肥厚型心肌病 -心血管疾病精准医疗离我们有多远

       自肥厚型心肌病（hypertrophic cardiomyopathy,HCM）被发现已逾50年，该疾病被认为是具有高猝死风险的遗传性疾病，并且临床表现多变、自然病程各异[1-5]，使该病早期诊断、预后判断存在了相当的困难。对于肥厚型心肌病的分子水平的认识时代始于上世纪90年代，研究者们发现其致病突变位于编码心肌肌小节相关蛋白的基因[4]，这一突破性的发现奠定了该疾病遗传学基础，并且预示着对于基因突变的检测与分析会为肥厚型心肌病的诊断、临床病程预测以及治疗指南带来一次革命[6,7]。

       随着基因检测技术手段的日新月异，检测效率的提高，许多与基因突变相关的疾病（如肿瘤）已借助分子诊断做到了超早期确诊，且能够指导治疗方向。精准医疗（Precision medicine）概念的提出便基于此，不同于原有的“一刀切”的治疗方法，而是从个体差异入手，深入了解不同患者最微小的分子和基因组信息，再根据这些信息的细微不同来调整制定个性化的诊疗方法。它的好处在于通过这种方法，把不同的患者个体进行分类，区别选择，预防和治疗都会集中在那些能够真正收到效果的患者身上，因而避免反复尝试各种治疗手段为患者带来的痛苦及对病情的延误，也避免了很多无用的治疗导致的医疗资源的浪费。作为心血管疾病中典型的遗传性疾病，并且是单基因心血管疾病中最为常见的疾病[8,9]，肥厚型心肌病无疑最有可能成为最先实现精准医疗的一个。

       肥厚型心肌病的精准医疗之路

       一、 疾病发现

       在上世纪50年代晚期，临床上出现了一种谜一样的心肌疾病，它困扰着当时的心血管病医生以及病理医生，它在不同患者中表现也有所差别，有的呈现室间隔不对称肥厚[1]、有的呈现主动脉瓣功能性狭窄[10,11]、有的呈现肥厚梗阻性心肌病变[12]、还有的呈现特发性主动脉瓣下肥厚狭窄[13]。最早的与不明原因心室肥厚相关的心源性猝死报道已有一个多世纪[14]，均是描述了具有戏剧性的临床事件，比如：14岁的健康青少年在学校操场追逐嬉戏时突然倒地身亡；一名自行车骑行者在雷电交加的天气中突然倒地身亡，却并未发现任何电击伤或来自于暴风雨造成的损伤[1]。尸检发现这些不幸猝死的人们都有着肥大的心脏，有的重量超过了500克，以及室间隔显著的不成比例的增厚。组织学上表现出肌束排列杂乱无章、细胞肥大以及显著的心肌纤维化。此后该类患者的解剖学、组织病理学以及血流动力学特点越来越多的被发现和描述，并且研究者们给各种异常起了很多的名称，这一方面说明了患者临床表现的多样性、另一方面也说明对于该疾病缺乏统一的专家共识。后经过包括美国心肺血液研究所（NHLBI）资助的贝塞斯达临床会议[17]在内的国际工作组织建立起了该疾病的诊断标准，对其解剖学、流出道梗阻压力阶差做出定义、评估了该病的自然病程，并提出了治疗策略。此后随着临床技术的提高以及对该疾病认识的深入，肥厚型心肌病相关指南在不断更新，最近一次正是高通量基因检测技术为病因诊断提供了良好平台后再次进行了调整[18,19]。

       二、 病因探索

       肥厚型心肌病被明确定义后，对其病因的讨论便广泛展开，大家认为潜在可能包括：心脏的良性肿瘤[1]、儿茶酚胺的过度激活[20]、心脏神经嵴细胞的异常增生[20]、以及人白细胞抗原介导的免疫反应[21]等等。但不论大家对此疾病感到如何迷惑，有两点临床特点是被统一认识的：1.左心室的肥厚是特发性的，其发生并不伴有常规的心肌肥厚诱因，比如主动脉瓣狭窄及高血压；2.患者呈家族聚集，患者的一级亲属患病风险较高。这就逐渐将病因的矛头指向了遗传性因素。

