運動量の観点から見た大動脈基部運動の検討—大動脈基部エコー図からの一回心拍出量変化量の推定

Assessment of aortic root echogram from the view-point of momenta of blood ejected from left ventricle: Estimation of stroke volume change from aortic root echogram

　解剖学的に見て大動脈基部は左室より駆出れる血液を直接受ける部位であることから，大動脈基部エコー図における収縮期前方運動と一回心拍出量（以下StrokeVolume：SV）との関係を見た研究がいくつかなされている^1〜5）。しかし収縮期に大動脈基部が前方に偏位する機序についての詳細な検討は余りなされていなかった。

　近年，Strunk, Biaminoらによって大動脈基部の動きと左房の容積変化の関係が指摘され，拡張期の大動脈壁後方運動が左房容量の減少に負うものであると主張されたが^6,7），収縮期，特に収縮早期の大動脈基部の前方運動を左房容量増加のみで解釈できるかについては検討を要する。

In the M-mode echogram of the aortic root, the momenta of the blood ejected from left ventricle was analyzed, and the formula estimating the stroke volume (SV) was derived ; SVao=D²×Vp^1/2×AOT, where D is the diameter of the aortic root, Vp is the mean anterior velocity of the pos-terior wall of the aortic root, and AOT is the aortic valve opening time. Varying the heart rate in the patients who were implanted programmable pace-maker. SV was changed. SVao was determined at various levels of heart rate from 50 to 140 bpm.Similarly, SV was obtained by Teichholz's method; SV_T. SV_T were compared with SVao, and they were found to decrease linearly when heart rate was increased. They also showed a high correla-tion during the change of heart rate in every patients. However, the slope of the regression line was dependent on the recording site of M-mode echocardiogram ; at 2nd, 3rd or 4th intercostal space. In the inter- as well as intra-individual comparison, it is important to record at the same site to estimate SV from the the aortic root motion.