Left ventricular twist and circumferential strain in dogs with myxomatous mitral valve disease

Relationship between syringomyelia and myxomatous mitral valve disease in Cavalier King Charles spaniels

BACKGROUND

Syringomyelia (SM) and myxomatous mitral valve disease (MMVD) are highly prevalent in Cavalier King Charles spaniels (CKCS). Cardiac status in CKCS with and without SM is currently unknown.

OBJECTIVES

To investigate the association between SM and MMVD severity in CKCS and CKCS with SM with and without clinical signs of SM.

ANIMALS

Fifty-five CKCS: 40 with SM (22 symptomatic and 18 asymptomatic) and 15 without SM.

METHODS

A combined retrospective and prospective study. MRI and echocardiography were used to diagnose SM and MMVD, respectively. The association between SM and MMVD severity (left ventricle internal diameter in diastole normalized to bodyweight [LVIDDN] and left atrium to aortic ratio [LA/Ao]) were tested using multivariable linear regression analysis adjusting for sex and age.

RESULTS

Overall, no significant difference in LVIDDN and LA/Ao was found between CKCS with or without SM. However, CKCS with symptomatic SM had significantly smaller LVIDDN (1.45 [1.30-1.50]) (median [IQR]) and LA/Ao (1.20 [1.10-1.28]) compared to CKCS with asymptomatic SM (1.60 [1.50-1.90] and 1.40 [1.20-1.75]) as well as CKCS without SM (0.24 [0.03-0.45] and 0.30 [0.05-0.56]) (all P values <.03).

CONCLUSIONS AND CLINICAL IMPORTANCE

An association between MMVD and SM was not confirmed in this cohort of CKCS, indicating that MMVD and SM do not co-segregate. However, CKCS with symptomatic SM had smaller left ventricle and atrial size compared to CKCS with asymptomatic SM and CKCS without SM.

Prognostic value of left atrial stiffness estimated using echocardiography in dogs with myxomatous mitral valve disease

INTRODUCTION

No studies have investigated the prognostic value of left atrial stiffness (LASt) estimated using echocardiography in dogs with myxomatous mitral valve disease (MMVD).

ANIMALS

Seventy-two dogs had MMVD and 46 dogs were healthy dogs.

MATERIALS AND METHODS

Clinical retrospective cohort study. The survival information of MMVD dogs that underwent echocardiographic examination was obtained. The peak velocities of early diastolic transmitral flow (E) and mitral annular motion as determined by pulsed wave Doppler (E') were determined. The left atrial reservoir strain (ε_S) was determined by two-dimensional speckle tracking echocardiography of the left atrium. The LASt was estimated by the formula: E/E'/ε_S. The 95% prediction interval of LASt was computed from the data of the healthy dogs.

RESULTS

Seventeen dogs having MMVD died of cardiac-related causes with 55 MMVD dogs censored. The MMVD dogs with LASt > its 95% upper prediction limit (LASt > 0.56; n = 26; median survival time, 484 days; 95% confidence interval, 283 days-indeterminable) had shorter survival times (P<0.001) than those with LASt ≤ its 95% upper prediction limit (LASt ≤ 0.56; n = 46; median survival time, >1112 days; 95% confidence interval, indeterminable). Multivariable Cox's proportional hazard analysis demonstrated that the ratio of the left atrial dimension to the aortic annulus dimension and LASt were independent predictors of cardiac-related death among conventional echocardiographic indices, ε_S and LASt in MMVD dogs.

CONCLUSIONS

In dogs with MMVD, increased LASt estimated using echocardiography is an independent predictor of cardiac-related death, and LASt can be more useful for prognostication than ε_S.

