Effect of coronary collaterals on FFR measurement

FFR is based on the hemodynamic principle of pressure drop when fluid or blood flows across a narrowed segment (similar to Bernoulli principle). If there is more than 25 % pressure drop across the lesion under maximum hyperemic condition (or steady-state) it is counted as significant.(FFR is .75) Now, if the distal vessel is supported by collaterals, what happens? When a vessel in question, is supplied by well-formed distal collaterals, it will prevent this pressure drop and hence lesion is underestimated. Similarly, if the donor artery has a suspicious intermediatory lesion, the FFR across it shows falsely low, overestimates the lesion, as the distal pressure drops, not because of the lesion but due to rapid collateral flow into the recipient artery.   Let us take a hypothetical case.  In a post anterior MI 90 % LAD lesion receiving well-formed collateral from RCA which also has a 70 % proximal lesion. FFR is artificially low in donar RCA (<.75) and makes an insignificant lesion as significant ( ie false positive) . Meanwhile, in the recipient artery LAD  FFR is artificially high, and give a false negative result, underestimating the severity   Clinical significance First, fix a lesion in the recipient artery and then reassess donor artery. This is especially important in LAD CTO If you open up CTO, a lesion in RCA might become insignificant and may not require intervention. Summary ...
Source: Dr.S.Venkatesan MD - Category: Cardiology Authors: Tags: Uncategorized FFR IFR wave free qfr imr ct ffr ffr in left main bifurcation lesion tandem lesion ffr vs tmt stress test impact of collateral on ffr oor man's ffr stres test equivalent Source Type: blogs