Accuracy of Doppler echocardiographic estimates of pulmonary artery pressures in a canine model of pulmonary hypertension

Retrospective evaluation of a right heart parameter score in the assessment of precapillary pulmonary hypertension in dogs (2017-2021): 135 cases

OBJECTIVE

To determine if emergency and critical care residents can identify moderate to severe precapillary pulmonary hypertension on cardiologist-obtained cineloops using a pulmonary hypertension score (PHS) and report the interobserver variability of the PHS.

DESIGN

Multicenter, retrospective, case-control study from 2017 to 2021.

SETTING

Private referral center and veterinary teaching hospital.

ANIMALS

One hundred and thirty-five client-owned dogs that underwent diagnostic echocardiography.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Medical records of dogs with stage B1 myxomatous mitral valve disease (MMVD) and dogs diagnosed with precapillary pulmonary hypertension (PCPH) via echocardiograms were reviewed. Dogs were categorized by a cardiologist into 5 groups (normal, B1 MMVD, mild, moderate, and severe PCPH) based on Doppler pulmonary pressure gradients and right heart morphology. Cineloops from each case were subjectively evaluated by emergency and critical care residents for the presence of right atrial and ventricular enlargement, right ventricular hypertrophy, interventricular septal flattening, and pulmonary artery and trunk enlargement to form a composite pulmonary hypertension score out of 8 (PHS8). When available, signs of peritoneal effusion and distention of the caudal vena cava were subjectively assessed to generate a pulmonary hypertension score out of 10 (PHS10). There was excellent discrimination of moderate to severe PCPH versus grouped absent to mild PCPH using PHS8 (area under the receiver operator curve [AUC] [95% confidence interval, CI] = 0.90 [0.84-0.95], P < 0.0001) and PHS10 (AUC [95% CI] = 0.89 [0.81-0.97], P < 0.0001). PHS8 ≥3 was 64% sensitive and 98% specific for moderate to severe PCPH (positive likelihood ratio [LR+] 32, negative likelihood ration [LR-] 0.37). PHS10 ≥ 3.3 was 64% sensitive and 92% specific for moderate to severe PCPH (LR+ 8, LR- 0.39). Interobserver agreement was good to excellent (intraclass correlation coefficient [ICC] = 0.74 [95% CI: 0.66-0.80], n = 135).

CONCLUSIONS

Residents identified moderate to severe PCPH in dogs using PHS on cineloops previously obtained by a cardiologist. The interrater agreement was good to excellent with limited training. Prospective studies to determine if residents can obtain diagnostic images for PHS are warranted.

Left ventricular eccentricity index to assess precapillary pulmonary hypertension in dogs

INTRODUCTION

Interventricular septal flattening, frequently present in pulmonary hypertension (PH) can be quantified by the left ventricular eccentricity index (EI) measured at end-diastole (EId), end-systole (EIs) and at maximal septal flattening (EIm). In humans, EI correlates with invasive pulmonary arterial pressure. The aim of this study was to evaluate if EI correlates with parameters of right heart remodeling (RHR) and if EI is a quantitative marker of PH in dogs.

MATERIALS AND METHODS

Left ventricular eccentricity indices were retrospectively measured in four groups (no, mild, moderate and severe PH) with interpretable tricuspid and/or pulmonary regurgitation.

RESULTS

Ninety-seven dogs were included, with no (n = 29), mild (n = 13), moderate (n = 25) and severe (n = 30) PH. The intra- and inter-observer variability for EI measurements ranged from 2 % to 11 %. All EI were significantly elevated in severe compared to no, mild and moderate PH (P < 0.0005). In the moderate group, EIs and EIm were higher compared to the no PH group (P < 0.01). Tricuspid and pulmonary regurgitation pressure gradients and RHR parameters correlated with EId, EIs and EIm in all groups. Optimal cut-off values discriminating moderate and severe PH from no and mild PH were 1.24 (Sensitivity (Se) 60 %; Specificity (Sp) 90 %) for EId, 1.34 (Se 67 %; Sp 95 %) for EIs and 1.37 (Se 76 %; Sp 83 %) for EIm.

CONCLUSIONS

Left ventricular eccentricity indices are reproducible echocardiographic variables increasing with severity of PH. Dogs with moderate and severe PH can be discriminated from dogs with no or mild PH using EIs and EIm.

Diagnostic value of two-dimensional echocardiographic measurements of the pulmonary artery diameter and the pulmonary artery distensibility index to detect pulmonary hypertension in horses

INTRODUCTION/OBJECTIVES

Echocardiographic diagnosis of pulmonary hypertension (PH) in horses is usually based on Doppler interrogation of tricuspid (TR) or pulmonic regurgitation (PR). This study aimed at investigating two-dimensional echocardiographic (2DE) variables, including pulmonary artery diameter (PAD) and pulmonary artery distensibility index (PADI), to diagnose PH.

ANIMALS, MATERIALS AND METHODS

41 healthy horses; 82 horses with TR or PR and normal intracardiac pressure gradients; and 35 horses with TR or PR velocities indicating PH. The 2DE variables were compared between groups, cut-offs for the diagnosis of PH were determined, and conditional inference trees served to identify the variable best predicting PH in the absence of TR or PR.

RESULTS

Horses with PH had larger end-diastolic cross-sectional (short-axis) PAD (PADed-sx) (5.8 ± 1.0 cm; mean ± SD) and smaller PADI[/PADps] (15.4 ± 7.7%) than healthy horses (5.0 ± 0.6 cm, P<0.0001; 20.5 ± 4.4%, P<0.001) and horses with TR or PR but no PH (5.3 ± 0.6 cm, P=0.003; 18.8 ± 4.2%, P=0.005). PADed-sx predicted PH with sensitivity (Se) = 36% and specificity (Sp) = 94% (cut-off 6.0 cm, AUC = 0.668, P=0.002), while PADI[/PADps] predicted PH with Se = 43% and Sp = 92% (cut-off 13.7%, AUC = 0.662, P=0.004). In the absence of TR, PADed-sx and the end-diastolic long-axis aortic diameter-to-PADed-sx ratio (AoDed-lx/PADed-sx) were most suitable to diagnose PH.

CONCLUSION

Pulmonary artery crosssectional (short-axis) diameter at end-diastole measured in a right-parasternal long axis view of the left ventricular outflow tract and Pulmonary artery distensibility index were moderately specific but not very sensitive to diagnosing PH. Nonetheless, they may be used as complementary indices suggesting PH in the absence of TR or PR.

Right ventricular size and function evaluated by various echocardiographic indices in dogs with pulmonary hypertension

BACKGROUND

Three-dimensional (3D) echocardiography and 2-dimensional (2D) strain measurements of the right ventricle (RV) are important indices in humans with pulmonary hypertension (PH) and need further evaluation in dogs with PH.

OBJECTIVES

To evaluate various RV size and function indices in dogs with PH and to examine differences between pre- and postcapillary PH.

ANIMALS

A total of 311 client-owned dogs: 100 dogs with PH, 31 with postcapillary and 69 with precapillary PH, and 211 healthy control dogs.

METHODS

Retro- and prospective, multicenter study. Size and function of the RV was determined using several indices, derived using dedicated RV software, including 3D RV end-diastolic volume (EDVn), end-systolic volume (ESVn), ejection fraction, 2D global and free wall RV longitudinal strain (RVLS), end-diastolic area, end-systolic area, fractional area change, tricuspid annular plane systolic excursion, and tissue Doppler imaging-derived systolic myocardial velocity of the lateral tricuspid annulus (S'n).

