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Impact of microbubble contrast on 2D strain quantification

Objective 2D strain analysis based on speckle tracking (EchoPAC, GE) allows semi-automatic quantification of myocardial deformation. Microbubble contrast (MBC) alters the speckle pattern, but the impact of MBC on speckle tracking has not been thoroughly studied. We investigated whether 2D strain analysis performed on contrast-enhanced recordings obtained with a normal mechanical index (MI) was possible, and evaluated if and how strain measurements and speckle tracking were affected by MBC. Methods and results Twenty-nine patients with normal echocardiograms were consecutively included and divided into two groups dependent on image quality (19 with high (HIQ) and 10 with low image quality (LIQ)). Before, during, three and seven minutes after MBC infusion (SonoVue, Bracco), the three standard apical loops were recorded (MI = 1.0) and analysed twice on two different days. Mean and regional (basal, md-ventricular and apical) left ventricular peak systolic strain were calculated at each time point. No significant changes over time were detected in mean or regional strain. Reproducibility worsened during and three minutes after MBC infusion and was generally poorer in the LIQ group. Tracking was impaired during MBC for the HIQ group, but improved throughout the examination for the LIQ group. Conclusions First, it was possible to quantify 2D strain from recordings obtained during or shortly after MBC infusion. Secondly, 2D strain measures were unaffected by the presence of MBC, and, thirdly, the reproducibility and the performance of the tracking algorithm were impaired when high intensities of MBC were present in the circulation.