BACKGROUND Conduction disease and arrhythmias represent a major cause of mortality in myotonic muscular dystrophy type 1 (MMD1). Permanent pacemaker (PPM) implantation is the cornerstone of therapy to reduce cardiovascular mortality in MMD1. Cardiovascular magnetic resonance (CMR) studies demonstrate a high prevalence of myocardial fibrosis in MMD1, however the association between CMR myocardial fibrosis with late gadolinium enhancement (CMR-LGE) and surface conduction abnormality is not well established in MMD1. We investigated whether myocardial fibrosis by CMR-LGE is associated with surface conduction abnormalities meeting criteria for PPM implantation according to current guidelines in a cohort of patients with genetically confirmed MMD1. METHODS Patients with genetically confirmed MMD1 were retrospectively evaluated. 12-lead electrocardiography (ECG) performed within 6 months of CMR was necessary for inclusion. The severity and extent of MMD1 was quantified using a validated Muscular Impairment Rating Scale (MIRS). Based on current guidelines for device-based therapy of cardiac rhythm abnormalities, we defined surface conduction abnormality as the presence of ECG alterations meeting criteria for PPM implant (class I or II indications): PR interval > 200 ms (type I atrioventricular (AV) block) and/or mono or bifascicular block (QRS > 120 ms), or evidence of advanced AV block. Balanced steady-state free precession sequences (bSSFP) were used for assessment of left ventricular (LV) volumes and ejection fraction. MOdified Look-Locker Inversion Recovery (MOLLI) acquisition schemes were used to acquire T1 maps. Patients' charts were reviewed up to 12 months post-CMR for occurrence of PPM implantation. RESULTS Fifty-two patients (38% male, 41 ± 14 years) were included. Overall, 31 (60%) patients had a surface conduction abnormality and 22 (42%) demonstrated midwall myocardial fibrosis by CMR-LGE. After a median of 57 days from CMR exam, 15 patients (29%) underwent PPM implantation. Subjects with vs. without surface conduction abnormality had significantly longer disease length (15.5 vs. 7.8 years, p = 0.015) and higher disease severity on the MIRS scale (p = 0.041). High prevalence of myocardial fibrosis by CMR-LGE was detected in subjects with and without surface conduction abnormality with no significant difference between the two cohorts (42% vs. 43%, p = 0.999). By multivariate logistic regression analysis, disease length was the only independent variable associated with surface conduction abnormality (OR 1.071, 95%CI 1.003-1.144, p = 0.040); while CMR-LGE was not associated with conduction abnormality (ρ = - 0.009, p = 0.949). CONCLUSIONS Myocardial fibrosis by CMR-LGE is highly prevalent in MMD1 but not related to surface conduction abnormality meeting current guideline criteria for PPM implantation .

中文翻译：

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强直性肌营养不良症 1 型晚期钆增强心血管磁共振导致的心肌纤维化：非常普遍，但与表面传导异常无关。


背景传导疾病和心律失常是强直性肌营养不良症1型(MMD1)死亡的主要原因。永久起搏器 (PPM) 植入是降低 MMD1 心血管死亡率的治疗基石。心血管磁共振 (CMR) 研究表明 MMD1 中心肌纤维化的发生率很高，但 MMD1 中 CMR 心肌纤维化伴晚期钆增强 (CMR-LGE) 与表面传导异常之间的关联尚未明确。我们根据当前指南，在一组经基因证实的 MMD1 患者中研究了 CMR-LGE 导致的心肌纤维化是否与符合 PPM 植入标准的表面传导异常相关。方法 对基因证实的 MMD1 患者进行回顾性评估。纳入研究需要在 CMR 6 个月内进行 12 导联心电图 (ECG)。使用经过验证的肌肉损伤评定量表 (MIRS) 对 MMD1 的严重程度和范围进行量化。根据当前基于设备的心律异常治疗指南，我们将表面传导异常定义为符合 PPM 植入标准的心电图改变（I 类或 II 类适应症）：PR 间期 > 200 ms（I 型房室 (AV)传导阻滞）和/或单束或双束传导阻滞（QRS > 120 ms），或晚期房室传导阻滞的证据。平衡稳态自由进动序列（bSSFP）用于评估左心室（LV）体积和射血分数。修改后的 Look-Locker 反转恢复 (MOLLI) 采集方案用于采集 T1 地图。在 CMR 后 12 个月内对患者的图表进行审查，以了解 PPM 植入的发生情况。结果 纳入 52 名患者（38% 为男性，41 ± 14 岁）。 总体而言，CMR-LGE 检测显示 31 名 (60%) 患者存在表面传导异常，22 名 (42%) 患者出现中壁心肌纤维化。 CMR 检查后平均 57 天后，15 名患者 (29%) 接受了 PPM 植入。具有表面传导异常的受试者与没有表面传导异常的受试者相比，其疾病持续时间显着更长（15.5 年与 7.8 年，p = 0.015），并且 MIRS 量表上的疾病严重程度更高（p = 0.041）。在有或没有表面传导异常的受试者中，CMR-LGE 检测到心肌纤维化的发生率很高，两个队列之间没有显着差异（42% vs. 43%，p = 0.999）。通过多变量逻辑回归分析，疾病长度是与表面传导异常相关的唯一自变量（OR 1.071，95%CI 1.003-1.144，p = 0.040）；而 CMR-LGE 与传导异常无关（ρ = - 0.009，p = 0.949）。结论 CMR-LGE 引起的心肌纤维化在 MMD1 中非常普遍，但与符合当前 PPM 植入指南标准的表面传导异常无关。