RESULTS

The EDVn (1.8 vs 2.5 mL/kg^0.942 , P < .01) and ESVn (0.8 vs 1.2 mL/kg^0.962 , P < .001) were significantly larger in the PH group compared to healthy controls. Free wall RVLS was decreased in dogs with severe PH compared to controls (-24% vs -29.6%, P < .001). Dogs with precapillary PH had worse RV systolic function than dogs with postcapillary PH.

CONCLUSION

Three-dimensional echocardiography of the RV is a promising tool to detect RV changes in dogs with PH. Also, 2D strain measurements are able to detect decreased RV function and offer several advantages compared to conventional indices.

Incremental predictive value of echocardiographic indices of right ventricular function in the assessment of long-term prognosis in dogs with myxomatous mitral valve disease

INTRODUCTION

Few studies have evaluated the utility of echocardiographic indices of right ventricular (RV) function in predicting prognosis in dogs with myxomatous mitral valve disease (MMVD).

ANIMALS

Sixty-seven client-owned dogs were diagnosed with MMVD.

MATERIALS AND METHODS

clinical cohort study. Dogs diagnosed with American college of veterinary internal medicine (ACVIM) stage B2, C or D between April 2014 and March 2017 were enrolled. Long-term outcomes were assessed by telephone or from the medical record. The primary end-point was defined as cardiac-related death. Echocardiographic indices of RV function, including the RV Tei index, free wall and septal RV longitudinal strain, were obtained. Univariable and multivariable Cox proportional hazard analyses were used to identify variables predictive of cardiac-related death.

RESULTS

Twenty-four dogs died during the follow-up period. The median follow-up time was 482 days, and the median survival time for dogs with cardiac-related death was 230 days. For cardiac-related death, peak early diastolic mitral inflow velocity, ACVIM stage C or D, tricuspid regurgitation velocity, RV Tei index and RV end-diastolic area were predictors in univariable Cox proportional hazard analysis. In multivariable Cox proportional analysis adjusted for the left atrial to aorta ratio, peak early diastolic mitral inflow velocity and ACVIM stage, an increase in the Tei index by 0.1 increased the hazard ratio of cardiac-related death by 33% (95% confidence interval, 16-70%; P = 0.002).

CONCLUSIONS

In dogs with MMVD, RV dysfunction assessed by the Tei index is an independent predictor of cardiac-related death.

Utility of Computed Tomographic Angiography for Pulmonary Hypertension Assessment in a Cohort of West Highland White Terriers With or Without Canine Idiopathic Pulmonary Fibrosis

West Highland white terriers (WHWTs) affected with canine idiopathic pulmonary fibrosis (CIPF) are at risk of developing precapillary pulmonary hypertension (PH). In humans, thoracic computed tomography angiography (CTA) is commonly used to diagnose and monitor patients with lower airway diseases. In such patients, CTA helps to identify comorbidities, such as PH, that could negatively impact prognosis. Diameter of the pulmonary trunk (PT), pulmonary trunk-to-aorta ratio (PT/Ao), and right ventricle-to-left ventricle ratio (RV/LV) are CTA parameters commonly used to assess the presence of PH. Pulmonary vein-to-right pulmonary artery ratio (PV/PA) is a new echocardiographic parameter that can be used in dogs to diagnose PH. The primary aim of this study was to evaluate the use of various CTA parameters to diagnose PH. An additional aim was to evaluate the correlation of RV/LV measurements between different CTA planes. CTA and echocardiography were prospectively performed on a total of 47 WHWTs; 22 affected with CIPF and 25 presumed healthy control dogs. Dogs were considered to have PH if pulmonary vein-to-right pulmonary artery ratio (PV/PA) measured on 2D-mode echocardiography was less than to 0.7. WHWTs affected with CIPF had higher PT/Ao compared with control patients. In WHWTs affected with CIPF, PT size was larger in dogs with PH (15.4 mm) compared with dogs without PH (13 mm, p = 0.003). A cutoff value of 13.8 mm predicted PH in WHWTs affected with CIPF with a sensitivity of 90% and a specificity of 87% (AUC = 0.93). High correlations were observed between the different CTA planes of RV/LV. Results suggest that diameter of the PT measured by CTA can be used to diagnose PH in WHWTs with CIPF.

Histopathological changes of pulmonary vascular remodeling in dogs affected with pulmonary hypertension secondary to degenerative mitral valve disease

INTRODUCTION/OBJECTIVES

Pulmonary hypertension (PH) can cause pulmonary arterial remodeling. Medial remodeling is a structural change of the pulmonary artery seen with PH. Hyperplasia and hypertrophy of pulmonary arterial smooth muscle cells (SMCs) are suggested as causes of medial remodeling. To demonstrate the histopathological changes of the pulmonary artery in dogs affected with PH secondary to degenerative mitral valve disease (DMVD) compared with DMVD without PH and control dogs.

ANIMALS

Lung samples obtained from the carcasses of 19 older small-breed dogs (Control, n = 5; DMVD, n = 7; DMVD + PH, n = 7).

MATERIALS AND METHODS

Lung tissue sections were stained with hematoxylin and eosin, Masson's trichrome, and proliferating cell nuclear antigen (PCNA) immunohistochemistry.

RESULTS

The internal diameters of the pulmonary artery in the three groups were not different. Masson's trichrome staining revealed no collagen deposition in the intimal layer of the pulmonary artery in all dogs. The external diameter, percentage of medial thickness (%MT), percentage of SMC layer and collagen deposition areas, average number of SMCs, and the percentage of PCNA positive cells (%PCNA) of the pulmonary artery were increased in the DMVD and DMVD + PH groups compared with the control group. The %PCNA in the DMVD + PH group was significantly decreased when compared with the DMVD group.

CONCLUSIONS

Medial remodeling was found in left-sided heart failure DMVD dogs with and without PH. The medial remodeling in DMVD dogs with and without PH is related to SMC hyperplasia, hypertrophy, and collagen deposition, leading to an increased medial layer thickness of the pulmonary artery.

The prevalence of pulmonary hypertension assessed using the pulmonary vein-to-right pulmonary artery ratio and its association with survival in West Highland white terriers with canine idiopathic pulmonary fibrosis

Background

Pulmonary hypertension (PH) is a known co-morbidity in West Highland white terriers (WHWTs) affected with canine idiopathic pulmonary fibrosis (CIPF). The pulmonary vein-to-right pulmonary artery ratio (PV/PA) has recently been described for the detection of pre-capillary PH in dogs. The objective of the present study was to estimate the prevalence of PH at diagnostic, in WHWTs affected with CIPF, by using PV/PA, in comparison with a group of healthy breed-matched controls (CTRLs). Additional study objective was to explore whether the presence of PH at initial diagnosis of CIPF impacted survival time in dogs treated with sildenafil.

Results

Twenty-five client-owned WHWTs presented with CIPF and 19 CTRLs were included in the study. PV/PA in either two-dimensional mode (2D) or time-motion mode or both were measured from cineloops in each dog. Dogs were classified according to PV/PA value into non/mild PH (PV/PA measured in 2D ≥ 0.7) or moderate/severe PH (PV/PA < 0.7). Survival data of WHWTs affected with CIPF were extracted from medical record to assess association between presence of PH at diagnosis and outcome. 60 % overall prevalence for moderate/severe PH was estimated in this cohort of WHWTs presented with CIPF vs. 5 % in CTRLS (P = 0.0002). The presence of moderate/severe PH at initial presentation was not associated with survival.