Novel Approach to Assess Cardiac Function Using Systolic Performance and Myocardial Performance Indices From Simultaneous Electrocardiography and Phonocardiography Recordings in Dogs With Various Stages of Myxomatous Mitral Valve Disease

Background and Objective: Myxomatous mitral valve disease (MMVD) progression entails changes in the structural and functional properties of the heart affecting cardiac timings and intervals within the cardiac cycle. Conventionally, echocardiography is used to determine the cardiac time intervals (CTIs) including systolic and myocardial performance indices (SPI and MPI) in evaluating cardiac function. Alternatively, these CTIs can also be measured using simultaneous recordings of electrocardiography (ECG) and phonocardiography (PCG), but their values in different MMVD stages remain to be established. This study aimed to establish and prove the use of derived SPI and MPI from a dedicated device as a novel approach to assess cardiac function in different stages of MMVD dogs. Materials and Methods: A prospective study in 52 dogs with different MMVD stages measured the CTIs using a novel device. These were compared and correlated with standard echocardiographic parameters. The predictive value of SPI and three new proposed formulas to estimate MPI (i.e., F1, F2, and F3) in association with asymptomatic from symptomatic MMVD dogs were investigated. Results: Our findings revealed that CTI parameters measured from a novel device including QS1, QS2, S1S2, MPI-F1, and MPI-F2 were altered at different stages of MMVD. The SPI and all proposed MPI formulas were comparable with the systolic time interval and Tei index from echocardiography. In addition, the SPI, MPI-F1, and MPI-F2 were significantly correlated with the Tei index. However, the SPI was not able to differentiate the various stages of MMVD. Conversely, only the MPI-F1 (i.e., (QS1 + S2)/S1S2) demonstrated good predictive accuracy when compared between asymptomatic and symptomatic MMVD dogs similar to the Tei index. Moreover, this formula was able to differentiate stages B1 and C with remarkable predictive accuracy, higher sensitivity, and high specificity when compared with the Tei index. Conclusion: We have successfully described the CTI parameters in different MMVD stages using simultaneous ECG and PCG recordings in dogs. Furthermore, we have proven that the concept of using the newly proposed parameters from a novel device is equivalent to the Tei index. Thus, we established a novel approach to evaluate cardiac function and its supportive use in the diagnosis of MMVD patients.

Role of Two-Dimensional Speckle-Tracking Echocardiography in Early Detection of Left Ventricular Dysfunction in Dogs

Simple Summary

Two-dimensional speckle-tracking echocardiography represents an advanced imaging technique that allows the analysis of global and regional myocardial function, cardiac rotation and synchronicity using deformation imaging. It has gained growing importance over the last decade, especially in human medicine as a method of evaluating myocardial function. This review aims to give an overview of the current understanding of this technique and its clinical applicability in the field of veterinary medicine with a focus on early detection of left ventricular dysfunction in dogs.

Abstract

Two-dimensional speckle-tracking echocardiography (2D–STE) is an advanced echocardiographic technique based on deformation imaging that allows comprehensive evaluation of the myocardial function. Clinical application of 2D–STE holds great potential for its ability to provide valuable information on both global and regional myocardial function and to quantify cardiac rotation and synchronicity, which are not readily possible with the conventional echocardiography. It has gained growing importance over the past decade, especially in human medicine, and its application includes assessment of myocardial function, detection of subclinical myocardial dysfunction and serving as a prognostic indicator. This review illustrates the fundamental concepts of deformation analysis and gives an overview of the current understanding and its clinical application of this technique in veterinary medicine, with a focus on early detection of left ventricular (LV) dysfunction in dogs.

Changes in Left Ventricular Ejection Fraction after Mitral Valve Repair for Primary Mitral Regurgitation

This study sought to identify the short- and long-term changes in left ventricular ejection fraction (LVEF) after mitral valve repair (MVr) in patients with chronic primary mitral regurgitation according to preoperative LVEF (pre-LVEF) and preoperative left ventricular end-systolic diameter (pre-LVESD). This study evaluated 461 patients. Restricted cubic spline regression models were constructed to demonstrate the long-term changes in postoperative LVEF (post-LVEF). The patients were divided into four groups according to pre-LVEF (<50%, 50–60%, 60–70%, and ≥70%). The higher the pre-LVEF was, the greater was the decrease in LVEF immediately after MVr. In the same pre-LVEF range, immediate post-LVEF was lower in patients with pre-LVESD ≥ 40 mm than in those with pre-LVESD < 40 mm. The patterns of long-term changes in post-LVEF differed according to pre-LVEF (p for interaction < 0.001). The long-term post-LVEF reached a plateau of approximately 60% when the pre-LVEF was ≥50%, but it seemed to show a downward trend after reaching a peak at approximately 3–4 years after MVr when the pre-LVEF was ≥70%. The patterns of short- and long-term changes in post-LVEF differed according to pre-LVEF and pre-LVESD values in patients with chronic primary mitral regurgitation after MVr.

