家兎大動脈弁閉鎖不全症モデルにおける急性期大動脈拡張期圧の低下—大動脈弁逆流重症度の指標としての妥当性の検討

Fall in aortic diastolic pressure immediately after aortic valve destruction can predict severity of regurgitation through the valve and chronic morphological changes in the left ventricle

　〔目的〕①大動脈弁閉鎖不全症（AR）において急性期の大動脈拡張期圧の低下（ΔAoDP）が弁逆流重症度の指標として妥当か否かを明らかにする。②中等度ARにおける左室代償機転を左室形態の変化より検討する。〔方法〕大動脈弁穿孔法により家兎ARを作成し，ΔAoDPと作成直後，1週後，4週後，8週後の左室形態指標との関連を検討した。〔結果と考案〕①ΔAoDPは作成直後における弁逆流率，弁穿孔面積と正相関した。また1週以降の左室容積，4週以降の左室重量と正相関し，一次回帰式の傾きは時間経過に伴い高値を示した。ΔAoDPは急性期から慢性期における弁逆流碓症度を予測する指標として妥当と考えられた。②ΔAoDPが15〜40mmHgの中等度ARでは1週以降に左室容積，重量が増加した。8週後では左室容積はさらに増加したが，重量は増加せず壁厚は減少する傾向を示した。8週後では左室壁応力の増加により左室代償機転が破綻し，心不全に向かう可能性を示した。

Aortic regurgitation (AR) has been studied ex-perimentally. however these reports did not inve-stigate compensatory mechanisms in AR in relation with the severity of regurgitation. If the severity of AR can be changed voluntarily, we can evaluate the pathophysiological response to AR in wide range. The purposes of this study were 1) to see if the extent of fall in aortic diastolic pressure im-mediately after the production of AR (ΔAoDP) was a reliable predictor of the severity of AR and 2) to evaluate the process of adaptation through acute and chronic stage in moderate AR in the rabbit model.

AR was produced by perforating the aortic va-lves in Japanese white rabbits. First, aortic pres-sure, volume, weight and wall thickness of the left ventricle were measured. Correlations between ΔAoDP and body weight-corrected volume (LVV/ BW) and weight (LVW/BW) were studied in 18 rabbits soon after, 19 one week after, 23 four weeks after and 10 eight weeks after the production of AR. ΔAoDP was closely correlated with LVV/BW after 1 week (1 week : R=0.667,p＜0.01, 4 weeks : R=0.733, p＜0.01, 8 weeks : R=0.757, p＜0.05) and with LVW/BW after 4 weeks (4 weeks : R=0.484, p＜0.05, 8 weeks : R=0.651, p＜0.05). The slope of these regression equations increased with time ΔAoDP and LVV/BW : 1 week : 0.0138, 4 weeks : 0.0361, 8 weeks : 0.0577ml/kg?mmHg ; ΔAoDP and LVW/BW : 4 weeks : 0.0142, 8 weeks : O.0310 g/kg･mmHg). Second, serial morphological changes in the left ventricle in moderate AR in which ΔAoDP was between 15 and 40 mmHg were stu-died. LVV/BW progressively increased after 1 week. LVW/BW and FWd increased during 1 week to 4 weeks. After 8 weeks neither LVW/BW nor FWd had changed. Therefore the calculated wall stress of the left ventricle was larger after 8 weeks than after 4 weeks, which may lead to heart failure. We concluded that 1) ΔAoDP is a reliable predictor of the severity of AR and the following morpho-logical changes in the left ventricles and 2) the left ventricle adapts to acute volume loading by its enlargement and following hypertrophy, how-ever, these compensatory mechanisms might be inadequate 8 weeks after AR production.