Today's Veterinary Practice

MAY-JUN 2018

Today's Veterinary Practice provides comprehensive information to keep every small animal practitioner up to date on companion animal medicine and surgery as well as practice building and management.

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25 MAY/JUNE 2018 ‚óŹ TVPJOURNAL.COM CONTINUING EDUCATION Congestive Heart Failure in Canines Simon Swift, MA, VetMB, CertSAC, DECVIM (Cardiology), MRCVS University of Florida College of Veterinary Medicine Heart failure is a syndrome of clinical signs that, although well recognized by clinicians, is difficult to define precisely. It involves the heart's inability to maintain output sufficient to meet the body's needs, or to do so at normal filling pressures. Elevated filling pressures can lead to congestion as increased venous pressures cause fluid to leak from the vessels, resulting in congestive heart failure (CHF), which moves the patient into stage C ( BOX 1 ). With right-sided heart failure, increased right atrial and vena caval pressures cause hepatomegaly to develop, and the fluid then weeps into the abdomen as ascites; drainage is only required if the effusion compromises respiratory function. The elevated filling pressures can also be documented as jugular venous distention. For left-sided heart failure, the increased left atrial and pulmonary venous pressures cause fluid to seep into the interstitial spaces and then flood the alveoli with pulmonary edema. Dogs occasionally present with pleural effusion when in CHF, and respiratory effort can increase significantly if this effusion is not drained. When heart failure develops, a number of mechanisms are activated to maintain cardiac output and blood pressure. Unfortunately, this neurohormonal activation is deleterious in the long run and increases the damage to the heart and circulation. The best-known mechanism is the renin-angiotensin-aldosterone system. Chronic elevations in angiotensin II and aldosterone are known to have harmful effects. shutterstock.com/Billion Photos CONTINUING EDUCATION CARDIOLOGY BOX 1. Classification scheme of canine heart disease STAGE A A dog at risk of heart disease B1 Signs of heart disease (eg, a murmur but no structural changes; eg, left atrial enlargement). The dog is asymptomatic. B2 Signs of heart disease (eg, a murmur with structural changes; eg, left atrial enlargement). The dog is asymptomatic. C Congestive heart failure is present or has been present and the dog is receiving treatment. D Congestive heart failure is present and refractory to standard therapies. The patient requires hospitalization.

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