Abnormal Cardiovascular Physical Exam
Cardiac murmurs, gallop sounds and arrhythmias are some obvious physical exam abnormalities that are clear indications for an echocardiogram. Cardiac murmurs can arise from multiple underlying abnormalities in the heart. Murmurs can be pathologic or phys1ologic (also called functional) and these can only be definitively differentiated by a cardiologist’s interpretation of an echocardiogram. Gallop sounds occur when the clinician is able to auscultate an S3 or S4 in addition to the normal S1 and 52 sounds. This can often be an indication for diastolic dysfunction and an echocardiogram is always warranted when this occurs in dogs and cats. Arrhythmias can be caused by intra-cardiac or extra-cardiac disease. An echocardiogram helps rule out primary cardiomyopathy and/or infiltrative cardiac disease that may explain the arrhythmia. The echocardiogram also helps to determine appropriate anti-arrhythmic therapy for the indivdiual patient.
Many dog and cat breeds have a heritable pre-disposition for heart disease. In some cases, auscultation by a board certified cardiologist is indicated to rule out the presence of a murmur (for example breeds with a pre-disposition for Subaortlc Stenosis include Golden Retrievers, Rottweilers, German Shepherds, Newfoundlands and Boxers). If a murmur is ausculted, then an echo is indicated for complete evaluation. In some breeds, however, an echo is always indicated to screen for heart disease.
Many cat breeds should be screened prior to breeding with echo. Maine Coons, Bengals,and Sphynx cats are popular breeds with known HCM in their lines. All labrador Retrievers should be screened prior to breeding for Tricuspid Valve Dysplasia. A mildly affected dog may produce off-spring with severe lesions. Not all mildly affected dogs have heart murmurs.
Finally, all Doberman Pinschers should be screened with echo prior to breeding to rule out occult Dilated Cardiomyopathy. Owners of pet Dobermans and Boxers are often curious about when and how to screen for cardiomyopathy in their dogs. Dobermans can be screened as early as 2 years of age. By age 5, most affected male Dobermans will have echo changes and by age 7, most affected females will have changes. Boxers should be screened with a Holter monitor. The above age grouping is appropriate for this breed as well.
Thoracic Radiographic Changes
Cardiomegaly noted on radiographs can be due to cardiac enlargement, pericardia! fat accumulation and/or patient variability. An echocardiogram is the most specific tool for determining the size of each individual cardiac chamber and is a very useful tool in delineating a cause for rad1ograph1c cardiomegaly. For example, pulmonary hypertension may result in right-sided cardiomegaly and often presents without a distinguishable murmur. Pulmonary vasculature changes are another indication for echocardiogram. If enlarged, this can be indicative of a left-to-right cardiac shunt, pulmonary hypertension and/or impending congestive heart failure. If small, this can be indicative of a right-to-left cardiac shunt. Pulmonary parenchymalchanges are another common indication for echocardiogram. The echocardiogram is highly specific and sensitive for congestive heart failure and pulmonary hypertension.
Cats can be particularly challenging cardiology patients because they can have severe cardiomyopathy despite the absence of physical exam abnormalities, radiographic changes and/or clinical signs. Echocardiogram is often the only appropnate diagnostic test that is both specific and sensitive for heart disease in cats. Purebred cats have a higher incidence of heart disease,and therefore echocardiographic evaluation is often high yield in these patients. It is our opinion that a screening echocardiogram is never inappropriate in a cat. Serum NTproBNP can also be considered in cats as a screemng tool and is often utilized prior to anesthesia in adult cats. If this test results 1n suspected heart disease, an echocardiogram is recommended in these patients to confirm the presence of heart disease and determine the therapeutic needs of the patient.
Prior to placing a dog or cat under anesthesia, it can be helpful to obtain a complete understanding of the patient’s cardiovascular status. An echocardiogram is the most specific and sensitive test to accomplish this goal. Beyond an abnormal physical exam or radiographic changes, there are a variety of clinical signs that can increase a clinic1an’s suspicion for heart disease and increase the indication for echocardiogram. These can include coughing, exercise intolerance, weakness and/or syncope.
If you are unsure whether it’s appropriate to make a referral, please call us. Our cardiologists are always happy to discuss cases with family veterinarians in order to help you make the best recommendations to your clients.