Pinak B. Shah, MD, FSCAI; Evelyn Baram Clothier, PhG, JD; and Faisal Latif, MD, FSCAI

Delayed PCI Complications: SAT and ISR

Less attention has been paid to long-term quality metrics for percutaneous coronary intervention (PCI) such as subacute stent thrombosis (SAT) and in-stent restenosis (ISR) occurring after hospital discharge from the initial PCI. It is often difficult for health systems to track these outcomes since patients may not be followed by the physician who performed the procedure or at the institution where the procedure was performed. Nonetheless, these complications may be as important of a quality indicator for PCI as commonly used short-term quality metrics such as bleeding and periprocedural myocardial infarction. A growing body of evidence has shown the importance of stent optimization utilizing intravascular imaging and post-dilation for the prevention of delayed complications after PCI such as SAT and ISR. In this Tip of the Month, we focus on the importance of routine use of intravascular imaging for PCI and the importance of imaging utilization as a PCI quality metric.

Intravascular Imaging

Intravascular imaging can be performed with either intravascular ultrasound (IVUS) or optical coherence tomography (OCT). Both modalities have their advantages and disadvantages, and both are considered acceptable forms of intravascular imaging, though one may be preferred over the other in specific situations. Intravascular imaging provides valuable diagnostic information for procedural planning. Data obtained from intravascular imaging provides information regarding optimal lesion preparation strategies, including the need for an atherectomy for calcium modification, and provides the operator accurate vessel sizing so that the appropriate stent size can be chosen. Undersizing of stents occurs frequently when visual estimation alone is used for size selection, and this is a major contributor to the risk of SAT or ISR¹. Imaging will also provide information after stent deployment for stent optimization. The ULTIMATE criteria are often used to determine optimal stenting with use of IVUS². These criteria include:

1. Minimum lumen cross-sectional area in a stented segment >5.0 mm² or 90% of the distal reference lumen cross-sectional area
2. Plaque burden at the 5 mm proximal or distal to the stent edge <50%
3. No edge dissection involving the media >3 mm in length

Criteria for optimal stenting with use of OCT come from a variety of studies, including ILUMIEN III³, include:

1. Proximal mean stent area > 90% of the proximal reference vessel minimum lumen area
2. Distal mean stent area > 90% of the distal reference vessel minimum lumen area
3. Full stent apposition (no more than > 3.0 mm from the vessel wall for longer than 3mm of the vessel)
4. No dissection that penetrates the media and > 90^◦ in arc

Failure to meet these optimal stent criteria should prompt the operator to consider additional interventions, including additional stent placement and/or post-dilation.

Several recent studies have shown important benefits of routine intravascular imaging during PCI. The ULTIMATE trial showed that at three years, IVUS-guided PCI was associated with important reductions in target vessel failure (cardiac death, myocardial infarction [MI], or target vessel revascularization) compared to angiography-guided PCI (2.9% vs. 5.4%, p=0.019). The ILUMIEN IV trial will further elucidate the benefits of OCT-guided PCI. Meta-analyses have shown significant benefits of routine use of intravascular imaging in the prevention of late major adverse cardiac events such as target lesion failure requiring repeat intervention^4,5. Therefore, the use of intravascular imaging is a quality metric that should be tracked by catheterization laboratories, not only for the lab as a whole, but for individual operators as well. This data should be presented in an anonymous fashion at catheterization laboratory quality assurance meetings and will be a powerful tool to affect change amongst PCI operators. This will also raise awareness and proficiency amongst technical staff so that over time, imaging will be viewed as a standard part of the procedure rather than as an add-on procedure. Figure 1 shows the use of intravascular imaging at Brigham and Women’s Hospital when the data was first presented at quality assurance meetings in 2019. In January of 2019, only 26% of PCI procedures utilized intravascular imaging. Figure 2 shows the same data in 2021 with imaging utilization up to 83% of PCI cases by July of 2021.

Summary

Given the benefits of routine intravascular imaging in preventing such delayed PCI complications, the use of imaging during PCI can be considered a surrogate indicator of long-term PCI quality. Imaging will assist operators in appropriate lesion preparation, stent selection, and stent optimization with enhanced post-dilation or additional stent placement. Catheterization laboratories should make a concerted effort to incorporate imaging into their routine PCI practice and present data regarding imaging use during PCI at quality assurance meetings on at least a quarterly basis.

References

1. Kang S, Mintz GS, Park D-W, et al. Mechanisms of in-stent restenosis after drug-eluting stent implantation: intravascular ultrasound analysis. Circ Cardiovasc Interv. 2011 Feb 1;4(1):9–14.
2. Gao X-F, Ge Z, Kong X-Q, et al. 3-Year Outcomes of the ULTIMATE Trial Comparing Intravascular Ultrasound Versus Angiography-Guided Drug-Eluting Stent Implantation. JACC Cardiovasc Interv. 2021 Feb 8;14(3): 247–257.
3. Ali ZA, Maehara A, Généreux P, et al. Optical coherence tomography compared with intravascular ultrasound and with angiography to guide coronary stent implantation (ILUMIEN III:OPTIMIZE PCI): a randomised controlled trial. Lancet 2016. Nov 26;388(10060):2618–2628.
4. Buccheri S, Franchina G, Romano S, et al. Clinical Outcomes Following Intravascular Imaging-Guided Versus Coronary Angiography-Guided Percutaneous Coronary Intervention With Stent Implantation: A Systematic Review and Bayesian Network Meta-Analysis of 31 studies and 17,882 Patients. JACC Cardiovasc Interv. 2017 Dec 26;10(24):2488–2498.
5. Darmoch F, Alraies MC, Al-Khadra Y, et al. Intravascular Ultrasound Imaging-Guided Versus Coronary Angiography-Guided Percutaneous Coronary Intervention: A Systematic Review and Meta-Analysis. J Am Heart Assoc 2020 Mar 3;9:e013678.

Figure 1: Percentage of PCI utilizing intravascular imaging from January 2019 through November 2019 at Institution A.

Figure 2: Percentage of PCI utilizing intravascular imaging from August 2020 through July 2021 at Institution A.