综述
心血管病领域人工智能的应用及展望
中华医学杂志, 2020,100(45) : 3649-3652. DOI: 10.3760/cma.j.cn112137-20200308-00642
摘要

人工智能作为变革性的新兴技术或能促进下一轮科技革命。医学领域人工智能技术虽然起步较晚但在国家政策的支持下发展迅速。心血管疾病作为我国的主要死因之一是社会重大的疾病负担,人工智能在心血管病领域的运用和发展则或能进一步促进该领域疾病诊治模式改变及管理水平的提升。本文就人工智能在该领域的现状做一综述及展望。

引用本文: 黄刚, 余秀琼, 刘汉雄, 等.  心血管病领域人工智能的应用及展望 [J] . 中华医学杂志, 2020, 100(45) : 3649-3652. DOI: 10.3760/cma.j.cn112137-20200308-00642.
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人工智能(artificial intelligence, AI)的出现将为精准医学的发展提供坚强支持。心血管疾病是当今全球的重大疾病负担,如何进一步提高心血管疾病的诊疗、管理、预防水平是心血管病学界的重要挑战,AI技术的发展及在心血管病领域的逐步应用将有望助力应对该挑战。本文就AI在心血管疾病辅助诊断[心电图、心脏彩超、心脏CT,心脏核磁共振(MRI)及心脏核素显像],心血管疾病介入治疗及疾病管理等方面的研究现状做一综述及展望。

一、AI概述

AI是可执行一般性人类智能任务的计算机程序,如鉴别模型、计划、识别物体、语言和声音、解决问题等。它也可视为机器或者仪器基于所收集数据自动做出决策的能力。而机器学习(machine learning,ML)是目前AI的主要亚类,它包括了监督学习,非监督学习及深入学习(deep learning,DL)等。监督学习中目前最常用的算法是人工神经网络(artificial neural network, ANN)和支持向量机。非监督学习包括了聚类算法和关联规则算法等。而DL包括了循环神经网络、卷积神经网络(convolutional neural networks,CNN)以及深度神经网络(deep neural networks, DNN)[1]

目前AI的应用研究多以现有"金标准"为参考(如医生对心电图、心脏彩超、MRI等检查结果的判断),依据所选择人群数据库建立、训练、优化模型,最后在不同的人群中验证、比较模型某方面的能力是否达到或超过"金标准"水平。

二、心血管疾病的辅助诊断
1.心电图:

心电图是心律失常及心肌梗死的重要诊断手段之一。目前的ML模型已能识别QRS波[2]、P波、T波及心电向量图[3],计算心率、电轴及间期。而DNN模型也可识别ST段改变,以及房颤、房扑、三联律、二联律、房室传导阻滞、室上速、交界性心律、室速、房性异位心律及心室自主心律,甚至其对房颤、三联律、房室传导阻滞等的诊断准确性超越了心电图医师[4]。同时,CNN辅助12导联心电图诊断心肌梗死并实现了心肌梗死定位(前壁和下壁)[5]。DL模型技术对胸痛患者中非ST段抬高性心肌梗死(NSTEMI)的鉴别诊断准确率高达93%[6]。在AI的帮助下心电图甚至超越了其传统的功能,如对无症状性心衰患者(射血分数<35%)的筛查[7]。总体而言,目前在心电图诊断中AI的应用已可实现常见心律失常以及心肌梗死的辅助诊断,与临床医师的诊断结论相比具有良好的准确性。

2.心脏彩超:

