Quantification of Left Ventricular Longitudinal Strain, Strain Rate, Velocity, and Displacement in Healthy Horses by 2-Dimensional Speckle Tracking

Preliminary study on the effects of pergolide on left ventricular function in the horses with pituitary pars intermedia dysfunction

BACKGROUND

Pituitary pars intermedia dysfunction (PPID), a neurodegenerative disease leading to reduced dopamine production, is a common disease in aged horses. The treatment is based on administration of the dopamine agonist pergolide. This drug has been related to valvular fibrosis in humans, but the cardiovascular effect of this drug has not yet been investigated in horses.

OBJECTIVES

To determine whether pergolide induces valvular disease in horses or affects the cardiac function.

METHODS

Standard, tissue Doppler (TDE) and two-dimensional speckle tracking (STE) echocardiography were performed in horses with diagnosed PPID based on adrenocorticotropic hormone dosage. Measurements taken in horses treated with pergolide were compared with those from untreated horses with nonparametric t-tests. Furthermore, measurements from follow-up examinations performed at least three months after the initial exam were compared with a Wilcoxon signed rank test for repeated measurements in each group.

RESULTS

Twenty-three horses were included. None of the 12 horses under treatment developed valvular regurgitation. Furthermore, no differences in the measurements of the left ventricular systolic or diastolic function could be seen between the group of horses with treatment and those without treatment. Measurements taken in the follow-up exam did not differ compared to those taken in the initial exam in both groups.

CONCLUSIONS

No changes of the left ventricular function assessed by TDE and STE could be shown in a small population of horses with confirmed PPID. Treatment with pergolide did not affect the ventricular function nor induce valvular disease.

Quantification of left atrial contractile function using two-dimensional speckle tracking echocardiography in horses after conversion of atrial fibrillation to sinus rhythm

INTRODUCTION/OBJECTIVES

In horses, persistent atrial dysfunction is a prognostic indicator of recurrence of atrial fibrillation (AF). The objective of this study was to quantify left atrial (LA) contractile function in Warmblood horses after successful cardioversion of AF to sinus rhythm, using standard two-dimensional echocardiography (2DE) and two-dimensional speckle tracking (2DST) analyses, and to provide proof-of-concept for use of 2DST to detect LA contractile dysfunction in horses.

ANIMALS, MATERIALS, AND METHODS

Nineteen Warmblood horses with AF and successful transvenous electrical cardioversion (TVEC) or medical cardioversion using quinidine sulfate (QS) were included. Echocardiography was performed at 24 hr, 72 hr, and 1-6 months after cardioversion. Conventional 2DE-derived indices of LA size and function and global longitudinal strain (S_L) and longitudinal strain rate (SR_L) during LA contractile function were measured to detect differences in LA size and function over time and between treatment modalities. The association between 2DE-derived indices and global S_L and SR_L, respectively, and the agreement of the variables to detect LA dysfunction were assessed.

RESULTS

Global S_L and SR_L, as well as active LA fractional area change (FAC) identified cases with LA dysfunction after TVEC and QS cardioversion and proved useful to demonstrate LA functional recovery over time. Agreement between active LA FAC and S_L and SR_L, respectively, to diagnose atrial dysfunction was substantial to fair at 24 hr after cardioversion and decreased with time.

CONCLUSION

This study shows that 2DST is useful to quantify LA contractile dysfunction in horses after cardioversion of AF.

Quantification of left atrial wall motion in healthy horses using two-dimensional speckle tracking

INTRODUCTION

The mechanical function of the left atrium (LA) plays a pivotal role in modulation of left ventricular filling. Assessment of LA function might be a clinically useful prognostic tool for horses with mitral regurgitation or atrial fibrillation. However, the most accurate, reliable, and clinically useful methods to assess LA myocardial function are yet to be determined. The objective of this study was to describe the methods for quantification of LA wall motion using two-dimensional speckle tracking (2DST) echocardiography in healthy Warmblood horses to quantify measurement variability, to calculate reference intervals for 2DST variables, and to investigate their relationship to sex, age, body weight, and heart rate.