Conclusions

Results of the present study confirm a high prevalence of PH at diagnosis in WHWTs affected with CIPF and highlight the utility of PV/PA as a non-invasive surrogate for assessment of PH in this population.

Accuracy of echocardiographically estimated pulmonary artery pressure in dogs with myxomatous mitral valve disease

INTRODUCTION

Echocardiographically identified pulmonary hypertension is an independent predictor of poor outcome in dogs affected by myxomatous valvular degeneration (MMVD). Systolic pulmonary arterial pressure is routinely estimated based on its relationship with the Doppler-determined velocity of tricuspid regurgitation as defined by the simplified Bernoulli equation (sPAP_D). Experimental studies suggest that the method is imperfect, but its accuracy in dogs with MMVD is not known.

ANIMALS

Twenty dogs affected by MMVD that had cardiac remodeling and measurable tricuspid regurgitation.

METHODS

A flow-directed thermodilution monitoring catheter was percutaneously placed in the right external jugular vein and advanced to the main pulmonary artery. Pulmonary arterial systolic pressure was recorded (systolic pulmonary arterial pressure obtained by right heart catheterization [sPAP_C]). A second operator contemporaneously acquired tricuspid regurgitant velocity spectra to calculate sPAP_D. Each operator was blinded to the result of the other techniques.

RESULTS

Technical difficulties prevented the analysis of catheterization data in two dogs. Eighteen measurement pairs were therefore used for comparison of sPAP_C and sPAP_D through correlation and Bland-Altman analysis. A statistically significant bias between sPAP_C and sPAP_D (mean difference = 0.5 mmHg; confidence interval = -6.5 mmHg, +7.5 mmHg) was not detected. The interval of agreement between the techniques was wide (-27.3 mmHg, +28.2 mmHg). A significant linear association between the two techniques was not identified (r = 0.11, p=0.17).

CONCLUSION

Echocardiographically estimated pulmonary artery pressure poorly agrees with sPAP_C measurement in dogs affected by MMVD and cardiac remodeling with or without previously diagnosed congestive heart failure. In these dogs, sPAP_D could under- or over-estimate sPAP_C by more than 20 mmHg, and therefore caution should be used when interpreting sPAP_D.

Intracardiac heartworms in dogs: Clinical and echocardiographic characteristics in 72 cases (2010-2019)

BACKGROUND

Heartworms, a cause of pulmonary hypertension (PH) in dogs, can migrate from the pulmonary arteries into the heart resulting in life-threatening caval syndrome (CS).

OBJECTIVES

To describe clinical and echocardiographic characteristics in dogs with intracardiac heartworms including estimated heartworm burden and frequency of PH and pigmenturia.

ANIMALS

Seventy-two client-owned dogs with heartworms.

METHODS

Retrospective study. Data collected from an electronic medical records search for dogs with intracardiac heartworms included clinicopathologic, echocardiographic, and procedural findings. Dogs with heartworms isolated to the pulmonary arteries were excluded.

RESULTS

Estimated intracardiac heartworm burden was low in 14 of 72 (19%) and high in 58 of 72 (81%) dogs. The majority were small breed (54/72; 75%; 29/72; 40% Chihuahuas) and had a high likelihood of PH (67/72; 93%). Pigmenturia was the second most common clinical finding (31/72; 43%) after lethargy (32/72; 44%). Anemia (37/55; 36%), pigmenturia (30/58; 52%), and bilirubinuria (28/36; 78%) were significantly more common in dogs with a high worm burden (P < .05). Based on the presence of anemia, pigmenturia, and clinical signs, 18 of 72 dogs (25%) were considered to have CS.

CONCLUSIONS AND CLINICAL IMPORTANCE

Although the majority of dogs with intracardiac heartworms had a high worm burden and high likelihood of PH, only 25% had clinical evidence of CS. Echocardiography is a useful tool to identify intracardiac heartworms, detect likelihood of PH, and could be useful for staging heartworm positive small breed dogs for intracardiac heartworm migration.

Utility of tricuspid annular plane systolic excursion normalized by right ventricular size indices in dogs with postcapillary pulmonary hypertension

Background

Tricuspid annular plane systolic excursion (TAPSE) is a common right ventricular (RV) function indicator. However, TAPSE was not decreased in dogs with myxomatous mitral valve disease (MMVD) and postcapillary pulmonary hypertension (PH) because of its load, angle, and body weight dependency, and TAPSE was considered a preload‐dependent index.

Objectives

To evaluate the utility of TAPSE normalized by RV size in dogs with postcapillary PH.

Animals

Twenty healthy dogs and 71 MMVD dogs with or without PH.

Methods

In this prospective observational study, end‐diastolic RV internal dimension (RVIDd), end‐diastolic and end‐systolic RV area, and end‐diastolic RV wall thickness were measured as RV size indices. The TAPSE was measured using B‐mode and M‐mode methods. Normalized TAPSE was calculated by dividing TAPSE by each RV size index. The RV strain was obtained as the detailed RV function using 2‐dimensional speckle tracking echocardiography. All indices were compared among the PH severity groups and in the presence of right‐sided congestive heart failure (R‐CHF).

Results

Although nonnormalized TAPSE was higher with PH severity progression, each normalized TAPSE showed a significant decrease in the severe PH group (P < .05). The TAPSE_B‐mode/RVIDd ratio had high area under the curve to predict R‐CHF and had moderate correlation with RV strain (P < .05). The TAPSE_B‐mode/RVIDd and left atrial‐to‐aortic diameter ratios were independent predictors for R‐CHF.

Conclusions and Clinical Importance

Normalized TAPSE could reflect RV systolic dysfunction in dogs with severe PH, which could not be detected by nonnormalized TAPSE. The TAPSE_B‐mode/RVIDd ratio might predict R‐CHF with high sensitivity and reproducibility.

Symmetric dimethylarginine in dogs with myxomatous mitral valve disease at various stages of disease severity

Symmetric dimethylarginine (SDMA) is a serum biomarker of renal damage in dogs. Moreover, SDMA concentration is an independent predictor of development of severe heart failure (HF) in humans with cardiac disease. This study evaluates whether the serum concentration of SDMA in dogs with myxomatous mitral valve disease (MMVD) is influenced by the severity of heart disease, pulmonary hypertension (PH) and treatment of HF. A total of 99 client-owned dogs were included in this retrospective case-control study; 78 dogs were affected by MMVD and classified according to the American College of Veterinary Internal Medicine (ACVIM) guidelines, and 21 were healthy controls. For each dog, history, physical examination, complete blood count, biochemical profile, thoracic radiography, 6-lead standard electrocardiogram and trans-thoracic echocardiography were available. Comparisons were performed between groups of dogs belonging to different ACVIM stages and between dogs with and without PH. The median SDMA concentration was neither significantly different among groups of dogs in different disease stages (overall P = 0.010), nor among dogs with MMVD, nor between those with [14.5 μg/dl (10.5–18.8)] and without PH [13 μg/dl (9–17.2)] (P = 0.295). The concentration of SDMA did not differ between dogs when considering the combined effect of the ACVIM group and cardiac treatment (overall P = 0.486). Furthermore, no correlation was found between SDMA concentration and radiographic and echocardiographic parameters associated with increased MMVD severity. In conclusion, this study failed to demonstrate the presence of renal impairment in dogs with MMVD, and the increase in renal parameters in some dogs in the more advanced stage of MMVD could be attributed to pre-renal azotemia.

