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tvpjournal.com | January/February 2016 | Today's VeTerinary PracTice aHs HearTWorM HoTLine Peer reviewed 67 1. history Findings • Presentation of patient in late winter or early spring • History of incomplete heartworm prevention • Acute onset of respiratory difficulty and weakness 2. Physical examination Findings • Polypnea or dyspnea • Pale mucous membranes (Figure 5) • Jugular distension with bounding pulse (Figure 6) • Distinct cardiac murmur suggestive of tricuspid regurgitation • Palpable hepatomegaly and/or splenomegaly 3. Diagnostic Findings • Dark red to coffee-colored urine (Figure 2) • Microfilaremia and/or positive antigen test result (Figure 7) • Cardiac ultrasonography confirming adult heartworms in the right heart (Figures 3, 4, and 8) Diagnosing Caval Syndrome: Step by Step FIGURE 5. Pet with CS; note pale mucous membranes and decreased capillary refll time. Courtesy Merial FIGURE 6. The jugular vein is visibly distended in this patient, and a bounding jugular pulse is readily apparent. It may be necessary to shave the hair of a thick- or long-haired dog in order to observe this fnding. Courtesy Merial FIGURE 7. Pets with CS are often infected by a high number of heartworms; therefore, it is common to fnd many microflariae even on direct evaluation of a single drop of blood. Courtesy Merial FIGURE 8. Cardiac ultrasonography is the defnitive test for CS. Adult worms are easily visualized within the right heart. Courtesy Merial 171:1065-1069. 4. strickland Kn. canine and feline caval syndrome. Clin Tech Small Anim Pract 1998; 13(2):88-95. 5. rawlings ca. other heartworm syndromes. Heartworm Disease in Dogs and Cats. Philadelphia: WB saunders, 1986, pp 191- 194. 6. atwell rB, Boreham PF. Possible mechanisms of the caval syndrome in dogs infected with Diroflaria immitis . Aust Vet J 1982; 59(5):161-162. 7. Kitagawa H, sasaki y, ishihara K. clinical studies on canine diroflarial hemoglobinuria: relationship between the presence of heartworm mass at the tricuspid valve orifce and plasma hemoglobin concentration. Jpn J Vet Sci 1986; 48(1):99-103. 8. atkins ce, Keene BW, McGuirk sM. investigation of caval syndrome in dogs experimentally infected with Diroflaria immitis. J Vet Intern Med 1988; 2(1):36-40. s tePhen l. Jones Stephen L. Jones, DVM, is the President of the American Heartworm Society and a general practitioner/practice partner at Lakeside Animal Hospital, Moncks Corner, South Carolina. He received his DVM from University of Georgia. Read more about Dr. Jones at lahmc.com/veterinarians.php.