Prognostic implications of late gadolinium enhancement at the right ventricular insertion point in patients with non-ischemic dilated cardiomyopathy: A multicenter retrospective cohort study

Introduction
The presence of late gadolinium enhancement (LGE) at the right ventricular insertion point (RVIP) on cardiac magnetic resonance (CMR) is generally believed to be nonspecific, but the clinical implication of this unique LGE pattern in patients with non-ischemic dilated cardiomyopathy (NICM) has not been elucidated.
Objectives
We investigated the prognostic significance of RVIP-LGE in NICM patients.
Methods
A total of 360 consecutive NICM patients referred for CMR (102 with no LGE, 50 with RVIP-LGE, 121 with left ventricular [LV]-LGE, and 87 with both an LV and RVIP-LGE) were studied. The primary endpoint was a composite of the all-cause death, hospitalization due to worsening of heart failure, and major arrhythmic events.
Results
During a mean follow-up of 45.2 ± 36.5 months, 149 (41.4%) patients (22 [21.6%] no LGE vs. 16 [32.0%] RVIP-LGE vs. 62 [51.2%] LV-LGE vs. 49 [56.3%] both LV and RVIP-LGE, P < 0.0001) reached the primary endpoint. A Kaplan Meier curve demonstrated that RVIP-LGE patients had an intermediate trend of an event free survival rate for the composite endpoint (log-rank P < 0.0001). In a multivariable Cox regression model, LV-LGE (P = 0.008) and both LV and RVIP-LGE (P = 0.003) were significantly associated with a worse outcome, whereas RVIP-LGE was not (P = 0.101). In addition, RVIP-LGE patients (n = 32) had a more favorable outcome compared to LV-LGE patients (n = 32) even after matching the extent of the LGE (median 3.4% [interquartile range, 3.1–3.8], 8 [25.0%] RVIP-LGE vs. 20 [62.5%] LV-LGE, P = 0.002).
Conclusions
LGE confined to the RVIP among NICM patients did not significantly increase the risk of adverse cardiac events, and also showed a better outcome than the same extent of LGE located in the LV. Identification of this unique LGE distribution may help refine the current risk stratification.

引言
目前学界普遍认为，心脏磁共振（cardiac magnetic resonance, CMR）成像中于右心室插入点（right ventricular insertion point, RVIP）处出现的钆延迟强化（late gadolinium enhancement, LGE）表现并无特异性，但该独特的LGE模式在非缺血性扩张型心肌病（non-ischemic dilated cardiomyopathy, NICM）患者中的临床意义尚未阐明。

研究目的
本研究旨在探讨NICM患者中RVIP-LGE的预后意义。

研究方法
本研究共纳入360例连续就诊、接受CMR检查的NICM患者，其中无LGE者102例、仅RVIP-LGE者50例、仅左心室（left ventricular, LV）-LGE者121例、同时存在LV-LGE与RVIP-LGE者87例。本研究的主要终点为复合终点，包括全因死亡、因心力衰竭恶化住院以及严重心律失常事件。

研究结果
在平均45.2±36.5个月的随访期间，共有149例（41.4%）患者达到主要复合终点：无LGE组22例（21.6%）、RVIP-LGE组16例（32.0%）、LV-LGE组62例（51.2%）、同时存在LV-LGE与RVIP-LGE组49例（56.3%），组间差异具有显著统计学意义（P < 0.0001）。Kaplan-Meier曲线分析显示，RVIP-LGE患者的复合终点无事件生存率呈中间趋势（对数秩检验P < 0.0001）。多变量Cox回归分析结果表明，LV-LGE（P=0.008）以及同时存在LV-LGE与RVIP-LGE（P=0.003）均与不良预后显著相关，而单纯RVIP-LGE则无此关联（P=0.101）。此外，在匹配LGE负荷程度（中位数3.4%，四分位数间距3.1~3.8）后，RVIP-LGE患者（n=32）的预后仍优于LV-LGE患者（n=32）：RVIP-LGE组有8例（25.0%）达到终点，LV-LGE组则为20例（62.5%），组间差异显著（P=0.002）。

研究结论
在NICM患者中，仅局限于RVIP的LGE并不会显著增加不良心脏事件的发生风险，且其预后优于负荷程度相当的左心室LGE。识别该独特的LGE分布模式，有助于优化当前的危险分层策略。