Research · Apr 4, 2026
IVUS-CHIP and OPTIMAL: optimization rates and the angiography arm
Conflict of interest: I am a proctor and speaker for Boston Scientific, specifically for CHIP interventions, and have been for years. These results challenge some of my own beliefs about how we practice interventional cardiology.
Results
The two European trials were published together in NEJM and were neutral, with estimates numerically against IVUS.
| Trial | Population | HR (95% CI) |
|---|---|---|
| IVUS-CHIP | Complex high-risk PCI, 2020 patients | 1.25 (0.97 to 1.60) |
| OPTIMAL | Unprotected left main, 806 patients | 1.11 (0.87 to 1.42) |
Optimization rates across IVUS trials
The most common defense is that IVUS-CHIP failed because only 48% of lesions met the predefined optimization criteria.
| Trial | Optimization in the IVUS arm |
|---|---|
| ULTIMATE | 53% |
| RENOVATE-COMPLEX-PCI | about 58% |
| OCTIVUS | 55% |
| IVUS-CHIP | 48% |
The difference is small, but the treatment is asymmetric. ULTIMATE at 53% is cited as proof that IVUS works; IVUS-CHIP at 48% is treated as a flawed trial. If incomplete implementation invalidates one, it invalidates all of them.
Anatomy and optimization
Optimization around 50 to 55% may be a limit set by the disease. In diffuse disease, heavy calcium and tortuous anatomy, an adequate landing zone sometimes does not exist.
| Trial | Severe calcification | Distal edge plaque burden |
|---|---|---|
| IVUS-CHIP | 45.8% | 47.6% |
| RENOVATE-COMPLEX-PCI | 13.5% | 40.6% |
A mean distal plaque burden of 47.6% is close to failing the optimization criterion by definition. Meeting the criteria may say more about the anatomy than about the technique. If so, the positive trials may have reflected their population more than the tool.
Use of IVUS findings in OPTIMAL
Another criticism is that, in OPTIMAL, operators acted on IVUS findings in about 30% of cases. This assumes there was something to correct in the other 70%. The angiographic result may already have been good, with IVUS only confirming it. In that case, the finding speaks to operator quality.
The angiography arm has changed
Post-dilation rate in the angiography arm:
| Trial | Post-dilation in the angiography arm |
|---|---|
| ULTIMATE | 57% |
| RENOVATE-COMPLEX-PCI | 75% |
| IVUS-CHIP | 84.5% |
| OPTIMAL | 96.0% |
Operators who have used IVUS for years have internalized sizing, post-dilation, POT and landing zone selection. Randomized to angiography, they keep applying that learning; in OPTIMAL, POT was performed in 85.1% of the angiography arm. The real comparison is formal IVUS against practice that IVUS has already shaped. When that gap narrows, the incremental gain from imaging disappears.
This does not mean IVUS is useless or that one should stop using it. It means that, in expert European centers, the marginal gain of formal IVUS over IVUS-informed angiography was close to zero.
The missing analysis
I would like to see in both trials the analysis done in ULTIMATE: outcomes in patients who met optimization criteria against those who did not. In ULTIMATE, target vessel failure was 4.2% against 9.2% (HR 0.44). If IVUS-CHIP and OPTIMAL show the same pattern, the problem becomes the inability to achieve optimization in half the patients. If they do not, that has to be accepted too.
Conclusion
Optimization failure cannot be invoked only when results disappoint. Using 53% in ULTIMATE as proof that IVUS works and 48% in IVUS-CHIP as proof of a flawed trial is fitting the interpretation to the desired result.