Early detection of myocardial dysfunction using two-dimensional speckle tracking echocardiography in a young cat with hypertrophic cardiomyopathy

Post-carvedilol myocardial function in cats with obstructive hypertrophic cardiomyopathy

Introduction

Hypertrophic cardiomyopathy (HCM) is the most prevalent cardiac disease in cats, and one phenotype includes obstructive HCM with dynamic left ventricular outflow tract obstruction (DLVOTO). Myocardial function has been reported to be lower in cats with obstructive HCM than in non-obstructive HCM. Carvedilol, because of its pharmacological action, is expected to reduce the pressure gradient associated with DLVOTO, but no previous reports have studied its effects on myocardial function. This study aimed to evaluate myocardial function in cats with obstructive HCM with left ventricular outflow tract obstruction treated by carvedilol administration.

Methods

This retrospective observational study included 16 cats with obstructive HCM and subsequent treatment of DLVOTO with carvedilol. In addition to conventional echocardiography, strain and strain rates in the left ventricular longitudinal and circumferential directions were measured using layer-specific two-dimensional speckle tracking echocardiography. Each variable was then compared before and after carvedilol medication.

Results

Systolic anterior motion of the mitral valve disappeared in 14 cats and all cats showed resolved DLVOTO with maximal left ventricular outflow tract blood flow velocity of <2.5 m/s after carvedilol administration (P < 0.01). Circumferential strain in the epicardial layer and in the whole layer was significantly increased after carvedilol administration (P < 0.01, P = 0.04, respectively). In contrast, systolic longitudinal strain showed no significant difference between before and after carvedilol administration.

Conclusion

Treatment of obstructive HCM with carvedilol improved DLVOTO and myocardial function without a negative inotropic effect. Carvedilol may be effective in treating cats with obstructive HCM.

Comparative study of myocardial function in cases of feline hypertrophic cardiomyopathy with and without dynamic left-ventricular outflow-tract obstruction

In recent years, hypertrophic cardiomyopathy (HCM) in cats has become much more common in clinical practice due to improvements in diagnostic techniques and equipment performance. One phenotype is obstructive HCM with left ventricular (LV) outflow tract obstruction (DLVOTO). It has been reported that the presence or absence of DLVOTO does not affect long-term prognosis in cats with HCM. In this study, we evaluated and compared myocardial function in HCM-affected cats with and without DLVOTO using the two-dimensional speckle-tracking echocardiography. LV longitudinal strain of the endocardial, epicardial, and whole layer and LV circumferential strain of the epicardium were significantly decreased in all HCM-affected cats compared to healthy cats. However, these values were not significantly different between those with and without DLVOTO. In contrast, the endocardial and whole layers of LV circumferential strain were only significantly decreased in HCM-affected cats with DLVOTO compared to healthy cats. This could be attributed to the fact that the LV pressure load associated with DLVOTO affected the endocardial myocardium more in the LV endocardial layer, and that lower values of LV endocardial strain lowered the values of LV strain in the whole layer. In conclusion, our results suggest that LV myocardial function may have been more compromised in the HCM-affected cats with DLVOTO.

Detection of Congestive Heart Failure and Myocardial Dysfunction in Cats With Cardiomyopathy by Using Two-Dimensional Speckle-Tracking Echocardiography

Congestive heart failure (CHF) is a life-threatening condition in cats with cardiomyopathy. We hypothesized that myocardial dysfunction may induce progression to CHF pathophysiology in cats with cardiomyopathy. However, no previous studies have evaluated the involvement of myocardial dysfunction in cats with CHF. In this study, we aimed to evaluate the relationship between CHF and myocardial function assessed using two-dimensional speckle-tracking echocardiography (2D-STE). Sixteen client-owned healthy cats and 32 cats with cardiomyopathy were enrolled in this study. Cats were classified into three groups: healthy cats, cardiomyopathy without CHF (CM group), and cardiomyopathy with CHF (CHF group). Left ventricular (LV) longitudinal and circumferential strains (SL and SC, respectively), and right ventricular (RV) SL were measured using 2D-STE. Logistic regression analysis was performed to assess the relationship between CHF and echocardiographic variables, including 2D-STE. Results comparing the healthy cats and CM vs. CHF groups showed that increased left atrial to aortic diameter ratio and decreased LV apical SC were significantly associated with the existence of CHF (odds ratio [95% confidence interval]: 1.40 [1.16-1.78] and 1.59 [1.06-2.36], respectively). Results comparing the CM vs. CHF group showed that increased end-diastolic RV internal dimension and decreased RV SL were significantly associated with the existence of CHF (odds ratio: 1.07 [1.00-1.13] and 1.34 [1.07-1.68], respectively). Left atrial enlargement and depressed LV apical myocardial function may be useful tools for predicting the progression to CHF in cats. Furthermore, RV enlargement and dysfunction may lead to the onset of CHF in asymptomatic cats with cardiomyopathy.

Early detection of myocardial dysfunction in a cat that gradually progressed to endomyocardial form of restrictive cardiomyopathy

Background

Restrictive cardiomyopathy (RCM) is a common myocardial disease in cats, characterized by diastolic dysfunction and atrial enlargement without myocardial hypertrophy. Especially, endomyocardial form of RCM, one of the subtypes in RCM, is characterized by endocardial fibrosis, endocardial scar bridging the interventricular septum and left ventricular (LV) free wall, and deformation and distortion of the LV. However, it is unclear how the myocardial dysfunction and the endocardial scar contribute to the pathophysiology of RCM disease progression.

