Combining Optical Coherence Tomography and Fractional Flow Reserve for Decision Making in Percutaneous Coronary Intervention: Insights From the FUSION Study

Abstract

Background

Physiological indices and intracoronary imaging provide additional and complementary information to coronary angiography, which may enhance procedural decision making during percutaneous coronary intervention (PCI). This study aimed to evaluate the impact of fractional flow reserve (FFR) and optical coherence tomography (OCT) on revascularization decision making and PCI strategy compared with angiography guidance alone.

Methods

In this secondary analysis from the prospective, observational FUSION (Validation of OCT-Based Functional Diagnosis of Coronary Stenosis) study, the impact of angiography, OCT, and FFR on procedural decision making was evaluated by comparing the intended treatment strategy after each step to the actual treatment strategy, which was left to the operator’s discretion and was guided by the totality of diagnostic testing.

Results

Among 224 patients (mean age, 67.4 ± 9.2 years; 30.8% women), 116 (51.8%) underwent coronary revascularization, while it was deferred in 108 (48.2%). Compared with the actual treatment strategy, the rate of intended revascularization was significantly higher when guided by angiography (62.5% vs 51.8%; P = .002) or OCT (66.5% vs 51.8%; P < .001), but similar when guided by FFR (53.6% vs 51.8%; P = .34). Among lesions undergoing PCI with available strategy information (n = 83), the intended stent size differed from the actual implanted stent size in 59.0% of cases based on angiography, compared with 12.1% of cases based on OCT findings (P < .001).

Conclusions

Fractional flow reserve and OCT provide distinct yet complementary information that significantly impacts decision making during PCI. Specifically, FFR informs revascularization decision making, while OCT plays a crucial role in device sizing. Combining anatomical, morphological, and physiological variables in a single modality may enhance decision making and reduce resource utilization.

Introduction

Invasive coronary angiography is the universal modality for guiding percutaneous coronary intervention (PCI) yet has significant limitations. First, angiographic assessment of lesion severity is often subjective, lacks reproducibility, and correlates poorly with downstream ischemia.^1,2 Second, its low-resolution and 2-dimensional lumenography limits accurate evaluation of vessel size and plaque morphology, which are critical for precise device selection.

Various interventional technologies can provide complementary information, overcoming these limitations. Physiological indices, such as fractional flow reserve (FFR), assess the physiological severity of lesions and allow identification of ischemia-causing stenoses. Intravascular imaging (IVI), such as optical coherence tomography (OCT), allows detailed anatomical and morphological lesion evaluation, enabling precise planning and optimization of PCI. Given their distinct yet complementary roles, coronary physiology and imaging play synergistic roles in guiding PCI. This study sought to evaluate their respective impacts on (1) revascularization decision making and (2) PCI strategy compared with angiography guidance alone.

Materials and methods

Study population

This study is a secondary analysis of the multicenter, prospective, observational FUSION study (Validation of OCT-Based Functional Diagnosis of Coronary Stenosis; ClinicalTrials.gov, NCT04356027), which evaluated the diagnostic performance of OCT-derived flow reserve (virtual flow reserve [VFR]) compared with pressure wire–derived FFR. The study design and primary results were reported previously.³ Briefly, 312 patients undergoing invasive coronary angiography for stable, unstable, or silent angina, or non–ST segment elevation myocardial infarction with at least 1 intermediate native coronary artery stenosis (diameter stenosis of 40%-90% on visual estimation) underwent both pressure wire–based physiological evaluation and OCT imaging of all target lesions. Culprit lesions in non–ST segment elevation myocardial infarction and lesions requiring predilation were excluded. The study protocol was approved by the institutional review boards or ethics committee of each participating center and was performed in accordance with the Declaration of Helsinki. All patients provided written informed consent.

Study procedures

All patients underwent diagnostic coronary angiography according to local site protocols. Eligible patients subsequently underwent intracoronary OCT imaging and pressure wire–based physiological assessment. The OCT was performed using the Dragonfly OPTIS Imaging Catheter (Abbott Vascular) with a motorized pullback in survey mode, allowing evaluation of all target lesions within the proximal 75 mm of the target vessel. Physiological measurements were obtained using the PressureWire X (Abbott Vascular). After pressure equalization at the guiding catheter and administration of 200 μg of intracoronary nitroglycerin, the pressure wire was advanced distal to the target lesion. The FFR was then measured following the induction of maximal hyperemia, achieved using either intravenous adenosine (140 μg/kg/min continuous infusion) or intracoronary adenosine (200 μg for the left coronary artery or 100 μg for the right coronary artery). A final drift check was performed after the pressure wire was pulled back to the coronary ostium. Repeat physiological assessment was performed in cases of significant drift (Figure 1).