ANIMALS, MATERIALS, AND METHODS

Twenty-six healthy Warmblood horses were included. 2DST analyses of LA wall motion were performed on digitally stored cine-loop recordings of a standardized right-parasternal four-chamber view focusing on the LA. Longitudinal strain, longitudinal strain rate, and time to peak LA contraction were measured to characterize LA contractile, reservoir, and conduit function. Intraobserver and interobserver measurement variability was quantified, and reference intervals were calculated.

RESULTS

The coefficient of variation for intraobserver and interobserver measurement variability ranged between 2.0-11.1% and 5.1-15.4%, respectively, for global strain, strain rate, and time to peak LA contraction. Reference intervals for healthy Warmblood horses were reported.

CONCLUSION

This study shows that 2DST is a feasible and reliable method to quantify LA wall motion throughout the cardiac cycle in healthy Warmblood horses. Further studies are required to establish the clinical value of 2DST for assessment of LA function.

Assessment of left ventricular function in horses with aortic regurgitation by 2D speckle tracking

Background

Aortic regurgitation (AR) may lead to left ventricular (LV) dilatation, cardiac arrhythmias and heart failure. Close follow-up of horses with AR is therefore paramount to detect onset of cardiac decompensation. The aim of this study was to examine whether two-dimensional speckle tracking (2DST) can be used to detect altered myocardial function in horses with chronic AR compared to control horses. Speckle tracking was performed on short axis and long axis images of the LV in 29 healthy Warmblood horses and 57 Warmblood horses with AR. Radial, circumferential and longitudinal strain, strain rate and displacement were measured for each segment separately and the average was calculated over all segments. Data generated from the apical segments were not included in the analysis.

Results

Radial (SR) and circumferential (SC) strain were significantly higher in horses with moderate AR (average SR 75.5 ± 24.3%, SC 19.3 ± 3.2%) but not in horses with severe AR (SR 65.5 ± 26.2%, SC 16.3 ± 3.5%), compared to control horses (SR 54.5 ± 18.0%, SC 16.8 ± 3.0%). Longitudinal strain did not show significant differences, but longitudinal displacement (DL) was larger in horses with moderate (average DL 29.5 ± 4.1 cm) and severe AR (DL 32.4 ± 6.1 cm) compared to control horses (DL 25.7 ± 4.0 cm), especially in the interventricular septum. Diastolic longitudinal strain rate was lower in early diastole in horses with severe AR (0.93 ± 0.18/s) compared to controls (1.13 ± 0.13/s).

Conclusions

2DST is able to detect altered myocardial motion in horses with AR, which showed significantly higher radial and circumferential strain. Further research is needed to determine whether these findings contribute to a more accurate diagnosis and prognosis in clinical cases.

The effect of varying intensities of lower limb eccentric muscle contractions on left ventricular function

Purpose

The effect of eccentric (ECC) resistance exercise (RE) on myocardial mechanics is currently unknown.

Method

This study investigated ECC RE at varying intensities on left ventricular (LV) function using LV strain (ε), wall stress and haemodynamic parameters. Twenty-four healthy male volunteers completed ECC leg extensions at 20%, 50% and 80% of their ECC maximal voluntary contraction (MVC), whilst receiving echocardiograms. Global longitudinal ɛ, strain rate (SR), longitudinal tissue velocity, heart rate (HR), blood pressure (BP), mean arterial pressure (MAP), LV wall stress and rate pressure product (RPP) were assessed at baseline and during exercise.

Results

Left ventricular global ɛ, systolic SR and wall stress remained unchanged throughout. Systolic blood pressure (sBP), MAP and RPP increased at 80% and 50% intensities compared to rest (P < 0.01). Eccentric RE increased HR and peak late diastolic SR at all intensities compared to rest (P < 0.02).

Conclusion

The findings suggest acute ECC RE may not alter main parameters of LV function, supporting future potential for wider clinical use. However, future studies must investigate the impact of multiple repetitions and training on LV function.

