Objective—To identify clinical, echocardiographic,
and electrocardiographic abnormalities in Boxers with
cardiomyopathy and echocardiographic evidence of
left ventricular systolic dysfunction.
Animals—48 mature Boxers.
Procedure—Medical records were reviewed for information
on age; sex; physical examination findings;
and results of electrocardiography, 24-hour ambulatory
electrocardiography, thoracic radiography, and
Results—Mean age of the dogs was 6 years (range, 1
to 11 years). Twenty (42%) dogs had a systolic murmur,
and 9 (19%) had ascites. Congestive heart failure was
diagnosed in 24 (50%) dogs. Seventeen (35%) dogs
had a history of syncope. Mean fractional shortening
was 14.4% (range, 1% to 23%). Mean left ventricular
systolic and diastolic diameters were 4.5 cm (range, 3
to 6.3 cm) and 5.3 cm (range, 3.9 to 7.4 cm), respectively.
Twenty-eight (58%) dogs had a sinus rhythm
with ventricular premature complexes (VPCs), and 20
had supraventricular arrhythmias (15 with atrial fibrillation
and 5 with sinus rhythm and atrial premature complexes).
Sixteen of the dogs with supraventricular
arrhythmias also had occasional VPCs. Morphology of
the VPCs seen on lead II ECGs was consistent with left
bundle branch block in 25 dogs, right bundle branch
block in 8, and both in 11.
Conclusions and Clinical Relevance—Results suggest
that Boxers with cardiomyopathy and left ventricular
dysfunction frequently have arrhythmias of supraventricular
or ventricular origin. Whether ventricular dysfunction
was preceded by electrical disturbances could
not be determined from these data, and the natural history
of myocardial disease in Boxers requires further
study. (J Am Vet Med Assoc 2005;226:1102–1104)