冠動脈バイパス術におけるグラフト材の収縮特性—伏在静脈と内胸動脈の比較

Contractile properties of coronary artery bypass conduit:Comparison between saphenous vein and internal mammary artery

　脈管収縮を誘発するエルゴノビン，セロトニン，フェニレフリンに対する伏在静脈（SV）および内胸動脈（IMA）の収縮特性を明らかにする目的で，10症例のIMAとSVを冠動脈バイパス術（CABG）中に挫滅なく採取し，等尺性張力記録装置を用いて薬剤濃度-張力曲線を記録した。その結果，SV，IMAともに各薬剤に対して濃度依存性に収縮反応を示し，CABG近接期のスパスムの背景にはhostの冠動脈スパスムのみならずグラフト自体のスパスムが関与する可能性が示唆された。グラフトスパスムはグラフト不全や閉塞の引き金となっているものと推察された。またSV,IMAともにフェニレフリンに対する収縮反応は近似していたが，エルゴノビン，セロトニンに対しては，SVの方がIMAより鋭敏に収縮反応を示した。すなわち冠動脈スパスムを生じやすい環境においては，IMAグラフトよりもSVグラフトのトーヌスが亢進しやすいことが判明した。

This study was designed to examine the response of coronary artery bypass conduit to serotonin, phe-nilephrine, and ergonovine as provocation agents of vasoconstriction. Saphenous veins (SV) and internal mammary arteries (IMA) were obtained during coro-nary artery bypass grafting (CABG), and their con-tractile properties were measured using isometric contraction recording apparatus.

Both SV and IMA showed sigmoid contraction curves indicating dose dependence to ergonovine, se-rotonin, and phenilephrine.

The concentration-response relations for phenile-phrine showed a similar curve in both SV and IMA, however, those for ergonovine and serotonin showed a leftward shift in SV compared with IMA. Half maximum effective dose for ergonovine and seroto-nine were less in SV than IMA.

From these results, it was suggested that “periope-rative spasm” during CABG might occur not only in coronary arteries but also in the graft conduit itself. Graft spasm might be a possible mechanism for oc-clusion of the bypass graft.

In conclusion, greater hyperreactivity of SV com-pared with IMA in response to ergonovine and sero-tonin was suggested, so it is concluded that, from this point of view, IMA is more suitable for use in CABG.