Echocardiographic Evaluation of Myocardial Function in Standardbreds During the First Year of Race Training

Several studies have shown the effect of training on myocardial deformation parameters in human athletes. The aim of this prospective, longitudinal study was echocardiographic evaluation of myocardial velocities and deformation in horses during the first year of training. Twelve Standardbred yearlings were examined using tissue Doppler imaging (TDI) and two-dimensional speckle tracking (2D-ST) during the first year of race training (short axis of left and right ventricle). The first examination was performed before the beginning of training (n = 12). At the last time point, horses were fully trained and had participated in their first races (n = 10). Radial myocardial velocities were evaluated using color (c-) and pulsed-wave (PW-)TDI in the left ventricular free wall, the interventricular septum (IVS) and the right ventricular free wall from a right parasternal short-axis image. Strain and strain rate were evaluated using 2D-ST in the LW and IVS using offline analysis of the 2D grayscale images. The radial, systolic myocardial velocities in the left ventricle (LVFW) increased significantly over the year in both c- and PW-TDI. In addition, the early diastolic velocity in the LW (in cTDI) and IVS (in c- and PW-TDI) and the systolic velocity in the IVS (in cTDI) increased significantly. The 2D-ST revealed significant increases of the radial systolic and early diastolic strain rate in the IVS and of the late diastolic strain rate in the LW. Training and aging/growing had both an impact on echocardiography.

Equine Echocardiography

This article provides an overview on the principles of transthoracic echocardiography in horses. Indications for echocardiography, equipment, and technical considerations are discussed and a systematic approach for a complete echocardiographic examination in horses is described. Methods for assessment of chamber dimensions, allometric scaling of measurements, assessment of systolic and diastolic ventricular function, assessment of atrial function, hemodynamic assessment, and evaluation of valvular regurgitation are explained, focusing on traditional 2-dimensional (2D), motion-mode, and Doppler echocardiographic methods. Selected applications of newer echocardiographic methods, such as tissue Doppler imaging and 2D speckle tracking are also described.

Speckle-tracking analysis of myocardial deformation in correlation to age in healthy horses

An effect of aging on cardiac morphology and function has been shown in humans. In horses, cardiac wall motion analysis using two-dimensional speckle tracking (2D-ST) has not yet been reported. Our study included 57 horses of different warmblood breeds between 3 and 30 years old. Age had a significant influence on left ventricular free wall (LVFW) systolic strain rate (p ≤ 0.05) and early diastolic relaxation (p ≤ 0.01). In the interventricular septum (IVS), systolic (p ≤ 0.01) and late diastolic (p ≤ 0.05) contraction velocities also increased with age. In our study, 2D-ST revealed important information on myocardial function, which was most evident in the LVFW, where measurements were highly reproducible. Aging seems to be associated with structural changes within the myocardium and with decreasing contraction capacity in old animals. These physiological, age-related processes should be considered when performing cardiac wall motion analysis of the 2D-ST results for the LVFW and IVS in horses.

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.

Allometric Relationships for Cardiac Size and Longitudinal Function in Healthy Chinese Adults - Normal Ranges and Clinical Correlates

BACKGROUND

Cardiac size measurements require indexing to body size. Allometric indexing has been investigated in Caucasian populations but a range of different values for the so-called allometric power exponent (b) have been proposed, with uncertainty as to whether allometry offers clinical utility above body surface area (BSA)-based indexing. We derived optimal values for b in normal echocardiograms and validated them externally in cardiac patients.

METHODS AND RESULTS

Values for b were derived in healthy adult Chinese males (n=1,541), with optimal b for left ventricular mass (LVM) of 1.66 (95% confidence interval 1.41-1.92). LV hypertrophy (LVH) defined as indexed LVM >75 g/m^1.66 was associated with adverse outcomes in an external validation cohort (n=738) of patients with acute coronary syndrome (odds ratio for reinfarction: 2.4 (1.1-5.4)). In contrast, LVH defined by BSA-based indexing or allometry using exponent 2.7 exhibited no significant association with outcomes (P=NS for both). Cardiac longitudinal function also varied with body size: septal and RV free wall s', TAPSE and lateral e' all scaled allometrically (b=0.3-0.9).