       在上世纪80年代中期，人类遗传学及心脏超声两项新的技术为肥厚型心肌病的深入研究提供了强大的手段。1980年Botstein和他的同事通过限制性内切酶将编码序列从基因组中分离出来的技术[23]，使遗传学家能够用于在染色体上定位与疾病相关的基因的生物学标记物不再限于ABO血型[24]、人白细胞抗原类型[25]。同时，结合统计方法学对于重组基因同源性进行评估[26]，使得该领域的家系连锁分析诞生。到1987年，人类第一张基因连锁图谱便被报道[28]。这一信息资源为发现所有遗传性疾病的基因突变提供了一个立足点，使得相关的实验设计变得简单、有效。同年，Seidman夫妇与McKenna团队对一个超过百人的肥厚型心肌病大家系进行了筛查，经过连锁分析将该家族与该病相关的基因变异定位于14号染色体长臂[35]，并很快发现其突变位点位于MYH7基因，确定了该疾病的病因为基因突变。后来，世界范围内不同团队又陆续发现TPM1[40]、TNNT2[41]、MYBPC3[42-44]、MYL3\MYL2[45]、TNNI3[46]、ACTC[47]等一系列编码肌小节相关蛋白的基因与肥厚型心肌病相关，其中NEXN基因就是由本研究组在世界范围内最先报道[48]。至今已发现40余个基因、至少1400个突变位点。

       心脏影像学是肥厚型心肌病的基因分析的重要依据，心脏介入造影手段一度成为该疾病的诊断金标准[29,30]，但这项有创手段在研究中应用也存在很大障碍，尤其是对于家族中临床上毫无症状和体征者。而心脏超声的出现与飞速发展解决了这一大难题，它使得家系筛查的成本及风险均大大降低[31-33]，也正是心脏超声技术的普及让研究者们对肥厚型心肌病的发病、患病情况有了更加深入的认识[8,9,34]。对于基因突变是通过何种途径影响了心肌功能，研究者们通过转基因动物等基础研究发现了以下可能：1.变异蛋白产生负性功能：由突变基因翻译出的发生改变的蛋白质被研究者们称为 “毒性蛋白”，它们与正常蛋白产生的功能不同，影响了肌小节正常的机械及电活动，一方面它们扰乱了肌纤维的排列使得心肌纤维收缩力改变[49，50,51]，另一方面它们增加了肌动蛋白激活的ATP酶敏感性导致心肌对于钙离子的敏感性和亲和力加强[52-54]、增加了心律失常甚至是猝死的风险；2.单倍体剂量不足：若患者染色体中其中一条的等位基因发生突变，则仅有一条正常等位基因能够翻译出功能正常的蛋白质，而异常蛋白或者mRNA会被泛素系统识别并降解[55]，从而使得正常蛋白量不足 [56]；3.能量代谢不平衡：由于对于钙离子的敏感性和亲和力增加，使得粗细肌丝横桥释放所需的能量增加，还有一种共识认为由于肌浆网上SERCA泵能量不足对钙离子重吸收下降、导致细胞间隙中钙离子浓度升高[57-58]，这些均使得心肌舒张功能下降，这一变化甚至早于心肌肥厚的发生。

       三、 预后判断及猝死危险分层

       肥厚型心肌病被人们所重视的很重要一个因素便是它能够导致猝死，尤其是年轻人猝死的主要因素（写上参考文献），然而除了猝死，其不良预后主要还包括心力衰竭、脑卒中等。据统计，患有肥厚型心肌病的患者中约6%发生猝死[60,61]，多为年轻患者，甚至可以发生在毫无任何症状者；约27%进展为心力衰竭，16%可通过药物控制症状、11%需要手术干预（心肌减容术或者酒精消融）[62]，术后患者生存率可以得到显著提高[63]，但仍有2%的患者其心衰无法通过以上手段得到控制而进入终末阶段，需要进行心脏移植[64，65]；另外还有约20%的患者会发生心房颤动和/或脑卒中[66]。通过以上数据我们可知，还有很大一部分患者（约一半）病情稳定、预后良好，和未患病者有着等长的预期寿命，这就提示对于患者的预后判断尤其是猝死风险的评估显得尤为重要：究竟哪些患者需要积极、早期的干预？哪些患者不需要过度治疗？成为了临床医生及患者最为关心的问题。

