Zhao Lei, Li Songnan, Ma Xiaohai, Greiser Andreas, Zhang Tianjing, An Jing, Bai Rong, Dong Jianzeng, Fan Zhanming
Department of Radiology, Beijing Anzhen Hospital, Capital Medical University, 100029, Beijing, China.
Department of Cardiology, Beijing Anzhen Hospital, Capital Medical University, Beijing, China.
J Cardiovasc Magn Reson. 2016 Mar 15;18:13. doi: 10.1186/s12968-016-0232-7.
T1 mapping enables assessment of myocardial characteristics. As the most common type of arrhythmia, atrial fibrillation (AF) is often accompanied by a variety of cardiac pathologies, whereby the irregular and usually rapid ventricle rate of AF may cause inaccurate T1 estimation due to mis-triggering and inadequate magnetization recovery. We hypothesized that systolic T1 mapping with a heart-rate-dependent (HRD) pulse sequence scheme may overcome this issue.
30 patients with AF and 13 healthy volunteers were enrolled and underwent cardiovascular magnetic resonance (CMR) at 3 T. CMR was repeated for 3 patients after electric cardioversion and for 2 volunteers after lowering heart rate (HR). A Modified Look-Locker Inversion Recovery (MOLLI) sequence was acquired before and 15 min after administration of 0.1 mmol/kg gadopentetate dimeglumine. For AF patients, both the fixed 5(3)3/4(1)3(1)2 and the HRD sampling scheme were performed at diastole and systole, respectively. The HRD pulse sequence sampling scheme was 5(n)3/4(n)3(n)2, where n was determined by the heart rate to ensure adequate magnetization recovery. Image quality of T1 maps was assessed. T1 times were measured in myocardium and blood. Extracellular volume fraction (ECV) was calculated.
In volunteers with repeated T1 mapping, the myocardial native T1 and ECV generated from the 1st fixed sampling scheme were smaller than from the 1st HRD and 2nd fixed sampling scheme. In healthy volunteers, the overall native T1 times and ECV of the left ventricle (LV) in diastolic T1 maps were greater than in systolic T1 maps (P < 0.01, P < 0.05). In the 3 AF patients that had received electrical cardioversion therapy, the myocardial native T1 times and ECV generated from the fixed sampling scheme were smaller than in the 1st and 2nd HRD sampling scheme (all P < 0.05). In patients with AF (HR: 88 ± 20 bpm, HR fluctuation: 12 ± 9 bpm), more T1 maps with artifact were found in diastole than in systole (P < 0.01). The overall native T1 times and ECV of the left ventricle (LV) in diastolic T1 maps were greater than systolic T1 maps, either with fixed or HRD sampling scheme (all P < 0.05).
Systolic MOLLI T1 mapping with heart-rate-dependent pulse sequence scheme can improve image quality and avoid T1 underestimation. It is feasible and with further validation may extend clinical applicability of T1 mapping to patients with atrial fibrillation.
T1 映射可用于评估心肌特征。心房颤动（AF）作为最常见的心律失常类型，常伴有多种心脏病变，AF 时不规则且通常较快的心室率可能因触发错误和磁化恢复不足导致 T1 估计不准确。我们假设采用心率依赖性（HRD）脉冲序列方案的收缩期 T1 映射可能会克服这一问题。
纳入 30 例 AF 患者和 13 名健康志愿者，在 3T 下进行心血管磁共振（CMR）检查。3 例患者在电复律后、2 名志愿者在心率降低后重复进行 CMR 检查。在静脉注射 0.1 mmol/kg 钆喷酸葡胺前及给药后 15 分钟采集改良 Look-Locker 反转恢复（MOLLI）序列。对于 AF 患者，分别在舒张期和收缩期采用固定的 5(3)3/4(1)3(1)2 和 HRD 采样方案。HRD 脉冲序列采样方案为 5(n)3/4(n)3(n)2，其中 n 根据心率确定以确保足够的磁化恢复。评估 T1 映射的图像质量。测量心肌和血液中的 T1 时间。计算细胞外容积分数（ECV）。
在重复进行 T1 映射的志愿者中，第一种固定采样方案生成的心肌固有 T1 和 ECV 小于第一种 HRD 和第二种固定采样方案。在健康志愿者中，舒张期 T1 映射中心肌固有 T1 时间和左心室（LV）的 ECV 总体上大于收缩期 T1 映射（P < 0.01，P < 0.05）。在 3 例接受电复律治疗的 AF 患者中，固定采样方案生成的心肌固有 T1 时间和 ECV 小于第一种和第二种 HRD 采样方案（均 P < 0.05）。在 AF 患者（心率：88 ± 20 次/分钟，心率波动：12 ± 9 次/分钟）中，舒张期发现有伪影的 T1 映射比收缩期更多（P < 0.01）。无论是采用固定还是 HRD 采样方案，舒张期 T1 映射中心肌固有 T1 时间和左心室（LV）的 ECV 总体上大于收缩期 T1 映射（均 P < 0.05）。
采用心率依赖性脉冲序列方案的收缩期 MOLLI T1 映射可提高图像质量并避免 T1 低估。该方法可行，经进一步验证后可能会将 T1 映射的临床适用性扩展至心房颤动患者。