CONCLUSIONS

An optimal b of 1.66 for LVM in healthy Chinese was found to validate well, with superior clinical utility both to that of BSA-based indexing and to b=2.7. The effect of allometric indexing of cardiac function requires further study.

Detection of subclinical left ventricular dysfunction by tissue Doppler imaging in horses with aortic regurgitation

BACKGROUND

Aortic regurgitation (AR) can have an important clinical impact and in some cases leads to left ventricular (LV) failure. Tissue Doppler imaging (TDI) is an echocardiographic technique that has been used in horses to detect LV dysfunction.

OBJECTIVES

To examine whether TDI detects changes in radial myocardial wall motion in horses with AR compared with control horses.

STUDY DESIGN

Case-control study.

METHODS

Echocardiography was performed in 30 healthy Warmblood horses and 34 Warmblood horses with AR, subdivided in groups with mild, moderate or severe AR. TDI measurements were performed on six segments of the short-axis images of the LV myocardial wall. Myocardial wall motion was evaluated by measuring velocity and deformation during isovolumetric contraction, systole, early and late diastole. Timing of different events was also measured.

RESULTS

In most segments, a significantly higher systolic myocardial velocity was found in horses with AR compared with controls. Horses with AR also had higher late diastolic velocity, although the difference was not significant in all segments. TDI measurement of timing intervals demonstrated less difference between groups.

MAIN LIMITATIONS

There was a significant difference in age between the control group and horses with AR, which may confound the results. The assessment of AR severity was based on subjective criteria as there is no gold standard.

CONCLUSIONS

TDI showed significant differences in radial systolic and late diastolic myocardial velocity in horses with AR. This could indicate an altered LV function in these horses, but further research is needed to investigate the prognostic value of these measurements.

Avaliação da depressão miocárdica por meio do feature tracking bidimensional em cadelas com sepse

RESUMO O objetivo deste estudo prospectivo foi analisar a função do ventrículo esquerdo de cadelas que apresentavam sepse ou não e diagnosticar a depressão miocárdica de forma precoce, por meio do feature tracking imaging bidimensional (FTI-2D).Vinte e nove cadelas diagnosticadas com piometra, patologia usada como modelo experimental para sepse, foram avaliadas. Os animais foram submetidos ao exame ecocardiográfico convencional e ao FTI-2D e divididos em três grupos: grupo I (controle), grupo II (piometra sepse) e grupo III (piometra não sepse). Em relação aos parâmetros da ecocardiografia convencional, não houve diferença estatística entre os grupos avaliados. Quanto ao strain radial, os grupos II e III apresentaram função ventricular inferior no momento do diagnóstico (22,805,80 grupo I; 18,455,96 grupo II; 18,719,45 grupo III; P=0,032) e o grupo III manteve essa redução no retorno. Já no strain rate radial, apenas o grupo III obteve função ventricular inferior no momento do diagnóstico (1,900,57 grupo I; 1,910,70 grupo II, 1,570,53 grupo III; P=0,021). Para o strain longitudinal, observou-se função ventricular mais baixa nos grupos II e III no momento do diagnóstico (11,043,38 grupo I; 8,593,97 grupo II; 8,211,99; P=0,048) e após 10 dias de pós-cirúrgico (11,043,38 grupo I; 9,002,16 grupo II; 8,122,27 grupo III; p=0,048). O FTI-2D foi capaz de detectar alterações precoces da função ventricular esquerda, que não foram observadas no exame ecocardiográfico convencional, sugerindo quadro de depressão miocárdica, até mesmo em cadelas com piometra sem quadro clínico evidente de sepse. Assim, essa modalidade pode ser útil no diagnóstico, pois pode detectar alterações cardíacas precoces, possibilitando uma intervenção terapêutica rápida.

Left Ventricular Function After Prolonged Exercise in Equine Endurance Athletes

BACKGROUND

Prolonged exercise in human athletes is associated with transient impairment of left ventricular (LV) function, known as cardiac fatigue. Cardiac effects of prolonged exercise in horses remain unknown.

