Banerjee Rupak K, Back Lloyd H, Back Martin R
Department of Mechanical, Industrial and Nuclear Engineering, University of Cincinnati, Cincinnati, OH 45221-0072, USA.
Biorheology. 2003;40(6):613-35.
This study gains insight on the nature of flow blockage effects of small guidewire catheter sensors in measuring mean trans-stenotic pressure gradients Deltap across significant coronary artery stenoses. Detailed pulsatile hemodynamic computations were made in conjunction with previously reported clinical data in a group of patients with clinically significant coronary lesions before angioplasty. Results of this study ascertain changes in hemodynamic conditions due to the insertion of a guidewire catheter (di=0.46 mm) across the lesions used to directly determine the mean pressure gradient (Deltap) and fall in distal mean coronary pressure (pr). For the 32 patient group of Wilson et al. [1988] (minimal lesion diameter dm=0.95 mm; 90% mean area stenosis; proximal measured coronary flow reserve (CFR) of 2.3 in the abnormal range) the diameter ratio of guidewire catheter to minimal lesion was 0.48, causing a tighter "artifactual" mean area stenosis of 92.1%. The results of the computations indicated a significant shift in the Deltap-Q relation due to guidewire induced increases in flow resistances (R=Deltap/Q) of 110% for hyperemic flow, a 35% blockage in hyperemic flow (Qh) and a phase shift of the coronary flow waveform to systolic predominance. These alterations in flow resulted in a fall in distal mean coronary pressure (at lower mean flow rates) below the patho-physiological range of prh approximately 55 mmHg, which is known to cause ischemia in the subendocardium (Brown et al. [1984]) and coincides with symptomatic angina. Transient wall shear stress levels in the narrow throat region (with flow blockage) were of the order of levels during hyperemic conditions for patho-physiological flow. In the separated flow region along the distal vessel wall, vortical flow cells formed periodically during the systolic phase when instantaneous Reynolds numbers Ree(t) exceeded about 110. For patho-physiological flow without the presence of the guidewire these vortical flow cells were much stronger than in the more viscous flow regime with the guidewire present. The non-dimensional pressure data given in tabular form may be useful in interpretation of guidewire measurements done clinically for lesions of similar geometry and severity.
本研究深入了解了小型导丝导管传感器在测量显著冠状动脉狭窄处的平均跨狭窄压力梯度Δp时的血流阻塞效应的本质。结合先前报道的一组血管成形术前具有临床显著冠状动脉病变患者的临床数据，进行了详细的脉动血流动力学计算。本研究结果确定了由于插入用于直接测定平均压力梯度（Δp）和远端平均冠状动脉压力（pr）下降的导丝导管（内径di = 0.46 mm）穿过病变处而导致的血流动力学状况变化。对于Wilson等人[1988年]的32例患者组（最小病变直径dm = 0.95 mm；平均面积狭窄90%；近端测量的冠状动脉血流储备（CFR）为2.3，处于异常范围），导丝导管与最小病变的直径比为0.48，导致更严重的“人为”平均面积狭窄达92.1%。计算结果表明，由于导丝导致充血血流的流动阻力（R = Δp/Q）增加110%，充血血流（Qh）阻塞35%以及冠状动脉血流波形相移至收缩期占优势，Δp - Q关系发生了显著变化。这些血流变化导致远端平均冠状动脉压力（在较低平均流速时）降至低于约55 mmHg的病理生理范围prh，已知这会导致心内膜下缺血（Brown等人[1984年]），并与症状性心绞痛相符。狭窄喉部区域（存在血流阻塞）的瞬态壁面剪应力水平与病理生理血流充血状态下的水平相当。在沿远端血管壁的分离流区域，当瞬时雷诺数Ree(t)超过约110时，在收缩期会周期性地形成涡流细胞。对于不存在导丝的病理生理血流，这些涡流细胞比存在导丝时更粘滞的血流状态下要强得多。以表格形式给出的无量纲压力数据可能有助于解释临床上针对具有相似几何形状和严重程度的病变进行的导丝测量结果。
