Collateral Donor Artery Physiology and the Influence of a Chronic Total Occlusion on Fractional Flow Reserve

Abstract

Although FFR is reported to be independent of changing hemodynamics, 10 it is intimately related to total coronary flow through a stenosis, which in turn is related to perfused myocardial mass. 11 In keeping with this, there have been several reports of large increases in collateral donor vessel FFR associated with PCI of a concomitant CTO and, therefore, reduction in perfused myocardium.12-16 However, there is inherent variability to FFR measurement, 10 and therefore selective reporting and publication bias might have exaggerated the magnitude (or even presence) of this phenomenon in the reported cases.Background-The presence of a concomitant chronic total coronary occlusion (CTO) and a large collateral contribution might alter the fractional flow reserve (FFR) of an interrogated vessel, rendering the FFR unreliable at predicting ischemia should the CTO vessel be revascularized and potentially affecting the decision on optimal revascularization strategy. We tested the hypothesis that donor vessel FFR would significantly change after percutaneous coronary intervention of a concomitant CTO. Methods and Results-In consecutive patients undergoing percutaneous coronary intervention of a CTO, coronary pressure and flow velocity were measured at baseline and hyperemia in proximal and distal segments of both nontarget vessels, before and after percutaneous coronary intervention. Hemodynamics including FFR, absolute coronary flow, and the coronary flow velocity-pressure gradient relation were calculated.

Letter by Saito Regarding Article, “Collateral Donor Artery Physiology and the Influence of a Chronic Total Occlusion on Fractional Flow Reserve”

“…(1) Thus, the increase in FFR in the donor artery is calculated as follows: The above inequality (3) indicates that the FFR increase in the donor artery stenosis monotonically decreases when the donor artery FFR becomes larger, which is in accordance with the results of the study of Ladwiniec et al 1 Similarly, the partial differentiation in Equation 2 with respect to FFR 2 and n are calculated as follows: (5) The inequality (4) demonstrates that the FFR increase in the donor artery stenosis is more significant when the recipient artery FFR is larger. This indicates that the richer the collateral, the stronger the effect of the recipient artery recanalization.…”

Response to Letter Regarding Article, “Collateral Donor Artery Physiology and the Influence of a Chronic Total Occlusion on Fractional Flow Reserve”

“…2 It is gratifying that some of the findings of their in vitro work have been borne out by our results. Many of their comments have already been addressed in the article.…”

“…Many of their comments have already been addressed in the article. 2 We agree that the mass of collateral dependent myocardium and extent of collateralization are likely to be important factors in the extent of change in donor vessel fractional flow reserve (FFR) in this setting. Our sample size was calculated to demonstrate a significant change in collateral donor vessel FFR; to assess all predictive factors, a much larger study would indeed be required.…”

“…At this initial FFR value, the reported change is larger than predicted both by our own study and Dr Saito's study, where the postrecanalization FFR was predicted to be 0.89. 2 This may simply be explained by measurement variability; it perhaps provides an example of selective reporting to exaggerate the magnitude of the phenomenon. A value of clinical studies like our own over in vitro models is that they put individual case reports such as this in context and provide a more reliable estimate of effect size and variability.…”

Diastolic Backward-Traveling Decompression (Suction) Wave Correlates With Simultaneously Acquired Indices of Diastolic Function and Is Reduced in Left Ventricular Stunning

“…BEW wave energy is territory dependent and has been shown to fall with a reduction in perfused myocardial mass. 15 BEW intensity is likely to be related to a combination of perfused myocardial mass and LV diastolic performance. We intentionally selected left anterior descending stenoses to attempt to control for myocardial mass, and differences in wave intensity analysis attributed to different myocardial territories.…”