慢性冠脉狭窄时局部心肌收缩功能与心肌血流的关系

The relations between regional myocardial contractile function and blood flow in chronic coronary stenoses

目的 评价慢性冠脉狭窄时心肌收缩功能与心肌血流 (MBF)的关系 ,以探讨慢性可逆性左室收缩功能低下的发生机制。方法 于左前降支 (LAD)和左回旋支 (LCX )近端以安放“水膨胀”式缩窄器的方法 ,建立 13只慢性多支冠脉狭窄犬模型。二维超声评价室壁增厚率 (%WT) ,放射性微球定量心肌血流量 (MBF)。结果 术后第 7dLAD和LCX供血区的平均 %WT较术前均已降低 (P <0 .0 5 ) ,但MBF在术后第 2 1d才出现降低 (P <0 .0 5 )。术后第 7d 2 6个 (2 6 /5 0 )心肌节段表现为局部室壁运动异常(RWMA) ;在 15对配对的RWMA和非RWMA中 ,两者的MBF差异无显著性意义 (P >0 .0 5 ) ;MBF与 %WT间无明显相关 (P >0 .0 5 )。然而术后第 42d ,在 13对配对的RWMA和非RWMA中 ,RWMA的MBF均明显低于非RWMA(P <0 .0 5 ) ,且 36个RWMA的MBF均与 %WT有良好的相关性 (P <0 .0 0 0 1)。结论慢性冠脉狭窄时 ,存活而收缩功能低下的心肌可伴或不伴MBF的降低 。

Objective To evaluate the relations between regional myocardial blood flow (MBF) and function at rest and to investigate the mechanisms of the reversible regional myocardial dysfunction in the setting of chronic coronary stenoses. Methods Thirteen chronically instrumented multivessel stenoses dogs were created by placing ameriod constrictors on the proximal portions of left anterior descending artery (LAD) and left circumflex artery (LCX). Percentage of wall thickening (%WT) with quantitative two dimensional echocardiography at pre operation and post operation and MBF with radiolabeled micospheres at post operation was measured.Results %WT was significantly decreased in both LAD and LCX at 7 days after operation (P< 0.05 ), while the decrease of MBF was noted until day 21(P< 0.05 ). At day 7, regional wall motion abnormality (RWMA, %WT<30%) was seen in 26 of 50 myocardial segments. There was no significantly difference in resting MBF between RWMA and no RWMA in 15 pairs at 7 day (P> 0.05 ). However, at day 42, the resting MBF in RWMA was lower than that in no RWMA in 13 pairs (P< 0.05 ). Meanwhile, a curvilinear relation was noted between %WT and MBF in the 36 RWMA at 42 days (P< 0.0001 ).Conclusions Resting MBF is reduced or normal in regional dysfunction of viable myocardium in the setting of chronic coronary stenoses. Chronic resting regional myocardial dysfunction could represent repetitive stunning, hibernation, or both.