去神经心肌可预测心脏猝死风险

加拿大不列颠哥伦比亚省温哥华——据第18届世界心脏病大会(WCHD)上报告的一项历时4年的前瞻性观察性研究的结果，心脏病发作后的去神经心肌量可预测心脏猝死的几率及是否需要使用置入式除颤器(ICD)。


Michael Cain博士

这项研究旨在更好地预测除颤器的潜在受益者，其招募的患者大部分在基线时都已接受了初次血运重建，并且都符合使用除颤器的条件。总体而言，受试者年龄均在65岁左右，左室射血分数约为26%，NYHA心功能分级为Ⅱ级心力衰竭；人口学特征不因是否满足研究的终点而有显著的差异。主要研究者、纽约大学布法罗分校医学与生物医学院院长Michael E. Cain博士及其合作者发现，对于符合使用ICD条件的缺血性心脏病患者而言，去神经心肌量可预测猝死，该指标独立于较多的传统终点，比如B型脑钠肽、左室射血分数以及纽约心脏病协会(NYHA)的心脏病分级。因此，分子影像学或可改善当前ICD候选者的风险分层。

在左室去神经心肌超过33%的心肌梗死后患者中有30%发生心律失常性死亡，或在心脏病发作的4年内因室性心动过速或室颤(＞240次/分)而导致发生除颤器放电(对于已发生这类事件的患者而言)；平均每年约有6.7%的患者满足这些终点。相比之下，采用正电子发射断层扫描检测评估心肌对去甲肾上腺素类似物的反应时发现，在左室去交感神经量＜22%的患者中仅有5%满足那些终点，而左室去神经量介于22%~33%的患者中有约10%如此；试验中去神经心肌发生心脏骤停的危险比为3.5(P=0.001)。204例心肌梗死后患者中有33例在试验过程中发生心律失常性死亡或出现除颤器放电。使用去神经量并结合以下3项其他因素时对心脏猝死的预测效果更好：左室舒张末期容量指数增加，肌酐＞1.5 mg/dl，未使用血管紧张素转化酶抑制剂或血管紧张素Ⅱ受体拮抗剂治疗。另外，无其中任一危险因素的患者4年无事件生存率约为98%，而有1项危险因素者约为85%，有≥2项者为50%。梗死或冬眠心肌量不能预测心脏骤停。

左室射血分数是目前已得到证实的较好指标，但这项指标以及其他许多经尝试的方法阴性预测准确度(而非阳性预测准确度)较高，因此有可能会给不需要除颤器的患者置入除颤器。但就目前而言，上述结果可能是从前瞻性观察性研究到真正运用去神经决定疗法的一次飞跃。

Cain医生报告称无相关利益冲突。

爱思唯尔版权所有  未经授权请勿转载

By: M. ALEXANDER OTTO, Cardiology News Digital Network

VANCOUVER, B.C. – The volume of denervated myocardium after a heart attack predicts the likelihood of sudden cardiac death and the need for an implantable defibrillator, according to results from a prospective, 4-year observational study.

"In this study, we found that in patients with ischemic cardiomyopathy who are eligible for an ICD [implantable cardioverter defibrillator], the volume of denervated myocardium predicts sudden death. It’s independent of more traditional endpoints that have been used," such as B-type natriuretic peptide, left ventricular ejection fraction, and New York Heart Association (NYHA) class. "Thus, molecular imaging may improve risk stratification for current ICD candidates," said investigator and cardiologist Dr. Michael E. Cain, dean of the School of Medicine and Biomedical Sciences, University at Buffalo (N.Y.).
 
The goal of the study is to better predict who will benefit from a defibrillator, he said at the 18th World Congress on Heart Disease.

He and his fellow investigators at the university found that about 30% of post-MI patients with more than 33% of their left ventricle denervated experienced arrhythmic death or – in those who had them – a defibrillator discharge for ventricular tachycardia or fibrillation greater than 240 beats per minute within 4 years of their heart attack; on average, about 6.7% met those endpoints each year.

In contrast, only about 5% of patients with less than 22% left ventricular sympathetic denervation met those endpoints, as did about 10% of those with 22%-33% left ventricular denervation, as assessed by myocardial response to a norepinephrine analogue on positron emission tomography. Denervated myocardium had a hazard ratio of 3.5 for sudden cardiac arrest or equivalent in the trial (P = .001).

Thirty-three of 204 post-MI patients experienced arrhythmic death or defibrillator discharge during the project. Most of the patients had undergone initial revascularization, and all were eligible for defibrillators at baseline. Overall, they were in their mid-60s, with left ventricular ejection fractions of about 26% and greater than NYHA class II heart failure. There were no significant demographic differences between patients who did and did not meet the study’s endpoints.

Prediction of sudden cardiac death events was even better when denervation was used in conjunction with three other factors: increase in the left ventricular end-diastolic volume index, creatinine greater than 1.5 mg/dL, and lack of angiotensin-converting enzyme inhibitor or angiotensin II receptor antagonist therapy.

Four-year event-free survival was about 98% in patients with none of those risk factors, about 85% in patients with one, and 50% in patients with two or more. The volume of infarcted or hibernating myocardium did not predict sudden cardiac arrest.

"The proven metric is left ventricle ejection fraction," but it and the many other methods that have been tried "have good negative predictive accuracy but not that good positive predictive accuracy, and so you are putting in defibrillators for people who don’t need them," he said.

For now, however, it would be "a leap of faith from a study that was prospective and observational" to actually use denervation "to determine therapies," he said.

Dr. Cain reported having no disclosures.