Survival characteristics and prognostic importance of echocardiographic measurements of right heart size and function in dogs with pulmonary hypertension

BACKGROUND

The clinical relevance of echocardiographic measurements of right heart size and function in dogs with pulmonary hypertension (PH) is unknown.

OBJECTIVE

To determine if echocardiographic measurements of right heart size and right ventricular (RV) function are associated with survival times in dogs with PH.

ANIMALS

Eighty-two client-owned dogs.

METHODS

Retrospective study where data from medical records and baseline echocardiographic examinations were collected and measured in a standardized manner. Owners or primary veterinarians were contacted for outcome data.

RESULTS

Enlargement of the right atrium (88%), RV (69%), and pulmonary artery (72%) was common. One-third of the cases had reduced RV function quantified by two-dimensional echocardiography-derived tricuspid annular plane systolic excursion (TAPSE). Decreased TAPSE was significantly (P = .008) more common in dogs with PH not secondary to left heart disease (LHD; 43%) compared to dogs with PH secondary to LHD (14%) but median survival times (182, 95% confidence interval [CI] = 39-309 versus 298, 95% CI = 85-314 days, respectively) were not significantly different (P = .78). Right atrial area (hazard ratio [HR] = 2.72, 95% CI = 1.58-4.70), TAPSE < 3.23 mm/kg^0.284 (HR = 2.19, 95% CI = 1.28-3.74), and right heart failure (HR = 2.05, 95% CI = 1.18-3.57) were independently associated with shorter survival time (P ≤ .04).

CONCLUSIONS AND CLINICAL IMPORTANCE

Right atrial area, RV function (TAPSE < 3.23 mm/kg^0.284 ), and right heart failure offer clinically relevant prognostic information in dogs with PH. Results support the quantitative assessment of right heart size and function in dogs with PH.

ACVIM consensus statement guidelines for the diagnosis, classification, treatment, and monitoring of pulmonary hypertension in dogs

Pulmonary hypertension (PH), defined by increased pressure within the pulmonary vasculature, is a hemodynamic and pathophysiologic state present in a wide variety of cardiovascular, respiratory, and systemic diseases. The purpose of this consensus statement is to provide a multidisciplinary approach to guidelines for the diagnosis, classification, treatment, and monitoring of PH in dogs. Comprehensive evaluation including consideration of signalment, clinical signs, echocardiographic parameters, and results of other diagnostic tests supports the diagnosis of PH and allows identification of associated underlying conditions. Dogs with PH can be classified into the following 6 groups: group 1, pulmonary arterial hypertension; group 2, left heart disease; group 3, respiratory disease/hypoxia; group 4, pulmonary emboli/pulmonary thrombi/pulmonary thromboemboli; group 5, parasitic disease (Dirofilaria and Angiostrongylus); and group 6, disorders that are multifactorial or with unclear mechanisms. The approach to treatment of PH focuses on strategies to decrease the risk of progression, complications, or both, recommendations to target underlying diseases or factors contributing to PH, and PH‐specific treatments. Dogs with PH should be monitored for improvement, static condition, or progression, and any identified underlying disorder should be addressed and monitored simultaneously.

Clinical features and outcome in 25 dogs with respiratory-associated pulmonary hypertension treated with sildenafil

Background

Pulmonary hypertension (PH) can develop secondary to many common cardiopulmonary diseases, and the use of sildenafil has improved care of affected dogs.

Objective

To evaluate response to sildenafil in dogs with respiratory‐associated PH.

Animals

Twenty‐five dogs with PH.

Methods

Prospective clinical trial. Doppler echocardiography identified dogs with moderate to severe PH, and additional tests were performed to detect underlying diseases. A 17‐point quality of life (QOL) questionnaire was completed, and sildenafil was prescribed, along with other medications deemed necessary for the management of clinically diagnosed respiratory diseases. After 30 days, dogs returned to the hospital for repeat echocardiogram and QOL survey.

Results

The median age was 12.4 years, and most dogs were small breed dogs (median weight, 6.5 kg). Syncope (64%), cough (56%), and respiratory difficulty (32%) were the most common presenting complaints. Respiratory diseases associated with PH included tracheobronchomalacia, pulmonary fibrosis, inflammatory airway disease, and brachycephalic syndrome, with multiple diseases in some dogs. Eight of 25 dogs (32%) died or were euthanized within 1 month. In the remaining dogs, tricuspid regurgitation pressure gradient (83.0 ± 17.4 mm Hg before, 55.4 ± 17.4 mm Hg after) and QOL scores were significantly improved after 1 month of sildenafil. Fifty percent mortality was reached 6 months after study entry, with 4 dogs alive 5 years after diagnosis.

Conclusions and Clinical Importance

Sildenafil responsiveness is variable in dogs with respiratory‐associated PH, but improved QOL was demonstrated in dogs surviving >1 month, and long‐term survival was noted in some cases.

Prognostic value of right pulmonary artery distensibility in dogs with pulmonary hypertension

The right pulmonary artery distensibility (RPAD) index has been used in dogs with pulmonary hypertension (PH) caused by heartworm infection, myxomatous mitral valve disease, or patent ductus arteriosus. We hypothesized that this index correlates with the tricuspid regurgitation pressure gradient (TRPG) assessed by echocardiography and could predict survival in dogs with PH secondary to various causes. To assess this hypothesis, the medical records of 200 client-owned dogs at a referral institution were retrospectively reviewed. The RPAD index and the ratios of acceleration time to peak pulmonary artery flow (AT) and to the ejection time of pulmonary artery flow (ET) were recorded for each dog. The owners were contacted for follow-up assessments. The findings indicated that the RPAD index was correlated with the TRPG (R² = 0. 362, p < 0.001). The survival time was significantly shorter in dogs with an RPAD index ≤ 21% that were followed up for 3 months and in dogs with an RPAD index ≤ 24% that were followed up for 1 year. Thus, the RPAD index was correlated with the TRPG and could predict the clinical outcome in dogs with PH caused by various diseases. This index could be used to evaluate the severity of PH in dogs without tricuspid regurgitation.

Relationship between right heart echocardiographic parameters and invasive pulmonary artery pressures in canine models of chronic embolic pulmonary hypertension

Basic information related to the association between right heart echocardiographic parameters and invasive pulmonary artery pressure (PAP) in dogs with pulmonary hypetension (PH) is scarce. The aim of this study was to examine the association between conventional right heart echocardiographic parameters and invasive PAP by right heart catheterization (RHC) before and after PH. Five female beagle dogs regarded as clinically healthy were used. Echocardiography and RHC were conducted before and after creating chronic embolic pulmonary hypertension (CEPH) models. The acceleration time to ejection time ratio in pulmonary artery flow profile (AT/ET), the ratio of the pulmonary artery and aortic diameter in diastole (PA/Ao), the right pulmonary artery distensibility index by M-mode method (RPAD _M-mode), the normalized right ventricular internal diameter in diastole (RVIDdn), and the normalized tricuspid annular plane systolic excursion (TAPSEn) were correlated with the invasive systolic PAP (sPAP), mean PAP (mPAP) and diastolic PAP (dPAP). Multiple linear regression analysis identified AT/ET and RVIDdn as independent predictors of sPAP, PA/Ao and RVIDdn as independent predictors of mPAP, and PA/Ao and RPAD _M-mode as independent predictors of dPAP. AT/ET and PA/Ao had high sensitivity and specificity for predicting CEPH. In conclusion, AT/ET, PA/Ao, RPAD _M-mode, RVIDdn and TAPSEn were significantly correlated with invasive PAP and alterations in PA/Ao or AT/ET might enable clinicians to predict PH, even if tricuspid regurgitation is not observed.

