Case Spotlight: Heartworm Disease
History: An intact male mixed breed dog was presented for evaluation of 4-5 days of progressive abdominal distension. Abnormalities on laboratory work were heartworm positive and anemia. Survey radiographs showed cardiomegaly and a possible abdominal mass.

Clinical Differential Diagnosis:
Cardiac - right heart failure secondary to heartworm, pericardial effusion, cardiomyopathy 
Abdominal mass - neoplasia/granuloma/abscess/cyst of spleen, liver, kidney.

Sonographic Interpretation: The echocardiogram revealed an enlarged right heart with right atrial enlargement and significant tricuspid regurgitation. Tricuspid insufficiency was noted at 3.87 m/sec. The main branch of the pulmonary artery was enlarged and a large amount of heartworms were noted. Smoke was noted in the right atrium. The mitral valve was insufficient. The left atrium was of normal size. Tricuspid insufficiency velocity 3.87 m/sec. Mitral insufficiency velocity 5.65 m/sec.

Sonographic Differential Diagnosis: Right sided heart failure. Large amount of heartworms noted in the main branch of the pulmonary artery. Pulmonary hypertension was noted with a jet of 3.87 m/sec. Given the changes seen on echocardiographic examination this patient would be an ideal candidate for basket retrieval of heartworms. Until this procedure is performed the patient should be treated with aspirin at 1 mg/kg every other day, Pimobendan at 0.25-0.3 mg/kg b.i.d. and Sildenafil at 1 mg/kg b.i.d. The Sildenafil dose can be increased to 1.5 mg/kg b.i.d. over 10 days. Lasix should be instituted at 1-2 mg s.i.d. Given the significant amount of heartworms noted in the pulmonary artery coupled with the patient's clinical signs the patient's prognosis is guarded at this time. Ideally, it would be prudent to perform a blood pressure and ECG in this patient.





Diagnosis: Heartworms, pulmonary hypertension.


La/Ao shows normal left atrial volume despite mitral insufficiency. The MR was therefore compensated and not clinically significant.
Note the echogenic linear heartworms in the lower left of the image at the 7 o`clock position at 10 cm of depth.
The LV m-mode shows normal left sided volume and function but note the flattening of the LV septum in the b-mode portion of the image. This indicates significant right sided volume overload and increased RV pressures.
Severe tricuspid insufficiency was seen consistent with pulmonary hypertension. Pulmonary hypertension was noted with a jet of 3.87 m/sec.
Right parasternal 4-chamber long axis view demonstrating severe right atrial and right ventricular volume overload owing to heartworm burden. The probe had to be slid dorsally along the rib cage to achieve this 4-chamber view given the cardiac rotation and displacement away from normal positioning owing to the severe right sided volume overload.
Apical 4-chamber view demonstrating an inversion of normal volumes as the left heart now has the lesser volume compared to the right heart (left of screen).
Right parasternal heart based view demonstrating a severely enlarged right atrium in the 9 o'clock position, overwhelming right ventricle and pulmonary artery (11-6 o'clock position), and visible echogenic heartworms in the main branch of the pulmonary artery in the 7 o'clock position at 10 cm of depth.
Patient Information

Age 5 Year
Gender Male, Intact
Species Canine

Clinical Signs
  • Abdominal Distension

Blood Chemistry

  • No significant findings
CBC
  • Anemia

Special Testing
  • Heartworm Antigen = Positive
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