Background: Diagnosis of pulmonary arterial hypertension (PAH) relies on Doppler measurement of pulmonic and tricuspid regurgitation (TR). However, these are not always detectable. Hypothesis: Tissue Doppler imaging (TDI), a novel noninvasive ultrasound technique, provides indirect but sensitive and specific assessment of elevated systolic pulmonary artery pressure (SPAP) in dogs. Animals: One hundred and five dogs with TR. Methods: Prospective observational study. Dogs were categorized as presenting normal (group 1, n=45), mildly increased (group 2, n=19), or moderately to severely increased (group 3, n=41) SPAP, based on TR peak velocities (<2.5, 2.5-3.0, and >3.0 m/s, respectively). Ten quantitative echo-Doppler- and TDI-derived variables were assessed, including the main pulmonary arterial diameter to aortic diameter ratio, pulmonary flow acceleration time, and acceleration-to-ejection time ratio, the Tei index of right ventricular function, and 6 longitudinal basal right ventricular TDI variables. Results: A significant correlation was observed between SPAP and each of the 10 tested variables (P<.05). Conventional echo-Doppler variables were less discriminating than the TDI for predicting increased SPAP. The combined systolic and diastolic right TDI index had the highest sensitivity and specificity (89% and 93% respectively, for a cutoff of 11.8 cm/s) and could discriminate between dogs in group 1 from dogs in group 2. Conclusions and Clinical Importance: TDI provided effective predictors of systolic PAH and demonstrated that both alterations in right-sided systolic and diastolic myocardial function can occur with mild increases in SPAP.