Correlation between Echocardiography and Cardiac Catheterization for the Assessment of Pulmonary Hypertension in Pediatric Patients

Introduction

Cardiac catheterization is widely considered the “gold standard” for the diagnosis of pulmonary hypertension. However, its routine use is limited due to its invasive nature. Therefore, the aim of this study was to evaluate the correlation between pulmonary artery pressures obtained by various parameters of transthoracic echocardiography and cardiac catheterization.

Methods

This study includes 50 consecutive patients with intracardiac shunt lesions diagnosed with severe pulmonary hypertension on echocardiography and admitted for cardiac catheterization at the National Institute of Cardiovascular Diseases (NICVD) in Karachi, Pakistan. Cardiac catheterization and transthoracic echocardiography were performed in all patients simultaneously and systolic (sPAP) and mean pulmonary artery pressure (mPAP) were assessed with both modalities. Correlations and agreement, in terms of Bland-Altman plot, were computed between both modalities for sPAP and mPAP.

Results

Out of 50 patients, 46% (23) were male and mean age was 7.49 ± 4.45 years. On cardiac catheterization, sPAP was 93.92 ± 17.91 mmHg and mPAP was 67.0 ± 14.28 mmHg. Correlation between cardiac catheterization and echocardiography for the assessment of sPAP was 0.917 (p<0.001), and mPAP was 0.832 (p<0.001) for mean gradient of tricuspid regurgitation (PGTRmean), 0.749 (p<0.001) for peak gradient of pulmonary regurgitation (PGPRpeak), 0.691 (p<0.001) for Acceleration time across right ventricular outflow tract (RVOT), and 0.752 (p<0.001) for end gradient of pulmonary regurgitation (PGPRend). Bland-Altman plot showed moderate agreement between two modalities.

Conclusion

A positive but modest correlation was observed between hemodynamic parameters of transthoracic echocardiography and cardiac catheterization for assessment of pulmonary artery pressures. Transthoracic echocardiography can reliably be used as an initial non-invasive modality for the assessment of pulmonary artery hypertension and can obviate the need of right heart catheterization in some patient especially with mild pulmonary hypertension.

Pulmonary hypertension secondary to respiratory disease and/or hypoxia in dogs: Clinical features, diagnostic testing and survival

Pulmonary hypertension (PH) is associated with substantial morbidity and if untreated, mortality. The human classification of PH is based on pathological, hemodynamic characteristics, and therapeutic approaches. Despite being a leading cause of PH, little is known about dogs with respiratory disease and/or hypoxia (RD/H)-associated PH. Therefore, our objectives were to retrospectively describe clinical features, diagnostic evaluations, final diagnoses and identify prognostic variables in dogs with RD/H and PH. In 47 dogs identified with RD/H and PH, chronic airway obstructive disorders, bronchiectasis, bronchiolar disease, emphysema, pulmonary fibrosis, neoplasia and other parenchymal disorders were identified using thoracic radiography, computed tomography, fluoroscopy, tracheobronchoscopy, bronchoalveolar lavage, and histopathology. PH was diagnosed using transthoracic echocardiography. Overall median survival was 276.0 days (SE, 95% CI; 216, 0-699 days). Dogs with an estimated systolic pulmonary arterial pressure (sPAP) ≥47mmHg (n=21; 9 days; 95% CI, 0-85 days) had significantly shorter survival times than those <47mmHg (n=16; P=0.001). Estimated sPAP at a cutoff of ≥47mmHg was a fair predictor of non-survival with sensitivity of 0.78 (95% CI, 0.52-0.94) and specificity of 0.63 (95% CI, 0.38-0.84). Phosphodiesterase-5 (PDE5) inhibitor administration was the sole independent predictor of survival in a multivariable analysis (hazard ratio: 4.0, P=0.02). Canine PH is present in a diverse spectrum of respiratory diseases, most commonly obstructive disorders. Similar to people, severity of PH is prognostic in dogs with RD/H and PDE5 inhibition could be a viable therapy to improve outcome.

Diagnostic value of the pulmonary vein-to-right pulmonary artery ratio in dogs with pulmonary hypertension of precapillary origin

INTRODUCTION

Non-invasive diagnosis of pulmonary hypertension (PH) relies on estimation of pulmonary arterial pressure (PAP) via Doppler echocardiographic measurement of tricuspid regurgitation pressure gradient (TRPG). The pulmonary vein-to-right pulmonary artery ratio (PV/PA) recently has been described for the detection of pulmonary venous congestion. Whether this variable could be used to detect the presence of precapillary PH is unknown. The objective of the present study was to investigate the diagnostic value of PV/PA for prediction of TRPG, as a surrogate of PAP, in dogs with PH of precapillary origin.

ANIMALS

Sixty-seven client-owned dogs were included in the study.

METHODS

This was a retrospective study. Dogs with a measurable TRPG were included and classified into group 1 (TRPG < 30 mmHg), group 2 (TRPG 30-49 mmHg), group 3 (TRPG 50-80 mmHg), or group 4 (TRPG > 80 mmHg). The PV/PA, acceleration time-to-ejection time ratio of pulmonary artery flow, main pulmonary artery diameter-to-aortic diameter ratio, and right pulmonary artery distensibility index were measured retrospectively from cineloops in each dog.

RESULTS

The PV/PA measured by both two-dimensional (2D) and time-motion mode(MM) echocardiography decreased proportionally with PH severity. Using regression analysis, PV/PA (2D) was identified as the strongest predictor for TRPG (R² = 0.70, p < 0.0001) among other variables studied, with a good diagnostic accuracy (area under the curve = 0.94) for moderate PH (TRPG > 50 mmHg) using a cutoff value of < 0.70 (sensitivity = 96%, specificity = 82%).

CONCLUSIONS

Results of the present study suggest that PV/PA can be useful as an additional, non-invasive, and indirect variable to identify precapillary PH in dogs.

The utility of point-of-care ultrasound right-sided cardiac markers as a screening test for moderate to severe pulmonary hypertension in dogs

Dogs with respiratory disease can develop pulmonary hypertension (PH), a comorbid condition that can impact therapy and prognosis. Without confirmation using the criterion standard of echocardiography, this complication may be missed. Point-of-care ultrasound (POCUS) is a simple, non-invasive screening test that may suggest PH. It was hypothesized that in dogs POCUS right-sided cardiac markers (R-SCM) at the subxiphoid view would predict moderate to severe PH confirmed by echocardiography. Forty-three client-owned dogs that underwent respiratory evaluation with POCUS and echocardiography were included. POCUS R-SCM evaluated in the subxiphoid view included subjective caudal vena cava distention (CVC_sx), CVC_sx >1cm, gallbladder wall edema and ascites. PH was defined by tricuspid regurgitation pressure gradient (TRPG) as mild (30-49.9mmHg), moderate (50-74.9mmHg) or severe (>75mmHg). POCUS subxiphoid views were blindly evaluated post hoc and compared to echocardiography. Chi square test and one-way ANOVA were used to evaluate correlations between POCUS R-SCM and echocardiographic diagnosis of moderate to severe PH. Twenty-six dogs with PH, and 17 dogs without PH, were enrolled. There was no significant difference in the presence or absence of any R-SCM between dogs with and without PH. When dogs with no PH and mild PH were grouped and compared to dogs with moderate to severe PH (i.e., dogs for which treatment for PH would be recommended), no significant differences in R-SCM were noted. POCUS R-SCM using the CVC_sx view was not a sensitive screening test to identify dogs with PH in this study population.

