Reliability of fractional flow reserve measurements in patients with associated microvascular dysfunction: Importance of flow on translesional pressure gradient

Fractional flow reserve (FFR) has been applied with success as a lesion-spe cific functional indicator of stenosis severity, at least in patients with normal microcirculation. This study sought to assess the reliability of FFR calculations in patients with associated microvascular dysfunction (e.g., post myocardial infarction, or post-MI). First, the effect of coronary flow changes on translesional pressure gradient was assessed. Therefore, intrac oronary pressure and flow was recorded simultaneously across 19 non-infarct -related lesions (both pre- and postinterventional lesions with a mean diam eter stenosis of 47% +/- 12%). Measurements were performed by means of a pr essure and Doppler wire during maximal hyperemia and also during submaximal hyperemia induced by low-dose adenosine. The drop of coronary flow from 48 +/- 23 ml/min during maximal hyperemia to 36 +/- 18 ml/min during submaxim al hyperemia was associated with a small decrease in translesional pressure gradient (from 22 +/- 12 mm Hg to 19 +/- 12 mm Hg; P = 0.02) and a small i ncrease in the mean distal/arterial pressure ratio (Pd/Pa) going from 77% /- 11% to 81% +/-: 11% (P = 0.003). Then, intracoronary pressure and flow m easurements were compared across 21 non-infarct-related lesions vs. 22 matc hed infarct-related lesions. For a similar angiographic stenosis severity ( % DS = +/- 44%), maximal flow was 48 +/- 22 ml/min in the non-infarct arter ies and 37 +/- 26 ml/min in the infarct arteries (P = 0.03), confirming the presence of severe microvascular dysfunction in infarct regions. Similar t o the earlier findings, this hyperemic flow reduction in Mi patients was as sociated with a small increase of FFR (= Pd/Pa): 79% +/- 12% in no MI vs. 8 3% +/- 12% in Mi patients (P = 0.3). A reduction of hyperemic flow by + 5%, such as can be found in patients with severely impaired microvascular func tion, has a limited effect on FFR calculations (+ 5%). This finding allows the application of standard FFR calculations in a more general population o f ischemic heart disease, including patients with recent (C) 2001 Wiley-Lis s, Inc.