Objective—To determine signalment, clinical signs,
diagnostic findings, treatment, and outcome for cats
with atrial fibrillation (AF).
Procedure—Medical records of cats that met criteria
for a diagnosis of AF (ECG consisting of at least 2
leads, clear absence of P waves, supraventricular
rhythm, and convincingly irregularly irregular rhythm)
and had undergone echocardiography were reviewed.
Results—There were 41 males (37 castrated) and 9
females (7 spayed). Forty-one were of mixed breeding;
9 were purebred. Mean ± SD age was 10.2 ± 3.7 years.
The most common chief complaints were dyspnea,
aortic thromboembolism, and lethargy. In 11 cats, AF
was an incidental finding. Mean ± SD ventricular rate
was 223 ± 36 beats/min. The most common echocardiographic
abnormalities were restrictive or unclassified
cardiomyopathy (n = 19), concentric left ventricular
hypertrophy (18), and dilated cardiomyopathy (6). Mean
± SD left atrial-to-aortic diameter ratio (n = 39) was 2.55
± 0.80. The most common thoracic radiographic findings
were cardiomegaly, pleural effusion, and pulmonary
edema. Median survival time (n = 24) was 165
days (range, 0 to 1,095 days). Eight of 24 cats lived for
≥ 1 year after a diagnosis of AF was made.
Conclusions and Clinical Relevance—Results suggest
that AF occurs primarily in older adult male cats
with structural heart disease severe enough to lead to
atrial enlargement. Atrial fibrillation in these cats was
most commonly first detected when signs of decompensated
cardiac disease were evident, but also was
commonly identified as an incidental finding. (J Am
Vet Med Assoc 2004;225:256–260)