Division of Cardiovascular Medicine, Radcliffe Department of Medicine, John Radcliffe Hospital, University of Oxford, West Wing, Headley Way, Oxford, UK.
The University of Oxford Centre for Clinical Magnetic Resonance Research (OCMR), Oxford, UK.
J Cardiovasc Magn Reson. 2021 Mar 22;23(1):29. doi: 10.1186/s12968-021-00729-0.
Four-dimensional (4D) flow cardiovascular magnetic resonance (CMR) allows sophisticated quantification of left atrial (LA) blood flow, and could yield novel biomarkers of propensity for intra-cardiac thrombus formation and embolic stroke. As reproducibility is critically important to diagnostic performance, we systematically investigated technical and temporal variation of LA 4D flow in atrial fibrillation (AF) and sinus rhythm (SR).
Eighty-six subjects (SR, n = 64; AF, n = 22) with wide-ranging stroke risk (CHADSVASc 0-6) underwent LA 4D flow assessment of peak and mean velocity, vorticity, vortex volume, and stasis. Eighty-five (99%) underwent a second acquisition within the same session, and 74 (86%) also returned at 30 (27-35) days for an interval scan. We assessed variability attributable to manual contouring (intra- and inter-observer), and subject repositioning and reacquisition of data, both within the same session (same-day scan-rescan), and over time (interval scan). Within-subject coefficients of variation (CV) and bootstrapped 95% CIs were calculated and compared.
Same-day scan-rescan CVs were 6% for peak velocity, 5% for mean velocity, 7% for vorticity, 9% for vortex volume, and 10% for stasis, and were similar between SR and AF subjects (all p > 0.05). Interval-scan variability was similar to same-day scan-rescan variability for peak velocity, vorticity, and vortex volume (all p > 0.05), and higher for stasis and mean velocity (interval scan CVs of 14% and 8%, respectively, both p < 0.05). Longitudinal changes in heart rate and blood pressure at the interval scan in the same subjects were associated with significantly higher variability for LA stasis (p = 0.024), but not for the remaining flow parameters (all p > 0.05). SR subjects showed significantly greater interval-scan variability than AF patients for mean velocity, vortex volume, and stasis (all p < 0.05), but not peak velocity or vorticity (both p > 0.05).
LA peak velocity and vorticity are the most reproducible and temporally stable novel LA 4D flow biomarkers, and are robust to changes in heart rate, blood pressure, and differences in heart rhythm.
四维（4D）血流心血管磁共振（CMR）可对左心房（LA）血流进行复杂的定量分析，并可能产生新的血栓形成和心内栓塞倾向的生物标志物。由于重复性对诊断性能至关重要，因此我们系统性地研究了心房颤动（AF）和窦性节律（SR）中 LA 4D 流的技术和时间变化。
86 名受试者（SR，n=64；AF，n=22）的卒中风险范围广泛（CHADSVASc 0-6），进行 LA 4D 流速的峰值和平均速度、涡流、涡旋体积和停滞的评估。85 名（99%）受试者在同一检查中进行了第二次采集，74 名（86%）受试者也在 30 天（27-35 天）内进行了间隔扫描。我们评估了归因于手动轮廓（内部和外部观察者）、受试者重新定位以及同一检查内（同日扫描-重扫描）和随时间（间隔扫描）重新获取数据的可变性。计算了受试者内变异系数（CV）和 bootstrap 95%置信区间，并进行了比较。
同日扫描-重扫描的 CV 分别为峰值速度的 6%、平均速度的 5%、涡流的 7%、涡旋体积的 9%和停滞的 10%，且在 SR 和 AF 患者之间相似（均 p>0.05）。峰值速度、涡流和涡旋体积的间隔扫描可变性与同日扫描-重扫描相似（均 p>0.05），而停滞和平均速度的间隔扫描可变性较高（间隔扫描 CV 分别为 14%和 8%，均 p<0.05）。同一受试者在间隔扫描时的心率和血压的纵向变化与 LA 停滞的变异性显著相关（p=0.024），但与其余血流参数无关（均 p>0.05）。SR 受试者的平均速度、涡旋体积和停滞的间隔扫描变异性明显大于 AF 患者（均 p<0.05），但峰值速度和涡流无差异（均 p>0.05）。
LA 峰值速度和涡流是最具可重复性和时间稳定性的新型 LA 4D 血流生物标志物，并且对心率、血压变化和节律差异具有稳健性。
