AV-block in dogs and cats

作者：Hildebrandt Nicolai^*; Schneider Christina; Henrich Estelle; Stosic Andreas; Schneider Matthias

来源：Kleintierpraxis, 2011, 56(2): 82-92.

• bradyarrhythmia
• syncope
• atropin response test
• pacemaker

AV-block in dogs and cats An atrioventricular block (AV-block) is present when the normal conduction of an impulse generated in the sino-atrial node to the ventricular myocardium is disturbed. Three degrees of AV-block are distinguished: first degree is only a prolongation of the AV conduction, while the second- and third-degree AV-blocks are characterised by intermittent conduction (second degree), or absent AV-conduction (third degree). AV-blocks are the most common bradycardic arrhythmias in dogs and cats. The ECG is the diagnostic tool of choice for all three forms of conduction disturbance. First-degree AV-block is a pure ECG diagnosis and is most commonly associated with a high vagal tone or drug toxicity. Second-degree AV-block includes two important subtypes, Mobitz type I (normally without clinical symptoms), and the potentially dangerous Mobitz type II, which is often connected with weakness or syncope. Second-degree AV-blocks may be vagally mediated, drug-induced (digitalis, beta-blocker) or pathological. Third-degree AV-block in dogs is nearly always associated with clinical symptoms. In contrast, in cats, 1/3 of patients are asymptomatic. The causes for third-degree AV-blocks include the idiopathic form, congenital malformations like ventricular septal defects, degenerative mitral valve disease, cardiomyopathy or endocrinological disease.
The management of symptomatic AV-blocks include three different treatment options. If possible, the treatment should be aimed at the underlying cause. Otherwise symptomatic management and, in the case of a refractory rhythm disturbance, pacemaker implantation should be performed. The aim of parasympatholytic and sympathomimetic drugs are to increase ventricular rate, thereby decreasing or eliminating clinical signs. The therapy of choice in the case of a symptomatic AV-block unresponsive to medical treatment is pacemaker implantation. In dogs, one- and two-chamber pacemaker (in cats only single-chamber pacemaker) implantations have been performed successfully.

• 出版日期2011-2