OBJECTIVES

To investigate the effects of prolonged exercise on LV systolic and diastolic function in horses.

ANIMALS

Twenty-six horses competing in 120-160 km endurance rides.

METHODS

Cross-sectional field study. Echocardiography was performed before and after rides, and the following morning, and included two-dimensional echocardiography, anatomical M-mode, pulsed-wave tissue Doppler imaging, and two-dimensional speckle tracking. Correlation between echocardiographic variables and cardiac troponin I was evaluated.

RESULTS

Early diastolic myocardial velocities decreased significantly in longitudinal (baseline: -17.4 ± 2.4cm/s; end of ride: -15.8 ± 3.2cm/s (P = .013); morning after: -15.4 ± 3.0cm/s (P = .0033)) and radial directions (-32.8 ± 3.4cm/s; -28.1 ± 5.8cm/s (P < .001); -26.4 ± 5.5cm/s (P < .001)). Early diastolic strain rates decreased significantly in longitudinal (1.58 ± 0.27s(-1) ; 1.45 ± 0.26s(-1) (P = .036); 1.41 ± 0.25s(-1) (P = .013)) and circumferential directions (2.43 ± 0.29s(-1) ; 1.96 ± 0.46s(-1) (P < .001); 2.11 ± 0.32s(-1) (P < .001)). Systolic variables showed ambiguous results. No correlations with serum cardiac troponin I concentrations were evident.

CONCLUSIONS AND CLINICAL IMPORTANCE

Prolonged exercise in horses is associated with impaired LV diastolic function. Reduced ventricular filling persisted for 7-21 hours despite normalization of biochemical indicators of hydration status, indicating that the observed changes were not entirely related to altered preload conditions. The clinical relevance of cardiac fatigue in horses remains uncertain.

The use of strain, strain rate, and displacement by 2D speckle tracking for assessment of systolic left ventricular function in goats: applicability and influence of general anesthesia

Background

Assessment of left ventricular (LV) systolic function can be achieved by conventional echocardiographic methods, but quantification of contractility, regional myocardial function, and ventricular synchrony is challenging. The goal of this study was to investigate the applicability of two-dimensional speckle tracking (2DST) to characterize segmental and global wall motion for assessment of LV function and LV synchrony in healthy goats. We aimed to describe the techniques, report normal values of a variety of 2DST indices, and determine the influence of general anesthesia.

Methods

Prospective study on 22 healthy female Saanen goats (3.7 ± 1.1 y, 60.2 ± 10.5 kg [mean ± SD]). All goats underwent two transthoracic echocardiographic examinations, the first standing and unsedated and the second 7.4 ± 3.5 days later during isoflurane anesthesia and positioned in sternal recumbency. Data analyses were performed offline, blinded, and in random order. Left ventricular longitudinal, radial and circumferential strain and strain rate as well as longitudinal and radial displacement were measured using 2DST methods. Summary statistics were generated and differences of 2DST variables between myocardial segments and treatments (i.e., awake vs. anesthetized) were assessed statistically (alpha level=0.05).

Results

Echocardiographic analyses by 2DST were feasible in all goats and at both time points. Longitudinal systolic strain, strain rate and displacement followed a gradient from apex to base. Absolute systolic strain was generally lower and strain rate was higher in awake goats compared to anesthetized goats. Circumferential and radial indices did not consistently follow a segmental pattern. Generally, peak strain occurred later in anesthetized goats compared to awake goats. General anesthesia did not significantly influence LV synchrony.

Conclusions

2SDT is a valid method for non-invasive characterization of LV wall motion in awake and anesthetized goats. The results of this study add to the understanding of LV mechanical function, aid in the diagnosis of global and segmental LV systolic dysfunction, and will be useful for future cardiovascular studies in this species. However, effects of anesthesia and species-specific characteristics should be considered when goats are used as animal models for human disease.

Electronic supplementary material

The online version of this article (doi:10.1186/s12947-015-0005-8) contains supplementary material, which is available to authorized users.

