心房細動を有する僧帽弁狭窄症の術後の脈拍数と弁機能に関する研究

Postoperative mitral vaIve function and pulse rate in mitral stenosis with atrial fibrillation

　僧帽弁狭窄症では僧帽弁口の機械的狭窄とともに弁および腱索，乳頭筋の肥厚，硬化，萎縮を伴い，交連切開術によって弁口の開大，狭窄の軽減を得た例においても弁，腱索，乳頭筋の器質的病変は残存し，その可動性の低下は術後の弁機能に大きな影響を及ぼし，手術の効果には限界を有することはよく知られている。

　心房細動を有する僧帽弁狭窄症では拡張期における左室の血液充満は急速流入期を欠き，拡張期全体を通じて緩徐流入がつづくため，左室の1回拍出量は先行するR-R時間に大きな影響をうける。この病態を利用して，開心交連切開術あるいは人工弁置換術を行った心房細動を有する僧帽弁狭窄症術後症例を対象とし，脈拍数の弁機能に及ぼす影響から弁の器質的病変と手術術式について検討したので報告する。

In order to evaluate mitral valve function, a cor-relation between heart rate and stroke volume or cardiac output were studied in mitral stenosis with atrial fibrillation by echocardiography pre-and postoperatively. Predicted stroke volume and cardiac output at 60 and 120 of pulse rate was cal-culated from regression equation obtained by a correlation between preceding pulse rate and sub-sequent stroke volume.

An increase of pulse rate was followed by a decrease of stroke volume. This tendency was most prominent in preoperative mitral stenosis with high coefficient of correlation. After the operation, in the cases with open mitral commissurotomy, a decrease of stroke volume following an increase of preceding pulse rate became more prominent according to the progress of organic lesion in mitral valve. On the other hand, in the cases with mitral valve replace-ment, a decrease of stroke volume following an in-crease of preceding pulse rate was slight, and predic-ted stroke volume at 120 of pulse rate was recog-nized to be higher value than that in the cases with open mitral commissurotomy.

Predicted cardiac output at 120 of pulse rate increased as compared with that at 60 of pulse rate in the group of Sellors 1 with open mitral commis-surotomy and mitral valve replacement, however, it decreased in the group of Sellors 2 and 3 with open mitral commissurotomy.

In conclusion, mitral valve function at tachycar-dia was seemed to be more efficient in the cases with mitral valve replacement than with open mitral commissurotomy.