Systematic Assessment of the Impact of Ultrasound-Enhancing Agents upon Measurements of Cardiac Size and Function by Echocardiography

Background Echocardiography with an ultrasound-enhancing contrast agent (CON) is a powerful tool for identifying the endocardial border. However, the precise relationship of measurements obtained from CON to the reference values of two-dimensional unenhanced echocardiography (BASL) remains undefined, especially regarding wall thickness. The aim of this study was to systematically determine the differences between unenhanced and enhanced images for a broad range of left ventricular (LV) measurements and to define reference values for the relationship between the two methods. Methods We examined the echocardiograms of 624 consecutive patients in whom CON was performed for clinical indications. We excluded 192 patients in whom studies were technically difficult for measurement by either or both methods. Echocardiograms were from standard parasternal and apical views according to American Society of Echocardiography guidelines. Recordings were measured for wall thickness and chamber dimension in 343 patients and for LV volumes and ejection fraction in 212 patients. Results LV wall thickness measurements were systematically reduced with a bias of 0.2 cm with limits of agreement (LOA) from −0.5 to 0.16 cm in interventricular septal thickness, and from −0.46 to 0.13 cm in posterior wall thickness in CON. LV dimensions and volumes systematically increased with a bias of 0.2 cm (LOA, −0.19 to 0.58 cm) and 14 to 16 mL (LOA, −11.9 to 42.8 mL), respectively. LV ejection fraction systematically decreased with a bias of 3.4% (LOA, −13.5% to 6.8%) in CON compared to BASL. All differences showed normal distribution in the Kolmogorov-Smirnov test. Conclusion CON yields significantly different measurements of cardiac size and function compared to unenhanced imaging. These data define the systematic differences in measurements between CON and BASL images; the range of differences is narrow. These differences may influence management when the measurement value is a borderline.