Isorhythmic atrioventricular dissociation during anesthesia in three cats

This case series documents the occurrence of isorhythmic atrioventricular dissociation (IAVD) in three anesthetized cats. There are several proposed mechanisms for the development of this dysrhythmia. The cardinal feature of IAVD is that the atrial and junctional rates are roughly equivalent, which aids in ruling out more severe types of atrioventricular dissociation (such as complete heart block), where atrial and ventricular rates are different. Two cats were treated with anticholinergic medication when hemodynamic variables indicated that the loss of coordinated cardiac conduction had negatively affected cardiovascular function as indicated by arterial hypotension. In one cat, IAVD was not considered to negatively affect the cat's hemodynamic status and anticholinergic medication was not administered. In this cat, IAVD spontaneously resolved.

Although this rhythm disturbance has been clinically recognized to manifest in domestic felids under general anesthesia, there remains a paucity of literature regarding the development, recognition and treatment of IAVD in this species. From extensive clinical experience, the authors consider this rhythm to occur frequently in clinical practice, and it behooves the feline anesthetist to be familiar and comfortable with the recognition and treatment of this dysrhythmia.