Canine pulmonary hypertension, Part 2: Diagnosis and treatment

Canine pulmonary hypertension, Part 2: Diagnosis and treatment

Once a death sentence, canine pulmonary hypertension no longer carries such a grave prognosis—in part, because of advanced diagnostic tools and the availability of sildenafil therapy.

Pulmonary hypertension is now being diagnosed in dogs relatively frequently.1 To help you manage this once uncommonly diagnosed disease, in this article we review how to diagnose and treat canine pulmonary hypertension—and what the prognosis is for dogs with this condition.

To better understand this complex syndrome, be sure to read the first article in this series, "Canine pulmonary hypertension: An in-depth review of pathophysiology and classification."

DIAGNOSIS

There are several goals in diagnosing pulmonary hypertension. The first is to identify the underlying cause or causes of pulmonary hypertension and to assign a clinical classification to the patient. The second is to quantify the degree of pulmonary hypertension based on clinical signs and diagnostic test results. The third is to assess for hemodynamic impairment. And the fourth is to decide on the best treatment option for the patient.

Signalment and history

Most dogs with pulmonary hypertension are small-breed and middle-aged to older, which coincides with the high prevalence of pulmonary hypertension in patients with degenerative mitral valve disease.2 Clients most often complain of exercise intolerance, as well as cough, dyspnea, and syncope.3 These signs occur because of pulmonary hypertension-induced impaired oxygen transport, reduced cardiac output, and systemic hypotension, resulting from systemic vasodilation and under filling of the right and left ventricles. Signs may also occur as a result of the underlying cause of pulmonary hypertension, such as interstitial lung disease.

Physical examination findings

Physical examination findings can include a heart murmur or a split S2 sound; the S2 heart sound is normally associated with the closure of the aortic and pulmonary valve leaflets. Abnormal lung sounds, ascites, and cyanosis have also been reported.2-5

Clinical pathology results

Given the vast assortment of underlying conditions that may lead to pulmonary hypertension, a thorough laboratory evaluation is recommended. A complete blood count, serum chemistry profile, heartworm antigen test, and urinalysis should be reviewed to help evaluate for systemic diseases that may predispose dogs to pulmonary hypertension. If indicated based on clinical signs, physical examination results, and baseline laboratory test results, patients may benefit from coagulation profiles, D-dimer concentrations, and endocrine testing.

Biomarkers

Biomarkers such as brain natriuretic peptide (BNP) and cardiac troponins may be of added value in diagnosing patients with pulmonary hypertension.

BNP is a hormone that is released from the ventricular myocardium in response to stress or strain.6 Although BNP is cleared quickly from circulation and is difficult to measure, cleavage of BNP produces a fragment—NT-proBNP—that remains in circulation longer and can be successfully measured. Traditionally, NT-proBNP measurements have been used in veterinary patients as a noninvasive means of determining the underlying cause of respiratory distress. More recent studies have shown that NT-proBNP values are higher in dogs with clinical class III pulmonary hypertension than in patients with respiratory disease without associated pulmonary hypertension, those with moderate to severe pulmonary hypertension as based on pulmonary arterial pressure, or those with clinical class I, III, IV, or V pulmonary hypertension.2,7 In people with pulmonary hypertension, NT-proBNP values correlate with survival and can help predict the patient's prognosis.8

Cardiac troponins are proteins released from the ventricular myocardium as a result of myocardial cell injury and necrosis.9 Cardiac troponin I concentrations are commonly increased in dogs with clinical class I, II, III, or IV pulmonary hypertension.10