Page 48 - Rapid Review of ECG Interpretation in Small Animal Practice, 2nd Edition

Treatment of Arrhythmias

Table 4.3 Drugs for treatment of ventricular arrhythmias
VetBooks.ir Drug Administration per os Intravenous administration Comments

Dog: 2 mg/kg IV bolus,
Cats have low seizure threshold

Lidocaine
repeat up to 4 times
CRI: 30–75 µg/kg/min
Cat: 0.25–2 mg/kg IV bolus
slowly
CRI: 10–40 µg/kg/min
Procainamide Dog: 5–15 mg/kg IV bolus Can decrease contractility
slowly over 2 minutes
CRI: 25–50 µg/kg/min
Amiodarone Dog: 5–15 mg/kg BID Dog: 2 mg/kg IV bolus Can combine with atenolol
for 1–2 weeks (loading slowly over 10 min for refractory ventricular
dose), then 6–15 mg/kg CRI: 0.8 mg/kg/h for 6 h, tachycardia; aqueous (water-
SID (maintenance dose) then 0.4 mg/kg/h based) formulations are better
tolerated than polysorbate 80/
alcohol-based formulations
Esmolol HCl Dog and cat: 50–100 µg/kg Can decrease contractility;
IV bolus, repeat up to max can combine with any other
500 µg/kg IV antiarrhythmic; use with
CRI: Titrate to effect: caution in combination with
50–200 µg/kg/min procainamide
Sotalol Dog: 1.5–2.5 mg/kg BID Can combine with mexiletine
Cat: 10 mg/cat BID for refractory ventricular
tachycardia; also useful if IV
drugs fail, as effect after oral
dosing starts within 2–3 hours
Mexiletine Dog: 4–8 mg/kg TID Not effective as monotherapy
Atenolol Dog: 0.5–2 mg/kg SID to Titrate to effect; can decrease
BID contractility; can combine
Cat: 6.25–12 mg with mexiletine for refractory
SID to BID ventricular tachycardia
Abbreviations: CRI, continuous rate infusion; IV, intravenous

Atrial standstill can be also be administered. For refractory cases
The two main types are (1) persistent atrial of hyperkalemia, calcium gluconate (0.5–1 mL of
standstill or “silent atrium” due to primary atrial a 10% solution/kg) may be given by very slow
muscle disease and (2) secondary atrial standstill intravenous administration, while monitoring
caused by hyperkalemia secondary to diseases such the ECG.
as renal failure, ruptured bladder, or Addison’s
disease. If atrial muscle disease is causing atrial AV block
standstill, pacemaker therapy is required. For atrial In complete (third-degree) AV block, the ventricular
standstill secondary to hyperkalemia, IV fluids, such escape rhythm is usually regular and below 40 bpm
as saline, half-strength saline with 2.5% dextrose, in dogs. In such cases, clinical signs such as lethargy
or 5% dextrose in water, will lower potassium or syncope are usually observed. If no underlying
values by dilution and increased excretion. The electrolyte abnormalities are present, a permanent
dextrose in fluid therapy leads to insulin secretion, pacemaker is the only effective treatment for this
+
which promotes entry of K ions back into the bradyarrhythmia. In cases with clinical signs due to
cells. More aggressive therapy involves IV sodium second-degree AV block, medical management as
bicarbonate (1–2 mEq/kg IV slowly over 20 min) described for sinus bradycardia can be attempted,
+
to drive K back into the cells. Slow intravenous but dogs might also require pacemaker implantation.
administration of 0.5 U/kg of regular insulin Complete AV block also occurs in cats, and is
coupled with 2 g of dextrose per unit of insulin occasionally associated with hyperthyroidism. Cats
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