Echocardiographic Assessment of the Pulmonary Vein to Pulmonary Artery Ratio in Canine Heartworm Disease

Abstract

Background:Dirofilaria immitis produces proliferative pulmonary endarteritis and pulmonary thromboembolism in infected dogs. The pulmonary vascular lesions lead to irreversible and persistent structural damage and, as a consequence, sustained precapillary pulmonary hypertension (PH). The purpose of this study was to assess the diagnostic value of the pulmonary vein to pulmonary artery ratio (PV:PA ratio) to determine moderate or severe PH (>50 mmHg) in dogs with heartworm disease. Methods: A total of 151 naturally heartworm-infected and 66 healthy dogs were included in the study. The presence/absence of PH was based on the right pulmonary artery distensibility index (RPAD index < 29.5%), and the PV:PA ratio was echocardiographically measured by the time–motion mode (M mode) and two-dimensional mode (2D mode). Other echocardiographic parameters were also assessed (pulmonary trunk to aorta ratio, tricuspid regurgitation pressure gradient, and AT:ET ratio). Results: The results of the PV:PA ratio showed a highly positive correlation between the M and 2D modes (r = 0.928). The PV:PA ratio obtained by the M mode was identified as the strongest predictor for RPAD index (R2 0.628, p < 0.0001) with a good diagnostic accuracy (AUC = 0.99). The results of PV/PA by the 2D mode showed a similar prediction for the RPAD index (R2 0.606, p < 0.0001) with a good diagnostic accuracy (AUC = 0.98). Both of the 2D and M modes’ PV:PA ratios decreased significantly with the presence of PH. A cut-off value of ≤0.845 showed high sensitivity and specificity for the M mode (97% and 94%, respectively) and the 2D mode (96% and 93%, respectively). Conclusions: The PV:PA ratio may be useful as a complementary diagnostic method for the estimation of moderate or severe PH in dogs with heartworm.

Right Ventricle Strain Assessed by 2-Dimensional Speckle Tracking Echocardiography (2D-STE) to Evaluate Pulmonary Hypertension in Dogs with Dirofilaria immitis

“…The employment of RPADi has been ratified by numerous studies as a useful method to help in the detection of PH in dogs infected with D. immitis . In this study, PH was identified in 41% of dogs with heartworm, and in all cases, RPADi was <30% [ 23 , 24 , 28 , 30 ]. Additionally, previous studies have demonstrated statistically significant differences in dogs with PH compared to those without, regardless of whether they were healthy or infected with D. immitis [ 1 , 2 , 8 , 9 , 10 , 11 , 12 ].…”

“…This produces an increase in right ventricular afterload, which leads to a decrease in ventricular contraction (strain). PH is common in dogs with heartworm disease (although it is often not present), occurring in 30–67% of infected dogs (41% in the current study) [ 2 , 23 , 24 , 28 ]. When severe, PH can lead to R-CHF [ 2 , 28 ].…”

“…PH is common in dogs with heartworm disease (although it is often not present), occurring in 30–67% of infected dogs (41% in the current study) [ 2 , 23 , 24 , 28 ]. When severe, PH can lead to R-CHF [ 2 , 28 ].…”

“…Previous studies have found no evidence that sex, breed, weight, or age are risk factors for D. immitis infection [ 27 , 28 , 29 , 30 ]. In the present study, dogs with PH had a higher relative worm burden.…”

“…The presence or absence of PH was determined according to the American College of Veterinary Internal Medicine (ACVIM) guidelines [ 1 ]. The peak tricuspid regurgitation velocity to calculate the tricuspid regurgitation pressure gradient (TRPG) was the main measurement, while other routine measurements were used as previously described [ 1 , 23 , 24 , 25 ], such as the right pulmonary artery distensibility index (RPADi), the ratio of the pulmonary trunk to the ascending aorta in the right parasternal short-axis view (PT:Ao), the systolic displacement of the tricuspid annular muscle using a one-dimensional mode (TAPSE), and the maximum myocardial velocity (S’) measured in the lateral portion of the tricuspid annulus by tissue Doppler imaging [ 26 , 27 , 28 ]. The RPADi results were used to evaluate the results, based on previous studies in dogs with heartworm disease and PH [ 23 , 24 ], which demonstrated strong correlation with invasive “gold standard” systolic pulmonary artery pressures.…”