Chronic type B aortic dissection (TBAD) is associated with poor long-term outcome, and accurate risk stratification tools remain lacking. Pressurization of the false lumen (FL) has been recognized as central in promoting aortic growth. Several surrogate imaging-based metrics have been proposed to assess FL hemodynamics; however, their relationship to enlarging aortic dimensions remains unclear. We investigated the association between aortic growth and three cardiovascular magnetic resonance (CMR)-derived metrics of FL pressurization: false lumen ejection fraction (FLEF), maximum systolic deceleration rate (MSDR), and FL relative pressure (FL ΔPmax). CMR/CMR angiography was performed in 12 patients with chronic dissection of the descending thoracoabdominal aorta, including contrast-enhanced CMR angiography and time-resolved three-dimensional phase-contrast CMR (4D Flow CMR). Aortic growth rate was calculated as the change in maximal aortic diameter between baseline and follow-up imaging studies over the time interval, with patients categorized as having either ‘stable’ (< 3 mm/year) or ‘enlarging’ (≥ 3 mm/year) growth. Three metrics relating to FL pressurization were defined as: (1) FLEF: the ratio between retrograde and antegrade flow at the TBAD entry tear, (2) MSDR: the absolute difference between maximum and minimum systolic acceleration in the proximal FL, and (3) FL ΔPmax: the difference in absolute pressure between aortic root and distal FL. FLEF was higher in enlarging TBAD (49.0 ± 17.9% vs. 10.0 ± 11.9%, p = 0.002), whereas FL ΔPmax was lower (32.2 ± 10.8 vs. 57.2 ± 12.5 mmHg/m, p = 0.017). MSDR and conventional anatomic variables did not differ significantly between groups. FLEF showed positive (r = 0.78, p = 0.003) correlation with aortic growth rate whereas FL ΔPmax showed negative correlation (r = − 0.64, p = 0.026). FLEF and FL ΔPmax remained as independent predictors of aortic growth rate after adjusting for baseline aortic diameter. Comparative analysis of three 4D flow CMR metrics of TBAD FL pressurization demonstrated that those that focusing on retrograde flow (FLEF) and relative pressure (FL ΔPmax) independently correlated with growth and differentiated patients with enlarging and stable descending aortic dissections. These results emphasize the highly variable nature of aortic hemodynamics in TBAD patients, and suggest that 4D Flow CMR derived metrics of FL pressurization may be useful to separate patients at highest and lowest risk for progressive aortic growth and complications.

中文翻译：

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使用 4D 血流心血管磁共振估计 B 型主动脉夹层假腔压力：与主动脉生长的比较


慢性 B 型主动脉夹层 (TBAD) 与长期预后不良相关，并且仍然缺乏准确的风险分层工具。假腔 (FL) 的加压已被认为是促进主动脉生长的核心。已经提出了几种基于替代成像的指标来评估 FL 血流动力学；然而，它们与主动脉尺寸扩大的关系仍不清楚。我们研究了主动脉生长与三个心血管磁共振 (CMR) 衍生的 FL 加压指标之间的关联：假腔射血分数 (FLEF)、最大收缩期减速率 (MSDR) 和 FL 相对压力 (FL ΔPmax)。对12例胸腹降主动脉慢性夹层患者进行了CMR/CMR血管造影，包括对比增强CMR血管造影和时间分辨三维相位对比CMR（4D Flow CMR）。主动脉生长率计算为一段时间内基线和后续影像学研究之间最大主动脉直径的变化，患者被分类为“稳定”（< 3 毫米/年）或“扩大”（≥ 3 毫米/年）年）的增长。与 FL 加压相关的三个指标被定义为：(1) FLEF：TBAD 入口撕裂处的逆行和顺行血流之比，(2) MSDR：近端 FL 的最大和最小收缩加速度之间的绝对差，以及(3 ) FL ΔPmax：主动脉根部和远端 FL 之间的绝对压力差。 FLEF 在扩大 TBAD 方面较高（49.0 ± 17.9% vs. 10.0 ± 11.9%，p = 0.002），而 FL ΔPmax 较低（32.2 ± 10.8 vs. 57.2 ± 12.5 mmHg/m，p = 0.017）。 MSDR 和传统解剖变量在各组之间没有显着差异。 FLEF 显示阳性（r = 0.78，p = 0。003）与主动脉生长率相关，而 FL ΔPmax 显示负相关（r = − 0.64，p = 0.026）。在调整基线主动脉直径后，FLEF 和 FL ΔPmax 仍然是主动脉生长速率的独立预测因子。对 TBAD FL 加压的三个 4D 血流 CMR 指标的比较分析表明，那些关注逆行血流 (FLEF) 和相对压力 (FL ΔPmax) 的指标与生长和分化的降主动脉夹层扩大且稳定的患者独立相关。这些结果强调了 TBAD 患者主动脉血流动力学的高度可变性，并表明 4D Flow CMR 导出的 FL 加压指标可能有助于区分进展性主动脉生长和并发症风险最高和最低的患者。