Figure 1.

FUSION study protocol. FFR, fractional flow reserve; OCT, optical coherence tomography; PCI, percutaneous coronary intervention; RFR resting full-cycle ratio.

Intended treatment strategy

This analysis evaluates the impact of angiography, OCT, and FFR on procedural decision making. Following each diagnostic modality, operators documented sequentially whether they intended to proceed with revascularization or defer treatment based on the findings. For cases in which revascularization was planned, the intended PCI strategy—including stent diameter and length—was also recorded after the initial angiographic assessment and after OCT analysis. These intended decisions regarding revascularization and PCI strategy were then compared with the actual treatment performed, which was left to the operator’s discretion and was guided by the totality of diagnostic testing. A change in stent size between the intended and the actual stent implanted was defined as an absolute difference of ≥0.25 mm in diameter or ≥4.0 mm in length.

Statistical analyses

Categorical variables are reported as absolute value (percentage), while continuous variables are summarized as mean ± SD or median (IQR), when appropriate. Baseline clinical and procedural characteristics were analyzed using the independent samples Student t test, the χ² test, Fisher exact test, or Wilcoxon rank-sum test. Paired data on treatment plan and PCI strategy were evaluated using the McNemar test or the 1-sample paired t test. Revascularization decision making was evaluated in the complete cohort and for the 3 major coronary arteries separately. A 2-sided P value of <.05 was considered statistically significant. All statistical analyses were performed using SAS version 9.4 (SAS Institute) and R version 4.3.

Results

Study population

After the core laboratory review of the coronary angiogram, physiology assessment and OCT images, a total of 224 patients were included in the study. The mean age of the population was 67.4 ± 9.2 years, and 30.8% of patients were women (Table 1). Stable (48.2%) and unstable angina (37.1%) were the predominant indications for invasive coronary angiography. Revascularization was performed in 116 (51.8%) patients, while it was deferred in 108 (48.2%) patients. Compared with those who did not undergo revascularization, patients who underwent revascularization had lower rates of hypertension (75.9% vs 88.9%; P = .01) and a history of myocardial infarction (9.5% vs 19.4%; P = .03) or PCI in a nontarget vessel (15.5% vs 35.2%; P < .001).

Table 1.

Baseline characteristics

Characteristic	Revascularization (n = 116)	No revascularization (n = 108)	P
Age, y	67 ± 9.6	67.7 ± 8.8	.70
Female sex	30 (25.9)	39 (36.1)	.10
Hypertension	88 (75.9)	96 (88.9)	.01
Dyslipidemia	92 (79.3)	94 (87.0)	.12
Diabetes	47 (40.5)	34 (31.5)	.16
Renal insufficiency	10 (8.6)	9 (8.33)	.94
Current smoker	20 (17.2)	16 (14.8)	.62
Prior MI in nontarget vessel	11 (9.5)	21 (19.4)	.03
Prior PCI in nontarget vessel	18 (15.5)	38 (35.2)	<.001
Presentation			.02
Stable angina	60 (51.7)	48 (44.4)	.28
Unstable angina	35 (30.2)	48 (44.4)	.03
Silent ischemia	21 (18.1)	10 (9.3)	.06
NSTEMI	0 (0.0)	2 (1.9)	.14

Values are mean ± SD or n (%).

MI, myocardial infarction; NSTEMI, non-ST-segment elevation myocardial infarction; PCI, percutaneous coronary intervention.

Target vessel and lesion characteristics

Vessel-level and lesion-level characteristics are summarized in Table 2. Among 226 target vessels, the majority were located in the left anterior descending artery (55.3%). The mean FFR was significantly lower in revascularized vessels compared with those in which revascularization was deferred (0.75 ± 0.10 vs 0.89 ± 0.07; P < .001). Across 228 target lesions, the mean maximal diameter stenosis was 65.7% ± 14.9%. The minimal lumen area was significantly smaller in revascularized lesions compared with deferred lesions (1.81 ± 1.48 vs 3.66 ± 2.88 mm²; P = .02).

Table 2.

Vessel-level and lesion-level characteristics

Characteristic	Revascularization	No revascularization	P
Vessel-level	n = 114	n = 112
Target vessel			<.001
Left anterior descending	75 (65.8)	50 (44.6)	.001
Left circumflex/ramus	26 (22.8)	27 (24.1)	.82
Right coronary artery	13 (11.4)	35 (31.3)	<.001
Fractional flow reserve	0.75 ± 0.10	0.89 ± 0.07	<.001
Lesion-level	n = 114	n = 114
Lesion length, mm	20.4 ± 8.9	18.3 ± 9.5	.01
Maximal diameter stenosis, %	73.9 ± 12.2	57.5 ± 12.6	<.001
Minimal lumen area, mm2	1.81 ± 1.48	3.66 ± 2.88	.02

Values are n (%) or mean ± SD.