Depleted Myocardial Coenzyme Q10 in Cavalier King Charles Spaniels with Congestive Heart Failure Due to Myxomatous Mitral Valve Disease

Congestive heart failure (CHF) has been associated with depleted myocardial coenzyme Q10 (Q10) concentrations in human patients. The aim of this study was to investigate associations between myocardial Q10 concentrations and myxomatous mitral valve disease (MMVD) severity in dogs. Furthermore, citrate synthase (CS) activity was analysed to determine if a reduction in myocardial Q10 was associated with mitochondrial depletion in the myocardium. Thirty Cavalier King Charles spaniels (CKCS) in MMVD stages B1 (n = 11), B2 (n = 5) and C (n = 14) according to the American College of Veterinary Internal Medicine (ACVIM) guidelines and 10 control (CON) dogs of other breeds were included. Myocardial Q10 concentration was analysed in left ventricular tissue samples using HPLC-ECD. CKCS with congestive heart failure (CHF; group C) had significantly reduced Q10 concentrations (median, 1.54 µg/mg; IQR, 1.36–1.94), compared to B1 (2.76 µg/mg; 2.10–4.81, p < 0.0018), B2 (3.85 µg/mg; 3.13–4.46, p < 0.0054) and CON dogs (2.8 µg/mg; 1.64–4.88, p < 0.0089). CS activity was comparable between disease groups. In conclusion, dogs with CHF due to MMVD had reduced myocardial Q10 concentrations. Studies evaluating antioxidant defense mechanisms as a therapeutic target for treatment of CHF in dogs are warranted.

Variability among strain variables derived from two-dimensional speckle tracking echocardiography in dogs by use of various software

OBJECTIVE

To determine variability of global longitudinal strain (GLS) and strain rate (SR) measurements in dogs with and without cardiac disease derived from 2-D speckle tracking echocardiography (STE) by use of various software.

ANIMALS

2 cohorts comprising 44 dogs (23 cardiovascularly healthy and 21 with cardiac disease) and 40 dogs (18 cardiovascularly healthy and 22 with cardiac disease).

PROCEDURES

Transthoracic echocardiographic images in each cohort were analyzed with vendor-independent software and vendor-specific 2-D STE software for each of 2 vendors. Values for GLS and SR obtained from the same left parasternal apical views with various software were compared. Intraobserver and interobserver variability was determined, and agreement among results for the various software was assessed.

RESULTS

Strain analysis was not feasible with vendor-independent software for 20% of images obtained with the ultrasonography system of vendor 1. Intraobserver and interobserver coefficient of variation was < 10% for GLS values, whereas SR measurements had higher variance. There was a significant difference in GLS and SR obtained for each cohort with different software. Evaluation of Bland-Altman plots revealed wide limits of agreement, with variance for GLS of up to 6.3 units in a single dog.

CONCLUSIONS AND CLINICAL RELEVANCE

Results of longitudinal strain analysis were not uniform among software, and GLS was the most reproducible measurement. Significant variability in results among software warrants caution when referring to reference ranges or comparing serial measurements in the same patient because changes of < 6.5% in GLS might be within measurement error for different postprocessing software.

Speckle tracking echocardiography in cats with preclinical hypertrophic cardiomyopathy

Background

Cats with hypertrophic cardiomyopathy (HCM) have decreased left ventricular (LV) longitudinal deformation detected by mitral annular plane systolic excursion (MAPSE) and speckle tracking echocardiography. People with preclinical HCM have decreased systolic LV longitudinal and radial strain (S) and strain rate (SR), with preserved circumferential S and SR.

Hypothesis/Objectives

Cats with preclinical HCM have decreased systolic LV deformation compared to normal cats.

Animals

Seventy‐three client‐owned cats with (n = 37) and without (n = 36) preclinical HCM.

