Introduction: The distal coronary-to-aortic pressure ratio (Pd/Pa) is a non-hyperaemic physiological index to assess the functional severity of coronary stenoses. Studies comparing Pd/Pa with fractional flow reserve (FFR) show superior diagnostic efficiency for myocardial ischaemia. Nevertheless, a direct comparison regarding long-term clinical outcomes is still not available. The present observational study compared the prognostic value of Pd/Pa and FFR for major adverse cardiac events (MACE) during a 10-year follow-up period after deferral of revascularisation.
Methods: Between April 1997 and September 2006, we evaluated 154 coronary stenoses (154 patients) in which revascularisation was deferred with intracoronary pressure and flow measurements during the resting and hyperaemic state. Long-term follow-up (median: 11.8 years) was performed to document the occurrence of MACE, defined as a composite of cardiac death, myocardial infarction and target vessel revascularisation.
Results: The study population comprised angiographically intermediate coronary stenoses, with a mean diameter stenosis of 53 ± 8%, and intermediate physiological severity with a median FFR of 0.82 (Q1, Q3: 0.76, 0.88). The association of Pd/Pa with long-term MACE was similar to that of FFR [FFR-standardised hazard ratio (sHR): 0.77, 95% confidence interval (CI): 0.61-0.98; Pd/Pa-sHR: 0.80, 95% CI: 0.67-0.96]. In the presence of disagreement between Pd/Pa and FFR, normal Pd/Pa was generally associated with high coronary flow reserve (CFR) and a favourable clinical outcome, whereas abnormal Pd/Pa was generally associated with CFR around the ischaemic cut-point and an impaired clinical outcome, regardless of the accompanying FFR value.
Conclusion: The present study suggests that Pd/Pa provides at least equivalent prognostic value compared with FFR. When Pd/Pa disagreed with FFR, the baseline index conferred superior prognostic value in this study population.
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