy for VT in for potential inheritance patterns. J Am Vet Med
Boxers with arrhythmogenic right ventricular car- Assoc 2016, 248, 1135–1138.
diomyopathy (ARVC) and can be used if sotalol is Ware WA, Reina-Doreste Y, Stern JA, Meurs KM.
deemed inadequate or proarrhythmic. Mexiletine Sudden death associated with QT interval
can cause GI side effects (anorexia, vomiting, or prolongation and KCNQ1 gene mutation in a
diarrhea) and might also raise owner compliance family of English Springer Spaniels. J Vet Intern
issues, as it has to be given 3 times daily. In cats Med. 2015, 29(2), 561–568. doi: 10.1111/
with occasional single VPCs and no clinical signs jvim.12550. Epub 2015 Mar 16.

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