Right Ventricular Function

Effects of chemotherapy treatment with doxorubicin on right ventricular function in dogs

Left ventricular dysfunction in dogs after the administration of doxorubicin (DOX) has been extensively examined. However, the effects of DOX on right ventricular (RV) function remain unknown. Therefore, the present study investigated whether the chemotherapy treatment with DOX decreases RV function. Twelve dogs (five with multicentric lymphoma, four with hemangiosarcoma, two with thyroid cancer, and one with lung adenocarcinoma) that received at least two doses of DOX were prospectively enrolled. Echocardiography and the measurement of troponin I were performed prior to each administration of DOX and approximately one month after the last administration. Right ventricular function was assessed by the RV fractional area change and RV Tei index. Two (n=4), three (n=3), four (n=3), and five (n=2) doses of DOX were administered. While no significant differences were observed in the RV fractional area change, the RV Tei index was significantly impaired after two doses of DOX. Troponin I level significantly increased after four doses. Cumulative doses of DOX correlated with the RV Tei index (r=0.77, P<0.001). The present results demonstrated that the chemotherapy treatment with DOX decreased RV function in a dose-dependent manner in dogs.

Platelet hyperresponsiveness and increased platelet-neutrophil aggregates in dogs with myxomatous mitral valve disease and pulmonary hypertension

BACKGROUND

Pulmonary hypertension (PH) in dogs with myxomatous mitral valve disease (MMVD) is caused by increased pulmonary venous pressure. Thrombosis, vascular remodeling, and vasoconstriction mediated by platelets could exacerbate PH.

HYPOTHESIS

Dogs with PH will exhibit a hypercoagulable state, characterized by increased platelet activation, platelet-leukocyte, and platelet-neutrophil aggregate formation.

ANIMALS

Eleven dogs (≥3.5 kg) diagnosed with MMVD and PH and 10 dogs with MMVD lacking PH.

METHODS

Prospective cohort ex vivo study. All dogs underwent echocardiographic examination, CBC, 3-view thoracic radiographs, and heartworm antigen testing. Severity of PH and MMVD were assessed by echocardiography. Viscoelastic monitoring of coagulation was assessed using thromboelastography (TEG). Platelet activation and platelet-leukocyte/platelet-neutrophil interactions were assessed using flow cytometry. Plasma serotonin concentrations were measured by ELISA.

RESULTS

Unstimulated platelets from dogs with MMVD and PH expressed more surface P-selectin than MMVD controls (P = .03). Platelets from dogs with MMVD and PH had persistent activation in response to agonists. The number of platelet-leukocyte aggregates was higher in dogs with MMVD and PH compared with MMVD controls (P = .01). Ex vivo stimulation of whole blood resulted in higher numbers of platelet-neutrophil aggregates in dogs with MMVD and PH (P = .01). Assessment of hypercoagulability based on TEG or plasma serotonin concentrations did not differ between groups.

CONCLUSION AND CLINICAL IMPORTANCE

Platelet hyperresponsiveness and increased platelet-neutrophil interaction occur in dogs with MMVD and PH, suggesting that platelets play a role of in the pathogenesis of PH. Clinical benefits of antiplatelet drugs in dogs with MMVD and PH require further investigation.

Application of Speckle Tracking Echocardiography for Evaluating Ventricular Function after Transcatheter Pulmonary Valve Replacement

Pulmonary regurgitation usually leads to right heart dilatation and eventually right heart dysfunction, which is associated with a poor prognosis. Transcatheter pulmonary valve replacement is a developing treatment for pulmonary valve dysfunction that can take the place of traditional surgery and make up for the shortcomings of a large injury. Echocardiography plays a significant role in assessing ventricular function; however, conventional echocardiographic parameters have several limitations. Speckle tracking echocardiography has been regarded as a more accurate tool for quantifying cardiac function than conventional echocardiography. Therefore, the aim of this review was to summarize the application of speckle tracking echocardiography for evaluating right and left ventricular functions in patients after transcatheter pulmonary valve replacement.

Evaluation of right ventricular diastolic function, systolic function, and circulating galectin-3 concentrations in dogs with pulmonary stenosis

BACKGROUND

Cardiovascular diseases with increased right ventricular (RV) afterload induce RV diastolic and systolic dysfunction, and myocardial fibrosis in humans. Studies in dogs with pulmonary stenosis (PS) evaluating RV diastolic function and markers of myocardial fibrosis are lacking.