       世界范围内的研究者们希望通过对临床特点进行详细分层以指导对预后的判断，我们研究组就曾对患者性别[67]、是否伴发心肌肌桥[68]、心房颤动[69]，甚至包括C-反应蛋白、大内皮素、尿酸[70]等一系列生化指标在内的临床信息与患者预后进行过分析报道。2011年，由美国心脏病学会基金会(ACCF)/美国心脏学会(AHA)联合发表的肥厚型心肌病(HCM)诊断和治疗指南建议，在最初评估HCM患者时需同时对其进行心源性猝死(SCD)危险分层，主要包括：心室颤动、持续性室性心动过速或SCD事件，包括对室性快速心律失常进行合理的ICD治疗等病史；SCD家族史，包括对室性快速心律失常合理的ICD治疗；不能解释的晕厥；动态心电图(Holter)记录到3阵以上心率≥120次／分的非持续性室性心动过速；最大左室壁厚度≥30 mm[18]。2014年欧洲心脏病协会（ESC）发表了《2014 ESC肥厚型心肌病诊断和管理指南》[19]。该指南对成人心源性猝死风险的评估和预防建议是其中的主要亮点：一个涉及3675例患者的多中心、回顾性、纵向队列研究（HCM Risk-SCD）有所进展，并验证了一种新的肥厚型心肌病预测模型。该模型提供了个体化的5年风险评估，并和使用了4大主要风险因素的模型正面比较，其性能有了实质性的提高（C-指数0.54 ~ 0.7），可和其他相类似的预测算法（如CHA2DS2-VASc评估量表）相媲美。方程式如下：5年心源性猝死可能性=1-0.998exp（预后指数），其中预后指数=[0.15939858×最大室壁厚度(mm)]-[0.00294271×最大室壁厚度2(mm2)]+[0.0259082×左房内径(mm)]+[0.00446131×最大（静息/Valsalva动作）左心室流出道压力阶差(mmHg)]+[0.4583082×心源性猝死家族史]+[0.82639195×NSVT]+[0.71650361×不能解释晕厥]-[0.01799934×临床评估年龄（岁）]。

       然而该建议是基于观察性、回顾性队列研究的结果决定了临床特点和预后的关系，有一定的局限性，特别是它只能评估相对的风险，而非绝对的风险。并且：1. 它并不能说明个别风险因素效应值的差别，而像左心室壁肥厚等风险因素和风险持续增加有联系时，则视其为二元变量。因此，现在的风险计算法在高风险患者和低风险患者间应做适当调整。同样的，所纳入的压力阶差指的是患者未经手术治疗的值，而术后患者药物控制后压力阶差的降低是否也能影响猝死风险并未进行评估；2. 其所纳入计算的指标仍是基于传统的危险因素，一些新的可能与猝死风险相关的指标并没有考虑在内，比如通过磁共振轧延迟显像发现的心肌纤维化[71]； 3. 作为病因的基因突变并未纳入评估。事实上，作为肥厚型心肌病的根本病因，其不同突变与各异的临床表型之间必然有一定联系。虽然目前由于该病涉及到的突变异质性较大仍然难以通过非亲缘关系的患者进行大样本比较来定义良恶性突变或是通过基因突变直接预测临床后果[75,76]，但部分研究已经发现了某些特定的突变导致了较为恶劣的预后[4,6,72，77,78]。随着测序手段的进步，研究发现至少7%以上的患者携带不止一个相关基因的突变，即携带了复合突变、双突变甚至是三突变[73，74，79,80]，而携带多突变者预后显著较差[73,74，81]。我们研究团队通过对529名患者长达平均5年的随访，证实了携带多突变的患者预后显著差于携带单突变者：多突变携带者的心血管死亡风险、猝死风险以及进展为心衰的风险分别是其他患者的3.74倍、3.57倍和4.62倍[74]。另外，除了直接致病的基因突变，一些与心肌肥厚、心律失常等相关的修饰基因[82]的单核苷酸多态类型也间接影响着患者预后。

       四、 遗传信息指导下的精准治疗

       目前对于肥厚型心肌病的治疗主要集中在预防猝死、改善左室流出道梗阻症状，而针对病因的治疗则是患者更为迫切需要的。以上已提到基因突变主要是通过改变心肌最大张力、对钙离子敏感性及能量代谢异常等影响心肌重构，故而新的治疗手段则集中在针对这些方面进行改善。首先，心肌小节相关突变，尤其是粗肌丝相关基因MYH7突变，严重影响了肌纤维产生张力的能力、从而使心肌代偿性增生肥厚[83]，而强效、高选择性的心肌球蛋白抑制剂完全可以成为该类患者的治疗手段[84]。其次，在几乎所有突变类型的肥厚型心肌病患者中，心肌细胞对于钙离子的敏感性及亲和力均有所增加，blebbistatin（一种肌凝蛋白抑制剂）能够有效控制心律失常的药物正是由于降低了肌纤维对钙离子的敏感性[85]，而大量的实验证据也证明通过抑制钙离子与肌钙蛋白C的结合或直接抑制肌凝蛋白的启动均可以实现对钙离子敏感性的下调[86-89]，所以钙离子减敏剂将成为未来最有希望的治疗药物之一。而针对突变导致的能量代谢需求供小于求，能够增加心肌能量储备的药物，如Perhexiline，则能够有效改善心衰症状[90]，尤其对于非梗阻性患者能够改善心脏舒张功能、提高运动耐量[91]。

