挑战：如何鉴别缩窄性心包炎？

斯诺马斯——在右心衰竭且射血分数正常的患者中鉴别缩窄性心包炎与限制性心肌病是“当今心脏病学领域最具挑战性的诊断之一”，但来自明尼苏达州罗彻斯特梅奥诊所的心脏病学教授Dr. Rick A. Nishimura在美国心脏病学会斯诺马斯心血管年度会议上称，应用一种步进式方法则能得到可靠结果。

当今心力衰竭领域的概念中，HFrEF和HFpEF分别指心力衰竭合并射血分数降低和心力衰竭和并射血分数保留。但是另有一种患者群体常被误认为存在HFpEF，即存在严重右心衰竭且射血分数正常的患者，这种病况通常是由缩窄性心包炎或限制性心肌病导致。

Dr. Nishimura提到，与HFpEF患者不同，此类患者血压并不偏高，也不存在肺充血。事实上，他们主要出现腹水、外周性水肿、疲乏和颈静脉压力明显升高。

在详细阐述其步进式方法之前，Dr. Nishimura重点指出了几个他认为不太可靠的诊断方法。其中一个是利用CT或MRI高清影像探寻心包增厚，而心包增厚被广泛认为是缩窄性心包炎的解剖结构标志。

Dr. Nishimura说：“要知道，确诊缩窄性心包炎的患者中，有22% CT或MRI显示心包厚度正常，而导致缩窄性心包炎的是心外膜纤维化。而应用放射疗法或冠脉旁路移植术且不存在缩窄性心包炎患者中，有约70%将会出现不同程度的心包增厚。所以，尽管CT和MRI会有帮助，但并不能作为诊断方法。”

他随后讲到，通常认为缩窄性心包炎可依据心脏导管插入术获得的血流动力学结果中的经典三联征进行诊断，即早期快速充盈时左室舒张末期压力等于右室舒张末期压力，右室舒张末期压力大于右室收缩压的1/3，以及肺动脉压力低于50mm Hg；但是在研究所纳入的最后100例到梅奥诊所置管室检查的患者中，这些标准同样不能可靠地区分缩窄性心包炎和限制性心肌病。

对于存在无法解释的右心衰竭且射血分数正常的患者，Dr. Nishimura的检查方法是从患者的病史和体格检查开始。缩窄性心包炎患者的病史通常都包括早期应用放射疗法治疗肿瘤，或者既往CABG手术；而体格检查则会发现存在颈静脉怒张。

Dr. Nishimura 断言：“无论患者超声心动图表现如何，如果没有因颈静脉压增强伴X和Y下降而出现的高颈静脉，则一定不存在缩窄性心包炎。”

然而，如果发现了颈动脉怒张，则应在2D超声心动图寻找3种发现，这3种发现则指向缩窄性心包炎：每次心跳的心室舒张早期快速充盈导致的快速中隔颤动；心室舒张早期室间隔后延运动，即室间隔反弹，这由心室壁顺应性变差导致；以及下腔静脉扩张，表明右心房压力增加。

如果2D超声心动图上出现了所有3种发现，则应利用多普勒超声心动图获取血流动力学的相关信息。如果多普勒仪显示，吸气时胸内压力下降但左心室压力并未下降，从肺部到心脏二尖瓣口的驱动压力降低，检查工作即完成，并可定论患者存在缩窄性心包炎，需转诊行心包切除术，该手术可快速改善患者病况。

然而，约四分之一的缩窄性心包炎患者中，所有这些2D超声心动图和多普勒超声心动图发现均不存在；此类患者有必要进一步进行心脏导管插入术。在导管室最重要的两点是确定有无舒张压升高和心输出量降低。

Dr. Nishimura说，如果患者进行到应用心脏导管插入术检查这一步，并且舒张压和心输出量均正常，则其并不存在临床上显著的缩窄性心包炎，无论超声心动图表现如何。所以以上提到的两点非常必要，不过很明显存在这两种特征也不能确诊。所以我们需继续进行下一步。

缩窄性心包炎患者的心室间相互作用会因心包病变僵化而增强，这是至关重要的。心室间相互作用增强表现为吸气时右心室体积增大，而左心室区域则变小。

比较而言，限制性心肌病患者在吸气和呼气时，右心室变小，左心室也变小。

Dr. Nishimura认为：“吸气时右心室/左心室压力曲线下面积和呼气时的比值是区别缩窄性心包炎和限制性心肌病的可靠指标。利用心室间相互作用增强判断缩窄性心包炎最具敏感性和特异性。”

他补充道，右心衰竭伴射血分数正常的原因除了缩窄性心包炎和限制性心肌病以外，还有一种原因，即重度三尖瓣返流，这种原因尚未得到足够重视。置有起搏器电极导线或植入式自动心律转复除颤器电极导线的患者中，通过超声心动图可能并不能轻易发现这种异常，因为导线会造成音波阴影，导致三尖瓣返流的严重性被低估。这里的线索是观察有无肝静脉收缩期逆流，因为只有重度三尖瓣返流才会造成这种现象。

Dr. Nishimura建议，对于存在起搏器导线或AICD的患者，以及慢性三尖瓣环扩张且三尖瓣返流因之更加严重的较年长的女性房颤患者，可考虑是三尖瓣返流造成右心衰竭伴射血分数正常，在导管室为这些患者行右心室造影可确定。

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SNOWMASS, COLO. (FRONTLINE MEDICAL NEWS) – Differentiating constrictive pericarditis from restrictive cardiomyopathy in patients with right heart failure with a normal ejection fraction is “one of the most difficult diagnostic challenges in cardiology today,” but reliable results can be achieved using a careful step-by-step approach, Dr. Rick A. Nishimura said at the Annual Cardiovascular Conference at Snowmass.

