DETERMINATION OF NORMAL LV VOLUME AND EF BY CONTRAST ECHO AND COMPARISON WITH CARDIAC MRI

BACKGROUND: Ultrasound contrast agents have been recommended for assessment of LV volume and EF when the acoustic windows are poor. There is limited data comparing these measurements directly to those obtained using cardiac MRI (cMRI), which is regarded as the gold standard for LV volume and EF assessment. Hence, in the recently published ASE guidelines for chamber quantification, no normal valuef end-diastolic and end-systolic LV volume by contrast echo are provided. We aimed to compare the LV volumes and EF measured by contrast echocardiography with cMRI in patients with normal cardiac chamber size. METHODS: The Alberta Heart study is a large provincial registry in whom healthy volunteers and patients with heart failure with preserved ejection fraction undergo both echocardiographic and cMRI scans for assessment of LV volumes and EF. Patients were included if they had a cMRI and contrast echocardiogram performed within seven days of each other, and had normal LV size by cMRI (using normal values from 2013 ESC guidelines). LVEF by contrast echo was measured by biplane method of disks using bolus Definity contrast to optimize the endocardial definition. Correlation and mean differences between LV end-diastolic volume index (LVEDVI), LV end-systolic volume index (LVESI) and EF measured by contrast echo were compared to cMRI using t-tests and Pearson’s method, respectively. RESULTS: There were 69 patients with normal LV volumes by cardiac MRI. Duration between echo and MRI was 0.6 +/1.0 days. Mean LVEDVI measured by cardiac MRI was 68.4 +/12.2mL/m2 and 56.9 +/12.3mL/m2 by contrast echo (p<.0001). LVESVI obtained from MRI was 27.8 +/9 mL/ m2 compared to 22.5 +/7.5 mL/m2 by contrast echocardiography (p<.0001). There was correlation of LVEDVI between the two modalities (K1⁄40.587, p<0.001). There was no significant difference in the mean LV ejection fraction between MRI and contrast echocardiography (59.7 +/9.7% vs. 60.6 +/9.6 % respectively, p1⁄44.3). CONCLUSION: In a group of patients with normal LV size according to the gold standard cMRI, contrast echo underestimated LVEDVI by 11.5mL/m2 (17%) and LVESVI by 5.3 mL/m2 (19%). These differences should be taken into consideration when comparing volume measurements done with these modalities. Contrast echo was accurate compared with cMRI in assessment of LVEF. Considering the growing use of contrast echocardiography, a national registry is suggested to broaden the basis for normal values in this modality.