HYPOTHESIS/OBJECTIVES

Dogs with PS have echocardiographic evidence of RV diastolic and systolic dysfunction and increased serum concentrations of galectin-3 (Gal-3), a surrogate biomarker for myocardial fibrosis.

ANIMALS

Forty client-owned dogs (10 controls, 30 with PS).

METHODS

Prospective study. All dogs had systemic blood pressure measurement, serum biochemical analysis, echocardiography, and measurement of serum Gal-3 concentration performed.

RESULTS

Variables of RV diastolic function were obtained in 39/40 dogs. Trans-tricuspid flow velocity in early diastole to trans-tricuspid flow velocity in late diastole ratios (RV E/A) were lower (P < .001) in dogs with PS (median, 0.94; range, 0.62-2.04) compared to controls (1.78; 1.17-2.35). Trans-tricuspid flow velocity in early diastole to tricuspid annular myocardial velocity in early diastole ratios (RV E/e') were higher (P < .001) in dogs with PS (11.55; 4.69-28) compared to control (6.21; 5.16-7.21). Variables of RV systolic function were lower in dogs with PS (P = <.001). Serum Gal-3 concentration was higher (P = .002) in dogs with PS (285.1 pg/mL; 94.71-406.97) compared to control dogs (162.83 pg/mL; 52.3-232.82).

CONCLUSIONS AND CLINICAL IMPORTANCE

Dogs with PS have RV diastolic and systolic dysfunction, and increased Gal-3 concentrations. These findings suggest the presence of RV myocardial fibrosis in dogs with PS, which could impact clinical management.

Cardiac Magnetic Resonance Imaging Detects Myocardial Abnormalities in Naturally Infected Dogs with Chronic Asymptomatic Chagas Disease

Trypanosoma cruzi infection causes inflammation and fibrosis, resulting in cardiac damage in dogs. The objectives of this study were to describe cardiac magnetic resonance imaging (CMR) in naturally infected dogs with chronic Chagas disease and the frequency of abnormalities for CMR and cardiac diagnostic tests. Ten asymptomatic, client-owned dogs seropositive for T. cruzi were prospectively enrolled in an observational study evaluating echocardiography, ECG (standard and ambulatory), cardiac troponin I (cTnI), and CMR. Standard ECG measurements (3/10) and cTnI concentration (1/10) outside the reference range were uncommon. Ambulatory ECG abnormalities were documented more frequently (6/10 dogs) than with standard ECG and included ventricular arrhythmias (4), supraventricular premature beats (3), second-degree atrioventricular block (2), and sinus arrest (1). Echocardiographic abnormalities were documented in 6/10 dogs including mildly increased left ventricular internal dimension in diastole (1) and decreased right ventricular (RV) systolic function based on reductions in tricuspid annular plane systolic excursion (3) and RV S' (4). Abnormalities were detected with CMR in 7/10 dogs including delayed myocardial enhancement in 5 of which 2 also had increased extracellular volume, abnormal wall motion in 5, and loss of apical compact myocardium in 1. In conclusion, CMR abnormalities were common, and the results of this study suggest CMR can provide useful information in dogs with T. cruzi infection and may support naturally infected dogs for future clinical investigation as an animal model for Chagas disease.

Effect of a single dose of pimobendan on right ventricular and right atrial function in 11 healthy cats

OBJECTIVES

The objective of this study was to investigate the effect of pimobendan on echocardiographic parameters of right ventricular and atrial function in healthy cats.

ANIMALS

Eleven privately owned, healthy adult cats.

MATERIAL AND METHODS

Each cat underwent five echocardiographic examinations: the first and second examinations were performed 1 h apart on day 0. On day 1, the third examination served as baseline, whereas the fourth and fifth examinations were performed one and 6 h after administration of a single oral dose of pimobendan (1.25 mg/cat), respectively. Parameters of right ventricular and atrial morphology and function were collected and compared among time points.

RESULTS

Pimobendan administration produced a change in some echocardiographic variables. Specifically, heart rate, right ventricular fractional shortening and peak velocity of systolic lateral tricuspid annular motion increased (P = 0.032, P = 0.002 and P < 0.001, respectively), whereas right ventricular end-systolic internal diameter and right atrial maximum and minimum internal diameters decreased (P = 0.004, P = 0.025 and P = 0.01, respectively). Right ventricular fractional area change and tricuspid annular plane systolic excursion did not change.