心脏彩超是评估心脏结构及功能最常用的手段,其准确性有赖于操作者的熟练度及对数据的正确分析。AI应用于心脏彩超评估心脏形态学及心功能测算,已实现超声影像辅助分析、检查变量的自动生成、心功能的自动测算以及部分疾病的辅助诊断。ML模型可在获得超声心动图像后,自动识别测量左室壁,且其效果与三维超声心动图和心脏MRI相当[8]。DL算法模型则可评估心肌梗死后有无局限性室壁活动障碍及部位范围,其准确性与专科医师水平一致且高于住院医师[9]。此外,AI模型分析计算的左室射血分数,纵向应变也与专科医师所得结果类似[10]。此外,AI也已用于疾病诊断及其表型的识别,如对二尖瓣反流严重程度的判断[11],运动员心脏与肥厚性心肌病的临床表型[12],限制性心肌病和缩窄性心包炎的鉴别[13],心肌淀粉样变,肺动脉高压等的诊断[14]。射血分数保留心衰患者临床表型的鉴别[15],心脏再同步化(CRT)治疗潜在获益患者的甄别等[16]

3.心脏CT:

AI在心脏CT中主要应用于冠状动脉狭窄、斑块性质、冠状动脉钙化的评估,冠状动脉血流建模等的自动分析诊断。AI辅助心脏CT中可自动降噪并保正最佳成像质量以明确冠状动脉狭窄程度。此外,DL模型的应用可降低CT图像采集的辐射剂量[17]。CNN可从常规冠状动脉CT血管成像(CTA)数据进行冠状动脉钙化评分,避免重复行CT并减少射线暴露[18]。AI还可辅助CTA识别冠状动脉狭窄、定量测定斑块[19]及冠状动脉血流灌注[20],生成清晰的血流储备分数(FFR)图像,较准确地识别冠状动脉斑块及其性质(如餐巾环征)[21]。AI助力冠状动脉CTA既可降低患者放射线暴露,又能提高CTA的诊断价值并减少诊断性冠状动脉造影数量。而AI深入辅助CTA评估冠状动脉病变及支持介入治疗决策的作用值得期待。

4.心脏MRI:

心脏MRI可评估心脏解剖结构、收缩功能,进行血流及灌注显像并显示心肌特征,因而它日益成为心肌病的重要诊断手段。但心脏MRI的图像质量受操作者、患者及仪器的影响,患者自身及患者间图像可比性较低[22],因而限制了AI在MRI中的应用。目前AI主要运用于心脏MRI图像自动分割[23]以及变量计算[24]。AI也应用于心脏MRI建模预测肺动脉高血患者生存率[25],评估法洛四联征手术患者心功能[26],辅助MRI心肌灌注显像判断冠心病患者预后[27]

5.心脏核素显像:

心脏核素显像中AI主要应用于评估心肌的灌注缺损,主要方法包括心肌灌注单光子发射计算机断层扫描和正电子发射断层扫描,它们都可与MRI或CT结合使用提高其临床价值,但检查中的放射暴露是限制其临床应用的一个重要因素。AI模型已用于辅助冠心病患者正常和异常心肌,静息/负荷状态下的心肌缺血的鉴别[28]。ML模型辅助的心肌核素显像比传统方法可以更好地预测重度冠状动脉狭窄[29]

6.心血管介入:

AI可应用于介入影像数据识别、分析以及决策支持。国内学者也已应用CNN模型分析冠状动脉造影结果[30]。ML模型已用于临界病变FFR的测定[31]、薄纤维帽粥样硬化斑块与斑块破裂的鉴别[32]。同时,AI也已辅助光学相干断层扫描(OCT)自动检测血管腔轮廓及支架撑杆,测量突出距离以及新生内膜厚度,进而评估支架内血栓和再狭窄[33]。ANN也被用于血管内超声(IVUS)对管腔边界、中层、外层界线的测量[34]

