Speckle tracking echocardiography (STE) is a relatively new imaging modality that enables the direct measurement of active contractile myocardial tissue in an offline analysis. This is accomplished through a software algorithm that tracks collections of acoustic markers, known as 'speckles', that are unique to a given section of myocardium. By measuring the displacement of these 'speckles' as the heart contracts and relaxes, STE produces parameters of the strain, or percent change in length, exhibited by the myocardium. As multiple studies have shown, this strain data produced by tracking of the global left atrium has the ability to accurately assess the physiologic functions of the atrium as a reservoir, conduit and booster pump in the cardiac cycle. Despite these valuable correlations, there are noted problems with STE regarding acoustic cluttering and disappearance of 'speckles' that can occur as the selected region of interest moves out of the field of view or becomes obscured. These problems may be increased when tracking an extended region of myocardium. Therefore, this present study sought to test a new method of assessing left atrial function with STE strain analysis by focusing on a concise region of the atrium, specifically the interatrial septum. To test this, the echocardiograms of 37 patients were obtained and grouped according to the designation of their cardiac function as normal (n=11), abnormal (n=12), or exhibiting signs of cardiac amyloidosis (n=14). In all patients, STE strain analysis was performed on the both the global left atrium and the interatrial septum. Measurements of the mean peak strain observed in the resultant strain curves were recorded for both STE scans of each patient. The curves produced by the tracking the segments of the entire atrium (6 segments) and interatrial septum (3 segments) were compared based on the exhibited changes in strain seen in the relative shapes of the curves, as well as the spread of the segmental strain curves about the calculated mean strain curve. Additionally, the number of segments that were either unsuccessfully or incorrectly tracked was recorded as a measure of the accuracy of STE. As a final step, the interatrial strain curves of four selected patients in the various states of ventricular diastolic dysfunction were chosen and compared with data obtained from scans of mitral flow echocardiography and tissue Doppler imaging (TDI) in an attempt to correlate the exhibited changes in strain shown in the interatrial septum with the physiologic functions of the atrium during ventricular diastole. The results showed that the mean peak strain of the global atrial strain trace decreased from normal (41.32%±10.8) to abnormal (21.69%±13.8) to the amyloid group (10.41%±6.9). This trend was echoed in the mean peak strain measured in the interatrial septum, as measured in normal (64.2%±15.6), abnormal (28.37%±13.4) and amyloid groups (12.21%±12.1). When the strain curves of the entire atrium and interatrial septum were compared, they demonstrated similar patterns in the timing of changes in strain, however the strain curves of the individual interatrial septum segments showed a much more concise grouping about the mean strain curve and were less likely to exhibit discordant segmental strain curves that deviated from the pattern established by all other segments in the trace. Additionally, within the STE scans of the global atrium, the interatrial septum exhibited a higher percentage of successfully tracked segments than did the lateral atrial wall; this trend was universally exhibited in all three groups. Finally, the interatrial septum strain curves, mitral flow echocardiography and TDI scans all demonstrated similar indications of left atrial function in the four selected patients. Ultimately, STE strain analysis of the interatrial septum appears to be a more accurate method of tracking the atrial myocardium than STE tracing of the global left atrium. Furthermore, it shows viable potential as a method for assessing the global physiologic function of the left atrium, as indicated by the similarities between the trends exhibited by these STE scans and the data gathered from scans produced by mitral flow echocardiography and TDI.

No description available.

Contexte: La maladie de Fabry (MF) se caractérise par l'accumulation de sphingolipides dans de multiples organes dont l'oreillette gauche (OG). La littérature existante ne permet pas d'établir si les fonctions réservoir, conduit et pompe de l'OG étudiées par échocardiographie de suivi des marqueurs acoustiques (speckle-tracking echocardiography, STE) sont affectées dans la MF et si la thérapie de remplacement enzymatique (TRE) permet d'améliorer la fonction de l'OG. Méthodes: Dans cette étude de cohorte rétrospective, la déformation, le taux de déformation et les volumes phasiques de l'OG ont été étudiés chez 50 patients atteints de la MF et comparés à 50 contrôles sains. Résultats: Les trois fonctions phasiques de l'OG étaient altérées. La déformation positive maximale (fonction réservoir) était de 38,9 ± 14,9 % vs. 46,5 ± 10,9 % (p=0,004) et la déformation télédiastolique (fonction pompe) était de 12,6 ± 5,9 % vs. 15,6 ± 5,3 % (p=0,010). Chez 15 patients ayant débuté la TRE pendant l'étude, la majorité des paramètres de fonction de l'OG se sont améliorés après un suivi d'un an (déformation positive maximale de 32,0 ± 13,5 % à 38,0 ± 13,5 %; p=0,006) alors qu'il y a eu une tendance vers une détérioration des paramètres chez 15 patients n'ayant jamais reçu de traitement (déformation positive maximale de 47,3 ± 10,8 % à 41,3 ± 9,3 %; p=0,058). Neuf patients atteints de la MF (21%) ont développé une fibrillation auriculaire ou un accident vasculaire cérébral pendant un suivi de quatre ans. La déformation positive maximale et la déformation protodiastolique étaient plus fortement associés aux événements cliniques que les paramètres cliniques et les paramètres échocardiographiques standards. Conclusions: Les fonctions réservoir, conduit et pompe de l'OG par STE étaient affectées dans la MF. La TRE a permis d'améliorer la fonction de l'OG. Les paramètres de déformation de l'OG étaient associés à la survenue de fibrillation auriculaire et d'accidents vasculaires cérébraux. / Background: Fabry disease (FD) is characterized by the accumulation of sphingolipids in multiple organs including the left atrium (LA). It is uncertain if the LA reservoir, conduit and contractile functions evaluated by speckle-tracking echocardiography are affected in Fabry cardiomyopathy and whether enzyme replacement therapy can improve LA function. Methods: In this retrospective cohort study, LA strain, strain rates and phasic LA volumes were studied in 50 FD patients and compared to 50 healthy controls. Results: All three LA phasic functions were altered. The peak positive strain (reservoir function) was 38.9 ± 14.9 % vs. 46.5 ± 10.9 % (p=0.004) and the late diastolic strain (contractile function) was 12.6 ± 5.9 % vs. 15.6 ± 5.3 % (p=0.010). In 15 patients who started enzyme replacement therapy during the study, most of the LA parameters improved at one-year follow-up (peak positive strain from 32.0 ± 13.5 % to 38.0 ± 13.5 %; p=0.006) whereas there was a trend towards deterioration in 15 patients who never received treatment (peak positive strain from 47.3 ± 10.8 % to 41.3 ± 9.3 %; p=0.058). Nine FD patients (21%) experienced new-onset atrial fibrillation or stroke during four-year follow-up. By univariate analysis, peak positive strain and early diastolic strain demonstrated significant associations with clinical events, surpassing conventional echocardiographic parameters and clinical characteristics. Conclusions: Left atrial reservoir, conduit and contractile functions by speckle-tracking echocardiography were all affected in FD. Enzyme replacement therapy improved LA function. Left atrial strain parameters were associated with atrial fibrillation and stroke.