Methods

Retrospective echocardiographic study. Left and right ventricular longitudinal S and SR, LV radial and circumferential S and SR were calculated by STE. Left ventricular mass was also calculated. Correlation between STE variables and LV hypertrophy was determined and receiver‐operating characteristic (ROC) curves were plotted for prediction of HCM.

Results

Cats with HCM had smaller absolute longitudinal S (−14.8 ± 3.3% vs −19.7 ± 2.7%, P < .001), longitudinal SR (−2.36 ± 0.62 vs −2.95 ± 0.68 second⁻¹, P < .001), radial S (46.2 ± 21.3% vs 66.7 ± 17.6%, P < .001), and radial SR (5.60 ± 2.08 vs 6.67 ± 1.8 second⁻¹, P < .001) compared to healthy controls. No difference was observed for circumferential S and SR. Cats with HCM had greater LV mass (13.2 ± 3.7 g vs 8.6 ± 2.7 g, P < .001). The ROC with the greatest area under the curve (AUC) for the identification of HCM (0.974) was plotted from a logistic regression equation combining LV mass, MAPSE at the free wall, and LV internal diameter in diastole (LVIDd).

Conclusions and clinical importance

Cats with preclinical HCM have decreased long axis and radial deformation. Decreased longitudinal deformation and decreased LVIDd are factors that would support a diagnosis of HCM.

Evaluation of the right parasternal four-chamber view for the assessment of left ventricular longitudinal strain and strain rate by two-dimensional speckle tracking echocardiography in dogs

Two-dimensional (2-D) speckle tracking echocardiography (STE) is a relatively new imaging technique, introduced in veterinary medicine to aid the assessment of left ventricular (LV) myocardial function. Among other indices, LV longitudinal strain and strain rate (SR) can be measured with this modality, and in dogs they are usually obtained from the left apical four-chamber (LAp4Ch) view. However, in this species, a good quality right parasternal four-chamber (RP4Ch) view can generally be attained, and the aim of this study was therefore to determine its feasibility and reliability for longitudinal strain and SR assessment, and to establish whether the two projections can be used interchangeably. Fifty-one healthy dogs and twenty-five dogs with various cardiac diseases were examined. Longitudinal global and segmental strains and global SR of the LV were obtained with 2-D STE by use of RP4Ch and LAp4Ch views. Intra-observer (within-day and between-day) and inter-observer variabilities were established, and strain and SR values obtained from the two views were compared. The RP4Ch view demonstrated to be feasible for the assessment of longitudinal strain and SR by use of 2-D STE in healthy and diseased dogs. However, out of sector motion of the apical segments could occur and induce tracking errors. The deformation parameters obtained from this view and the LAp4Ch view were often significantly different, and therefore they should not be used interchangeably. Further, the software employed in the present study performed better global than segmental strain analysis for both views.

Echocardiographic Assessment of Cardiac Function by Conventional and Speckle-Tracking Echocardiography in Dogs with Patent Ductus Arteriosus

Background

Patent ductus arteriosus (PDA) is one of the most common congenital heart defects in dogs. Advanced echocardiographic techniques such as speckle‐tracking echocardiography (STE) have not been extensively used to evaluate cardiac function in affected dogs.

Hypothesis

Advanced echocardiographic techniques are more sensitive than standard echocardiographic techniques in analyzing systolic function in dogs with PDA.

Animals

Forty‐four client‐owned dogs: 34 dogs with PDA (preoperative evaluation) and 10 healthy sex‐ and weight‐matched controls.

Methods

Prospective study. Dogs were recruited over a 2‐year period. Complete echocardiographic evaluation was performed, including conventional (end‐diastolic volumes indexed to body surface area in B and M‐mode [EDVI_B/M], end‐systolic volumes indexed to body surface area in B and M‐mode [ESVI_B/M], allometric scaling in diastole and systole [AlloD/S], pulmonary flow to systemic flow [Qp/Qs], ejection fraction [EF] and fractional shortening [FS]) and speckle‐tracking echocardiography ([STE]: global longitudinal, radial and circumferential strain [S] and strain rate [SR]).

