Physiologic Assessment after Coronary Stent Implantation

Abstract

The presence of myocardial ischemia is a prerequisite for the benefit of coronary revascularization. In the cardiac catheterization laboratory, fractional flow reserve and non-hyperemic pressure ratios are used to define the ischemia-causing coronary stenosis, and several randomized studies showed the benefit of physiology-guided coronary revascularization. However, physiology-guided revascularization does not necessarily guarantee the relief of ischemia. Recent studies reported that residual ischemia might exist in up to 15-20% of cases after angiographically successful percutaneous coronary intervention (PCI). Therefore, post-PCI physiologic assessment is necessary for judging the appropriateness of PCI, detecting the lesions that may benefit from additional PCI, and risk stratification after PCI. This review will focus on the current evidence for post-PCI physiologic assessment, how to interpret these findings, and the future perspectives of physiologic assessment after PCI.

Keywords: Fractional flow reserve; Non-hyperemic pressure ratio; Outcomes; Percutaneous coronary intervention.

Figure 1. A case with residual ischemia after angiographically successful stent implantation. Fractional flow reserve measured after stent implantation at the distal LAD was 0.75. Pressure wire pullback under hyperemia showed a pressure step up at the proximal LAD, and there was no significant pressure change across the stented segment. Intravascular ultrasound showed diffuse atherosclerotic disease at the left main coronary artery and proximal LAD.

LAD = left anterior descending artery.

Figure 2. Rate of TVF according to post-PCI FFR. The rates of TVF at 2 years decreased along with the increase of post-PCI FFR from the International Post-PCI FFR registry.

FFR = fractional flow reserve; PCI = percutaneous coronary intervention; TVF = target vessel failure.

Figure 3. Risk prediction model based on machine learning after coronary stenting. From the International Post-PCI FFR registry, the risk prediction model after coronary stenting was developed using a machine learning technique by incorporating clinical, angiographic, and post-PCI FFR data. Six important features were identified, and total stent length and post-PCI FFR were the most important features for predicting target vessel failure at 2 years. Post-PCI FFR had an additive value for risk prediction in addition to clinical and angiographic data.

ACS = acute coronary syndrome; C-index = concordance index; DS = diameter stenosis; DM = diabetes mellitus; FFR = fractional flow reserve; HTN = hypertension; LAD = left anterior descending artery; MI = myocardial infarction; PCI = percutaneous coronary intervention.

Figure 4. PCI optimization strategy with post-PCI physiologic assessment.

FFR = fractional flow reserve; NHPR = non-hyperemic pressure ratio; PCI = percutaneous coronary intervention.

Figure 5. Novel modalities to predict post-PCI physiologic status before stent implantation.

CT-FFR = computed tomography-based computation of fractional flow reserve; iFR = instantaneous wave-free ratio; PCI = percutaneous coronary intervention; QFR = quantitative flow ratio.