Echocardiographic characterization of dilatation cardiomyopathy in the English cocker spaniel
Gooding, J.P.; Robinson, W.F.; Mews, G.C.
American Journal of Veterinary Research 47(9): 1978-1983
1986
ISSN/ISBN: 0002-9645 PMID: 3767104 Document Number: 278223
The echocardiographic characterization of a dilatation cardiomyopathy in small-breed dogs is reported. Twelve clinically healthy adult English Cocker Spaniel dogs (between 2 and 9 years old and weighting 11.5 to 15.4 kg [mean 12.9 .+-. 1.00 kg]) from a kennel population with a history of cardiomyopathy were assessed, using M-mode echocardiography. The dogs were selected on ECG and/or radiographic evidence of ventricular enlargement. Nine dogs had R-wave amplitude in lead 11 of > 3.0 mV. Two dogs had unusual right-axis deviation, the result of deep Q waves in the limb leads and deep S waves in chest leads CV6LL and CV6LU, indicating that there was right ventricular enlargement. All dogs had increased end-systolic dimensions (mean 3.0 .+-. 0.6 cm). End-diastolic dimensions were increased in 9 dogs (mean 4.0 .+-. 0.5 cm), and there was a decrease of left ventricular (LV) function as measured by fractional shortening in 8 dogs. Mean fractional shortening for the 12 dogs was 25.4 .+-. 5.7%. There was significant correlation between LV dimensions and age at echocardiographic assessment, indicating that LV dilatation was progressive. Three of the oldest dogs had severe dilatation of the LV, and in 2 of these, LV function was severely decreased. Left ventricular function in the 3rd dog, however, was within the acceptable range. Fractional shortening and thickness of the LV caudal wall and interventricular septum were significantly correlated (P < 0.01 for interventricular system and P < 0.05 for LV caudal wall). R-Wave amplitude and LV mass and LV cross-sectional area calculated from the echocardiographic measurements correlated significantly in the 9 dogs in which R-wave amplitude exceeded 3.0 mV (P < 0.01 and P < 0.05, respectively). The dilatation cardiomyopathy described differs from the idiopathic congestive cardiomyopathies of persons and of large- and giant-breed dogs in that it is generally benign. The course of the disease is variable and there is usually a long, clinically asymptomatic period, although affected animals may show early ECG abnormalities. However, progressive reduction in myocardial function eventually leads to congestive heart failure.