Clinical efficacy of tadalafil compared to sildenafil in treatment of moderate to severe canine pulmonary hypertension: a pilot study

INTRODUCTION

Canine pulmonary hypertension (PH) is associated with high morbidity and mortality. Tadalafil, a phosphodiesterase-5 inhibitor used commonly in humans with PH, has not been evaluated in a clinical trial in dogs with naturally occurring PH. Our objectives were to compare the efficacy of tadalafil and sildenafil on PH assessed by peak tricuspid regurgitant flow velocity, estimated systolic pulmonary arterial pressure gradient, voluntary activity, quality of life, and safety profiles in dogs with moderate to severe PH.

ANIMALS

Twenty-three dogs with echocardiographic evidence of moderate to severe PH were enrolled.

METHODS

A prospective short-term, randomized, double-blinded pilot study was carried out. Dogs with PH were randomly allocated to receive sildenafil or tadalafil for 2 weeks and assessed via echocardiography, activity monitors, and owner-reported outcomes.

RESULTS

Collectively, phosphodiesterase-5 inhibition significantly decreased (improved) quality of life scores (p = 0.003) and visual analog score (p = 0.024) without significant between-treatment difference of these variables. Phosphodiesterase-5 inhibition did not significantly affect peak tricuspid regurgitant flow velocity (p = 0.056) or voluntary activity (p = 0.27). A total of 33% (7/21) of dogs experienced at least one adverse event during the study (tadalafil, n = 5; sildenafil, n = 2) with no significant difference between treatment type and incidence of adverse events (p = 0.36).

DISCUSSION

In this pilot study, phosphodiesterase-5 inhibition led to apparent improvement in quality of life scores without documenting superiority of tadalafil over sildenafil.

CONCLUSION

Tadalafil at a dose of 2 mg/kg once daily appears to be a viable alternative to sildenafil in dogs with moderate to severe PH.

The prevalence of pulmonary hypertension in Cavalier King Charles spaniels compared with other breeds with myxomatous mitral valve disease

INTRODUCTION

Pulmonary hypertension (PH) is a common consequence of myxomatous mitral valve disease (MMVD). Cavalier King Charles spaniels (CKCS) are frequently affected with MMVD and appear to have different disease progression compared to other dogs. This study aimed to determine if CKCS are more likely to develop PH as a result of MMVD than dogs of other breeds. A secondary aim was to explore whether breed or PH impacted survival.

ANIMALS

A total of 187 dogs diagnosed with MMVD, 94 CKCS and 93 non-CKCS, were included in this study.

METHODS

This is a retrospective review of dogs with MMVD. Data were analyzed for presence of PH, congestive heart failure (CHF) and echocardiographic variables including the ratio between mitral E wave velocity (E vel) and isovolumic relaxation time (E/IVRT) and were compared between CKCS/non-CKCS and dogs with/without PH. Survival analysis was also performed.

RESULTS

American College of Veterinary Internal Medicine (ACVIM) stage (p < 0.001), CKCS (p = 0.005), left atrium-to-aortic ratio (LA/Ao) (p < 0.001), E vel (p < 0.001) and log₁₀(E/IVRT) (p < 0.001) were significant at the univariate level for PH development. At the multivariate level, only ACVIM stage remained significant (p = 0.044), suggesting that worsening MMVD was the predominant determinant of PH development in this study. Pulmonary hypertension was associated with greater likelihood of CHF (p < 0.001) and death (both cardiac [p < 0.001] and all-cause mortality [p = 0.011]). Cavalier King Charles spaniels were more likely to experience cardiac death than non-CKCS (p = 0.004).

CONCLUSIONS

In this study, development of PH was associated with worse MMVD, according to ACVIM stage.

A Large Animal Model of Right Ventricular Failure due to Chronic Thromboembolic Pulmonary Hypertension: A Focus on Function

Chronic thromboembolic pulmonary hypertension (CTEPH) is a debilitating disease that progresses to right ventricular (RV) failure and death if left untreated. Little is known regarding the progression of RV failure in this disease, greatly limiting effective prognoses, and therapeutic interventions. Large animal models enable the use of clinical techniques and technologies to assess progression and diagnose failure, but the existing large animal models of CTEPH have not been shown to replicate the functional consequences of the RV, i.e., RV failure. Here, we created a canine embolization model of CTEPH utilizing only microsphere injections, and we used a combination of right heart catheterization (RHC), echocardiography (echo), and magnetic resonance imaging (MRI) to quantify RV function. Over the course of several months, CTEPH led to a 6-fold increase in pulmonary vascular resistance (PVR) in four adult, male beagles. As evidenced by decreased cardiac index (0.12 ± 0.01 v. 0.07 ± 0.01 [L/(min^*kg)]; p < 0.05), ejection fraction (0.48 ± 0.02 v. 0.31 ± 0.02; p < 0.05), and ventricular-vascular coupling ratio (0.95 ± 0.09 v. 0.45 ± 0.05; p < 0.05), as well as decreased tricuspid annular plane systolic excursion (TAPSE) (1.37 ± 0.06 v. 0.86 ± 0.05 [cm]; p < 0.05) and increased end-diastolic volume index (2.73 ± 0.06 v. 2.98 ± 0.02 [mL/kg]; p < 0.05), the model caused RV failure. The ability of this large animal CTEPH model to replicate the hemodynamic consequences of the human disease suggests that it could be utilized for future studies to gain insight into the pathophysiology of CTEPH development, following further optimization.

Tricuspid valve dysplasia and a patent foramen ovale resulting in severe tricuspid regurgitation and right-heart dilation in a Red Angus calf

A two-month-old Red Angus heifer calf presented to the University of Wisconsin Veterinary Care for evaluation of suspected severe bronchopneumonia. Pertinent physical exam findings included tachycardia, tachypnea, dyspnea with a significant abdominal component, and cyanotic mucous membranes. On thoracic auscultation, wheezes were present bilaterally, as well as a grade 2/6 right apical systolic murmur. Thoracic radiographs revealed cardiomegaly, most severely affecting the right side. Echocardiography showed tricuspid valve dysplasia, resulting in severe tricuspid regurgitation and right-heart dilation, as well as a patent foramen ovale. A postmortem examination confirmed the presence of the aforementioned cardiac abnormalities and revealed only mild pulmonary changes. This case report is the first to describe tricuspid dysplasia in the absence of multiple, complex congenital cardiac abnormalities in a calf, and it highlights the value of echocardiography for an antemortem diagnosis.

Quantitative assessment of systolic and diastolic right ventricular function by echocardiography and speckle-tracking imaging: a prospective study in 104 dogs

Our aim was (1) to determine the within-day and between-day variability of several indices of systolic and diastolic right ventricular (RV) function by using conventional echocardiography and speckle-tracking echocardiography (STE) (Study 1), (2) to quantify these variables in a large healthy canine population (n = 104) with Doppler-derived estimated systolic pulmonary arterial pressure (SPAP) and left ventricular (LV) function, and (3) to establish the corresponding reference intervals (Study 2). For both studies, RV variables included tricuspid annular plane systolic excursion (TAPSE), right fractional area change (RFAC), STE longitudinal systolic strain (StS) of the RV free wall (RVFW) and of the entire RV (i.e., global RV StS), STE longitudinal systolic RVFW strain rate (SRS), and the diastolic early:late strain rate ratio. All but one within- and between-day coefficients of variation (13/14) were < 15%, the lowest being observed for TAPSE (3.6–9.8%), global RV StS (3.8–9.9%), and RVFW StS (3.7–7.3%). SPAP was weakly and negatively correlated with the TAPSE:body weight ratio (r_s = −0.26, p = 0.01) and RVFW SRS (r_s = −0.23, p < 0.05). Reference intervals (lower and upper limits with 90% confidence intervals) were provided for all variables. STE provides a non-invasive evaluation of RV function that may be used for clinical investigations in canine cardiology.

