Just a nice review

Radiographic Features of Pulmonary Hypertension in Dogs and Cats

Elodie E. Huguet, Clifford R. Berry, Robert C. Cole

Background
Pulmonary hypertension (PH) is defined as increased pulmonary arterial pressure, often secondary to cardiovascular, pulmonary, or systemic disease. Affected animals may develop right-sided cardiomegaly, progressing to right-sided heart failure in severe cases. Clinical signs include dyspnea, syncope, exercise intolerance, lethargy, and coughing. Diagnosis is primarily achieved via Doppler echocardiography, though invasive catheterization remains the gold standard. Thoracic radiography is a practical, noninvasive screening tool that can help detect PH and associated comorbidities. This study reviews the radiographic features of PH in dogs and cats.

Methods
The study examined thoracic radiographs of dogs and cats with confirmed PH to identify characteristic imaging features. Key measurements included right-sided cardiomegaly, main pulmonary artery enlargement, lobar pulmonary artery enlargement, and vascular abnormalities. Objective metrics, such as the “3/5 to 2/5 cardiac ratio” and pulmonary artery-to-rib width ratios, were analyzed to assess PH severity. The study also reviewed radiographic signs of PH-related diseases, including left-sided cardiac disease, respiratory disorders, thromboembolism, and parasitic infections.

Results
Common radiographic findings in dogs with PH included right-sided cardiomegaly, a “reverse D” cardiac silhouette on ventrodorsal views, and main pulmonary artery enlargement at the 1–2 o’clock position. Pulmonary artery-to-rib width ratios greater than 1.2 were indicative of vascular enlargement. Cats with PH exhibited similar features, though cardiac silhouette changes were less distinct. PH was frequently associated with conditions such as degenerative mitral valve disease, interstitial pulmonary fibrosis, and dirofilariasis. Advanced cases showed tortuous and blunted pulmonary arteries, suggestive of chronic hypertension.

Limitations
Thoracic radiography lacks sensitivity for detecting mild PH, as vascular changes may only be apparent in moderate to severe cases. The study was retrospective, with inherent variability in radiographic interpretation. No direct correlation with echocardiographic pressure measurements was performed, limiting diagnostic precision.

Conclusions
Radiographic features, particularly right-sided cardiomegaly and pulmonary artery enlargement, can support a diagnosis of PH, but echocardiography remains the preferred diagnostic method. Radiography is useful for identifying comorbidities contributing to PH and guiding further diagnostics. Early recognition and management of PH can help prevent progression to right-sided heart failure. Further studies should refine objective radiographic criteria for diagnosing PH.

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