Treatment decision making based on different modalities

Compared with the actual treatment strategy, revascularization was more frequently intended based on angiographic (62.5% vs 51.8%; P = .002) and OCT (66.5% vs 51.8%; P < .001) findings (Figure 2). The intended revascularization rate based on physiological assessment was similar to the actual treatment performed (53.6% vs 51.8%; P = .34). Subgroup analyses per coronary artery demonstrated consistent results (Supplemental Figure S1).

Figure 2.

Intended and actual treatment strategies. FFR, fractional flow reserve; OCT, optical coherence tomography.

Operator-determined PCI strategy based on angiography and OCT was available for 83 lesions. In paired comparisons with the actual length and diameter of the stent implanted, the intended stent length and diameter differed significantly more frequently when determined by angiography (59.0%) compared with OCT (12.1%; P < .001) (Figure 3). Specifically, stent length determined by angiography differed from the actual implanted stent length in 41.0% of cases, compared with 2.4% when determined by OCT (P < .001). Similarly, discrepancies in stent diameter occurred in 45.8% by angiography vs 10.8% by OCT (P < .001). Furthermore, the mean absolute differences between intended and actual stent length and diameter were significantly greater for angiography vs OCT guidance (stent length: 4.43 ± 6.2 vs 0.22 ± 0.86 mm, respectively; P < .001; stent diameter: 0.18 ± 0.23 vs 0.03 ± 0.10 mm, respectively; P < .001).

Figure 3.

Changes in percutaneous coronary intervention strategy. ∗Defined as an absolute change in stent diameter of ≥0.25 mm and/or stent length of ≥4.0 mm. ^†Defined as an absolute change of ≥0.25 mm. ^‡Defined as an absolute change of ≥4.0 mm. OCT optical coherence tomography.

Discussion

This study evaluated the individual impact of various diagnostic modalities in guiding revascularization decisions and PCI strategy. The main findings were as follows: (1) physiology assessment with FFR closely aligned with the final revascularization decisions, whereas angiography and OCT guidance led to significantly higher intended revascularization rates; and (2) OCT played a crucial role in determining the PCI strategy, frequently prompting adjustments to stent length and diameter beyond angiography alone (Central Illustration).

Central Illustration.

Impact of angiography, OCT, and FFR on periprocedural decision making. Among patients in whom the intended percutaneous coronary intervention decision making was recorded based on angiographic findings, OCT findings, and FFR findings (upper panel), FFR-guided decision making closely resembled the actual treatment decision, while the intended revascularization rate was higher based on angiographic and OCT findings (left panel). In those undergoing revascularization, the intended stent size based on OCT differed in 12.1% of cases from the final stent size selected, compared with in 59.0% of cases based on angiography (right panel). FFR, fractional flow reserve; OCT, optical coherence tomography.

As expected, this study indicates that the rate of intended revascularization based on angiography or IVI findings was substantially higher than that based on physiology, which ultimately had the greatest influence on the final treatment decision. These findings are consistent with prior randomized trials comparing FFR-guided vs IVI-guided revascularization strategies.4, 5, 6 In the FORZA trial, revascularization was performed in 50.7% in the OCT-guided arm compared with only 29.3% in the FFR-guided group.^4,5 Similarly, in the FLAVOUR (Fractional FLow Reserve And IVUS for Clinical OUtcomes in Patients with InteRmediate Stenosis) trial, intravascular ultrasound guidance resulted in a significantly higher revascularization rate than FFR guidance (65.3% vs 44.4%, respectively).⁶ Despite these differences in revascularization rates, both trials demonstrated no significant difference in clinical outcomes between IVI-guided and FFR-guided strategies, leading to substantial increases in resource utilization and cost among patients undergoing IVI-guided PCI.^4,7

As opposed to these trials, this study evaluated revascularization decisions for the same lesions using multiple modalities, demonstrating that IVI and physiology assessment fundamentally evaluate different procedural aspects and lead to changes in clinical decision making independent of each other. The safety and effectiveness of the FFR-based strategy—characterized by decreased utilization of stents and comparable clinical outcomes—further underscore the value of physiology assessment in guiding revascularization decisions in routine practice.