Echocardiographic Evaluation of the Right Atrial Area Index in Dogs with Pulmonary Hypertension

Background

Right atrial area (RAA) is a prognostic factor in human patients with pulmonary arterial hypertension (PAH). Reference intervals for RAA have been described in healthy dogs.

Objectives

To evaluate RAA indexed to the body surface area in dogs with PAH as an indicator of right atrial size, PAH severity and right‐sided congestive heart failure (R‐CHF).

Animals

A total of 119 client‐owned dogs, 48 dogs with PAH and 71 control dogs.

Methods

Prospective observational study. Pulmonary arterial hypertension was classified according to the tricuspid regurgitation pressure gradient (TRPG) as mild (36–50 mmHg), moderate (51–75 mmHg), or severe (>75 mmHg). The RAA index was calculated as the RAA divided by body surface area.

Results

The RAA index was higher in dogs with moderate PAH (13.3 cm²/m²; range, 3.4–24.7 cm²/m²) and severe PAH (12.1 cm²/m²; range, 5.4–21.8 cm²/m²) than in those with mild PAH (6.7 cm²/m²; range, 4.8–10.7 cm²/m²) or in controls (7.3 cm²/m²; range, 4.2–10.2 cm²/m²; P < 0.001). The RAA index was higher (P < 0.0001) in dogs with R‐CHF (17.5 cm²/m²; range, 12.7–24.7 cm²/m²) compared to those without R‐CHF (7.6 cm²/m²; range, 4.4–19.4 cm²/m²). The most accurate cutoff value of the RAA index to identify R‐CHF was >12.3 cm²/m² (sensitivity, 100%; specificity, 89.5%). In dogs with PAH, severity of tricuspid regurgitation (TR) was the only independent predictor of RAA index based on multivariate analysis (P < 0.02).

Conclusions and Clinical Importance

The RAA index can be used to evaluate right atrial size in dogs and may be more effective than TRPG in predicting R‐CHF in dogs with PAH. The severity of TR is the main determinant of the RAA index in dogs with PAH.

Utility of Tissue Doppler Imaging in the Echocardiographic Evaluation of Left and Right Ventricular Function in Dogs with Myxomatous Mitral Valve Disease with or without Pulmonary Hypertension

Background

In human medicine, right ventricular (RV) functional parameters represent a tool for risk stratification in patients with congestive heart failure caused by left heart disease. Little is known about RV alterations in dogs with left‐sided cardiac disorders.

Objectives

To assess RV and left ventricular (LV) function in dogs with myxomatous mitral valve disease (MMVD) with or without pulmonary hypertension (PH).

Animals

One‐hundred and fourteen dogs: 28 healthy controls and 86 dogs with MMVD at different stages.

Methods

Prospective observational study. Animals were classified as healthy or having MMVD at different stages of severity and according to presence or absence of PH. Twenty‐eight morphological, echo‐Doppler, and tissue Doppler imaging (TDI) variables were measured and comparison among groups and correlations between LV and RV parameters were studied.

Results

No differences were found among groups regarding RV echo‐Doppler and TDI variables. Sixteen significant correlations were found between RV TDI and left heart echocardiographic variables. Dogs with PH had significantly higher transmitral E wave peak velocity and higher E/eʹ ratio of septal (sMV) and lateral (pMV) mitral annulus. These 2 variables were found to predict presence of PH with a sensitivity of 84 and 72%, and a specificity of 71 and 80% at cut‐off values of 10 and 9.33 for sMV E/eʹ and pMV E/eʹ, respectively.

Conclusions and clinical importance

No association between variables of RV function and different MMVD stage and severity of PH could be detected. Some relationships were found between echocardiographic variables of right and left ventricular function.

Measurement Variation and Repeatability of Echocardiographic Variables Used to Estimate Pulmonary Artery Pressure in Dogs

Background

Pulmonary hypertension (PH) is an important clinical entity in dogs. Pulmonary hypertension is generally identified based on echocardiographic findings, but measurement variation of the variables most often used in this context has not been reported.

Objective

To define measurement variation of echocardiographic variables that are used to estimate pulmonary artery pressure.

Animals

Four dogs with subclinical tricuspid valve regurgitation were selected from a hospital population.

Methods

Prospective descriptive study ‐ dogs were subject to repeated echocardiographic examination by 2 operators. Each dog was echocardiographically examined 12 times, once by each operator during mornings and afternoons of 3 nonconsecutive days. Measurement variation was defined by coefficients of variation and by mean square errors (MSE) from ANOVA models. Repeatability coefficients (RC) were calculated from MSE.

Results

Of 50 within‐day, between‐day, and interoperator coefficients of variation (CVs), 37 were less than 10% and 46 were less than 15%. The range of peak velocity of tricuspid valve regurgitation (VTR) V_TR was 1.87–3.34 m/s. Analysis of variance revealed a significant effect (P < 0.05) of operator for 7 of 10 measurements. Within‐operator/between‐day/within‐subject and between‐operator/between‐day/within‐subject RCs of V_TR were, respectively, 0.3 and 0.6 m/s.

Conclusions and Clinical Importance

With regard to repeatability, V_TR is superior to other methods used for echocardiographic estimation of systolic pulmonary artery pressure. When TR is absent, the acceleration time of pulmonary ejection and the acceleration‐to‐ejection time ratio are alternative measures. A change in V_TR exceeding 0.3 m/s might be outside the range of expected within‐operator variation.

Review of Diagnostic and Therapeutic Approach to Canine Myxomatous Mitral Valve Disease

The most common heart disease that affects dogs is myxomatous mitral valve disease. In this article, we review the current diagnostic and therapeutic approaches to this disease, and we also present some of the latest technological advancements in this field.

Effect of Body Position, Exercise, and Sedation on Estimation of Pulmonary Artery Pressure in Dogs with Degenerative Atrioventricular Valve Disease

Background

Severity of pulmonary hypertension (PH) in dogs is related to clinical signs and prognosis.

Hypothesis/Objectives

We hypothesized that Doppler echocardiographic (DE) indices of pulmonary artery pressure (PAP) and pulmonary vascular resistance (PVR) are influenced by independent factors that create clinically important variability of DE‐based estimates of PH in dogs.

Animals

Thirty‐eight client owned dogs with naturally acquired degenerative atrioventricular valve disease and tricuspid regurgitation (TR).

Methods

Dogs were prospectively enrolled, and target variables were acquired during 4 echocardiographic study periods (lateral recumbency, standing, lateral recumbency after a 6‐minute walk test [6MWT], and lateral recumbency after sedation with butorphanol 0.25 mg/kg IM). Statistical methods included repeated measures ANOVA, mixed model analysis, and Chi‐squared test of association.

Results

There was a significant increase in peak TR flow velocity (TRFV; P < 0.01) after sedation in 78% of dogs, with TRFV increasing by >0.4 m/s in 42% of dogs, independent of stroke volume. A significant effect of study period on DE‐estimated PVR was not found (P = 0.15). There were negligible effects of sonographer, body position, and 6MWT on echocardiographic variables of PH. Clinically relevant cyclic variation of TRFV was found. There was an association between estimation of right atrial pressure based on subjective assessment and estimation based on cranial vena cava collapsibility (P = 0.03).

