Abstract 13069: Prescribed Flow Reserve as a Novel Method for Diagnosis of Coronary Artery Ischemia Under Physiologically-Realistic Conditions
Background. Failure to achieve maximal hyperemia in coronary arteries during fractional flow reserve (FFR) may result in under-estimation of pressure drop (ΔP) and over-estimation of FFR, and possibly lead to misdiagnosis of hemodynamically-significant lesions. Further, induction of hyperemia does not allow for precise determination of ischemic thresholds for physiologically-realistic conditions, such as for increasing levels of exercise. We investigated the influence of prescribed flow rates on the pressure ratio (Pd/Pa) of coronary artery stenoses of varying severities.
Methods. Prescribed flow reserves (PFR) were evaluated using an in vitro experimental flow loop with a pump circulating water at steady-state flow (Figure 1A). Three stenoses of 30%, 50% and 70% diameter stenosis (DS) severity with smooth Gaussian shapes were fabricated using VeroClear rigid material in an Objet260 Connex printer. Mean proximal pressure (Pa) was maintained at 90 and 140 mm Hg using a linear flow needle valve that allowed for adjustment of physiologically-realistic microcirculatory resistance. Pd/Pa at differing prescribed flow rates (Q), titrated by a flow meter, applied to each of the stenosis, were assessed for the 2 levels of Pa. A PFR of Pd/Pa ≤0.80 was considered diagnostic of coronary ischemia.
Results. The ΔP-Q characteristics demonstrated a quadratic relationship. The Pd/Pa-Q curve (Figure 1B and 1C) followed a similar trend, with decreasing slope. Further, the average slope of the Pd/Pa-Q decreased with increasing DS at either levels of the Pa. When compared amongst lesions of increasing severity (Figure 1C and 1B), Pd/Pa-Q curve slopes at the 0.80 ischemic threshold increased by 9%, 20% and 25%, respectively, for 30%, 50% and 70% DS.
Conclusions. Coronary artery ischemia, as determined by Pd/Pa, differs under increasing flow rates. PFR may be a potential alternative to FFR for determination of coronary ischemia under precise physiologically-realistic conditions.
Author Disclosures: K. Kolli: None. G. Xiong: None. H. Soohoo: None. J. Min: Research Grant; Modest; GE Healthcare. Ownership Interest; Modest; MDDX, Autoplaq. Consultant/Advisory Board; Modest; Abbott Vascular, HeartFlow, NeoGraft Technologies, MyoKardia, CardioDx, Arineta.
- © 2015 by American Heart Association, Inc.