This study was a sub-analysis of the ST-Elevation myocardial infarction treated with Laser Atherectomy (STELA) registry, which was a retrospectively collected, multicenter registry of consecutive patients with STEMI who underwent primary PCI within 24 hours of the onset of myocardial infarction from January 2015 to December 2019. Twelve regional healthcare centers in Japan providing continuous emergency care, including primary PCI for STEMI, participated in the registry. Details of the registry protocol are described elsewhere. From a total of 2,777 patients enrolled in the registry, 184 patients were excluded due to insufficient image quality of angiography (n = 3), loss of clinical follow-up information within 30 days (n = 134), unidentifiable culprit lesion (n = 40), and bypass graft failure (n = 7), and the remaining 2,593 patients with sufficient image and clinical data were investigated ( Figure 1 ). For the present analysis, we selected the patients who were treated with intravascular image guidance, specifically with OCT guidance or IVUS guidance, excluding those who underwent multiple intravascular imaging modalities (n = 244) or patients with angiography guidance alone (n = 58). STEMI was diagnosed according to the fourth universal definition of myocardial infarction. Patients were divided into 2 groups according to the intravascular imaging modality used: OCT guidance group and IVUS guidance group, and the clinical outcomes were compared between the 2 groups. The study protocol was approved by Institute of Science Tokyo ethics committee (M2020-342) and by each participating hospital, and registered with the University Hospital Medical Information Network Clinical Trials Registry of Japan (UMIN-CTR number: 000043818). This study was performed in accordance with the principles of the Declaration of Helsinki.

Figure 1. Study flow diagram. Flow diagram illustrating patient selection from the STELA (ST-Elevation myocardial infarction treated with laser atherectomy) registry. Of 2,777 consecutive STEMI patients undergoing primary PCI within 24 hours of symptom onset at 12 Japanese centers (2015 to 2019), 184 patients were excluded due to insufficient data or technical issues. From the remaining 2,593 patients, 302 were further excluded for using multiple imaging modalities (n = 244) or angiography-only guidance (n = 58), resulting in 2,291 patients in the total cohort (244 OCT-guided, 2,047 IVUS-guided). Propensity score (PS) matching yielded 187 matched pairs for the primary analysis. Clinical outcomes were assessed at a median follow-up of 2.0 years.

Clinical information, encompassing baseline characteristics, laboratory data, medications at discharge, procedural details, outpatient visit records, and subsequent adverse events were obtained from medical records and anonymized at each participating institution. Cardiac enzymes were measured every 3 to 6 hours until their levels began to decline, and maximum results are marked as peak values. The anonymized data were entered into password-protected electronic spreadsheets and securely transferred to the research laboratory at the Department of Cardiovascular Medicine, Institute of Science Tokyo (IST). Angiographical and intravascular imaging results were saved and sent to the laboratory for further investigation.

All PCI procedures were performed fundamentally according to the operator’s discretion, including the use of intravascular imaging modalities and the selection of stents, complying with the social and institutional guidelines. Workflow of OCT-guided PCI and IVUS-guided PCI were dependent on the institutional protocol as well. OCT was performed using frequency domain-OCT (AptiVue imaging system and Dragonfly OPTIS imaging catheter, Abbott Medical Japan, Tokyo, Japan) or optical frequency-domain imaging (LUNAWAVE imaging system and FastView imaging catheter) based on institutional availability. IVUS was performed according to the institutional protocol and the devices were chosen per their availability, in which AltaView imaging catheter with VISICUBE imaging system (Terumo, Tokyo, Japan) or OptiCross imaging catheter with iLab imaging system (Boston Scientific Japan, Tokyo, Japan) were predominantly used.

Coronary angiograms were analyzed by independent observers blinded to the clinical characteristics or outcomes at the imaging laboratory of IST. Quantitative coronary angiography (QCA) analyses were performed on the baseline and final angiograms for each patient using QAngio software (Medis, The Netherlands). The Thrombolysis in Myocardial Infarction (TIMI) flow grade was determined at baseline and on final angiography. Slow flow phenomenon was defined as TIMI flow grade ≤2 on final angiography. The corrected TIMI frame count was evaluated adjusted by the frame rate to 30 frames per second in the final angiograms. The TIMI thrombus grade was assessed in baseline angiograms.

The primary endpoint was the incidence of target vessel-related major adverse cardiac events (TV-MACE) defined as the composite of cardiovascular death, target vessel revascularization (TVR) and target vessel nonfatal myocardial infarction (TV-AMI) during the follow-up period. The secondary endpoints included individual components of TV-MACE, peak cardiac enzyme levels, and angiographic outcomes immediately after primary PCI including final TIMI flow grade, corrected TIMI frame count, and myocardial blush grade (MBG).

Statistical analyses were performed using R statistical software (version 4.4.1, R Foundation for Statistical Computing, Vienna, Austria). Categorical variables are summarized as frequencies and percentages and were compared between groups using the χ ² test or Fisher’s exact test, as appropriate. Continuous variables are expressed as mean ± SD or median (interquartile range) and were compared between groups using 2-tailed, unpaired t-tests or the Mann–Whitney U test according to the distribution. Kaplan–Meier analysis with Log-rank test was used to determine the difference in event-free survival between groups. Cox proportional hazard model was utilized to determine the predictors of adverse cardiac events. A 2-sided p-value <0.05 was considered statistically significant. The propensity score was derived based on the variables showing statistically significant differences between OCT guidance and IVUS guidance groups, and clinically relevant variables at baseline. Propensity score matching was then performed with a 1:1 algorithm using nearest-neighbor matching with a caliper width of 0.2 of the standard deviation of the logit of the propensity score, without replacement.

