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12-12-2016 | Interventional cardiology | News | Article

Pre-PCI coronary flow reserve predicts adverse outcomes

medwireNews: Study results suggest that coronary flow reserve (CFR) measured prior to elective percutaneous coronary intervention (PCI) is an independent predictor of adverse cardiovascular outcomes.

Measuring pre-PCI CFR “might allow identification of patients […] who may require adjunctive therapeutic interventions despite otherwise successful PCI,” say the researchers.

Tsunekazu Kakuta (Tsuchiura Kyodo General Hospital, Otsuno, Japan) and study co-authors found that the mean pre-PCI CFR – defined as the ratio of basal to hyperemic mean transit time – was 1.91 among 38 patients who experienced an adverse cardiac event over a median follow-up of 24.3 months, compared with 2.52 among 180 patients not experiencing adverse events, a significant difference.

Additionally, low pre-PCI CFR was shown to be a significant predictor of adverse events in multivariable analysis (hazard ratio=0.73). The optimal cutoff was 2.42; event-free survival was significantly worse among patients with lower (≤2.42) versus higher (>2.42) pre-PCI CFR, with corresponding rates of approximately 60% and 90% after 4 years. Adverse events included revascularization, hospitalization for heart failure, arrhythmia, and myocardial infarction.

As reported in the Journal of the American Heart Association, Kakuta and colleagues also analyzed the relationship between changes in the CFR and fractional flow reserve (FFR) indices. FFR is “the standard in decision making for revascularization in the catheter laboratory,” they note.

FFR increased in all 220 patients studied, from a mean of 0.73 at baseline to 0.87 post-PCI. However, CFR increased in only 71.8% of patients, and decreased in a “nonnegligible” 28.2% (mean pre- and post-PCI values for all patients of 2.34 and 3.41, respectively), indicating that “FFR and CFR increases after PCI were not necessarily concordant.”

The authors observed a significant correlation between the two indices prior to PCI, but there was no relationship between post-PCI FFR and CFR. An increase in CFR after PCI was associated with pre-PCI indices including low FFR, low CFR, and high microvascular resistance, in addition to post-PCI hyperemic coronary flow increase. No increase in hyperemic coronary flow was observed in patients with post-PCI CFR decrease.

“Multifactorial mechanisms between microvascular resistance and hemodynamics may be involved in the determination of individual functional status of coronary circulation before and after PCI, although precise mechanisms relating microvascular resistance and hemodynamics remain elusive,” note the authors. They add that further research is needed to clarify the effect of PCI on microvascular status and hemodynamics.

Looking to the future, Kakuta and colleagues recommend that “a prospective large clinical study” should be carried out to evaluate the ability of CFR and other physiologic indices to “risk stratify patients at higher risk of future events in the presence of epicardial stenosis, regardless of PCI performance.”

By Claire Barnard

medwireNews is an independent medical news service provided by Springer Healthcare Limited. © Springer Healthcare Ltd; 2016

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