PARIS – Optical coherence tomography guidance of percutaneous coronary intervention resulted in a change in PCI strategy in two-thirds of patients in the multicenter ILUMIEN I study.
“We were surprised by the high rate at which the OCT [optical coherence tomography] findings influenced practice. Physician decision making was influenced by OCT findings pre-PCI and/or post PCI in 65% of patients, mostly those with more complex disease,” Dr. William Wijns reported at the annual congress of the European Association of Percutaneous Cardiovascular Interventions.
Another unexpected finding: The acute MI rate through 1 year of follow-up was zero among patients whose cardiologists altered their initial stenting strategy in response to the pre-PCI OCT findings and then performed post-PCI stent optimization because they deemed the initial deployment unacceptable based upon the post-PCI OCT findings.
In contrast, the MI rates were 10.3%-13.2% when cardiologists didn’t alter their strategy in response to either of the OCT results or when they altered it only once, based upon either the pre- or post-PCI OCT images. The great majority of these MIs occurred periprocedurally.
“These were true MIs with symptoms, not just enzyme bumps. The reduced MI rate in the subgroup of patients in whom operators changed the procedure based on OCT data, both pre- and post-PCI, was a surprise. The more you work on the artery, the more you’d expect to have troponin increases, at least,” observed Dr. Wijns of the cardiovascular center at Aalst, Belgium, and principal investigator in ILUMIEN I.
He was quick to add that the observed disparity in MI rates based upon the extent to which interventional cardiologists acted upon OCT findings was the result of a post hoc analysis and therefore must be considered merely hypothesis generating. It is, however, an exciting hypothesis, and one which will be tested prospectively in future randomized trials.
ILUMIEN I was a 40-center, 418-patient, prospective, randomized, observational study conducted in the United States, Europe, and Asia. The purpose of the study was to learn what impact OCT imaging had on procedural technique and to identify OCT findings that predict clinical outcomes.
All participants underwent paired fractional flow reserve and OCT studies at the time of angiography prior to their planned PCI and once again immediately post PCI. If the post-PCI imaging showed a suboptimal initial result – stent underexpansion with greater than 20% in-stent residual diameter stenosis, malapposition, flow-limiting edge dissection, or thrombus and/or tissue protrusion causing flow reduction – cardiologists had the option of optimizing the results. If they elected to do so, then OCT imaging was performed once again post optimization to see if in fact the technical outcomes had been improved as assessed in a core laboratory.
Pre-PCI measurements of fractional flow reserve and OCT were successfully accomplished in 91% and 98% of patients, respectively. Armed with the fractional flow reserve data, the interventional cardiologists developed their initial PCI strategy. Then they received the OCT results. Based upon these preprocedural OCT findings, cardiologists changed their PCI strategy in 57% of cases.
Post-PCI fractional flow reserve and OCT results were acquired in 83% and 98% of patients, respectively. Based upon what interventionalists saw as an unacceptable initial PCI result apparent upon the second OCT findings, they performed PCI optimization in 27% of patients.
OCT is known to have superior resolution, compared with angiography or, for that matter, intravascular ultrasound, so it’s not surprising that analysis of the post-PCI OCT findings at the central core laboratory identified a high rate of abnormal findings following what interventionalists deemed a successful result based upon angiographic appearance. Malapposition was present in 32% of cases, stent underexpansion in 27%, edge dissection in 32%, malapposition plus edge dissection in 9%, and tissue or thrombus protrusion in 4%.
Cardiologists performed PCI optimization based upon the second OCT findings in 106 patients. The third and final round of OCT in those patients showed that OCT-guided optimization achieved a sharp decrease in the rates of malapposition and malapposition plus edge dissection.
The 1-year major adverse cardiovascular event rate ranged from a low of 11.5% in the 65 patients who had a change in PCI strategy based upon the preprocedural OCT findings and who also underwent OCT-guided post-PCI optimization to 15.9% in the 137 patients who had neither. Stent thrombosis rates were very low in all four groups, as was in-hospital mortality.
Dr. Wijns noted that analysis of OCT guidance parameters predictive of 1-year clinical outcomes is ongoing.
The ILUMIEN I study was sponsored by St. Jude Medical. Dr. Wijns is a consultant to the company.