Today's Veterinary Practice

MAR-APR 2018

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29 MARCH/APRIL 2018 ● TVPJOURNAL.COM CONTINUING EDUCATION CLASSIFICATION OF CARDIOVASCULAR–RENAL DISORDERS In 2015, an international group of 16 board-certified veterinary experts reviewed the cardiovascular–renal syndrome. 1 They defined cardiovascular–renal disorders as "disease, toxin, or drug-induced structural and/or functional damage to the kidney and/or cardiovascular system, leading to disruption of the normal interactions between these systems, to the ongoing detriment of one or both." The group proposed the following veterinary classifications: primarily cardiovascular, primarily renal, and concurrent disease. Primarily Cardiovascular Disease Leading to Kidney Dysfunction Mechanisms by which cardiovascular disease can lead to kidney dysfunction include activation of the RAAS and the sympathetic nervous system or glomerular injury secondary to deposition of antigen–antibody complexes. Examples include: ■ Systemic hypertension leading to glomerular disease ■ Cardiac shock, low cardiac output, and systemic hypotension leading to decreased renal perfusion, azotemia, and acute kidney injury (AKI) ■ Heartworm infection leading to glomerulonephritis ■ Caval syndrome leading to AKI Primarily Renal Disease Leading to Cardiovascular Dysfunction Mechanisms by which renal disease can lead to cardiovascular dysfunction involve fluid volume, hemodynamic status, electrolyte disorders, and altered clearance rates for cardiac drugs. Examples include: ■ Kidney-mediated systemic hypertension, leading to increased afterload, left ventricular hypertrophy, and worsening mitral or aortic valve insufficiency ■ Volume overload, leading to congestion or systemic hypertension ■ Hypokalemia or hyperkalemia, leading to cardiac arrhythmias ■ Uremic hypodipsia, anorexia, or emesis, leading to volume depletion and reduced cardiac output and perfusion ■ Activation of the RAAS, leading to sodium and water retention and cardiac and vascular remodeling or congestion ■ Anemia secondary to chronic kidney disease (CKD), leading to volume overload and reduced cardiac tissue oxygenation Concurrent Disease of Both Systems This classification applies to cardiovascular and renal disease that develop independently or arise from a common trigger. Examples of common triggers include: ■ Septic or neoplastic emboli leading to renal and cardiac infarction ■ Gastric dilation and volvulus leading to cardiac arrhythmias and azotemia RECOGNIZING CARDIOVASCULAR AND RENAL DISEASE Cardiac and renal disease develop differently in dogs and cats, thereby limiting our ability to generalize among species. In dogs, common cardiac conditions include: degenerative mitral valve disease and dilated cardiomyopathy; in cats, they are hypertrophic cardiomyopathy and systemic hypertension. In dogs, common renal conditions include: glomerular disease, pyelonephritis, and acute tubular injury; in cats, they include idiopathic tubulo-interstitial disease. 2 Recognizing Cardiovascular Disease in Dogs and Cats with Renal Disease Cardiovascular disease is indicated by a history of a respiratory problem, collapse, abdominal distension, heart murmur, arrhythmia, muffled heart sounds, or abnormal pulses. Appropriate diagnostics to assess the cardiovascular system (eg, echocardiography, electrocardiography, blood pressure measurement, and thoracic radiography, with or without a heartworm test) should be accompanied by a systemic health evaluation, including a complete blood count, biochemical profile (with or without thyroid testing), and urinalysis. Dogs Most heart disease in dogs is unmasked by clues detected during physical examination (eg, murmur, arrhythmia, or jugular pulses). At a minimum, if a murmur is heard, 2-view thoracic radiography

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