Innovation in Boxers with Cardiac Disease
Cardiomyopathy is a common affliction of the Boxer breed with as many of one-third of Boxers developing cardiomyopathy during their lifetime. Early in the disease affected dogs develop ventricular arrhythmias, which are often isolated and infrequent. At this stage a routine ECG may identify ventricular arrhythmias and lead to suspicion of disease, but the definitive diagnosis usually is established from a combination of a 24-hour ambulatory ECG (Holter) recording and echocardiography. As the disease progresses and arrhythmia worsens, severe ventricular arrhythmias can result in clinical signs of syncope or sudden death. Some proportion of dogs will develop features of dilated cardiomyopathy (DCM), with ventricular dilation and reduced contractile function, often progressing to overt congestive heart failure. Recent studies have indicated that dogs that go on to develop the DCM phenotype of the disease are likely to be homozygous for the same genetic mutation (in the striatin gene) associated with the arrhythmic form of the disease. This suggests that DCM in Boxers is likely a continuum of the same disease.
The myocardial pathology in Boxers with cardiomyopathy closely resembles that of arrhythmogenic right ventricular cardiomyopathy (ARVC) in people, characterized by fatty or fibrofatty replacement of cardiomyocytes and active myocarditis. The degree of myocarditis has been found to correlate with the severity of the disease may be related to development of left ventricular involvement and the DCM form of arrhythmogenic cardiomyopathy in people. Recent studies in people with ARVC have also identified increased levels of circulating inflammatory markers in affected individuals, suggesting that systemic inflammation might play some role in the disease process.
We are currently studying whether Boxers with ARVC (both arrhythmic and structural forms) will have elevations in circulating inflammatory markers and cardiac biomarkers compared to a comparable population of healthy Boxers. If evidence of systemic inflammation is found in affected Boxers this will improve our understanding of the disease process and potentially open new avenues for diagnosis, therapy or prevention of this important disease.
We are working to advance healthcare for Boxers with ventricular arrhythmias or DCM. If you have clients who may benefit from clinical studies, please direct them to Dr. Suzanne Cunningham at firstname.lastname@example.org or call 508-887-4696. The study will cover the costs of a cardiac physical examination, electrocardiogram, echocardiogram, 24-hour Holter monitor recording, and blood sample collection for CBC, serum chemistry analysis, cardiac and inflammatory biomarkers, and genetic testing at North Carolina State University Veterinary Cardiac Genetics Laboratory.