Of the 2,291 patients in the final analysis after excluding angiography-guided PCI and cases using multiple imaging modalities, 244 patients (10.7%) received OCT-guided PCI and 2,047 patients (89.3%) received IVUS-guided PCI ( Figure 1 ). Table 1 shows the baseline patient characteristics of both groups in the total cohort (n = 2,291). Compared to the IVUS group, the OCT group had higher rates of prior myocardial infarction (10.7% vs 6.1%, p = 0.013), prior PCI (13.9% vs 8.1%, p = 0.004), and prior statin use (32.0% vs 19.7%, p <0.001). Demographics and comorbidities were similar between groups. The OCT group showed less frequent presentation with Killip class IV (6.6% vs 12.6%, p = 0.029) and better baseline coronary flow (TIMI 3: 20.9% vs 14.8%, p <0.001). In terms of angiographic findings, culprit lesions in the OCT group were more frequently located in LAD (59.8% vs 48.8%, p = 0.009), had smaller percent diameter stenosis (83.4% vs 88.5%, p <0.001), and lower thrombus burden (grade 4 to 5: 74.6% vs 85.4%, p <0.001), while multivessel disease was less common (31.6% vs 40.8%, p = 0.006) ( Table 1 ).

There was substantial variation in the selection of intravascular imaging modalities across the 12 participating hospitals ( Supplementary Figure 1 ). IVUS predominated at most centers, while OCT usage was concentrated in a limited number of institutions with the usage rate of OCT ranging from 0% to 30%. Notably, 2 hospitals did not utilize OCT during the study period, highlighting the heterogeneous adoption of this technology across institutions. Analysis of temporal trends revealed dynamic changes in imaging modality utilization over the 5-year study period ( Supplementary Figure 2 ). IVUS usage showed a gradual decline from 91% in 2015 to 84% in 2019, while OCT utilization nearly doubled from 12% to 23% during the same period.

Angiographic and in-hospital clinical outcomes are summarized in Table 2 . Regarding angiographic findings, corrected TIMI frame count was significantly lower in the OCT group compared to the IVUS group, whereas no significant difference was observed in TIMI flow grade or MBG. Peak values of cardiac enzymes, including CK-MB and cardiac troponin, were significantly greater in the IVUS group than in the OCT group. During the median follow-up period of 722 (322 to 1,268) days, TV-MACE occurred in 320 patients (13.9%), which included 169 cardiovascular deaths (7.4%), 141 TVR (6.1%) and 19 TV-AMI (0.8%) ( Table 2 ). A multivariable Cox proportional-hazard model demonstrated that culprit lesions in left main trunk (LMT), severe angiographic calcification, a smaller reference vessel diameter, Killip class IV, maintenance hemodialysis, a history of prior PCI, and the need for ECMO before PCI were independent predictors of TV-MACE. OCT guidance was associated with lower TV-MACE rate in the univariable analysis (hazard ratio [HR] 0.66, 95% confidence interval [95% CI] 0.43 to 1.00; p = 0.049), although it did not reach statistical significance after multivariable adjustment (HR 0.70, 95% CI 0.43 to 1.13; p = 0.140) ( Table 3 ).

Table 2

Postprocedural angiographic findings and clinical outcomes in the total cohort

	IVUS N = 2,047	OCT N = 244	p-value	SMD
Postprocedural angiographic findings
Diameter stenosis, %	19.1 ± 12.0	16.7 ± 11.5	0.003	0.206
Minimal lumen diameter, mm	2.56 ± 0.61	2.49 ± 0.60	0.066	0.126
Reference diameter, mm	3.12 ± 0.61	2.96 ± 0.59	<0.001	0.254
Corrected TIMI frame count	30.99 ± 20.68	27.75 ± 18.24	0.020	0.166
Slow flow	348 (17.0)	35 (14.3)	0.319	0.073
TIMI flow grade			0.863	0.072
0	13 (0.6)	0 (0.0)
1	41 (2.0)	4 (1.6)
2	289 (14.1)	31 (12.7)
3	1,699 (83.0)	209 (85.7)
Myocardial blush grade			0.697	0.128
0	15 (0.7)	3 (1.2)
1	68 (3.3)	7 (2.9)
2	491 (24.0)	55 (22.5)
3	1,461 (71.4)	179 (73.4)
Cardiac enzymes
Peak CK, U/l	3269.8 ± 3335.2	2791.3 ± 3021.4	0.033	0.150
Peak CK-MB, ng/ml	293.8 ± 286.3	261.6 ± 254.2	0.095	0.119
Peak troponin I, pg/ml	108784.2 ± 305982.1	106299.7 ± 181857.6	0.931	0.010
Clinical events
TV-MACE	296 (14.5)	24 (9.8)	0.051	0.142
Cardiovascular death	158 (7.7)	11 (4.5)	0.070	0.134
TVR	130 (6.4)	11 (4.5)	0.323	0.036
Target vessel AMI	16 (0.8)	3 (1.2)	0.446	0.045
Nontarget vessel-related revascularization	144 (7.0)	15 (6.1)	0.690	0.036
Any nonfatal MI	37 (1.8)	4 (1.6)	1.000	0.013

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