Page 241 - Clinical Small Animal Internal Medicine

21 Supraventricular Arrhythmias 209

Table 21.2 Drug dosages and indications
VetBooks.ir Drug name Dosage Indications

Atropine SC, IM, IV: 0.02–0.04 mg/kg (D, C) Sinus bradycardia
Sick sinus syndrome,
First‐ and second‐degree AV block
Glycopyrrolate SC, IM, IV: 0.005–0.01 mg/kg (D, C) Sinus bradycardia
Sick sinus syndrome,
First‐ and second‐degree AV block
Terbutaline Oral: 0.2 mg/kg q8–12h (D) Sinus bradycardia
0.625 mg q8–12h (C) Sick sinus syndrome
IV: 0.01 mg/kg IV (D, C)
Isoproterenol CRI: 0.04–0.09 μg/kg/min, to effect (D,C) Second‐ and third‐degree AV block
Aminophylline/ Oral: 10 mg/kg q12h (extended release) (D, C) Sick sinus syndrome
Theophylline IV: 10 mg/kg (D)
Digoxin Oral: 0.005 mg/kg q12h (D) AF (rate control)
Diltiazem IV bolus: 0.1–0.4 mg/kg over 5 min (D, C) SVT (rate control or conversion)
CRI: 0.05–0.15 mg/kg/h (D, C) AF (rate control)
Oral: 1–2 mg/kg q8h (D, C)
3 mg/kg q12h (extended release) (D)
15–30 mg q12–24h (extended release) (C)
Atenolol Oral: 0.2–1 mg/kg q12‐24h (D) SVT (rate control or conversion)
6.25–12.5 mg q12–24h (C) AF (rate control)
Esmolol IV bolus: 0.2–0.5 mg/kg over 1 min, repeat q5min (D, C) SVT conversion
Procainamide IV bolus: 5–15 mg/kg over 1 min (D) SVT conversion
1–2 mg/kg (C)
CRI: 20–50 μg/kg/min (D)
Lidocaine IV bolus: 2 mg/kg over 30 s. Maximum 3 boluses (D) SVT conversion
0.25–0.5 mg/kg (C) Vagally mediated AF conversion
Sotalol Oral: 1–3 mg/kg q12h (D, C) SVT conversion
SR maintenance
AF, atrial fibrillation; AV, atrioventricular; C, cat; CRI, constant rate infusion; D, dog; IM, intramuscular; IV, intravenous; SC, subcutaneous;
SR, sinus rhythm; SVT, supraventricular tachycardia.

primary cardiac disease, myocarditis, or as a manifesta­ Signalment
tion of a neuromuscular disorder. However, the etiology Atrial standstill has been identified in various dog
often remains unknown. breeds, with a possible higher prevalence in English
Hyperkalemia is described as a cause for transient
atrial standstill. Other possibilities include quinidine or springer spaniels. It usually affects young adults, but
can be diagnosed as early as 4–6 months of age. Most
digoxin toxicity, myocardial infarction, hypoxia, and cats diagnosed with atrial standstill have echocardio­
hypothermia. graphic changes consistent with hypertrophic
In the presence of persistent atrial standstill, the combi­
nation of chronic bradycardia, lack of atrial contribution cardiomyopathy.
to ventricular filling and decreased atrial natriuretic pep­
tide production results in low cardiac output, increased History and Clinical Signs
circulating blood volume, and ultimately heart failure.
Most animals show signs of low cardiac output, includ­
ing profound lethargy and syncope, in addition to
Epidemiology
evidence of left‐ or right‐sided congestive heart failure.
It is a rare arrhythmia in dogs, and there are only a few In rare cases of muscular dystrophies, progressive skele­
documented cases in cats. tal muscle wasting may occur.