Spectral analysis of femoral artery blood flow waveforms of conscious domestic cats

The qualitative and quantitative aspects of femoral artery blood flow waveform spectra were evaluated in 15 male and 15 female Persian and mixed breed domestic cats (Felis catus), which were healthy and not sedated, using duplex Doppler ultrasonography (DDU). Spectral Doppler demonstrated a biphasic characteristic in 16 (53.34%) of the animals evaluated, and a triphasic characteristic in the 14 (46.66%) remaining animals. The systolic blood pressure and heart rate values were within the normal range for the species. The quantitative parameters evaluated, based on the spectral Doppler, were as follows: systolic velocity peak (SVP), recent diastolic velocity peak (RDVP), end diastolic velocity peak (EDVP), mean velocity (MV), integral velocity time (ITV), artery diameter (AD), femoral flow volume (FFV), pulsatility index (PI), resistive index (RI), systolic peak acceleration time (AT) and deceleration time (DT). The respective mean values were: 36.41 ± 7.33 cm/s, 4.69 ± 0.90 cm/s, 10.74 ± 2.74 cm/s, 23.06 ± 4.86 cm/s, 3.91 ± 1.05 cm, 0.17 ± 0.04 cm, 0.11 ± 0.08 cm(3), 3.85 ± 0.19, 1.40 ± 0.20, 39.84 ± 7.38 ms, and 114.0 ± 22.15 ms. No significant differences were found between males and females. The analyses carried out on the femoral artery flow spectrum obtained by DDU showed that it is easy to use and highly tolerated in non-sedated, healthy cats. It appears that DDU may be a useful diagnostic technique, but further studies are needed to evaluate how it compares with invasive telemetric methodology or high-definition oscillometric waveform analytic techniques.

Evaluation of tissue Doppler imaging for regional quantification of radial left ventricular wall motion in healthy horses

OBJECTIVE

To compare the feasibility and repeatability of tissue Doppler imaging (TDI) for quantification of radial left ventricular (LV) velocity and deformation from different imaging planes and to correlate cardiac event timing data obtained by TDI to M-mode and pulsed-wave Doppler-derived time intervals in horses.

ANIMALS

10 healthy adult horses.

PROCEDURES

Repeated echocardiography was performed by 2 observers from right and left parasternal short-axis views at papillary muscle and chordal levels. The TDI measurements of systolic and diastolic velocity, strain rate, strain peak values, and timing were performed in 8 LV wall segments (LV free wall and interventricular septum from right parasternal views; left and right region of LV wall from left parasternal views). The inter- and intraobserver within- and between-day variability and measurement variability were assessed. The correlation between TDI-based measurements and M-mode and pulsed-wave Doppler-based time measurements was calculated.

RESULTS

TDI measurements of velocity, strain rate, and strain were feasible in each horse, although deformation could often not be measured in the LV free wall. Systolic and diastolic time intervals could be determined with low to moderate variability, whereas peak amplitude variability ranged from low to high. The TDI-based time measurements were significantly correlated to M-mode and pulsed-wave Doppler measurements.

CONCLUSIONS AND CLINICAL RELEVANCE

TDI measurements of radial LV velocity and deformation were feasible with low to moderate variability in 8 LV segments. These measurements can be used for evaluating LV function in further clinical studies.

How similar are the mice to men? Between-species comparison of left ventricular mechanics using strain imaging

BACKGROUND

While mammalian heart size maintains constant proportion to whole body size, scaling of left ventricular (LV) function parameters shows a more complex scaling pattern. We used 2-D speckle tracking strain imaging to determine whether LV myocardial strains and strain rates scale to heart size.

METHODS

We studied 18 mice, 15 rats, 6 rabbits, 12 dogs and 20 human volunteers by 2-D echocardiography. Relationship between longitudinal or circumferential strains/strain rates (S(Long)/SR(Long), S(Circ)/SR(Circ)), and LV end-diastolic volume (EDV) or mass were assessed by the allometric (power-law) equation Y = kM(β).

