ABSTRACT
Cardiac rhythm disturbances are frequently noted in critically ill animals. All cardiac tissues depolarize and conduct electrical impulses. The sequence of electrical impulse spread occurs in an orderly fashion. Conduction abnormalities result in either slow rate or fast rate arrhythmia formation. Bradyarrhythmias are noted when temporal delay or complete block of electrical impulse spread delays normal depolarization sequence. Tachyarrhythmias are associated with abnormal myocardial tissue or accessory conduction pathways. Disorders of impulse formation encompass enhanced or depressed impulse formation by normal pacemaker cells and abnormal impulse formation by nonautomatic cells. Premature ventricular contractions (PVC) are one of the most common rhythm disturbances diagnosed in critically ill dogs and cats. The clinical presentation of animal will depend upon the primary clinical disorder associated with PVCs. Ventricular complexes are relatively easy to recognize on the electrocardiogram. Prognosis depends upon the underlying disease process. Delayed ventricular conduction occurs when one or more of the His bundle branches do not support impulse conduction.