Under current terminology for heart failure, cardiologists speak of HFrEF, or heart failure with reduced ejection fraction, and HFpEF, or heart failure with preserved ejection fraction. But there is a third group of patients who are often mistakenly thought to have HFpEF: those with severe right heart failure and a normal ejection fraction, classically caused by constrictive pericarditis or restrictive cardiomyopathy. 

Unlike patients with HFpEF, these people are not hypertensive and they don’t have pulmonary congestion. Instead, they present predominantly with ascites, peripheral edema, fatigue, and marked elevation in jugular venous pressure, noted Dr. Nishimura, professor of medicine at the Mayo Clinic in Rochester, Minn.

Before elaborating on his own tried-and-true, step-by-step approach, he highlighted several diagnostic procedures he considers less than reliable. One is advanced imaging with CT or MRI looking for the pericardial thickening that is widely viewed as an anatomic hallmark of constrictive pericarditis.

“Remember, 22% of patients with proven constrictive pericarditis actually have a normal pericardium on CT or MRI, because it’s their fibrotic epicardium that’s causing the constrictive pericarditis. And roughly 70% of patients are going to have some thickened pericardium after radiation therapy or coronary artery bypass graft surgery without having constrictive pericarditis. So CT and MRI are helpful, but they’re not going to be diagnostic,” according to the cardiologist. 

Similarly, while it’s often been said that constrictive pericarditis can be diagnosed based upon a classic trio of hemodynamic findings obtained through heart catheterization – namely, early rapid filling with a left ventricular end-diastolic pressure equal to the right ventricular end-diastolic pressure, a right ventricular end-diastolic pressure greater than one-third of the right ventricular systolic pressure, and a pulmonary artery pressure below 50 mm Hg – these criteria didn’t reliably separate the last 100 patients who came to the catheterization lab at the Mayo Clinic with either constrictive pericarditis or restrictive cardiomyopathy, he continued. 

Dr. Nishimura’s approach to the work-up of patients with unexplained right heart failure and a normal ejection begins with the history and physical examination. The history in a patient with constrictive pericarditis is classically one of radiation therapy years earlier for a malignancy, or prior CABG surgery. And the physical exam has to reveal the presence of high neck veins. 

“If you don’t see high neck veins due to elevated jugular venous pressure with rapid x and y descents, the patient doesn’t have constrictive pericarditis, no matter what the echocardiogram shows,” Dr. Nishimura asserted. 

If those findings are present, however, then on 2-D echocardiography he’s looking for three things that point to constrictive pericarditis: a brisk septal shudder due to rapid filling in early diastole with every heart beat; an early diastolic posterior motion of the intraventricular septum, known as the septal bounce, that occurs as a consequence of the less compliant ventricular walls; and dilation of the inferior vena cava indicative of increased right atrial pressure. 

When all three findings are present on 2-D echo, he turns to Doppler echo for hemodynamic information. If Doppler shows a reduction in transmitral driving pressure from the lungs to the heart during inspiration, as the intrathoracic pressure drops but the left ventricular pressure does not, the work-up is done. That patient has constrictive pericarditis and needs to be referred to surgery for pericardiectomy, which will bring rapid improvement. 

In roughly one-quarter of patients with constrictive pericarditis, however, that full constellation of 2-D and Doppler echocardiographic findings isn’t present. It then becomes necessary to move on to cardiac catheterization. The first two things to look for in the cath lab are elevated end-equalization of diastolic pressures and low cardiac output. 

“If they’re in the cath lab and they’ve got normal filling pressures and a normal cardiac output, they do not have clinically significant constrictive pericarditis, no matter what the echo shows. So those two things are necessary to see, but of course they’re not diagnostic. So we go further,” Dr. Nishimura said.

A patient with constrictive pericarditis will have enhanced ventricular interaction arising from the restraint imposed by a rigid, diseased pericardium. That’s crucial. This increased ventricular interaction is manifest as an increase in the size of the right ventricle during inspiration while the area of the left ventricle is getting smaller. 

In contrast, during inspiration and expiration in a patient with restrictive cardiomyopathy, as the right ventricle gets smaller, so does the left ventricle. 

“The ratio of the right ventricle to left ventricle area under the curve during inspiration versus expiration gives a very nice distinction between constrictive pericarditis and restrictive cardiomyopathy. Enhanced ventricular interaction is the most sensitive and specific finding for constrictive pericarditis,” according to Dr. Nishimura. 

He added that, in addition to constrictive pericarditis and restrictive cardiomyopathy, there is a third and underappreciated cause of right heart failure with a normal ejection fraction: severe tricuspid regurgitation. This abnormality may not be readily apparent upon echocardiography in a patient with a pacemaker lead or automatic implantable cardioverter-defibrillator lead, which can cause acoustic shadowing that results in underestimation of the severity of tricuspid regurgitation. The clue here is the observation of hepatic vein systolic flow reversal, which can only be caused by severe tricuspid regurgitation. 

“Think tricuspid regurgitation in patients who have a pacemaker lead or AICD, and also in older women with longstanding atrial fibrillation who dilate their tricuspid annulus and develop more and more tricuspid regurgitation. Take those patients to the cath lab and do a right ventriculogram, which will show tricuspid regurgitation,” Dr. Nishimura advised. 

He reported having no financial conflicts.

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