Layer-specific myocardial function in asymptomatic cats with obstructive hypertrophic cardiomyopathy assessed using 2-dimensional speckle-tracking echocardiography.

BACKGROUND: Hypertrophic cardiomyopathy (HCM), a primary disorder of the myocardium, is the most common cardiac disease in cats. However, determination of layer-specific myocardial function with 2D speckle-tracking echocardiography in cats with asymptomatic HCM has not yet been reported. OBJECTIVES: To quantitatively measure layer-specific myocardial function of asymptomatic cats with HCM. ANIMALS: Ten client-owned, asymptomatic cats with obstructive HCM and 13 healthy cats. METHODS: A retrospective, case-control study. Cats underwent assessment of layer-specific myocardial function (whole, endocardial, and epicardial) in the longitudinal and circumferential directions by using 2D speckle-tracking echocardiography. RESULTS: Longitudinal strains were significantly lower in cats with HCM than controls in the whole (-15.5% vs -19.1%), endocardial (-18.3% vs -21.8%), and epicardial (-13.1% vs -16.8%) layers. Circumferential strains in whole and epicardial layers also were significantly lower in cats with HCM as compared with controls (-15.0% vs -20.2% and - 4.4% vs -9.4%, respectively). However, no significant difference was found between cats with HCM and controls in the global circumferential strain in the endocardial layer (-31.2% vs -34.2%). The circumferential endocardial-to-epicardial strain ratio was significantly higher in cats with HCM than in controls (6.1 vs 3.5). CONCLUSIONS AND CLINICAL IMPORTANCE: Layer-specific myocardial function assessed by 2D speckle-tracking echocardiography differed in asymptomatic cats with obstructive HCM compared to controls despite their apparently normal systolic function, as determined by conventional echocardiography. The maintained endocardial circumferential strain and higher circumferential endocardial-to-epicardial strain ratio may reflect compensation for occult systolic dysfunction in cats with obstructive HCM.

Full-field analysis of epicardial strain in an in vitro porcine heart platform.

The quantitative assessment of cardiac strain is increasingly performed to provide valuable insights on heart function. Currently, the most frequently used technique in the clinic is ultrasound-based speckle tracking echocardiography (STE). However, verification and validation of this modality are still under investigation and further reference measurements are required to support this activity. The aim of this work was to enable these reference measurements using a dynamic beating heart simulator to ensure reproducible, controlled, and realistic haemodynamic conditions and to validate the reliability of optical-based three-dimensional digital image correlation (3D-DIC) for a dynamic full-field analysis of epicardial strain. Specifically, performance assessment of 3D-DIC was carried out by evaluating the accuracy and repeatability of the strain measurements across multiple cardiac cycles in a single heart and between five hearts. Moreover, the ability of this optical method to differentiate strain variations when different haemodynamic conditions were imposed in the same heart was examined. Strain measurements were successfully accomplished in a region of the lateral left ventricle surface. Results were highly repeatable over heartbeats and across hearts (intraclass correlation coefficient = 0.99), whilst strain magnitude was significantly different between hearts, due to change in anatomy and wall thickness. Within an individual heart, strain variations between different haemodynamic scenarios were greater than the estimated error of the measurement technique. This study demonstrated the feasibility of applying 3D-DIC in a dynamic passive heart simulator. Most importantly, non-contact measurements were obtained at a high spatial resolution (~ 1.5 mm) allowing resolution of local variation of strain on the epicardial surface during ventricular filling. The experimental framework developed in this paper provides detailed measurement of cardiac strains under controlled conditions, as a reference for validation of clinical cardiac strain imaging modalities.

Analysis of three-dimensional endocardial and epicardial strains from cardiac magnetic resonance in healthy subjects and patients with hypertrophic cardiomyopathy.

Hypertrophic cardiomyopathy (HCM) is a genetic disease that leads to left ventricle (LV) hypertrophy with or without the presence of LV outflow tract obstruction. The aim of this study was to find an easy and useful indicator based on cardiac magnetic resonance (CMR) images for control subjects and patients with and without obstruction. CMR scans were performed for 19 control subjects and 19 HCM patients. Endocardial strain was defined as [Formula: see text], with [Formula: see text] being the length of endocardium at end-diastole (end-systole); similarly for epicardial strain ([Formula: see text]). The strains were evaluated in cine CMR two-, three- and four-chamber views. Six atrioventricular junction (AVJ) points from three CMR views were semi-automatically tracked. The peak systolic velocity (Sm1), peak early diastolic velocity and late diastolic velocity (Em, Am) were extracted and analysed. Compared with control subjects, HCM patients had significantly smaller three-dimensional strains and AVJ motion incorporating measurements from three long-axis views (all P < 0.05). Moreover, ROC analysis found that three-dimensional global epicardial strain <17.2% had the best sensitivity 94.4% and specificity 94.7% to differentiate HCM from control (AUC = 0.97). Therefore, three-dimensional endocardial and epicardial strains provide an easy and effective approach to manage and triage hypertrophic cardiomyopathy patients.

Comparison of magnetic resonance feature tracking with CSPAMM HARP for the assessment of global and regional layer specific strain.

PURPOSE: Layer specific strain assessment is increasingly being employed clinically. Cardiac magnetic resonance (MR) Feature Tracking (FT) is considered to be an adequate alternative for strain assessment. The aim of this study is to investigate the feasibility of FT derived layer specific strain assessment. METHODS: CSPAMM and SSFP-Cine sequences were acquired in 38 individuals (19 patients with HFpEF, 19 controls) in identical midventricular short-axis locations. Global endocardial-, midmyocardial-, epicardial- peak systolic circumferential strain (PSCS) and regional epicardial PSCS were calculated and intra- as well inter-observer variability were assessed. RESULTS: FT derived global epicardial and endocardial PSCS (7.9±2.3%; -19.6±4.9%) were significantly lower than tagging derived global epicardial and endocardial PSCS (-13.2±2.8%; -32.3±5.9%) (each p<0.001), while FT derived endocardial PSCS and tagging derived midmyocardial PSCS showed a strong correlation (r=0.71) and no significant differences. Global intra- and inter-observer variability of FT derived endocardial PSCS circumferential measures were acceptable (coefficient of variation 6.5% and 5.7%) while reproducibility of epicardial PSCS (coefficient of variation 16.8% and 18.1%) was poor. CONCLUSION: The FT algorithm allows for reliable assessment of midmyocardial strain, while underestimating epicardial and endocardial strain and delivering less reproducible results than the gold standard of tagging.