Supportive care and treatment of underlying conditions
Patients with pulmonary hypertension often require supportive therapy and additional therapies based on the underlying cause
of the pulmonary hypertension. These therapies may include oxygen supplementation, treatment of pulmonary disease with anti-inflammatory
or bronchodilating agents, treatment of neoplasia with appropriate chemotherapy, or treatment of congestive heart failure
with diuretics. Patients with thromboembolic disease may benefit from anticoagulant medications and corticosteroids, and patients
with heartworm disease may require heartworm adulticide therapy.
Once therapy is instituted, monitoring is most often based on the patient's clinical signs. Sildenafil therapy may be increased
or decreased within the dose range according to clinical signs, but the World Health Organization's Evian Functional Classification
scheme (see Table 2 in the "Canine pulmonary hypertension, Part 1: An in-depth review of its pathophysiology and classifications") more objectively assesses the therapeutic response. For instance, a patient may initially be categorized as functional class
IV, but after four weeks of therapy be reevaluated as functional class II.
Recheck thoracic radiography may show improvement in pulmonary infiltrates and right-sided cardiac enlargement. A repeat echocardiographic
examination may show partial or complete resolution of right-sided heart changes and improved pulmonary artery velocity flow
profiles. Evidence of decreased pulmonary arterial pressure may be noted in the form of decreased maximum tricuspid regurgitation
or pulmonary insufficiency velocities.
The prognosis for dogs with pulmonary hypertension varies and often depends on the underlying cause. Before the availability
of sildenafil, dogs with pulmonary hypertension had grave prognoses, with many surviving only days past diagnosis.3 With the introduction of sildenafil therapy, the average published survival has increased to 91 days, with some patients
surviving almost two years.28 Negative prognostic factors may include advanced functional class, high right atrial pressure, severe right ventricular dysfunction,
and increased NT-proBNP values.14,29
Although several diagnostic tools may be used to help diagnose canine pulmonary hypertension, an echocardiographic examination
is the gold standard in veterinary medicine. By using echocardiography, you can estimate pulmonary arterial pressures and
assess the severity of pulmonary hypertension. Historically, the prognosis for dogs with pulmonary hypertension was grave.
However, with the advent of advanced diagnostic tools, the ability to recognize and treat underlying diseases, and the availability
of sildenafil, prognosis has improved significantly.
Rebecca L. Quinn, DVM, DACVIM (internal medicine)
Department of Cardiology
Angell Animal Medical Center
350 S. Huntington Ave.
Boston, MA 02130
Justin G. Williams, DVM, DACVIM (cardiology)
VCA Animal Care Center of Sonoma County
6470 Redwood Drive
Rohnert Park, CA 94928