Background

Reduced coronary flow reserve in aortic stenosis and after transcatheter aortic valve implantation is usually attributed to physiological factors taking place during systole, such as an increase in coronary resistance, and backward waves intensity. In this paper, we suggest an additional factor related to the diastolic hemodynamics in the aortic root.

Methods

We measured left ventricle, aortic and coronary pressure and coronary perfusion in in-vitro models of healthy, aortic stenosis and an artificial valve at different heart rates and cardiac output conditions, to isolate the effect of hemodynamic factors in the aortic root during diastole.

Findings

Our results show that during diastole, coronary perfusion depends on the pressure gradient between the aorta and the coronary inlet. This aorta-coronary pressure gradient is influenced by the hemodynamic flow field in the aortic root. The ratio between the aorta-coronary pressure gradient magnitude in stress to that under rest conditions of a healthy model is ten times higher than the same ratio in the aortic stenosis model and twice higher as compared to the artificial valve model result. The coronary flow reserve of the healthy model is correspondingly higher compared to the artificial valve and the aortic stenosis models. These results are in agreement with the clinical evidence.

Interpretation

This study supports the hypothesis of a hemodynamic mechanism in the aortic root that increases coronary flow during rest but reduces the coronary flow reserve in aortic stenosis and artificial valve cases. The results may provide valuable insights regarding valve design.

中文翻译：

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主动脉瓣和心律对冠状动脉灌注的血流动力学影响。

背景

主动脉瓣狭窄和经导管主动脉瓣植入后冠状动脉血流储备的减少通常归因于收缩期发生的生理因素，例如冠状动脉阻力增加和后向波强度增加。在本文中，我们提出了与主动脉根舒张期血流动力学有关的其他因素。

方法

我们在健康，主动脉瓣狭窄和人工瓣膜的体外模型中，在不同的心率和心输出量条件下，测量了左心室，主动脉和冠状动脉的压力以及冠状动脉灌注，以隔离舒张期主动脉根部血流动力学因素的影响。

发现

我们的结果表明，在舒张期，冠状动脉灌注取决于主动脉和冠状动脉入口之间的压力梯度。该主动脉-冠状动脉压力梯度受主动脉根部血流动力学场的影响。健康模型在压力下的主动脉-冠状动脉压力梯度大小与静止状态下的比率比主动脉瓣狭窄模型中相同比率高十倍，而与人工瓣膜模型结果相比则高两倍。与人工瓣膜和主动脉瓣狭窄模型相比，健康模型的冠状动脉血流储备相应更高。这些结果与临床证据一致。

解释

这项研究支持主动脉根部血流动力学机制的假设，该机制在休息时增加冠状动脉血流，但在主动脉瓣狭窄和人工瓣膜病例中会降低冠状动脉血流储备。结果可以提供有关阀门设计的宝贵见解。