Determination of Tricuspid Regurgitation Velocity to Pulmonary Artery Flow Velocity Time Integral Ratio in Dogs with Pulmonary Hypertension

Abstract

Pulmonary hypertension (PH) is a hemodynamic state in which the pressure of the pulmonary arterial vasculature is elevated. It causes variable range of clinical signs, such as cough, dyspnea, syncope and right-sided congestive heart failure (RCHF). The importance in veterinary clinics is associated with myxomatous mitral valve disease (MMVD), because of negative prognostic influence of PH. Right-heart catheterization is known to be a gold standard technique for diagnosing PH, however, alternative echocardiography is widely used for the clinical diagnosis because of its availability and non-invasiveness. There are many echocardiographic indices for evaluation of PH such as tricuspid regurgitation pressure gradient (TRPG), flow profile of right ventricular outflow tract, a ratio between main pulmonary artery: aorta ratio (MPA:Ao) and right pulmonary artery distensibility index (RPAD index). This study was to determine the diagnostic value of systolic tricuspid regurgitation velocity to pulmonary artery flow velocity time integral ratio (TRV/VTIPA), as a novel index in veterinary medicine, to predict the Doppler estimates of dogs with TRPG compared with other cardiac indices of PH. Furthermore, a cutoff value was investigated to evaluate patients with potentially poor outcome. 144 dogs were recruited with clear systolic tricuspid regurgitation on Doppler echocardiography. The dogs were allocated into four groups based on the echocardiography estimated TRPG. The groups were: (1) the normal group, dogs with a TRPG less than 36 mmHg, (2) mild PH, dogs with a TRPG from 36 to 50 mmHg, (3) moderate PH, dogs with a TRPG from 50 to 75 mmHg and (4) severe PH, dogs with a TRPG over 75 mmHg. The correlation between the TRPG and cardiac indices was investigated. To define patients with poor outcome, dogs showed evidence of right sided congestive heart failure (RCHF) were included. Furthermore, the dogs in this group were compared with those without RCHF with TRPG more than 36 mmHg, in whom at least mild PH was suggested to be present. A TRV/VTIPA value increased significantly as the severity of PH increased (P < 0.001) and had correlation coefficient that was analogous to those of other conventional cardiac indices. A TRV/VTIPA value greater 1.65 provided the best-balanced sensitivity (84%) and specificity (80%) in determining patients with poor prognosis. The TRV/VTIPA, which is readily obtained using routine echocardiography, could provide a non-invasive novel and supplementary index for evaluating dogs with PH, which could provide clinically good prognostic criteria, particularly for those with advanced PH.