Results

Dogs with PDA had significantly different EDVI_B/M, ESVI_B/M, AlloD/S, Qp/Qs and all STE‐derived parameters (global longitudinal S and SR, global circumferential S and SR, global radial S and SR)compared to healthy dogs. No correlation was found between standard techniques (EDVI_B/M, ESVI_B/M, AlloD/S, Qp/Qs) and STE‐derived parameters (global longitudinal, circumferential and radial S and SR).

Conclusion and Clinical Importance

Conventional parameters routinely used to assess systolic function (EF and FS) were not different between the groups; STE‐derived parameters identified subtle changes in cardiac systolic function and contractility between the 2 groups of dogs. Based on these findings, STE may be a more appropriate tool to assess cardiac contractility in dogs with PDA.

Assessment of Left Atrial Deformation and Function by 2-Dimensional Speckle Tracking Echocardiography in Healthy Dogs and Dogs With Myxomatous Mitral Valve Disease

Background

The assessment of left atrial (LA) function by 2‐dimensional speckle tracking echocardiography (STE) holds important clinical implications in human medicine. Few similar data are available in dogs.

Objectives

To assess LA function by STE in dogs with and without myxomatous mitral valve disease (MMVD), analyzing LA areas, systolic function, and strain.

Animals

One hundred and fifty dogs were divided according to the American College of Veterinary Internal Medicine classification of heart failure: 23 dogs in class A, 52 in class B1, 36 in class B2, and 39 in class C + D.

Methods

Prospective observational study. Conventional morphologic and Doppler variables, LA areas, and STE‐based LA strain analysis were performed in all dogs and results were compared among groups. Correlation analysis was carried out between LA STE variables and other echocardiographic variables.

Results

Variability study showed good reproducibility for all the tested variables (coefficient of variation <16%). Left atrial areas, fractional area change, peak atrial longitudinal strain (PALS), peak atrial contraction strain, and contraction strain index (CSI) differed significantly between groups B2 and C + D and all the other groups (overall P < .001), whereas only PALS differed between groups B1 and A (P = .01). Left atrial areas increased with progression of the disease, whereas LA functional parameters decreased. Only CSI increased nonsignificantly from group A to group B1 and then progressively decreased. Thirty‐one significant correlations (P < .001, r > .3) were found between conventional left heart echocardiographic variables and LA areas and strain variables.

Conclusions and Clinical Importance

Left atrial STE analysis provides useful information on atrial function in the dog, highlighting a progressive decline in atrial function with worsening of MMVD.

Contractile properties of the right atrial myofilaments in patients with myxomatous mitral valve degeneration

Background

Myxomatous degeneration of the mitral valve is a common pathological finding in mitral valve surgery and the most common reason for severe mitral valve regurgitation. Considering the importance of right ventricular remodeling and global function after mitral valve surgery we tried to elucidate a possible association of myxomatous mitral valve and impairment of right atrial and ventricular function, which might have an impact on global ventricular performance after mitral valve surgery.

Methods

Right atrial tissue was harvested from 47 patients undergoing mitral valve surgery. We took the trabeculae from the right auricle, which was resected at the right auricle for implementation of extracorporal circulation. The tissue was skinned and prepared in a 24 h-lasting procedure to create small fibers for hinging them in the "muscle machine", an experimental set-up, created for pCa-force measurements.

Results

Patients without myxomatous mitral valve developed significantly more force (4.0 mN ± 0.8 mN) at the highest step of calcium concentration compared to 2.7 mN ± 0.4 mN in group of patients with myxomatous valve degeneration (p 0.03). Calcium sensitivity in the myxomatous valve group was at pCa 6.0 and in the non-myxomatous group at pCa 5. Furthermore we observed a significant difference in ejection fraction (EF) among the groups: 49% in the non-myxomatous group versus 57% in the myxomatous group (p 0.03). In the non-myxomatous group 5 patients had diastolic dysfunction grade I-II (22,7%), in group I 10 patients (40%). This was also significant (p 0.04).

Conclusions

Patients with myxomatous mitral valve degeneration seem to have reduced force capacities. Calcium sensitivity is higher compared to the non-myxomatous group, which might be a compensatory mechanism to cover the physiological demand. Furthermore we suggest a higher incidence of diastolic dysfunction in patients with myxomatous mitral valve degeneration, which might have an impact on ventricular remodeling after mitral valve surgery.