Determinants of transstenotic gradients observed during angioplasty: An experimental model

Abstract Pressure gradient measurement across a stenosis is used during angiopiasty to aid catheter positioning and estimate dilatation efficacy. The angiopiasty catheter itself, however, further reduces lumen size, and therefore augments the transstenotic gradient. To more precisely define the catheter influence on gradient, we derived a theoretical expression relating the measured gradient with the angiopiasty catheter in situ to the “true” gradient; that is, the gradient in the absence of the angiopiasty catheter. We then tested this theoretical construct in a canine femoral artery angiopiasty model. Fifty-four measurements were performed using 23 separate, 3-mm-long, 40 to 70% stenoses. As predicted by the theoretic model, “true” gradient is compounded by the angiopiasty catheter principally as a function of the angiopiasty catheter diameter (Dc) and the stenosis diameter (Ds). The best-fit curve of data points relating “true” and compounded gradients to various Dc and Ds combinations can be expressed as: Measured gradient = K × true gradient, where K = 0.25 (e) 4.47 (Dc÷Ds and e = 2.718. Thus, the transstenotic gradient measured at angiopiasty overestimates “true” resting gradient in a predictable manner, which is dependent on the ratio of Dc to Ds.