Accuracy of Noninvasively Determined Pulmonary Artery Pressure in Dogs With Myxomatous Mitral Valve Disease

Development of pulmonary hypertension is an independent predictor of poor outcome in dogs affected by myxomatous valvular degeneration (MMVD). Systolic pulmonary arterial pressure is routinely estimated by Doppler echocardiography applying the simplified Bernoulli equation to the velocity of tricuspid regurgitation (sPAP_D). The accuracy of this estimation is unknown in dogs with MMVD, but experimental studies suggest that the method is imperfect. In order to fill this knowledge gap we prospectively enrolled dogs affected by MMVD and cardiac remodeling - American College of Veterinary Internal Medicine (ACVIM) stages B2 and C MMVD for which treatment had been unchanged for at least one month. A flow-directed thermodilution monitoring catheter was percutaneously placed in the right jugular vein and advanced to the main pulmonary artery. Pulmonary arterial systolic pressure was recorded through this catheter connected to a pressure-transducer and data acquisition-analysis system (sPAP_C). A second operator simultaneously acquired tricuspid regurgitant velocity spectra to calculate sPAP_D. Each operator was blinded to the result of the other technique. Twenty dogs were enrolled. Technical difficulties prevented catheterization in 2 dogs. Eighteen measurement pairs were therefore used for comparison of sPAP_C and sPAP_D through Bland-Altman analysis and linear regression. A statistically significant bias between sPAP_C and sPAP_D (mean difference=0.5mmHg; Confidence interval: -6.5mmHg, +7.5mmHg) was not detected. The limits of agreement between the techniques were wide (-27.3mmHg, +28.2mmHg). Regression analysis failed to identify a significant linear association between the two techniques (r=0.11, p=0.17). In conclusion, sPAP_D poorly agrees with sPAP_C measurement in dogs affected by MMVD in ACVIM stages B2 and C. In these dogs, sPAP_D could under- or over-estimate sPAP_C by more than 20mmHg, and therefore caution should be used when interpreting PASP_D.