CONCLUSIONS

This novel study showed that pimobendan had positive effects on right ventricular and right atrial function in healthy cats. Further studies are needed to determine whether pimobendan has similar effects in cats with cardiac diseases.

Echocardiographic assessment of dilated cardiomyopathy in dogs

Dilated cardiomyopathy (DCM) is a frequent cause of cardiac disability, congestive heart failure (CHF), and arrhythmic death in dogs. The etiology of DCM is usually idiopathic/genetic, but some causes of a DCM phenotype are reversible. The disease is classified into preclinical (occult) and clinical (overt) stages; the latter stems from heart failure with reduced ejection fraction. DCM is further characterized by clinical, electrocardiographic, circulating biomarker, and imaging abnormalities. The diagnosis of clinical DCM with CHF is straightforward; however, identification of the preclinical stage can be challenging. Echocardiography is central to the diagnosis of both stages and characterized by left ventricular (LV) systolic dysfunction with progressive chamber dilation and variable enlargements of the left atrium and right-sided chambers. Left ventricular dilation is defined by increased LV end-diastolic volumes, areas, and internal dimensions normalized to body size or indexed to the aorta. Systolic dysfunction is characterized by decreased LV ejection fraction, increased end-systolic volume, and reduced shortening across minor and longitudinal LV axes. Dyssynchrony can confound the interpretation of linear indices of systolic function. A comprehensive echocardiogram in DCM includes two-dimensional and M-mode studies, spectral and tissue Doppler imaging, and potentially three-dimensional echocardiography and myocardial strain imaging. Echocardiographic findings should be interpreted within the context of identifiable risks and comorbidities, physical diagnosis, complementary diagnostic testing, and limitations of current reference intervals. Ambiguous examinations should be repeated. Specific echocardiographic criteria for the diagnosis of DCM are proposed to encourage discussion and additional outcome and breed-specific echocardiographic studies of canine DCM.

Repeatability, reproducibility, and reference intervals for indices of right atrial longitudinal strain derived from speckle-tracking echocardiography in healthy dogs

OBJECTIVE

To determine repeatability, reproducibility, and reference intervals of indices of right atrial longitudinal strain (RALS) derived from speckle-tracking echocardiography (STE) in dogs without heart disease.

ANIMALS

110 client-owned dogs and 10 laboratory Beagles.

PROCEDURES

To determine intraobserver within-day (repeatability) and interobserver (reproducibility) coefficients of variation, RALS during ventricular systole (ϵS), ventricular early diastole (ϵE), and atrial systole (ϵA), as derived with STE, were obtained by 2 investigators for 5 randomly selected client-owned dogs and analyzed by linear regression. Reference intervals were estimated from the results of all dogs. Correlations between RALS indices (ϵS, ϵE, and ϵA) and sex, age, body weight, heart rate, and blood pressure were determined.

RESULTS

RALS derived from STE showed good intraobserver within-day repeatability and interobserver reproducibility, with coefficients of variation of < 20%. Both ϵS and ϵE were significantly negatively correlated with age, but ϵA was not correlated with age. Indices were not correlated with sex, body weight, or blood pressure.

CONCLUSIONS AND CLINICAL RELEVANCE

RALS indices derived from STE were repeatable and reproducible and were affected by the age of dogs without heart disease. Age should be considered in the interpretation of RALS indices in clinical settings. Further studies are needed to apply RALS indices for assessing dogs with heart disease.

Assessment of right ventricular systolic function by tissue motion annular displacement in healthy dogs

INTRODUCTION/OBJECTIVES

There are few parameters for assessment of right ventricular (RV) systolic function on echocardiographic examination. Morphofunctional studies are limited by the irregular shape of the RV. Recently, tissue motion annular displacement (TMAD), a technique that evaluates valve annulus displacement toward the cardiac apex, has shown a good correlation with left ventricular global longitudinal strain (GLS) in healthy dogs. Therefore, the aim of this study was to evaluate the longitudinal systolic function of the RV of healthy dogs using TMAD.

ANIMALS

A hundred healthy client-owned dogs.

MATERIALS AND METHODS

Cross-sectional study. Physical examination, electrocardiogram, blood pressure measurement, and echocardiography were recorded. The systolic function of the RV was evaluated by GLS free wall and TMAD. Data were compared with those derived from conventional echocardiography.

