Abstract

Myocardial bridging is a congenital anomaly wherein a segment of a coronary artery passes under a ‘bridge’ of heart muscle rather than resting upon the heart’s surface. Although it is usually benign, myocardial bridging has been associated with adverse clinical events including ischaemia, arrhythmia and sudden death. Moreover, there is a tendency for atherosclerotic lesions to develop upstream of the bridge. These lesions may be the result of adverse fluid dynamic phenomena induced by the periodic compression of the artery by the overlying myocardial bridge. It is not possible to visualise these phenomena in vivo, and in this study we present an in vitro model capable of replicating the bridging conditions. This model is comprised of a pressure-measuring guide wire and catheter, a piston pump, a scaled artery model, and a ‘myocardial bridging mechanism’ which periodically compresses the artery model. A proportional-integral-derivative (PID) controller allowed the piston pump to recreate a patient-specific aortic pressure waveform upstream of the occluded artery model segment for each study. Stationary occlusions—achieved by placing 3D printed ‘stenosis inserts’ within the artery model—induced globally reduced pressures downstream of the stenosis when compared against the upstream pressure waveform. Conversely, the pressures downstream of the dynamic stenoses generated by the bridging mechanism closely matched the upstream pressures at all stages of the cardiac cycle except at the end of systole. This divergent pressure behaviour at the end of systole was similarly observed in vivo within a patient with a myocardial bridge. Flow visualisation using a laser sheet enabled dynamic flow structures to be observed, including recirculating flow regions, which may be precursors to arterial dysfunction.

Graphic abstract

中文翻译：

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研究心肌桥的血流动力学

摘要

心肌桥接是一种先天性异常，其中冠状动脉的一部分通过心肌的“桥”下而不是停留在心脏表面上。尽管通常是良性的，但心肌桥联与不良临床事件有关，包括缺血，心律不齐和猝死。而且，动脉粥样硬化病变倾向于在桥的上游发展。这些损伤可能是由于上层心肌桥周期性压缩动脉引起的不利的流体动力学现象的结果。不可能在体内可视化这些现象，在这项研究中，我们提出了一种能够复制桥接条件的体外模型。该模型由压力测量导线和导管，活塞泵，比例动脉模型，以及“心肌桥接机制”，该机制会定期压缩动脉模型。对于每个研究，比例积分微分（PID）控制器允许活塞泵在闭塞的动脉模型段的上游重建特定于患者的主动脉压力波形。通过与动脉压力波形相比，将3D打印的“狭窄插入物”放置在动脉模型中可实现固定闭塞，从而导致狭窄下游的压力整体降低。相反，桥接机制所产生的动态狭窄的下游压力与心动周期所有阶段（收缩末期除外）的上游压力紧密匹配。在具有心肌桥的患者体内类似地观察到收缩末期的这种发散压力行为。

图形摘要