AI支持下的影像学分析、计算机视觉技术与机器人技术相结合,可能将促进未来机器人在心脏导管室中的运用,降低术者射线暴露、改善职业防护。一代、二代的机器人(CorPath GRX)已被引入心脏导管室[35]。一代机器人可通过机械臂完成导丝、球囊、支架的推送和后撤,但不能很好控制指引导管的运动。二代机器人则可主动操作控制指引导管沿长短轴的运动和旋转运动。目前机器人(CorPath 200 System)已可完成简单的经皮冠状动脉介入(PCI)手术(除外旋切、分叉病变、双支架植入、慢性闭塞病变、杂交手术等复杂情况),即便手术耗时略长,患者的临床结局、支架相关不良事件及射线暴露时间和人工组相比均无差异[36]。而国内学者尝试建立定性及定量评估介入医生操作技巧的新方法[37],利用隐马尔可夫模型能准确地识别医生导管操作手部细微动作,有望进一步助力改进机器人辅助的PCI手术平台性能[38]

虽然目前AI在导管室里的应用尚处于早期阶段,但未来基于AI技术的心脏导管室可能将由如下四部分组成:增强现实技术平台(全息手术指导平台上实时观看、测量、处理患者血管解剖学数据)、半自动/自动机器人系统(连接云超级计算机、采用ML、计算机视觉程序等技术、术者远处实施手术)、临床决策支持系统(集成电子病历、医学文献、指南及各种互联网信息,整合术中影像信息和患者状态以分析手术全过程,采用认知计算预测性分析,做出最佳临床决策)及智能语音辅助控制系统[39]。该导管室集各种功能于一体,一旦面世必将深刻促进心脏介入学的发展。

三、心血管疾病管理及临床决策

AI也运用于心血管疾病的危险分层及终点结局的预测,如ML模型技术运用于急诊胸痛患者分诊中急性心肌梗死诊断准确率高达94%[40]。同样,较传统风险预测工具,DL模型对心血管结局有更好的预测准确性[41],ML模型对无症状冠心病患者的5年全因死亡有更高的预测能力[42]。DL模型对急性心衰患者病死率也有良好的预测能力[43]。ML模型对收缩压的变异性以及对高血压患者不良结局的预测也有较好效果[44]。AI实质也已具体应用于疾病的全程诊疗链之中,以冠心病为例,目前AI已可辅助心电图、心脏彩超、CTA到冠状动脉造影、OCT及IVUS等各种诊疗决策检查。AI也已经被应用于临床决策[45],辅助临床指南的制定[46]以及基于指南的慢性病治疗策略[47]以及慢性病管理之中。

四、人工智能未来可期

AI模型能力的高低较大程度取决于所选择训练数据库,其运用范围的拓展主要取决于其算法的改进优化,以尽可能地让模型的能力达到人类智能水平。AI辅助医学诊断并提高临床诊断决策能力,但在短期内也无法取代临床医师独立完成任务,临床医生在建立训练、应用及解释AI模型中仍居主导地位。AI技术在人类社会中扮演的角色仍值得进一步思考及准确定位,是"人工智能"还是"智能人工"?而AI在临床医学中的应用也需注意潜在的伦理问题。

目前AI在心血管病领域有助于危急重症的快速识别诊断(如心肌梗死),降低漏诊率(如房颤),疑难病症的病因寻找(如心肌病),介入手术全程决策优化及术者保护,以及慢性病的管理及预后的判断(如高血压、冠心病、心力衰竭等)。此外,AI也可对以患者为中心的全程疾病诊疗、决策和管理发挥重要作用。如急性心肌梗死,患者就医时AI可辅助心电图快速检出,助力心脏彩超对局限性室壁活动障碍准确识别及心功能的评估,鉴别诊断中影像学数据的分析支持,临床处理决策流程支持,导管室冠状动脉造影中对靶血管病变及临界病变的判断和处理决策,以及不良事件的预测,后期康复治疗的全程管理。同时,AI进一步与可穿戴智能设备及5G技术的结合也将对慢性心血管疾病的诊断、治疗和康复的全程综合管理大有裨益。

未来AI以临床大数据及不断改进的算法为基础,若能整合基础研究领域如生物标志物、基因组学、蛋白质组学和代谢组学等的数据,预期可进一步提高其临床预测、决策价值,助力实现精准医疗并为患者提供更佳的个体化医疗服务,改善患者预后。

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