Long-term prognostic implications of PCI in ACS patients without ischemia on the basis of computational pressure-flow dynamics derived fractional flow reserve
Authors: Lam L Y , Leung C K L , Li K Y , Li H L , Wu M Z , Ren Q W , Yu A S Y , Wong P F , Tse Y K , Yu S S Y , Feng Y , Huo Y , Tse H F , Yiu K H 
Published: October 2021

Abstract

Background
A substantial proportion of patients with acute coronary syndrome (ACS) may have intermediate lesion that are non-ischemic during emergency coronary angiography. The prognosis of such patients, compared to those with stable ischemic heart disease (SIHD) without ischemic lesion is however uncertain. Recently, a novel index, computational pressure-flow dynamics derived fractional flow reserve (caFFR), has been developed to assess myocardial ischemia, without the need of invasive pressure wire and hyperaemic stimulus as required in conventional fractional flow reserve (FFR). By utilizing caFFR to assess for ischaemic status during coronary angiography, the aim of our study is first to assess the prognostic difference between ACS and SIHD with non-ischaemia intermediate lesions. Second, we ascertain whether PCI in patients with ACS with non-ischaemia intermediate lesions provides survival benefit in addition to medical therapy.

Methods
We retrospectively recruited 551 patients (mean age 64.4 years; male 59.9%) with absence of myocardial ischaemia, defined as caFFR ≥0.80 in all vessels, from our Hospital. Patients were stratified into those with index presentation of ACS (n=132) and those with SIHD (n=491). Among the ACS cohort, patients were further divided into those with PCI (n=83) and with medical therapy alone (n=49). The SIHD cohort (n=491), all of whom were treated with medical therapy alone, was considered as referent group. The primary end point was major adverse cardiovascular events (MACE) at 3 years, which was defined as a composite of all-cause mortality, non-fatal myocardial infarction (MI), and any unplanned revascularization.

Results
During a median follow-up of 36 months, 54 composite events occurred, including 38 all-cause mortality, 5 MI, and 14 unplanned revascularization. Compared to those with SIHD, patients with ACS was independently associated with MACE even in the absence of myocardial ischaemia (adjusted Hazard Ratios=2.531; 95% confidence interval=1.397–4.586; P=0.002). The 3-year incidence rate of MACE was the highest in ACS patients with medical therapy alone, followed by ACS patients with immediate PCI; the SIHD cohort had the lowest incidence rates (30.6% vs 12.0% vs 5.9%, P&lt;0.001). This was mainly driven by the rate of all-cause death (26.5% vs 12.0% vs 3.1%; P&lt;0.001). Similar findings were observed for hospitalisation due to heart failure (14.3% vs 6.0% vs 3.1%, P=0.031) and cardiac death (8.2% vs 4.8% vs 0.4%, P&lt;0.001) at 3 years.

Conclusion
In patients with intermediate lesion without myocardial ischaemia (defined as caFFR ≥0.8), those presented with ACS had a higher risk of MACE at 3 years compared to SIHD. Among ACS patients with intermediate lesion without myocardial ischaemia, PCI significantly reduces the rate of MACE. In patients with ACS, our finding suggests that PCI should be advocated to intermediate lesion even without myocardial ischaemia.

Funding Acknowledgement
Type of funding sources: None. Kaplan-Meier curve for MACECumulative Events at 3 Years