NEW METHODS FOR DIAGNOSING HEART DISEASE: BLOOD-BASED CARDIAC TESTING

摘要

Blood-based testing for heart disease in dogs and cats using natriuretic peptide and/or troponin assays is an exciting possibility. There are three primary uses for such tests: 1) detection of early asymptomatic (occult) disease, 2) enhanced diagnosisof dyspnea due to cardiac vs. respiratory disease, and 3) as a guide for medical therapy and prognosis. The prospect of identifying animals with asymptomatic heart disease via biochemical testing is exciting from several perspectives. First, it would likely permit individuals without extensive training in cardiology to identify animals with heart disease more accurately and at an earlier point in time. Such testing could facilitate the delivery of medical treatment at an earlier stage of the disease process than is currently accomplished while avoiding unnecessary treatment of unaffected or mildly affected animals. Biochemical testing might also help clarify the status of dogs with equivocal results when evaluated by other diagnostic modalities, e.g.,dogs with "cardiomegaly" on thoracic radiographs or large breed dogs with mildly reduced contractile indices on an echocardiogram. Some obvious applications might include screening the breeding populations of cats for hypertrophic cardiomyopathy and asymptomatic Doberman pinschers for dilated cardiomyopathy. For screening purposes, a test must have very high sensitivity, i.e., it should detect at least 90 percent of the target group(s). It must also have a reasonable level of specificity, as this population of animals will subsequently require additional evaluation, such as echocardiography, at substantial cost to the owner to confirm the diagnosis. The required level of specificity is debatable, but it is reasonable to assume that a useful test wouldhave a specificity exceeding 70 percent. Blood-based tests may also facilitate distinguishing dyspnea due to cardiac vs. respiratory disease. In the animal that presents with respiratory distress, blood-based tests can rapidly identify those with cardiogenic edema vs. those with other primary respiratory afflictions (i.e., pneumonia, COPD, etc.). Finally, it is likely that blood-based tests will track improvements in cardiac function following appropriate medical treatment and help the practitioner "fine-tune" therapy for each individual patient. The results of these tests may also permit more accurate prognostication of outcome, life-span, and risk for adverse events (i.e., sudden arrhythmic death, heart failure, etc.).