       而且，通过基因检测能够将仅凭临床手段难以鉴别的很多拟表型疾病区别出来，而这些疾病的治疗方法则与肥厚型心肌病有巨大差异。比如：1. 溶酶体贮积性疾病，如Anderson-Fabry（法布里）病，是a-半乳糖苷酶缺乏所导致的一种X-连锁隐性遗传病，其突变位于GLA 基因可通过补充α－半乳糖苷酶或转基因治疗；Hurler氏综合征，是a－L－艾杜糖醛苷酸酶缺乏所致，骨髓移植一直是治疗Hurler综合征的主要手段。2. 糖原贮积性疾病，如pome氏病、PRKAG2基因突变导致糖原贮积型心肌病、Forbes氏综合征，Danon氏综合征。3. 脂肪酸代谢障碍：如肉毒碱缺乏、磷酸化酶B激酶缺乏、线粒体细胞病。4. 其他与肥厚型心肌病相关的综合征：Noonan（努南）氏综合征、Leopard（豹斑）综合征、Friedreich共济失调、Beckwith-Wiedermann综合征、Swyer综合征。确诊肥厚型心肌病之前，特别是年轻、以心肌肥厚为主、多系统受累患者，尤其应当排除上述疾病，基因检测是非常重要的辅助手段。

       另外，某些特殊位点或基因突变可能导致某些相应的预后，虽然大部分信息来自家系研究，但也为临床判断提供了一定的依据。比如：某些突变位点有导致猝死的高风险[4,6,77,78]，需要尽早安装ICD预防猝死；携带TPM1基因突变患者心肌肥厚进展较快、肥厚程度较重，往往进展至终末期仅需几年，需要早做心脏移植供体准备[92]；携带TNNI3突变患者发生脑卒中比例较高，需警惕脑血管意外的发生等。而更为可靠的非亲缘关系大样本前瞻性研究，将更为准确地揭示基因型与表型之间的联系。

       展望

       提到精准医疗，肿瘤的治疗是最先进入人们视线的，作为与基因突变相关的疾病，基因检测结果对于治疗方法选择的指导性研究日新月异；而安吉丽娜朱莉对抗乳腺癌预防性切除乳房的行为也震撼性的将基因诊断推向了公众视野。今天我们谈精准医疗，“精准”二字是体现在从准确诊断到治疗指导再到预后评估的整个医疗过程中，它强调了需要承认和重视患者个体的特异性，而基因的差异在个体化特点中占重要地位。所以在分子水平，对基因变异的研究和应用必将是精准医疗的重要一环。当然，生活习惯以及外部环境对于疾病进展的影响也是确定的，但这些因素的影响程度大小又与个体之间的基因易感性相关。所以我们正处在一个需要大量积累信息的阶段，高通量测序技术使人类基因这本书在人类眼前展开，然而如不将基因信息很好的解读（即找到其所对应的表型找到），则这本书便是毫无意义的“天书”。大样本量，临床及遗传信息详尽的数据库的建立，准确的生物信息学分析将成为解决这一问题的有力武器。精准医疗之路可谓曙光在前，但任重而道远，需要临床医生、基础研究者乃至患者们的精诚合作，使我们的医疗过程的各个环节日益精准！

参考文献

1.Teare D. Asymmetrical hypertrophy of the heart in young adults. Br Heart J 1958:20:1– 8

2.Maron BJ. Hypertrophic cardiomyopathy: a systematic review. JAMA 2002;287:1308 –1320

3.Maron BJ, McKenna WJ, Danielson GK, et al. ACC/ESC clinical expert consensus document on hypertrophic cardiomyopathy. JACC 2003;42:1687–1713

4.Seidman CE, Seidman JG. Identifying sarcomere gene mutations in hypertrophic cardiomyopathy: a personal history. Circ Res 2011;108:743–750

5.Maron MS, Maron BJ, Harrigan C, et al. Hypertrophic cardiomyopathy phenotype revisited after 50 years with cardiovascular magnetic resonance. J Am Coll Cardiol 2009;54:220–228

6.Watkins H, Rosenzweig A, Hwang DS, et al. Characteristics and prognostic implications of myosin missense mutations in familial hypertrophic cardiomyopathy. N Engl J Med 1992;326:1108 –1114

7.Ho C. Genetics and clinical destiny: improving care in hypertrophic cardiomyopathy. Circulation 2010;122:2430–40

8.Maron BJ, Gardin JM, Flack JM, et al. Prevalence of hypertrophic cardiomyopathy in a general population of young adults. Circulation 1995;92:785–789

9.Zou Y, Song L, Wang Z, et al. Prevalence of idiopathic hypertrophic cardiomyopathy in China: a population-based echocardiographic analysis of 8080 adults. Am J Med. 2004 Jan 1;116(1):14-18.