RESULTS

TMAD values varied according to body weight. There was a correlation of TMAD in millimeters with all indices of RV systolic function, including GLS free wall (R:-0.239; p:0.017). TMAD had a correlation with age and heart rate; whereas there was no relationship with sex and blood pressure. The coefficient of variation for the intraobserver evaluation was lower for the TMAD in millimeters (9.9%) compared with the GLS free wall (17.9%). In addition, the mean time to perform TMAD (8.1 s) was lower than that of the GLS free wall (37.7 s).

CONCLUSIONS

TMAD is a fast, reproducible, and promising method for assessing RV systolic function in healthy dogs. However, further studies are needed to understand the applicability of this technique in patients with heart disease.

Acute effects of intravenous pimobendan administration in dog models of chronic precapillary pulmonary hypertension

INTRODUCTION

Pulmonary hypertension (PH) is a progressive and potentially life-threatening disease. Several drugs are used for the treatment of dogs with precapillary PH. Pimobendan is an inotropic drug with phosphodiesterase 3 inhibitory and calcium-sensitizing effects. Pimobendan administration improved right ventricular (RV) function and lowered pulmonary arterial pressure in some human patients with precapillary PH. However, the efficacy of pimobendan in dogs with precapillary PH is unknown.

ANIMALS, MATERIAL, AND METHODS

An implantable port device was percutaneously placed in the cranial vena cava of five laboratory beagles. Chronic embolic precapillary PH was induced via the repeated injection of microspheres every 1-2 days. Microsphere injection was continued until systolic pulmonary arterial pressure reached 50 mmHg. Right heart catheterization and echocardiography were performed at baseline and after injections of placebo and pimobendan (0.15 mg/kg).

RESULTS

Repeated injections of microspheres caused an increase in pulmonary vascular resistance, a decrease in stroke volume, RV dilation, left ventricular (LV) and RV dysfunction, and RV dyssynchrony as assessed using echocardiography. Compared with placebo, pimobendan improved LV and RV function based on the LV Tei index from 0.48 to 0.38 (p=0.002) and the RV Tei index from 0.76 to 0.61 (p=0.008), as well as the stroke volume index from 29.4 to 36.7 ml/m² (p=0.012), respectively.

CONCLUSIONS

In dog models of chronic PH, intravenous pimobendan effectively improved RV and LV function and increased stroke volume. However, pimobendan administration did not decrease pulmonary arterial pressure or produce hypotension.

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.

Transverse Right Ventricle Strain and Strain Rate Assessed by 2-Dimensional Speckle Tracking Echocardiography in Dogs with Pulmonary Hypertension

Right ventricular (RV) strain analysis using 2-dimensional speckle tracking echocardiography (2D STE) permits practitioners to assess regional and global deformation of the myocardium. Recently, assessment of the longitudinal right ventricle (RV) strain and strain rate using 2D STE has been reported in dogs. Although longitudinal deformation is the dominant component of the RV systole, RV myocardial fibers of the superficial layer are oriented circumferentially and these contribute to the RV pump function (radial deformation). Because this strain component has not been investigated in dogs, we have assessed radial RV strain and strain rate using 2D STE in healthy dogs and dogs with pulmonary hypertension (PH). We have recruited 74 dogs (40 healthy dogs and 34 dogs with PH) in which we have analyzed radial RV free wall strain and strain rate using XstrainTM software. We have used the left apical 4-chamber view optimized for the RV for analysis of the radial strain and strain rate variables (XstrainTM software denoted radial strain as "transverse"). Seven dogs were excluded during the analysis for low quality images. Transverse strain and strain rate obtained in healthy dogs showed no relationship with heart rate, body weight or age (r2 < 0.09 and p > 0.05 for all variables). Moreover, no relationship between transverse strain/strain rate variables and left atrial-to-aortic ratios was observed (r2 < 0.06 and p = 0.2, for both). Transverse strain and strain rate obtained in dogs with PH, showed weak negative relationships with tricuspid regurgitation velocity (r2 < 0.25 and p = 0.006, for both). Transverse RV strain and strain rate using 2D STE is feasible in most dogs and decrease with worsening of the PH, but these advanced echocardiographic indices do not help in identifying dogs with PH.

Echocardiographic assessment of right heart size and function in dogs with pulmonary valve stenosis

INTRODUCTION/OBJECTIVES

We sought to determine the prevalence and clinical significance of right heart remodeling and right ventricular (RV) dysfunction in dogs with pulmonary valve stenosis (PS). We also sought to evaluate repeatability of several measurements of severity of PS, right heart size, and RV function in dogs with PS.

