本综述【图文详析】稍后推送

Cardiac Physiology for Radiologists: Review of Relevant Physiology for Interpretation of Cardiac MR Imaging and CT

Cardiac computed tomography (CT) and magnetic resonance (MR) imaging provide clinicians with important insights into cardiac physiology and pathology. However, not all radiologists understand the language and concepts of cardiac physiology that are used daily by cardiologists. This review article covers basic cardiac physiology as it relates to cardiac CT and MR imaging. Topics include a review of the cardiac cycle and left ventricular pressure-volume loops as they relate to different pathologic states, evaluation of cardiac function, and calculation of key parameters such as left ventricular volumes and the ejection fraction. The hemodynamics of cardiac shunts are covered, with an emphasis on factors important to cardiologists, including the ratio of pulmonary flow to systemic flow. Additionally, valvular physiologic function is reexamined, with a focus on understanding pressure gradients within the heart and also the changes associated with valvular pathologic conditions, including measurement of regurgitant fractions in patients with valvular insufficiency. Understanding these basic concepts will help radiologists tailor the reporting of cardiac studies to clinically relevant information. Online supplemental material is available for this article.

放射科医生的心脏生理学：复习用于解释心脏MRI和CT的相关的生理学

摘要

心脏计算机断层成像（CT）和磁共振（MR）成像为临床医生对心脏生理学和病理学提供了深入了解。但不是所有放射科医生能理解心脏科医生每天使用的心脏生理学术语和概念。这篇综述覆盖了和心脏CT和MR有关的基本心脏生理学。题目包括不同病理状态下心动周期和左心室压力容量环，评价心脏功能，计算关键参数如左心室容量和射血分数。覆盖了心脏分流的血液动力学，强调了对心脏科医生重要的因素，包括肺循环血流和体循环血流的比率。此外，再次检查瓣膜生理学功能，重点在理解心脏内压力梯度以及瓣膜病理状态时这种梯度的变化，包括测量瓣膜关闭不全患者返流分数。理解这些基本概念能帮助放射科医生针对临床相关信息订制心脏检查的报告。（可以获取本文的在线补充材料）。

TEACHING POINTS

■■ The pressure-volume loop is affected by multiple factors, including

preload and afterload.

■■ The degree of valvular stenosis affects management and can be quantified with a variety of imaging modalities, including direct measurement of the valve area with MR imaging or CT, as well as measurement of the velocity of blood flow through a valve by using velocity-encoded MR imaging.

■■ When valvular insufficiency exists, the blood from one chamber regurgitates and causes a discrepancy in the ventricular stroke volumes; this discrepancy is quantified by the regurgitant fraction.

■■ Shunts are quantified with a ratio of the measured pulmonary blood flow to the systemic blood flow.

■■ In cardiac CT, images are usually acquired during diastole, ideally during the phase of isovolumetric relaxation, in which imaging of the coronary arteries is optimal because of relatively little cardiac motion.

教学要点

l 压力-容量环受多种因素影响，包括前负荷和后负荷。

l 瓣膜狭窄程度影响处理，能通过多种影像学方法定量，包括用MRI或CT直接测量瓣膜面积，以及采用速率编码MR来测量通过瓣膜的血流速率。

l 当瓣膜关闭不全存在时，血流从一个心腔返流，导致心室射血容量差异，这个差异通过返流分数定量。

l 分流通过测量肺循环血流和体循环血流比率定量。

l 在心脏CT，图像通常在舒张期采集，最理想是在等容舒张期采集，因为在这个时期心脏运动几乎没有，冠状动脉图像最佳。

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