10.Brock R. Functional obstruction of the left ventricle; acquired aortic subvalvar stenosis. Guys Hosp Rep. 1957;106:221–238

11.Morrow AG, Braunwald E. Functional aortic stenosis; a malformation characterized by resistance to left ventricular outflow without anatomic obstruction. Circulation. 1959;20:181–189

12.Goodwin JF, Hollman A, Cleland WP, et al. Obstructive cardiomyopathy simulating aortic stenosis. Br Heart J. 1960;22:403– 414

13.Braunwald E, Ebert PA. Hemogynamic alterations in idiopathic hypertrophic subaortic stenosis induced by sympathomimetic drugs. Am J Cardiol. 1962;10:489–495

14.Coats CJ, Hollman A. Hypertrophic cardiomyopathy: lessons from history. Heart. 2008;94:1258 –1263

15.Liouville H. Retrecissement cardiaque sous aortique. Gazette Medicale de Paris. 1869;24:161–163

16.Hallopeau M. Retrecissement ventriculo-aortique. Gazette Medicale de Paris. 1869;24:683– 687

17.Maron BJ, Gottdiener JS, Goldstein RE, et al. Hypertrophic cardiomyopathy: the great masquerader. Clinical conference from the Cardiology Branch of the National Heart, Lung, and Blood Institute, Bethesda, Md. Chest. 1978;74:659–670

18.Gersh BJ, Maron BJ, Bonow RO, et al. 2011 ACCF/AHA guideline for the diagnosis and treatment of hypertrophic cardiomyopathy: executive summary: a report of the American College of Cardiology Foundation/American Heart Association Task Force on Practice Guidelines.Circulation. 2011 Dec 13;124(24):2761-2796

19.Elliott PM, Anastasakis A, Borger MA, et al. 2014 ESC Guidelines on diagnosis and management of hypertrophic cardiomyopathy: the Task Force for the Diagnosis and Management of Hypertrophic Cardiomyo et al. pathy of the European Society of Cardiology (ESC).Eur Heart J. 2014 Oct 14;35(39):2733-79

20.Goodwin JF. Prospects and predictions for the cardiomyopathies. Circulation. 1974;50:210 –219

21.Darsee JR, Heymsfield SB, Nutter DO. Hypertrophic cardiomyopathy and human leukocyte antigen linkage: differentiation of two forms of hypertrophic cardiomyopathy. N Engl J Med. 1979;300:877– 882

22.Nutter DO, Heymsfield SB, Glenn JF, et al. Hypertrophic cardiomyopathy and human leukocyte antigen linkage: differentiation of two forms of hypertrophic cardiomyopathy. N Engl J Med 1979;300:877– 882. N Engl J Med. 1983;308:1400

23.Botstein D, White RL, Skolnick M, et al. Construction of a genetic linkage map in man using restriction fragment length polymorphisms. Am J Hum Genet. 1980;32:314 –331

24.Smith CA. Linkage in blood group genetics. Bibl Haematol. 1965;23: 263–267

25.Svejgaard A, Platz P, Ryder LP, et al. HL-A and disease associations–a survey. Transplant Rev. 1975;22:3– 43

26.Ott J. Estimation of the recombination fraction in human pedigrees: efficient computation of the likelihood for human linkage studies. Am J Hum Genet. 1974;26:588 –597

27.Gusella JF, Wexler NS, Conneally PM, et al. A polymorphic DNA marker genetically linked to Huntington’s disease. Nature. 1983;306:234 –238

28.Donis-Keller H, Green P, Helms C, et al. A genetic linkage map of the human genome. Cell. 1987;51:319 –337

29.Braunwald E, Lambrew CT, Rockoff SD, et al. Idiopathic hypertrophic subaortic stenosis. I. A description of the disease based upon an analysis of 64 patients. Circulation. 1964;30(suppl IV): 3–119

30.Wigle ED, Auger P, Marquis Y. Muscular subaortic stenosis. The direct relation between the intraventricular pressure difference and the left ventricular ejection time. Circulation. 1967;36:36–44

31.Popp RL, Harrison DC. Ultrasound in the diagnosis and evaluation of therapy of idiopathic hypertrophic subaortic stenosis. Circulation. 1969; 40:905–914.

