Key result
Isorhythmic atrioventricular dissociation type I was diagnosed in a cat with bradycardia and wide QRS complexes resembling type II IAVD during clinical evaluations.
This case report describes a rare presentation of Isorhythmic Atrioventricular Dissociation type I mimicking type II in a feline patient.
Emphasizes accurate ECG interpretation in feline bradycardia; extends known variability of isorhythmic AV dissociation in cats.
An 11-year-old male neutered Birman cat was referred for investigation of pyelonephritis. On physical examination gallop sounds and bradycardia were noted. There was mild azotemia and marked neutrophilia, attributed to the pyelonephritis. Transthoracic echocardiography revealed a nonspecific cardiomyopathy phenotype with biatrial enlargement. Electrocardiography showed wide QRS complexes, bradycardia and synchronous dissociation between atrial and ventricular activity. While during the first examination the synchronisation appeared mostly fixed, with consistent PR intervals, on subsequent evaluations the PR intervals appeared to vary on a beat-to-beat basis. The diagnosis was of Isorhythmic Atrioventricular Dissociation (IAVD) type I, with an initial long phase of fixed synchronisation, mimicking an IAVD type II, and concomitant ventricular depolarisation with a left bundle branch block morphology.
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Salvati et al. (2026) studied this question. Isorhythmic atrioventricular dissociation type I was diagnosed in a cat with bradycardia and wide QRS complexes resembling type II IAVD during clinical evaluations.
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