Not surprisingly, among patients undergoing PCI, the actual strategy on stent diameter and length, more closely aligned with OCT-based assessment rather than with those derived from angiography. Operators ultimately modified the initial angiography-based PCI strategy in approximately 60% of cases, with the final plan reflecting the OCT findings. Although we could not investigate the reasons why the actual stent dimensions differed from the OCT-based dimensions in 12.1% of cases, we hypothesized that this may be caused by operators also including angiographic and physiological findings into the final decision making, likely reflecting clinical judgment in routine practice. Our findings are consistent with early evidence from the ILUMIEN I (Observational Study of Optical Coherence Tomography in Patients Undergoing Fractional Flow Reserve and Percutaneous Coronary Intervention) study, where OCT-guided stent sizing influenced decision making in 57% of lesions compared with angiography.⁸ Similarly, in the LightLab initiative, a dedicated pre-PCI OCT workflow altered lesion assessment and procedural planning in 80% of lesions.⁹ Furthermore, randomized clinical trials have consistently demonstrated the benefits of IVI-guided PCI over angiography-guided PCI.¹⁰ Collectively, these results underscore the value of OCT in PCI planning, contributing to enhanced procedural safety and efficacy.

Our results overall highlight the complementary roles of FFR and OCT—FFR informs revascularization decision making, while OCT guides PCI strategy. Despite their significant impact on precision PCI, time and resource constraints remain key challenges in routine practice because simultaneous use of pressure wires and imaging catheters is often impractical and cost prohibitive. Recently, it was demonstrated that OCT-based computational flow indices such as VFR allow conversion of anatomical information to physiological information with high accuracy.³ As a result, anatomical, morphological, and functional information can be obtained with a single OCT pullback, potentially leveraging the strengths of both modalities (Figure 4). This integrated approach enables simultaneous lesion assessment and precise device selection, offering a more streamlined and effective strategy than using either modality alone. However, the clinical utility of VFR has yet to be fully validated in prospective studies.

Figure 4.

Combined anatomical, morphological, and physiological procedural planning using VFR. (A) The distal VFR was computed at 0.63, which is below the revascularization threshold of ≤0.80. Based on the VFR, the region of interest was identified in the distal LAD artery with a lesion length of 8.8 mm. (B) Following angiographic stent sizing, the intended stent length was 12.0 mm, which resulted in a maximum anticipated postprocedural VFR of 0.84. (C) By combining the physiological information with the OCT imaging data, the stent length was extended to 38.0 mm, resulting in a maximum anticipated postprocedural VFR of 0.92. LAD, left anterior descending; OCT, optical coherence tomography; VFR, virtual flow reserve.

This study has several limitations. First, the intended PCI strategy based on each individual modality was only available in 72.8% of lesions that were subsequently revascularized. Second, the study predominantly included patients with silent, stable or unstable angina, potentially limiting generalizability to patients with myocardial infarction. Third, evaluations were restricted to the proximal 75-mm segment of each coronary artery, and it remains unclear whether the findings extend to more distal lesions with smaller vessel diameters. Fourth, the actual decisions regarding revascularization and the PCI strategy were left to the discretion of individual operators, and detailed rationales for these decisions were not systematically recorded. Finally, whether differences in revascularization decision making and PCI strategy impacts clinical outcome could not be evaluated in this study.

Conclusion

Fractional flow reserve and OCT provide complementary information for decision making on revascularization and PCI strategy. Combining anatomical, morphological, and physiological variables in a single modality may enhance decision making and reduce resource utilization.

Peer review statement

Section Editor Ziad A. Ali had no involvement in the peer review of this article and have no access to information regarding its peer review. Full responsibility for the editorial process for this article was delegated to Associate Editor Andrew M. Goldsweig.

Declaration of competing interest

Rick H.J.A. Volleberg has received fellowship grants from Foundation De Drie Lichten and Netherlands Heart Institute. Doosup Shin reports research grants from SCAI and Abbott. Kanitha Phalakornkule, Jana Buccola, Nutte Teraphongphom, Ajay Gopinath, and Ashley Netravali are employees of Abbott Vascular. Allen Jeremias has received consulting fees from Abbott Vascular, Philips, ACIST Medical Systems, Boston Scientific, Shockwave Medical, and CathWorks. Ziad A. Ali reports institutional grants from Abbott, Abiomed, ACIST Medical Systems, Boston Scientific, Cardiovascular Systems Inc, Medtronic, Opsens Medical, Philips, and Shockwave Medical; personal fees from Amgen, AstraZeneca, and Boston Scientific; equity in Elucid, Lifelink, SpectraWAVE, Shockwave Medical, and Vital Connect. The other authors reported no financial interests.

Funding sources

This study was supported through grant funding from Abbott Vascular. The sponsor funded the trial and participated in site selection and data analysis.

Ethics statement and patient consent

The study protocol was approved by the institutional review boards or ethics committee of each participating center and was performed in accordance with the Declaration of Helsinki. All patients provided written informed consent.