田中 伸明

Nobuaki TANAKA

山口大学医学部附属病院検査部・超音波センター

Yamaguchi University Hospital, Department of Clinical Laboratory

キーワード : color M-mode, diastolic function, diastology, Doppler echocardiography, pulmonary venous flow, tissue Doppler imaging, transmitral flow

心臓は収縮と拡張を繰返して血液を拍出している. 心臓の主要な役割は生体機能維持のために必須な血液を拍出するポンプ機能であり, この意味では収縮機能であると考えられるが, 収縮期に十分な拍出を行なうためには, 直前の拡張期に一旦血液を心室に蓄える必要があり, 実は収縮能と拡張能は表裏一体で切り離すことはできないものである. 収縮能の評価はここでは触れないが, 拡張能の評価は, 元来, 観血的な心臓カテーテル検査によって行なわれていた. しかし, 近年, 拡張不全(拡張期性心不全)の概念の広まりとともに, 拡張能評価への関心が高まり, また, 心臓超音波検査においてもパルス・ドプラ法による経僧帽弁血流波形への理解が深まり, 検査室及びベッドサイドで日常的に心エコー・ドプラ法により左室拡張機能の評価が行われるようになった. 経僧帽弁血流波形以外にも肺静脈血流波形が経胸壁アプローチで容易に得られるようになり, 最近では組織ドプラ法やカラーMモード図も拡張機能評価に応用され, より適切な拡張機能評価が可能となってきている.

The heart propels the blood through the repeated sequence of contraction and relaxation. An essential role of the heart is the systolic function: pumping out the oxygenated blood necessary to maintain the biological function of the body. Before the heart ejects blood during systole, however, it must be filled with blood during the preceding diastole. When diastolic function is poor, the heart does not eject enough blood and congestion of the upper stream of the heart becomes inevitable. Thus the diastolic function is as important as the systolic function. Today the diastolic function, originally assessed by hemodynamic parameters obtained in the cardiac catheterization laboratory, is routinely assessed by Doppler echocardiography in the many settings of clinical cardiology as the concept of diastolic failure spreads and the role of transmitral flow for assessing diastolic function is recognized. There are now modalities for assessing left ventricular diastolic function as well as transmitral flow in the clinic. Pulmonary venous flow, for example, is now easily measured via the transthoracic approach; tissue Doppler imaging provides important information about diastolic function; and color M-mode is used to measure flow propagation velocity of left ventricular inflow. These modalities using Doppler echocardiography enable us to assess left ventricular diastolic function more precisely.