Guidewire flow obstruction effect on pressure drop-flow relationship in moderate coronary artery stenosis

To evaluate the local hemodynamic effects of coronary artery balloon angioplasty, computational fluid dynamics was applied to representative stenoses geometry post-angioplasty (minimal lesion diameter dm=1.8mm which produced 64% mean area stenoses) based on a group of patients and measured values of coronary flow reserve (CFR) returning to a normal range (3.6±0.33.6±0.3). The computations were at mean flow rates (Q˜) of 50, 100, 150 and 170 ml/min. The study indicates changes in the hemodynamic conditions due to insertion of a guidewire, which can be used to determine the mean pressure drop (Δp˜) and fall in distal mean coronary pressure (p˜r), and thus give quantitative estimate of uncertainty expected in diagnosis of moderate lesions. The guidewire to minimal lesion diameter ratio is 0.26, causing tighter “artifactual” mean area stenoses of 65.5%. During hyperemia, p˜m dropped to 72 mmHg as compared to 75 mmHg under patho-physiological condition without guidewire. Q˜h (subscript h: hyperemia) decreased from 180 without guidewire to 170 ml/min with the guidewire present. Thus, there was a significant ∼43%∼43% increase in Δp˜h and a ∼51%∼51% increase in the hyperemic flow resistance (R˜h=Δp˜h/Q˜h) over the patho-physiological condition. This could cause an overestimation of the severity of the moderate stenoses. Transient and steady flow guidewire surface shear stress was 35–50% higher than corresponding values for arterial wall shear stress. The non-dimensional data given in tabular form may be useful in interpretation of clinical guidewire measurements for moderate lesions of similar geometry and size.