左冠状動脈本幹における拍動波形の観察

Blood Flow Patterns of the Main Left Coronary Artery

緒言

　冠状動脈における血行動態の研究は古くから種々の方法で試みられているが，最近血流計の開発にともない，かなり細部にわたった観察ができるようになった。とくに血流計probeの小型化によって生体内埋没が可能になるにつれ冠状動脈の分枝に埋没して血流量を測定した報告も見られている^{5）8）12）〜14）23）24）}。しかし冠状動脈の本幹における測定は技術的な問題とともに適合する血流計probeの作製が困難なためほとんど報告されていない^{8）12）13）24）}。著者は自作した血流計probeを左冠状動脈の本幹に埋没させ安静時の拍動波形を記録するとともに測定上問題となる諸点について検討を加えた。

General flow patterns of the main left coro-nary artery were observed in the unanesthetiz-ed dog under unrestrained, resting condition in the study. The experiment was carried out with chronic preparations, by fitting the newly designed transducer of the electromag-netic flowmeter to the main left coronary artery.

Magnet core of the flow transducer was made by stacking specially designed transfor-mer laminations, and the coil was wound di-rectly over and encapsulated by plastic. The transducer possesses an oval lumen for inser-tion of the artery, and the long and short di-ameters of the lumen were 3.5 and 2.5 mm respectively. The probe is characterized by its light weight and good adaptation as well as fixation to the vessel and surrounding tis-sues.

The method of determining zero blood flow level in the main left coronary artery has been technically very difficult. The author established the technique of zero determination by adoption of "snare technique" with newly deviced instrument.

The observations of phasic flow patterns generally started one or two weeks postopera-tively, at which time the dogs were capable of walking and running nearly as well as be-fore the operation. When the dogs were not isolated from environmental stimuli, some tranquilizers were injected intramuscularly. Following the onset of isometric contraction, the rate of coronary blood flow decreased abruptly and sharply and formed a notch on the curve. It rose with the onset of ejection from the left ventricle, and formed a small spike in early systole, thereafter. At proto-diastole, the flow abruptly dropped to near zero. With the closure of the aortic valves, the coronary flow went up rapidly to its maximum rate and showed hump-shaped pat-tern.