P4762d strain in patients with reduced image quality: effect of microbubble contrast (MBC) on segmental tracking

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2Dstrain analysis requires an acceptable image quality for speckles to be tracked. MBC alters the myocardial speckle pattern and improves identification of the left ventricle endocardial border. We have previously shown that segmental tracking and reproducibility is reduced in patients with acceptable image quality when MBC is present in the circulation. The purpose of this study was to assess how MBC affects the performance of the speckle tracking algorithm in patients with reduced image quality.Methods: Before, during, 3 and 7 minutes after MBC infusion (Sonovue), three standard apical loops were recorded on a Vivid-7 machine (mechanical index: 1.0) and analysed off line twice on two different days, using an 18 segments model of the left ventricle. Strain analyses (EchoPac, GE) were performed on different days with the operator blinded to the results of the analyses from the other time points. Tracking quality (TQ) was defined as the percentage of acceptable tracked segments. Changes over time were analysed as repeated measurements by univariate ANOVA. Reproducibility of peak systolic segmental strain (PSSS) was assessed with the Bland Altman method and expressed as the coefficient of repeatability (COR).Results: Twenty-nine consecutive patients with normal echocardiograms were included. All had stable angina but no previously known heart disease. Patients were divided into two groups: Baseline TQ<80% (10 patients) and baseline TQ≥80% (19 patients). TQ significantly improved during and after MBC infusion in the TQ<80% group (p=0.002), but was impaired in the TQ≥80% group (p=0.008). Baseline PSSS (mean (SD)) was -22.74 (6.34) % in the TQ<80% group and -22.94 (5.66) % in the TQ≥80% group (p=0.77). Reproducibility of PSSS was significantly impaired during and after MBC infusion, table.Conclusion: MBC seems to improve TQ in patients with reduced image quality but the reproducibility of the readings is compromised.

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