ANIMALS, MATERIALS AND METHODS

Several indices of right atrial (RA) size and RV size and function were prospectively evaluated in 48 dogs with PS. Regression analysis was used to determine if indices of right heart size and function were independently associated with maximum transpulmonary pressure gradient (max PG) and adverse clinical findings (exercise intolerance, syncope, or right heart failure). Eight dogs underwent a second echocardiogram performed by the same operator to assess repeatability of the echocardiographic indices, which was quantified by coefficient of variation (CV) and repeatability coefficient.

RESULTS

Increased RA size (81%), increased RV wall thickness (83%), and decreased tricuspid annular plane systolic excursion (TAPSE [81%]) were common. Right atrial size, end-diastolic RV area, and RV wall thickness were independently associated with max PG. Decreased TAPSE was independently associated with adverse clinical findings. All indices except RA area (18.6%) and RV systolic velocity (20.7%) had CVs <15%. Repeatability coefficients are available to help distinguish a true change versus measurement variability during serially obtained exams.

CONCLUSIONS

Right heart remodeling and RV dysfunction are common in dogs with PS and are associated with echocardiographic and clinical severity. Results support the quantitative assessment of right heart size and function in dogs with PS.

Right ventricular function and dyssynchrony measured by echocardiography in dogs with precapillary pulmonary hypertension

INTRODUCTION

Assessment of the right ventricular (RV) function by echocardiography is important in dogs with pulmonary hypertension (PH). Few reports are available on RV function and dyssynchrony in dogs, especially in the context of precapillary PH.

ANIMALS

The study included 79 client-owned dogs: 25 dogs with precapillary PH and 54 control dogs.

METHODS

Dogs with precapillary PH were prospectively enrolled between December 2013 and February 2017. The echocardiographic indices of RV function, including RV strain and the dyssynchrony index by speckle-tracking echocardiography, were measured. Multivariate analysis was used to determine independent predictors of the RV dyssynchrony index.

RESULTS

Dogs with precapillary PH showed RV dilation, hypertrophy and right atrial dilation. Impaired echocardiographic indices of RV function, including RV strain, were observed. In addition, RV dyssynchrony occurred in dogs with precapillary PH. Multivariate analysis revealed that tricuspid regurgitation velocity and RV dilation were independent predictors of the RV dyssynchrony index.

CONCLUSIONS

Echocardiographic RV function indices are impaired in dogs with precapillary PH. In addition, RV dilation and elevated systolic pulmonary arterial pressure estimated by echocardiography are associated with RV dyssynchrony.

Echocardiographic evaluation of the right ventricular dimension and systolic function in dogs with pulmonary hypertension

Background

Right ventricular (RV) enlargement and dysfunction are associated with prognosis in humans with pulmonary hypertension (PH).

Hypothesis/Objectives

To assess RV size and systolic function in dogs with PH and to determine if they are associated with disease severity and right‐sided congestive heart failure (R‐CHF).

Animals

89 dogs with PH and 74 healthy dogs.

Methods

Prospective observational study. PH was classified according to the tricuspid regurgitation pressure gradient. RV end‐diastolic area (RVEDA) index was calculated as RVEDA divided by body surface area. RV systolic function was assessed with the tricuspid annular plane systolic excursion (TAPSE) and the RV fractional area change (FAC) normalized for body weight (TAPSEn and FACn, respectively).

Results

RVEDA index was higher in dogs with moderate PH (10.8 cm²/m²; range, 6.2‐14.4 cm²/m²) and severe PH (12.4 cm²/m²; range, 7.7‐21.4 cm²/m²) than in those with mild PH (8.4 cm²/m²; range, 4.8‐11.6 cm²/m²) and control dogs (8.5 cm²/m²; range, 2.8‐11.6 cm²/m²; P < .001). RVEDA index was significantly higher in dogs with R‐CHF (13.7 cm²/m²; range, 11.0‐21.4 cm²/m²) than in dogs without R‐CHF (9.4 cm²/m²; range, 4.8‐17.1 cm²/m²; P < .001). The severity of tricuspid regurgitation (TR) was the only independent predictor of the RVEDA index (P < .001). TAPSEn and FACn were not significantly different among varying degrees of PH severity and between dogs with and without R‐CHF.

Conclusions and Clinical Importance

The RVEDA index can be used to evaluate RV size in dogs. It can provide additional information in dogs with PH and predict R‐CHF. Severity of TR is the main determinant of RV enlargement in dogs with PH.