• 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.

• Adams DS, Marolf AJ, Valdés- Marnnez A, Randall EK, Bachand AM. Associations between thoracic radiographic changes and severity of pulmonary arterial hypertension diagnosed in 60 dogs via Doppler echocardio-graphy: a retrospective study. Vet Radiol Ultrasound. 2017;58:454–462.
• Kellihan HB, Waller KR, Pinkos A, et al. Acute resolution of pulmonary alveolar infiltrates in 10 dogs with pulmonary hypertension treated with Sildenafil citrate: 2005-14. J Vet Cardiology (2015).