Conclusions and Clinical Importance

The increase in TRFV observed with sedation could change assessment of PH severity and impact prognostication and interpretation of treatment response. Further studies with invasive validation are needed.

Pulmonary arterial strain- and remodeling-induced stiffening are differentiated in a chronic model of pulmonary hypertension

Pulmonary hypertension (PH) is a debilitating vascular disease that leads to pulmonary artery (PA) stiffening, which is a predictor of patient mortality. During PH development, PA stiffening adversely affects right ventricular function. PA stiffening has been investigated through the arterial nonlinear elastic response during mechanical testing using a canine PH model. However, only circumferential properties were reported and in the absence of chronic PH-induced PA remodeling. Remodeling can alter arterial nonlinear elastic properties via chronic changes in extracellular matrix (ECM) content and geometry. Here, we used an established constitutive model to demonstrate and differentiate between strain-stiffening, which is due to nonlinear elasticity, and remodeling-induced stiffening, which is due to ECM and geometric changes, in a canine model of chronic thromboembolic PH (CTEPH). To do this, circumferential and axial tissue strips of large extralobar PAs from control and CTEPH tissues were tested in uniaxial tension, and data were fit to a phenomenological constitutive model. Strain-induced stiffening was evident from mechanical testing as nonlinear elasticity in both directions and computationally by a high correlation coefficient between the mechanical data and model (R²=0.89). Remodeling-induced stiffening was evident from a significant increase in the constitutive model stress parameter, which correlated with increased PA collagen content and decreased PA elastin content as measured histologically. The ability to differentiate between strain- and remodeling-induced stiffening in vivo may lead to tailored clinical treatments for PA stiffening in PH patients.

Red Blood Cell Distribution Width, Hematology, and Serum Biochemistry in Dogs with Echocardiographically Estimated Precapillary and Postcapillary Pulmonary Arterial Hypertension

Background

Red blood cell distribution width (RDW) is a quantitative measurement of anisocytosis. RDW has prognostic value in humans with different cardiovascular and systemic disorders, but few studies have investigated this biomarker in dogs.

Objectives

To compare the RDW in dogs with precapillary and postcapillary pulmonary hypertension (PH) and a control population of dogs and to correlate RDW with demographic, echocardiographic, and laboratory variables.

Animals

One hundred and twenty‐seven client‐owned dogs including 19 healthy dogs, 82 dogs with myxomatous mitral valve disease (50 dogs without PH and 32 dogs with postcapillary PH), and 26 dogs with precapillary PH.

Methods

Prospective study. Dogs were allocated to groups according to clinical and echocardiographic evaluation. RDW and selected laboratory and echocardiographic variables were compared among dog groups. Associations between RDW and demographic, laboratory, and echocardiographic variables were analyzed using correlation and multiple regression analysis.

Results

Median RDW in dogs with precapillary PH (13.8%, interquartile range 13.2–14.9%) and postcapillary PH (13.7, 13.2–14.7%) was significantly increased compared to healthy dogs (13.3, 12.3–13.7%; P < .05 for both comparisons), but only dogs with severe PH had significantly increased RDW compared to dogs without PH (P < .05). Peak tricuspid regurgitation pressure gradient was significantly associated with increased RDW (rho = 0.263, P = .007). Serum urea concentration, hematocrit, age, and white blood cell number were significantly associated with RDW in the multivariate analysis.

Conclusions and Clinical Importance

Underlying pathophysiologic processes associated with PH instead of severity of PH are likely responsible for increased RDW in dogs with PH.

Diagnostic Value of Right Pulmonary Artery Distensibility Index in Dogs with Pulmonary Hypertension: Comparison with Doppler Echocardiographic Estimates of Pulmonary Arterial Pressure

Background

Noninvasive diagnosis of pulmonary hypertension (PH) primarily relies upon Doppler echocardiography of tricuspid regurgitation (TR). However, TR might be absent or difficult to measure.

Hypothesis/Objectives

To determine the diagnostic value of right pulmonary artery distensibility (RPAD) index for prediction of Doppler‐derived estimates of pulmonary artery (PA) pressure compared to other indices of PH in dogs.

Animals

Sixty‐nine client‐owned dogs with TR.

Methods

Prospective observational study. Dogs were allocated to groups according to TR pressure gradient (TRPG): TRPG <36 mmHg (control, n = 22), TRPG 36–50 (n = 16), TRPG 50–75 (n = 14) and TRPG >75 mmHg (n = 17). Right pulmonary artery distensibility index, acceleration time to peak PA flow (AT), AT: ejection time of PA flow (AT:ET) and main PA size: aorta size (MPA:Ao) were calculated in each dog.

Results

Right pulmonary artery distensibility index demonstrated the strongest correlation (r = −0.90; P < .0001) to TRPG followed by MPA:Ao (r = 0.78; P < .0001), AT (r = −0.69; P < .0001) and AT:ET (r = −0.68; P < .0001). RPAD index possessed the most accurate cutoff (<29.5%; Sensitivity [Sn] 0.84, Specificity [Sp] 0.95) to predict TRPG >50 mmHg compared to AT (<53.9 ms; Sn 0.74, Sp 0.87), AT:ET (<0.30; Sn 0.61, Sp 0.97) and MPA:Ao (>1.04; Sn 0.94, Sp 0.74). All intra‐ and interobserver measurement variabilities exhibited coefficients of variation ≤13%.

Conclusions and Clinical Importance

Right pulmonary artery distensibility index is an accurate predictor of TRPG and should be particularly useful if TR is absent or difficult to measure.

Diagnostic Value of Selected Echocardiographic Variables to Identify Pulmonary Hypertension in Dogs with Myxomatous Mitral Valve Disease

Background

Pulmonary hypertension (PH) is commonly associated with myxomatous mitral valve disease (MMVD). Because dogs with PH present without measureable tricuspid regurgitation (TR), it would be useful to investigate echocardiographic variables that can identify PH.

Aim

To investigate associations between estimated systolic TR pressure gradient (TRPG) and dog characteristics and selected echocardiographic variables.

Animals

156 privately owned dogs.

Materials and Methods

Prospective observational study comparing the estimations of TRPG with dog characteristics and selected echocardiographic variables in dogs with MMVD and measureable TR.

Results

Tricuspid regurgitation pressure gradient was significantly (P < .05) associated with body weight corrected right (RVIDDn) and left (LVIDDn) ventricular end‐diastolic and systolic (LVIDSn) internal diameters, pulmonary arterial (PA) acceleration to deceleration time ratio (AT/DT), heart rate, left atrial to aortic root ratio (LA/Ao), and the presence of congestive heart failure. Four variables remained significant in the multiple regression analysis with TRPG as a dependent variable: modeled as linear variables LA/Ao (P < .0001) and RVIDDn (P = .041), modeled as second order polynomial variables: AT/DT (P = .0039) and LVIDDn (P < .0001) The adjusted R²‐value for the final model was 0.45 and receiver operating characteristic curve analysis suggested the model's performance to predict PH, defined as 36, 45, and 55 mmHg as fair (area under the curve [AUC] = 0.80), good (AUC = 0.86), and excellent (AUC = 0.92), respectively.

Conclusion and Clinical Importance

In dogs with MMVD, the presence of PH might be suspected with the combination of decreased PA AT/DT, increased RVIDDn and LA/Ao, and a small or great LVIDDn.