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HF. Note the severe diffuse alveolar pattern and slight pleural effusion on both the dorsoventral (A) and lateral (B) projection that obscures assessment of heart size and pulmonary vessels. Focused echocardiogram from a cat with congestive HF secondary to hypertrophic cardiomyopathy. Note easy recognition of left atrial enlargement and pleural and pericardial effusion (arrows) on the right-sided long-axis view (A). On the right-sided short-axis view, the diameter of left atrium is more than 2 times of the aortic diameter suggestive of left HF (B). Ao, aorta; LA, left atrium; LV, left ventricle; PC eff, pericardial effusion; PL eff, pleural effusion; RV, right ventricle. View Large ImageFigure ViewerDownload Hi-res imageDownload (PPT) echocardiogram from 2 dogs, one with left HF (A) and the other with right HF (B). Note the severe left atrial and ventricular enlargement in the dog with MVD viewed from a left-sided 4-chamber view. (A) Note the severe right heart enlargement in the dog with right HF caused by severe pulmonary hypertension viewed from a right-sided long-axis view. In this view, the left heart should normally be 3 to 4 times larger than the right heart. LA, left atrium; LV, left ventricle; MV, mitral valve; PA, pulmonary artery; RA, right atrium; RV, right ventricle. Thoracic radiography is still one of the highest-yield tests for the diagnosis of both suspected left and right HF. In most cases, the diagnosis of HF is based on the finding of venous distention, presence of cardiomegaly, and a consistent pulmonary pattern (Fig. 4). Distention of either pulmonary veins or the caudal vena cava is very suggestive of either left or right HF, respectively.32, 33, 34 The pulmonary vein is considered distended if it is larger than its accompanying pulmonary artery. If radiographs are taken after several doses of empiric furosemide and clinical improvement, the pulmonary veins may not always appear distended with resolving pulmonary edema. Heart enlargement is usually present but may not always be a consistent finding in the diagnosis of HF. In dogs, the radiographic pulmonary pattern consistent with left HF is typically a perihilar interstitial to alveolar pattern. The pulmonary pattern is commonly asymmetric in dogs with MVD with an eccentric jet of mitral valve regurgitation or more symmetric in canine DCM.33 The distribution of radiographic pulmonary patterns is notoriously variable in cats with cardiogenic pulmonary edema.26 In severe HF cases, a diffuse, severe interstitial to alveolar pulmonary pattern or pleural effusion will make the cardiac silhouette and pulmonary veins impossible to visualize. radiographs from a dog with left HF. Note the severe left atrial (LA) enlargement, pulmonary venous distention (arrowhead), and perihilar interstitial pulmonary pattern indicating pulmonary edema on the lateral projection (A). On the dorsoventral projection (B), the caudal pulmonary pattern is asymmetric, with the right caudal lung fields being more affected. Another recent advancement in the diagnosis of HF in veterinary medicine is the use of cardiac biomarkers, such as amine terminal pro B-type natriuretic peptide (NTproBNP), BNP, and cardiac troponin I (cTnI). Cardiac biomarkers are blood tests for heart disease. NTproBNP and BNP are peptide hormones released by the ventricles in response to increased stretch. Both are elevated in dogs and cats with active congestive HF.35, 36, 37, 38 Used in conjunction with other clinical information, the measurement of NTproBNP (Canine and Feline Cardiopet proBNP, Idexx Laboratories, Inc, Westbrook, ME) and BNP (Canine Cardio-BNP, Antech Diagnostics, Irvine, CA) are useful in establishing, increasing confidence for, or excluding the diagnosis of congestive HF in patients presenting with acute dyspnea or cough.39 Samples need to be obtained when the animal is symptomatic for HF because the concentrations of the natriuretic peptides will decrease with treatment. Unfortunately, these assays are currently only available as send-out tests, limiting their usefulness in the emergency management of HF. Development of point-of-care testing, more accurate reference values, and a better understanding of the influence of systemic disease on these biomarkers are in progress. Special sample handling with transfer of the EDTA plasma into a stabilizer tube is required for analysis. At the time of this writing, the only point-of-care cardiac biomarker commercially available is cTnI, a marker of myocardial injury (i-STAT Cardiac Troponin I, Abaxis, Inc, Union City, CA). cTnI may have some utility in the emergency diagnosis of HF in cats but not dogs.40, 41 Most cats with HF have a markedly elevated cTnI; however, cats with severe, primary respiratory disease may also have elevated values. Typically, the magnitude of elevation is higher in cats with HF than those with respiratory disease. In rare circumstances, the measurement of pulmonary venous and central venous pressure (CVP) can be performed when the HF diagnosis is still uncertain. A CVP greater than 15 mm Hg is suggestive of right HF. The immediate goal of emergency therapy is to reduce abnormal fluid accumulations and to provide adequate or improved cardiac output. Strict cage rest and minimization of stress are of the utmost importance. Initially, treatments include sedation, oxygen, furosemide, or thoracocentesis in patients with large amounts of pleural effusion. Sedation is generally administered if patients are dyspneic and anxious. Butorphanol is a very effective sedative for patients in respiratory distress, in the author’s opinion. The butorphanol ranges from 0.05 to 0.3 mg/kg IV, intramuscularly (IM), or subcutaneously but is generally dosed at 0.1 mg/kg in patients with respiratory distress. Painful cats with aortic thromboembolism respond well to buprenorphine (see Table 5). Supplemental oxygen therapy is recommended to reduce the work of breathing. Oxygen can be delivered by oxygen cage/incubator or nasal catheter. Furosemide (Lasix or Salix), a loop diuretic, is a mainstay in the management of congestive HF, regardless of the cause. Despite its usefulness in HF management, furosemide never improves cardiac output. The dose of furosemide is usually