32.Shah PM, Gramiak R, Adelman AG, et al. Role of echocardiography in diagnostic and hemodynamic assessment of hypertrophic subaortic stenosis. Circulation. 1971;44:891– 898.

33.Henry WL, Clark CE, Epstein SE. Asymmetric septal hypertrophy. Echocardiographic identification of the pathognomonic anatomic abnormality of IHSS. Circulation. 1973;47:225–233

34.Maron BJ, Gardin JM, Flack JM, et al. Prevalence of hypertrophic cardiomyopathy in a general population of young adults. Echocardiographic analysis of 4111 subjects in the CARDIA Study. Coronary Artery Risk Development in (Young) Adults. Circulation. 1995;92:785–789

35.Jarcho JA, McKenna W, Pare JA, et al. Mapping a gene for familial hypertrophic cardiomyopathy to chromosome 14q1. N Engl J Med. 1989;321:1372–1378.

36.Geisterfer-Lowrance AA, Kass S, Tanigawa G, et al. A molecular basis for familial hypertrophic cardiomyopathy: a beta cardiac myosin heavy chain gene missense mutation. Cell. 1990;62:999 –1006

37.Watkins H, Rosenzweig A, Hwang DS, et al. Characteristics and prognostic implications of myosin missense mutations in familial hypertrophic cardiomyopathy. N Engl J Med. 1992;326:1108 –1114

38.Marian AJ, Yu QT, Mares A Jr, et al. Detection of a new mutation in the beta-myosin heavy chain gene in an individual with hypertrophic cardiomyopathy. J Clin Invest. 1992;90: 2156–2165.

39.Dufour C, Dausse E, Fetler L, et al. Identification of a mutation near a functional site of the beta cardiac myosin heavy chain gene in a family with hypertrophic cardiomyopathy. J Mol Cell Cardiol. 1994;26: 1241–1247

40.Schleef M, Werner K, Satzger U, et al. Chromosomal localization and genomic cloning of the mouse alphatropomyosin gene Tpm-1. Genomics. 1993;17:519 –521

41.Thierfelder L, Watkins H, MacRae C, et al. Alpha-tropomyosin and cardiac troponin T mutations cause familial hypertrophic cardiomyopathy: a disease of the sarcomere. Cell. 1994;77:701–712

42.Gautel M, Zuffardi O, Freiburg A, et al. Phosphorylation switches specific for the cardiac isoform of myosin binding protein-C: a modulator of cardiac contraction? EMBO J. 1995;14:1952–1960.

43.Bonne G, Carrier L, Bercovici J, et al. Cardiac myosin binding protein-C gene splice acceptor site mutation is associated with familial hypertrophic cardiomyopathy. Nat Genet. 1995;11:438–440.

44.Watkins H, Conner D, Thierfelder L, et al. Mutations in the cardiac myosin binding protein-C gene on chromosome 11 cause familial hypertrophic cardiomyopathy. Nat Genet. 1995;11:434–437

45.Poetter K, Jiang H, Hassanzadeh S, et al. Mutations in either the essential or regulatory light chains of myosin are associated with a rare myopathy in human heart and skeletal muscle. Nat Genet. 1996;13: 63–69

46.Kimura A, Harada H, Park JE, et al. Mutations in the cardiac troponin I gene associated with hypertrophic cardiomyopathy. Nat Genet. 1997;16:379 –382

47.Olson TM, Doan TP, Kishimoto NY, et al. Inherited and de novo mutations in the cardiac actin gene cause hypertrophic cardiomyopathy. J Mol Cell Cardiol. 2000;32: 1687–1694

48.Wang H, Li Z, Wang J, et al. Mutations in NEXN, a Z-disc gene, are associated with hypertrophic cardiomyopathy. Am J Hum Genet. 2010 Nov 12;87(5):687-93.

49.Bottinelli R, Coviello DA, Redwood CS, et al. A mutant tropomyosin that causes hypertrophic cardiomyopathy is expressed in vivo and associated with an increased calcium sensitivity. Circ Res. 1998; 82:106–115

50.Seebohm B, Matinmehr F, Köhler J, et al. Cardiomyopathy mutations reveal variable region of myosin converter as major element of cross-bridge compliance. Biophys J. 2009; 97:806–824

51.Sommese RF, Sung J, Nag S, et al. Molecular consequences of the R453C hypertrophic cardiomyopathy mutation on human β-cardiac myosin motor function. Proc Natl Acad Sci USA. 2013; 110:12607–12612

52.Elliott K, Watkins H, Redwood CS. Altered regulatory properties of human cardiac troponin I mutants that cause hypertrophic cardiomyopathy. J Biol Chem. 2000; 275:22069–22077

