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

Abstract

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 d m = 1.8 mm 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 ± 0.3 ). 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 ( Δ p ˜ ) 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 % increase in Δ p ˜ h and a ∼ 51 % increase in the hyperemic flow resistance ( R ˜ h = Δ p ˜ 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.