RESULTS

Mean LV mass in individual species varied from 0.038 to 134 g, LV EDV varied from 0.015 to 102 ml, while RR interval varied from 81 to 1090 ms. While S(Long) increased with increasing LV EDV or mass (β values 0.047±0.006 and 0.051±0.005, p<0.0001 vs. 0 for both) S(Circ) was unchanged (p = NS for both LV EDV or mass). Systolic and diastolic SR(Long) and SR(Circ) showed inverse correlations to LV EDV or mass (p<0.0001 vs. 0 for all comparisons). The ratio between S(Long) and S(Circ) increased with increasing values of LV EDV or mass (β values 0.039±0.010 and 0.040±0.011, p>0.0003 for both).

CONCLUSIONS

While S(Circ) is unchanged, S(Long) increases with increasing heart size, indicating that large mammals rely more on long axis contribution to systolic function. SR(Long) and SR(Circ), both diastolic and systolic, show an expected decrease with increasing heart size.

Cardiac changes in horses with atypical myopathy

BACKGROUND

Atypical myopathy (AM) is an acute, fatal rhabdomyolysis in grazing horses that mainly affects skeletal muscles. Postmortem examinations have shown that myocardial damage also occurs. Limited information is available on the effect of AM on cardiac function in affected and surviving horses.

OBJECTIVES

To describe electrocardiographic and echocardiographic changes associated with AM in the acute stage of the disease and after follow-up.

ANIMALS

Horses (n = 12) diagnosed with AM in which cardiac ultrasound examination and ECG recording were available.

METHODS

All horses underwent clinical examinations, serum biochemistry, electrocardiography, and echocardiography. Four surviving horses underwent the same examinations after 2-10 weeks.

RESULTS

All but 1 horse had increased cardiac troponin I concentrations and 10 horses had ventricular premature depolarizations (VPDs). All horses had prolonged corrected QT (QT(cf) ) intervals on the day of admission and abnormal myocardial wall motion on echocardiography. One of the surviving horses still had VPDs and prolonged QT(cf) at follow-up after 10 weeks.

CONCLUSIONS AND CLINICAL IMPORTANCE

The AM results in characteristic electrocardiographic and echocardiographic changes and may be associated with increased cardiac troponin I concentrations and VPDs. In survivors, abnormal cardiac function still may be found at follow-up after 10 weeks. Additional research in a larger group of horses is necessary to identify the long-term effects of AM on cardiac function.

Two-dimensional speckle tracking for quantification of left ventricular circumferential and radial wall motion in horses

REASONS FOR PERFORMING STUDY

The use of two-dimensional speckle tracking (2DST) for quantification of left ventricular (LV) function has recently been described in horses using long-axis images and short-axis images at chordal but not at papillary muscle level.

OBJECTIVES

To compare the feasibility and reliability of 2DST for quantification of circumferential and radial LV function in short-axis images at papillary muscle and chordal level.

METHODS

Repeated echocardiographic examinations were performed on 10 healthy trotter horses by 2 observers from a right parasternal short-axis view at papillary muscle and chordal level. Segmental and averaged peak values and timing of circumferential and radial strain and strain rate, radial displacement and rotation were measured in 6 LV wall segments in each imaging plane. Global peak values were calculated for circumferential strain and strain rate. The inter- and intraobserver within- and between-day variability was assessed by calculating coefficients of variation for repeated measurements.

RESULTS

2DST analysis was feasible in each cardiac cycle, although tracking was often inadequate during early diastole. Measurements of averaged systolic circumferential and radial strain and strain rate and radial displacement as well as global circumferential strain and strain rate could be determined with low variability. Early and late diastolic strain rate and systolic rotation showed a moderate variability. Radial segmental measurements were more reliable than circumferential measurements. The interventricular septum showed a higher circumferential and lower radial strain compared with the LV free wall. Peak timing was earlier at papillary muscle compared with chordal level.

CONCLUSIONS

2DST measurements of global and regional circumferential and radial LV wall motion are feasible both at papillary muscle and chordal level.

POTENTIAL RELEVANCE

Several measurements had good reliability and should be used for evaluation of the technique in a clinical setting.