53.Hernandez OM, Housmans PR, Potter JD. Pathophysiology of cardiac muscle contraction and relaxation as a result of alterations in thin filament regulation. J Appl Physiol. 2001; 90:1125–1136

54.Marston SB. How do mutations in contractile proteins cause the primary familial cardiomyopathies? J Cardiovasc Transl Res. 2011; 4:245–255

55.Vignier N, Schlossarek S, Fraysse B, et al. Nonsense- mediated MRNA decay and ubiquitinproteasome system regulate cardiac myosinbinding protein C mutant levels in cardiomyopathic mice. Circ Res 2009; 105: 239–248

56.Marston SB, Copeland O, Jacques A, et al. Evidence from human myectomy samples that MYBPC3 mutations cause hypertrophic cardiomyopathy through haploinsufficiency. Circ Res. 2009; 105:219–222

57.Javadpour MM, Tardiff JC, Pinz I, et al. Decreased energetics in murine hearts bearing the R92Q mutation in cardiac troponin T. J Clin Invest. 2003; 112:768–775

58.Spindler M, Saupe KW, Christe ME, et al. Diastolic dysfunction and altered energetics in the alphaMHC403/+ mouse model of familial hypertrophic cardiomyopathy. J Clin Invest. 1998; 101:1775–1783

59.Roma-Rodrigues C, Fernandes AR. Genetics of hypertrophic cardiomyopatyh: advances and pitfalls in molecular diagnosis and therapy. Appl Clin Genet. 2014 Oct 3;7:195-208.

60.Maron BJ, Olivotto I, Spirito P, et al. Epidemiology of hypertrophic cardiomyopathy-related death: revisited in a large non-referral-based patient population.Circulation. 2000 Aug 22;102(8):858-864

61.Maron BJ, Spirito P, Shen WK. Implantable cardioverter-defibrillators and prevention of sudden cardiac death in hypertrophic cardiomyopathy.JAMA. 2007 Jul 25;298(4):405-412.

62.Maron MS, Olivotto I, Betocchi S, et al. Effect of left ventricular outflow tract obstruction on clinical outcome in hypertrophic cardiomyopathy.N Engl J Med. 2003 Jan 23;348(4):295-303.

63.Ommen SR1, Maron BJ, Olivotto I, et al. Long-term effects of surgical septal myectomy on survival in patients with obstructive hypertrophic cardiomyopathy.J Am Coll Cardiol. 2005 Aug 2;46(3):470-476.

64.Harris KM1, Spirito P, Maron MS, et al. Prevalence, clinical profile, and significance of left ventricular remodeling in the end-stage phase of hypertrophic cardiomyopathy. Circulation. 2006 Jul 18;114(3):216-225.

65.Rowin EJ, Maron BJ, Kiernan MS, et al. Advanced heart failure with preserved systolic function in nonobstructive hypertrophic cardiomyopathy: under-recognized subset of candidates for heart transplant.Circ Heart Fail. 2014 Nov;7(6):967-975.

66.Olivotto I, Cecchi F, Casey SA, et al. Impact of atrial fibrillation on the clinical course of hypertrophic cardiomyopathy. Circulation. 2001 Nov 20;104(21):2517-2524.

67.Wang Y, Wang J, Zou Y, et al. Female sex is associated with worse prognosis in patients with hypertrophic cardiomyopathy in China.PLoS One. 2014 Jul 21;9(7):e102969.

68.Tian T, Wang YL, Wang JZ, et al. Myocardial bridging as a common phenotype of hypertrophic cardiomyopathy has no effect on prognosis. Am J Med Sci. 2014 Jun;347(6):429-433

69.Tian T, Wang Y, Sun K, et al. Clinical profile and prognostic significance of atrial fibrillation in hypertrophic cardiomyopathy. Cardiology. 2013;126(4):258-264.

70.Zhu L, Wang J, Wang Y, et al. Plasma Uric Acid as a Prognostic Marker in Patients With Hypertrophic Cardiomyopathy. Can J Cardiol. 2015 Feb 20. pii: S0828-282X(15)00132-4.

71.Chan RH, Maron BJ, Olivotto I, et al. Prognostic value of quantitative contrast-enhanced cardiovascular magnetic resonance for the evaluation of sudden death risk in patients with hypertrophic cardiomyopathy. Circulation. 2014 Aug 5;130(6):484-495

72.Wang Y, Wang Z, Yang Q, et al. Autosomal recessive transmission of MYBPC3 mutation results in malignant phenotype of hypertrophic cardiomyopathy. PLoS One. 2013 Jun 28;8(6):e67087.

