Case Studies In Small Animal

Cardiovascular Medicine

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Third Visit

Case 31

Two Months Later

Presenting Complaints

bulletHeartworm Disease
bulletRespiratory arrest last night @ the referring veterinarian's clinic

Pertinent History

bulletBoris presented to the VMTH two months ago and was diagnosed with heartworm disease. At that time his PCV was 25% and hemoglobinuria was present. He was placed on prednisone @ 5 mg BID for 7 days, then 5 mg SID x 14 days, then 5 mg every other day for 14 more days with a recheck in 4 to 6 weeks. The referring veterinarian also placed him on a monthly heartworm preventative (ivermectin).
bullet2/3/98: Yesterday at 4:30 pm, Boris was noted to have fallen over and then defecated. He then became limp and unconscious but could still be seen to be breathing. He was taken to the referring veterinarian's facility with sudden onset of weakness and dyspnea (open mouth breathing). The cat was put on an oxygen mask and went into respiratory arrest. He was intubated and provided with positive pressure ventilation until he was able to breath on his own. He was treated with 5 mg of dexamethasone IV, 2 cc aminophylline, & 0.5 cc of Lasix IV. Chest films were taken at this time and revealed severe pulmonary infiltrates. Dexamethasone injections were repeated IV q 3 hrs and the cat spent the evening in their oxygen chamber.

Physical Examination

bulletGrade V/VI right sided holosystolic murmur, HR=170 (regular), R=57 with increased effort. Presumptive hemoglobinuria (urine was red). Urine from pad was not saved. Urinalysis could not be obtained as the bladder was too small to obtain a cystocentesis. Pale pink MM that were later slightly lavender after venipuncture Temperature was not taken due to desire to not stress the cat. Body condition score=3/9. Jugular veins were distended with pulses visible at least 1.5 inches dorsal to the thoracic inlet. Strong femoral pulses were present with pulse deficits which corresponded on auscultation in timing to what sounded like premature beats. Expiratory crackles palpable on sternum when carried from Radiology. Extremities were cool and the cat was very quiet for all medical procedures though he was alert. He was also approximately 8% dehydrated and drank thirstily when offered water. Bladder was very small.


bulletHeartworm disease
bulletPresumptive hemoglobinuria/ hematuria
bulletMixed interstitial alveolar infiltrates, severe on referral films; greatly improved on VMTH films 24 hours later
bulletRespiratory arrest episode, historical
bulletAbnormalities on CBC (see details in the Comments section)
bulletAbnormalities on Chemistry panel (please see Comments)


bulletCBC: Thrombocytopenia (35,000), moderate hyperproteinemia (9.0), mild neutrophilia (12,150), and moderate lymphopenia (675). The marked thrombocytopenia is of concern as it may be due to shearing secondary to caval syndrome or consumption at the site of the probable pulmonary worm embolism. A platelet count will need to be rechecked tomorrow and followed closely to see if he is continuing to lose platelets or if prednisone is aiding his thrombocytopenia. The neutrophilia, though mild, is notably increased above his previous values and so for Boris this likely represents a moderate amount of inflammation (compare: 6/97: 4836, 12/97: 3750). He also had a mildly low Hct (27%), Hgb (8.4) and RBC count (6.21 M/ul). His Hct, however, has remained reasonably stable (6/97: 29%, 12/97: 25%).
bulletChemistry panel: Elevated ALT (552 IU/L), AST (455 IU/L), and BR (0.9). Cats with right sided CHF may have increased serum liver enzyme levels but usually not to this degree. Moderate hyperproteinemia (TP=8.9, globulins=5.8, albumin=3.1). Mild azotemia (BUN=52, Cr=2.8). In light of Boris' dehydrated state his azotemia is likely prerenal and hyperproteinemia secondary to this as well. Hyperglobulinemia is often seen in cats with heartworm disease and presumed to be secondary to chronic antigen stimulation. Hyperglycemia=294 (probably stress related). Very mild decreases in Na (149), K (3.3), Cl (112), PO4 (3.0).
bulletECG: R waves seemed decreased at 0.25 mV with a bifid component. Arrhythmia is ventricular in origin (occasional PVCs were present).
bulletRadiographs: A referral lateral thoracic radiograph taken last night after Boris' respiratory arrest revealed marked pulmonary infiltrates in the caudal lung fields. Today's films (VMTH) showed a marked improvement with respect to pulmonary infiltrates but the caudal vena cava remains dilated. The radiologists felt that the cardiac silhouette was also notably decreased in size compared to yesterday.
bulletEchocardiogram: The RV was very dilated as was the RA. Diastolic septal flattening was again observed. One heartworm was visualized entwined within the tricuspid valve apparatus, extending into the right atrium. More worms were seen in the pulmonary artery.

Discharge Instructions

bulletToday we have found evidence of caval syndrome in Boris. One heartworm was visualized entangled in the tricuspid valve of his heart. However the remainder of the worms visualized were present in his pulmonary artery. When worms are present in this location they can cause tricuspid regurgitation with resultant shearing of his red blood cells and the hemoglobin from the red cells can then be passed out in the urine. The finding that his urine was red today is supportive evidence that this is most likely happening.
bulletAnother finding today was that Boris has a decreased number of platelets (35,000) which could increase his tendency to bleed. He should have his blood parameters checked tomorrow and Saturday to see if he is continuing to lose platelets (CBC).
bulletBoris is also showing some elevation in his BUN and creatinine which measure kidney function. These should also be checked at the same time.
bulletIf Boris is noticed to have increased respiratory effort or respiratory distress you should call your veterinarian and/or return to a veterinary hospital as a new worm may have lodged in his lungs.
bulletPlease refer to your drug label for instructions on prednisone.


Correct Quiz

Mark D. Kittleson, D.V.M., Ph.D. All rights reserved.