Page 261 - Clinical Small Animal Internal Medicine

23 Pulmonary Hypertension 229

(a) (b)
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Figure 23.5 Pulmonic insufficiency in a dog with severe pulmonary hypertension secondary to interstitial lung disease. (a) Color Doppler
showing pulmonic insufficiency. White arrow shows the pulmonic insufficiency jet. PA, pulmonary artery; RV, right ventricle. (b) Spectral
Doppler of the pulmonic insufficiency jet. ** shows the peak velocity (estimated mean pulmonary artery pressure, 3.4 m/s, 46 mmHg) and
* shows the end‐diastolic velocity (estimated diastolic pulmonary artery pressure, 2 m/s, 16 mmHg).

Sildenafil

Sildenafil (Viagra® and Revatio®) is a selective phosphodi-
esterase‐5 inhibitor that specifically targets receptors in
the pulmonary vasculature and results in pulmonary
artery vasodilation. In dogs with PH, sildenafil is admin-
istered at a dose of 1–2 mg/kg orally q8h. Sildenafil has
been shown to lower the estimated pulmonary artery
pressures in dogs and to improve clinical signs, survival
times and quality of life. For the most part, sildenafil has
minimal side‐effects (i.e., gastrointestinal upset) in most
cases of PH, with the exception of left‐sided heart dis-
ease. Sildenafil can lower the pulmonary artery pressure
to a dangerous level in dogs with elevated pulmonary
venous pressure, resulting in flooding of the pulmonary
Figure 23.6 Septal flattening in a dog with severe pulmonary capillaries and subsequent congestive heart failure. In
hypertension secondary to pulmonary neoplasia. Severe septal dogs with left‐sided heart disease, sildenafil is indicated
flattening at end‐diastole indicating high right ventricular
pressures. * shows the flat interventricular septum bowing over to only if the patient is syncopal or in right‐sided congestive
the left side. LV, left ventricular lumen; RV, right ventricular lumen. heart failure and pimobendan should be considered a
viable alternative treatment option in these cases as a
pulmonary artery vasodilator.

congestive heart failure, anticoagulants for pulmonary
thromboembolism, oxygen for respiratory disease) in Prognosis
conjunction with directly lowering PA pressures is often
necessary. The prognosis for patients with PH is variable and
There are multiple treatment options that target the dependent on the underlying disease process. With the
different pathways involved in PH. Unfortunately, in advent of sildenafil, the prognosis for PH in dogs has
veterinary medicine many are extremely cost prohibitive improved. Now that there is a viable treatment option,
(i.e., endothelin antagonists cost ~$50 000/year) or clinicians are more readily recognizing PH as a clinical
require frequent and impractical administration of syndrome in patients with clinical signs, physical exami-
medication (i.e., prostacyclins require a continuous rate nations findings, and diagnostic testing results consist-
infusion or 6–12 times daily dosing). ent with PH.