I read with interest the paper by Kweon and colleagues1 in which they proposed a prediction model for post-stenting fractional flow reserve (FFR) in a tandem lesion with a side branch. The authors derived the following two equations that predicted the FFR after treatment of distal (Equation 1) or proximal stenosis (Equation 2):
where w=Pa/(Pa−Pw)=1.33 and k=Q1/Q0. Their efforts are praiseworthy; however, they committed a serious error in their calculation. The authors calculated the hyperaemic coronary flow to each branch by using the P=QR equation. The problem is that the authors always ...
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