16-year-old castrated male Shih Tzu

2017 Image Interpretation - Case 4

  • Hacking, coughing, vomited once; progressive dyspnea.
  • Recently fainted after coughing.
  • Grade V/VI systolic heart murmur bilaterally.

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  • Moderate right-sided cardiomegaly characterized by a rounded ranial/right border of the heart, with increased sternal contact
    • “Reverse-D” ad “3/5 – 2/5 cardiac ratio”
  • Caudal pulmonary enlargement.
  • Patchy intersitial lung pattern, worst caudodorsally.
  • Predominately right-sided cardiogemaly with patchy intersitial lung pattern. Considerations are given to non-cardiogenic pulmonary edema secondary to pulmonary hypertension. Cardiogenic pulmonary edema secondary to mitral/tricuspid insufficiency, interstitial pneumonia and neoplasia can also be considered.
  • Echocardiogram showed severe pulmonary hypertension (high gradient; tricuspid regurgitation, minimal mitral regurgitation; no left-sided enlargement.
  • Responded well to Sildenafil.

Pulmonary Hypertension

  • Classic presentations
    • Small breed dogs with concurrent myxomatous valve (mitral and tricuspid) and history of congestive heart failure.
    • Terrier-type dogs with chronic history (pulmonary fibrosis).
    • Young dog or rescue dogs from the south (heartworm disease).
  • No-so-classic presentations
    • Small breed dog with no left atrial enlargement, no prior history of congestive heart murmur, +/- murmur, no chronic airway disease in the history (including no prior abnormal lung pattern), and heartworm negative.
  • History
    • Collapse episode may be described as a seizure or wobbliness.
    • Collapse episode tends to happen after excitement or exercise.

Sildenafil-responsive non-cardiogenic pulmonary edema

  • Results from pulmonary hypertension where there are regions of high pulmonary blood flow (no vasoconstriction) and low pulmonary blood flow (vasoconstriction).
  • The high flow areas experience higher hydrostatic pressure.
  • The capillary beds of the high flow areas become more permeable leading to edema with high proetin and RBCs.
  • Sildenafil reduces “perfusion heterogeneity”.
  • Pulmonary infiltrates are often “patchy”.
  • Misdiagnosis as cardiogenic pulmonary edema or pneumonia is common.
  • Fails to respond to lasix/enalapril alone.
  • Sildenafil is safe and can improve the lung pattern shortly after administration.

24 hours post Lasix and Sildenafil.