Today's Veterinary Practice

NOV-DEC 2017

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62 ADVANCES IN FELINE CARDIAC DIAGNOSTICS PEER REVIEWED misleading in the diagnosis of feline cardiac disease. Murmurs can be auscultated in cats with and without underlying heart disease, and up to half of all feline murmurs are found in cats without primary cardiac disease. 1 Conversely, cats can exhibit heart disease, potentially severe, without a murmur. Case notes: The presence of a new murmur in Tux does not equate to heart disease but does warrant further investigation. Likewise, the inability to auscultate a murmur in Elvis does not rule out heart disease. Additional physical examination findings that may prompt cardiac diagnostic testing include a precordial thrill, muffled heart and lung sounds, gallop sound, arrhythmia, changes in pulse quality, pulse deficits, or jugular venous distention or pulsation. Diastolic heart sounds are abnormal in small animals, and S4 gallops, in particular, are often associated with advanced heart disease in cats. This extra sound in diastole indicates atrial contraction into a stiff ventricular cavity. Common arrhythmias in cats include sinus tachycardia, premature beats, and, in cases of severe heart disease and atrial enlargement, atrial fibrillation. Pulse deficits may accompany some of these arrhythmias. Jugular venous distention or pulsation indicates elevated right atrial pressures or arrhythmias demonstrating atrioventricular dissociation. Case notes: Tux does not have physical examination abnormalities other than a murmur. Elvis, on the other hand, is tachycardic, tachypneic, and hypothermic and has dull ventral lung sounds, all of which could be consistent with congestive heart failure (CHF). He should be placed in an oxygen cage after a brief examination. ECHOCARDIOGRAPHY Echocardiography is used to definitively diagnose heart disease in cats and to determine disease severity. It provides information on cardiac size and function, as well as blood flow direction and speed. It is reasonable to recommend echocardiography as the first test in a cat with a murmur but without clinical signs of heart disease and then pursue further guided testing if the echocardiogram is abnormal. Detection of cardiac disease at this preclinical stage is considered important because medications can be initiated in an attempt to reduce thromboembolic risk, and the client can be educated regarding monitoring and further evaluations. If echocardiography is not pursued initially, then N-terminal pro B-type natriuretic peptide (NT-proBNP) would be a reasonable screening test (see Biomarkers). Case notes: Echocardiography should be offered to Tux's owner to determine whether heart disease is present, whether any medications are indicated, and when he should be rechecked. The most common cardiac disease in cats is hypertrophic cardiomyopathy (HCM), which is characterized by primary left ventricular concentric hypertrophy detected by echocardiography ( Figure 1 ). Secondary causes of hypertrophy (eg, systemic hypertension, hyperthyroidism) should be ruled out before HCM is diagnosed. Other, less common cardiac diseases in cats are listed in Box 1 . Although treatment of CHF is similar regardless of the underlying cause, more tailored treatment recommendations and prognostic information may be obtained by determining the underlying cardiac disease with echocardiography (eg, taurine analysis and supplementation for dilated cardiomyopathy). In addition to facilitating a definitive diagnosis, echocardiography can also be used to determine disease severity, monitor progression, and guide treatment. For example, the severity of HCM can be assessed by the thickness of the left ventricle, the size of the atria, left atrial appendage velocity, and the presence or absence of spontaneous echo contrast. Estimating thromboembolic risk based on left atrial parameters is pertinent in light of a FIGURE 1. Two-dimensional short-axis ultrasonographic view of Tux showing concentric left ventricular hypertrophy and papillary muscle hypertrophy, consistent with hypertrophic cardiomyopathy. His left atrium was normal in size on other images. LV, left ventricle.

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