73.Zou Y, Wang J, Liu X, et al. Multiple gene mutations, not the type of mutation, are the modifier of left ventricle hypertrophy in patients with hypertrophic cardiomyopathy. Mol Biol Rep. 2013 Jun;40(6):3969-3976

74.Wang J, Wang Y, Zou Y, et al. Malignant effects of multiple rare variants in sarcomere genes on the prognosis of patients with hypertrophic cardiomyopathy. Eur J Heart Fail. 2014 Sep;16(9):950-957

75.Landstrom AP, Ackerman MJ. Mutation type is not clinically useful in predicting prognosis in hypertrophic cardiomyopathy. Circulation 2010;122:2441–9.

76.Semsarian C, Yu B, Ryce C, et al. Sudden cardiac death in familial hypertrophic cardiomyopathy: are ”benign” mutations really benign? Pathology 1997;29:305– 8

77.Saltzman AJ, Mancini-DiNardo D, Li C, et al. Short communication: the cardiac myosin binding protein C Arg502Trp mutation: a common cause of hypertrophic cardiomyopathy. Circ Res 2010;106:1549 –1552.

78.Olivotto I, Girolami F, Ackerman MJ, et al. Myofilament protein gene mutation screening and outcome of patients with hypertrophic cardiomyopathy. Mayo Clin Proc 2008;83:630–638

79.      Ingles J, Doolan A, Chiu C. et al. Compound and double mutations in hypertrophic cardiomyopathy patients: implications for genetic testing and counseling. J Med Genet 2005;42:e59.

80.Kelly M, Semsarian C. Multiple mutations in genetic cardiovasculardisease: a marker of disease severity? Circ Cardiovasc Genet 2009;2: 182–90.

81.Maron BJ, Maron MS, Semsarian C. Double or compound sarcomere mutations associated with sudden death in hypertrophic cardiomyopathy in the absence of conventional risk factors. Heart Rhythm 2012;9:57– 63

82.Su M, Wang J, Kang L, et al. Rare variants in genes encoding MuRF1 and MuRF2 are modifiers of hypertrophic cardiomyopathy. Int J Mol Sci. 2014 May 26;15(6):9302-9313.

83.Witjas-Paalberends ER, Piroddi N, Stam K, et al. Mutations in MYH7 reduce the force generating capacity of sarcomeres in human familial hypertrophic cardiomyopathy. Cardiovasc Res. 2013; 99:432–441

84.Bond LM, Tumbarello DA, Kendrick-Jones J, et al. Small-molecule inhibitors of myosin proteins. Future Med Chem. 2013; 5:41–52

85.Baudenbacher F, Schober T, Pinto JR, et al. Myofilament Ca2+ sensitization causes susceptibility to cardiac arrhythmia in mice. J Clin Invest. 2008; 118:3893–3903

86.Robertson IM, Li MX, Sykes BD. Solution structure of human cardiac troponin C in complex with the green tea polyphenol, (–)–epigallocatechin 3-gallate. J Biol Chem. 2009; 284:23012–23023

87.Oleszczuk M, Robertson IM, Li MX, et al. Solution structure of the regulatory domain of human cardiac troponin C in complex with the switch region of cardiac troponin I and W7: the basis of W7 as an inhibitor of cardiac muscle contraction. J Mol Cell Cardiol. 2010; 48:925–933

88.Li Y, Charles PY, Nan C, et al. Correcting diastolic dysfunction by Ca2+ desensitizing troponin in a transgenic mouse model of restrictive cardiomyopathy. J Mol Cell Cardiol. 2010; 49:402–411.

89.Liu B, Lee RS, Biesiadecki BJ, et al. Engineered troponin C constructs correct disease-related cardiac myofilament calcium sensitivity. J Biol Chem. 2012; 287:20027–20036

90.Ashrafian H, Watkins H. Reviews of translational medicine and genomics in cardiovascular disease: new disease taxonomy and therapeutic implications cardiomyopathies: therapeutics based on molecular phenotype. J Am Coll Cardiol. 2007; 49:1251–1264

91.Abozguia K, Elliott P, McKenna W, et al. Metabolic modulator perhexiline corrects energy deficiency and improves exercise capacity in symptomatic hypertrophic cardiomyopathy. Circulation. 2010; 122:1562–1569

92.Jongbloed RJ, Marcelis CL, Doevendans PA, et al. Variable clinical manifestation of a novel missense mutation in the alpha-tropomyosin (TPM1) gene in familial hypertrophic cardiomyopathy.J Am Coll Cardiol. 2003 Mar 19;41(6):981-986