What diagnostic criteria confirm pulmonary hypertension in dogs and when is treatment indicated?

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Accepted Answer

Pulmonary hypertension (PH) in dogs is confirmed echocardiographically using a combination of Doppler-derived pressure estimates and supporting structural indices, with treatment indicated when clinical signs are present or when PH severity reaches intermediate-to-high probability thresholds. The ACVIM consensus defines PH by increased pressure within the pulmonary vasculature and requires comprehensive evaluation integrating signalment, clinical signs, echocardiographic parameters, and ancillary diagnostics — no single measurement is sufficient alone.1 Right heart catheterization remains the gold standard for direct pulmonary arterial pressure and pulmonary capillary wedge pressure measurement, but is impractical in dogs due to anesthetic risk in severe cardiorespiratory disease; transthoracic echocardiography is the diagnostic test of choice in clinical practice.68 The primary echocardiographic pressure estimate is the tricuspid regurgitation pressure gradient (TRPG), derived from the tricuspid regurgitation jet velocity. An estimated systolic pulmonary arterial pressure (sPAP) ≥47 mmHg identifies dogs with significantly shorter survival times compared to those with sPAP <47 mmHg (median 9 days versus a substantially longer survival; P = 0.001), and at this cutoff the TRPG carries a sensitivity of 0.78 and specificity of 0.63 for predicting non-survival in dogs with respiratory disease-associated PH.4 The CT pulmonary trunk-to-aorta diameter ratio correlates moderately with TRPG (r = 0.61) and is significantly elevated in moderate and severe PH compared to normal dogs, but does not differ significantly between normal dogs and those with mild PH; an elevated ratio on thoracic CT should prompt follow-up echocardiography.7 Hemodynamic classification into precapillary versus postcapillary PH is essential before initiating pulmonary vasodilator therapy. Precapillary PH arises from increased pulmonary vascular resistance with normal pulmonary capillary wedge pressure an