Case presentation

A 3 years and 2 months old, intact male, Domestic shorthaired cat was presented for consultation of cardiac murmur. At the first visit (day 0), the notable abnormal finding was echocardiography-derived chordae tendineae-like structure bridging the interventricular septum and the LV free wall, resulting high-speed blood flow in the left ventricle. Electrocardiography, thoracic radiography and noninvasive blood pressure measurements were normal. No left atrial enlargement was observed, and LV inflow velocity showed an abnormal relaxation pattern. Although there was no abnormality in tissue Doppler imaging-derived myocardial velocity, two-dimensional speckle tracking echocardiography (2D-STE) revealed a decrease in the LV longitudinal strain and an increase in endocardial to epicardial ratio of the LV circumferential strain on day 0. On day 468, obvious left atrium enlargement and smoke like echo in the left atrium were observed. The LV inflow velocity was fused, and the tissue Doppler imaging-derived early-diastolic myocardial velocity of the septal mitral annulus decreased. Regarding 2D-STE, LV circumferential strain was further decreased, and right ventricular strain was additionally decreased. Although the general condition was good, we made a clinical diagnosis of endomyocardial RCM based on the above findings. On day 503, the cat showed the radiographic evidence of pulmonary edema and congestive heart failure signs.

Conclusions

Cats with abnormal LV structure and associated myocardial dysfunction like this case needs careful observation. Additionally, 2D-STE indices may be useful for early detection of myocardial dysfunction in feline RCM.

Left and Right Myocardial Functionality Assessed by Two-Dimensional Speckle-Tracking Echocardiography in Cats with Restrictive Cardiomyopathy

Simple Summary

The endomyocardial form of restrictive cardiomyopathy, a primary disorder of the myocardium, is one of the diseases with poor prognosis in cats. While two-dimensional speckle-tracking echocardiography has been known to identify myocardial deformations, its function relative to cats with the endomyocardial form of restrictive cardiomyopathy has yet to be characterized. We hypothesized that both the left and right myocardial functional abnormalities may occur in cats with the endomyocardial form of restrictive cardiomyopathy, causing this disease pathophysiology and clinical status. In the current study, cats were assessed for layer-specific myocardial function (whole, endocardial, and epicardial) in the left ventricular longitudinal and circumferential directions, and right ventricular longitudinal direction, via two-dimensional speckle-tracking echocardiography. Our study indicated that cats with restrictive cardiomyopathy have reduced left ventricular myocardial function. Notably, left ventricular systolic circumferential endocardial strain and circumferential endocardial-to-epicardial strain ratio were lower in cats with restrictive cardiomyopathy. Furthermore, some right ventricular myocardial deformations were also differerent in cats with restrictive cardiomyopathy. Myocardial function assessed by two-dimensional speckle-tracking echocardiography could reveal left and right myocardial dysfunction.

Abstract

The endomyocardial form of restrictive cardiomyopathy (EMF-RCM), a primary disorder of the myocardium, is one of the diseases with poor prognosis in cats. We hypothesized that both the left and right myocardial functional abnormalities may occur in cats with EMF-RCM, causing this disease pathophysiology and clinical status. Out of the 25 animals included in this study, 10 were client-owned cats with EMF-RCM, and 15 were healthy cats. In this study, cats were assessed for layer-specific myocardial function (whole, endocardial, and epicardial) in the left ventricular longitudinal and circumferential directions, and right ventricular longitudinal direction, via two-dimensional speckle-tracking echocardiography (2D-STE). Cats with EMF-RCM had depressed left ventricular myocardial deformations both in systole (whole longitudinal strain, epicardial longitudinal strain, and endocardial circumferential strain) and diastole (early and late diastolic longitudinal strain rates, and late diastolic circumferential strain rate) compared to controls. Furthermore, some right ventricular myocardial deformations (systolic longitudinal strain in epicardial layers, and endocardial-to-epicardial strain ratio) were significantly differerent in cats with EMF-RCM. Myocardial function assessed by 2D-STE could reveal left and right myocardial dysfunction.

Assessment of myocardial function in obstructive hypertrophic cardiomyopathy cats with and without response to medical treatment by carvedilol

BACKGROUND

Inconsistency of treatment response in cats with obstructive hypertrophic cardiomyopathy is well recognized. We hypothesized that the difference in response to beta-blockers may be caused by myocardial functional abnormalities. This study was designed to compare myocardial function in cats with obstructive hypertrophic cardiomyopathy with and without response to beta-blockers. Twenty-one, client-owned, hypertrophic cardiomyopathy cats treated with carvedilol were analyzed. After carvedilol treatment, cats with decreased left ventricular outflow tract velocity were categorized as responders (n = 10); those exhibiting no response (no decrease in the left ventricular outflow tract velocity) were categorized as non-responders (n = 11). The cats were examined using layer-specific assessment of the myocardial function (whole, endocardial, and epicardial layers) longitudinally and circumferentially by two-dimensional speckle-tracking echocardiography, before and after carvedilol treatment.

RESULTS

The non-responder cats had a significantly higher age, end-diastolic left ventricular posterior-wall thickness, peak velocity of left ventricular outflow tract, and dose of carvedilol than the responders (p = 0.04, p < 0.01, p < 0.01, and p < 0.01, respectively). The circumferential strain in the epicardial layer was lower and circumferential endocardial to epicardial strain ratio was higher in non-responders than responders (p < 0.001 and p = 0.006). According to the multivariate analysis, circumferential strain in the epicardial layer was the only independent correlate of treatment response with carvedilol.

CONCLUSIONS

Myocardial function, assessed by two-dimensional speckle-tracking echocardiography, differed in cats with hypertrophic cardiomyopathy with and without response to beta-blockers. The determination of layer-specific myocardial function may facilitate detailed pathophysiologic assessment and treatment response in cats with hypertrophic cardiomyopathy.