Quantifying Atrial Volumetric Measures
Atrial volumetric quantities, such as end-diastolic and end-systolic volumes (ml), their indices (ml/m2), as well as ejection fractions (%), may be determined using electrocardiogram (ECG)-gated, balanced steady state free precession sequences. To acquire these measures, each atrium is analyzed separately (F1-F3). However, the analysis for each cavity is the same and proceeds accordingly:
Atrial end diastole –the phase usually occurring within the first 40% of the cardiac cycle and during which these chambers are largest— and atrial end systole—the phase occurring during the end of the cardiac cycle and during which these chambers are smallest—are chosen from all phases of one complete cardiac cycle on a 2-chamber, short-axis view. (It is important to recall that atrial and ventricular volumes are inverted relative to one another throughout the cardiac cycle.) Next, volumetric data may be acquired manually or automatically using suiteHEARTTM software.
To obtain these measures manually, for each atrium, the atrial epicardial borders of all slices belonging to the end-diastolic phase are traced (F1, F2). The software subsequently sums the volumes from each slice, generating the total atrial end-diastolic volume. The process is repeated for the end-systolic slice, generating the total atrial end-systolic volume, as well as other volumetric measures (F1, F2).
Software automation also may be employed to acquire these data using “Fast” mode. On a 4-chamber, long-axis view, the epicardial border of a single, end-diastolic slice—containing the greatest atrial volume—is traced (F3). The software then automatically draws a center-of-rotation line, which may be adjusted such that it parallels the long axis of the atrium, across the cavity. Subsequently, the epicardial border of a single, end-systolic slice —containing the least atrial volume—is traced on the 4-chamber, long-axis view. The software then automatically draws the adjustable center-of-rotation line. Volumetric measures are reported automatically.