The Impact of Foreshortening on Regional Strain – A Comparison of Regional Strain Evaluation Between Speckle Tracking and Tissue Velocity Imaging

Abstract

Purpose: The conventional parameter of systolic function is global left ventricular (LV) ejection fraction (EF), but this parameter will be replaced by global strain because it seems to be more robust. However, regional strain differences can have a significant impact on global strain. Thus, the aim of the present study was to evaluate the effect of non-standardized scanning on regional strain values determined by 2D speckle tracking and tissue velocity imaging (TVI). Regional longitudinal peak systolic strain (PSS) was measured in standardized data sets of the apical 4-chamber view (ChV) and in a standardized oblique foreshortened view in patients with normal wall motion patterns.

Materials and Methods: A standardized 4ChV and a foreshortened 4ChV – defined by distinct cardiac structures – were acquired using a Vivid E9 system in 54 patients. All regional PSS values measured in monoplane 2D loops in lateral and septal regions were analyzed to detect the differences between regional strain measured in the standard and the foreshortened view.

Results: Significant PSS differences due to FS were detected in patients using 2D speckle tracking for the basal septal regions (p < 0.001). No significant differences due to FS were detected in patients during the analysis of TVI-based strain values (p > 0.05, paired sample T-test).

Conclusion: To our knowledge this is the first study focusing on methodological aspects – especially standardization – using speckle tracking and TVI. Due to the lower accuracy of strain calculation based on TVI in basal regions, foreshortening has no significant impact on quantitative parameters of TVI-derived strain values in normal contracting hearts. Using speckle tracking, however, foreshortening induces significant differences of basal septal strain in normal contracting hearts. In the presence of regional wall motion defects, a lack of standardization of the views will cause inhomogeneous patterns of regional strain depending on the scan planes through the center of the infarction or its penumbra. Thus, non-standardization will have a significant impact on deformation parameters in 2D echocardiography.

Zusammenfassung

Ziel: Der konventionelle Parameter der globalen systolischen Funktion ist die linksventrikuläre (LV) Ejektionsfraktion (EF). Es ist anzunehmen, dass dieser Parameter durch den wohl robusteren Parameter des globalen Strains ersetzt wird. Regionale Unterschiede des Strains könnten jedoch einen signifikanten Einfluss auf den globalen Strain-Wert haben. Daher war das Ziel der vorliegenden Arbeit, den Einfluss eines nicht standardisierten, fehlerhaften Scannens auf die Strain-Werte zu ermitteln, die mittels 2D-Speckle-Tracking und Gewebe-Doppler (TVI – tissue velocity imaging) bestimmt wurden. Der regionale longitudinale maximale systolische Strain (PSS) wurde in standardisierten Datensätzen des apikalen 4-Kammerblicks (ChV) sowie in einem standardisierten „foreshortening view” des sogenannten 5-Kammerblicks bei Patienten mit normalen LV-Kontraktionsmustern gemessen.

Material und Methoden: Standardisierte Schnittebenen des 4- und 5-Kammerblicks wurden in 54 Patienten mit einem Vivid-E9-Ultraschall-System aufgenommen. Alle regionalen PSS-Werte wurden in monoplanen 2D-Cineloops jeweils in der lateralen und septalen Region ermittelt, um eventuelle methodenbedingte Unterschiede der regionalen Strain-Werte zu detektieren.

Ergebnisse: Signifikante PSS-Unterschiede infolge des „foreshortening” zeigten die basalen septalen Regionen bei der 2D-Speckle-Tracking-Analyse (p < 0,001). Dagegen wurden keine signifikanten methodenbedingten Unterschiede bei der TVI-basierten Strain-Analyse ermittelt (p > 0,05; paired sample T-test).

Schlussfolgerung: Nach unserem Wissen ist diese Arbeit die erste Studie, die sich mit methodischen Aspekten – speziell der Standardisierung – des Deformations-Imagings für die Anwendung des 2D-Speckle-Trackings und des Gewebe-Dopplers befasst. Aufgrund der geringeren Genauigkeit der Strain-Berechnungen der TVI-basierten Daten in den basalen Septumregionen hat das „foreshortening” des apikalen 4-Kammerblicks keinen signifikanten Effekt auf die quantitativen Parameter des TVI-basierten Strains im normal kontrahierenden menschlichen Herzen. Bei 2D-Speckle-Tracking finden sich jedoch selbst unter Normalbedingungen bei „foreshortening views” des 4-Kammerblicks signifikante Unterschiede des basalen regionalen Strains. Bei regionalen Wandbewegungsstörungen kann eine fehlende Standardisierung durch schräge apikale Anlotungen des Herzens unterschiedliche und falsche Muster der regionalen Kontraktion verursachen. Es ist dabei essenziell, ob die Infarktregion zentral oder in der Penumbra des Infarkts getroffen wird. Aus diesem Grund hat eine fehlende Standardisierung in der 2D-Echokardiografie einen signifikanten Einfluss auf die myokardialen Deformations-Parameter des 2D-Strains.

Key words

heart - ultrasound 2 D - technical aspects - foreshortening - peak systolic strain

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