The result of a study, presented at ACC 2019 in March, 2019 and recently published in JACC Interventional Cardiology, showed that despite angiographically successful percutaneous coronary intervention (PCI), physiological assessment detected residual ischemia in 1 out of 4 patients after coronary stenting. The majority of the cases were due to inappropriate focal lesions which seem amenable to treatment with additional PCI.
Invasive physiological assessment of the coronary lesions to guide PCI is increasingly used in clinical practice. The most frequently used measure is the fractional flow reserve (FFR), which is calculated directly from hyperemic pressure measurements. Recently, another physiological index, the instantaneous wave-free ratio (iFR), has been shown to be non-inferior to FFR in guiding decisions in patients with intermediate coronary artery disease. The iFR does not require vasodilator administration for maximal hyperemia. DEFINE PCI (Physiologic Assessment of Coronary Stenosis Following PCI) was a prospective, single-arm, multi-center study, designed to assess the incidence and mechanisms of an abnormal distal vessel iFR after operator-assessed angiographically successful PCI.
Inclusion criteria were stable or unstable angina with either multi-vessel or multi-lesion coronary artery disease with an abnormal baseline iFR. The primary endpoint was the rate of residual ischemia, defined as iFR < 0.90 after operator-assessed angiographically successful PCI. Secondary endpoints included categorization of residual ischemia, the proportion of the cases in which optimizing stent-related issues or stenting untreated residual focal disease could theoretically improve iFR to ≥ 0.90, and the correlation between post-PCI quantitative coronary angiographic (QCA) assessment and residual iFR. All vessels which had at least 40% visually-estimated angiographic severity and deemed suitable for PCI were interrogated with the iFR. An iFR measurement was obtained under resting conditions and those with iFR < 0.90 in at least one vessel were formally enrolled in the study, considering they met all other inclusion and exclusion criteria. After successful completion of the PCI, a blinded iFR pull back was performed at the distal vessel and along the length of the vessel to determine residual trans-stenotic pressure gradients.
A total of 500 patients undergoing PCI in 562 vessels were included. Mean pre-procedural iFR for all vessels was 0.69 ± 0.22, which improved to 0.93 ± 0.07 post-PCI. Residual ischemia (post PCI iFR < 0.09) after angiographically successful PCI was present in 114 vessels (21.9%) and in 112 patients (24%). Of 114 vessels with abnormal post-PCI iFR, 93 (81.6%) had single or multiple residual focal lesions, and 21 (18.4%) had diffuse disease only. Among those with a focal disease, 38.4% were located within the stent segment, while 31.5% and 30.1% were proximal and distal to the stent, respectively. Assuming all focal lesions with post-PCI iFR < 0.90 were successfully treated with additional PCI, only 23 vessels (4.4%) with qualified post-PCI iFR pull backs would remain under the iFR ischemic threshold of < 0.90.
“The findings of the present study indicate that the vast majority of residual pressure gradients contributing to significant post-PCI ischemia are focal and thus could be potentially treated with additional PCI. Also of note, more than one-third of residual focal pressure gradients were found within the stented segment (despite their angiographically benign appearance), while about two thirds were present at the site of angiographically mild untreated lesions, indicating that further PCI (ideally with intravascular imaging) could lead to improved post-procedural physiology in the majority of patients”.- Dr. Jeremias, et al.
Residual stenosis by quantitative coronary angiographic assessment and post-procedural iFR were poorly correlated (R² = 0.03, p = 0.005). Post-PCI vessel angiographic diameter stenosis was not a predictor of impaired post-procedural iFR (p = 0.08).
Of note, the follow-up phase of this study is still ongoing and might be able to answer the question of whether post-PCI iFR-based optimization is safe or effective.
The study had some limitations. Owing to the specific inclusion criteria of the study, the results might not be generalizable to real-world cases. The prevalence of post-PCI ischemia might be underestimated because the investigators have not interrogated angiographically normal-appearing vessels in which PCI was not performed, some of which may have abnormal iFR and contribute to recurrent angina. Also, the presence of non-epicardial coronary-related causes of ischemia, such as microvascular disease, was not assessed.
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