Tabla 1. Reason for OCT.

Tabla 2. Tipo de angioplastia.

Figura 1. Flow diagram of the procedures performed between February 2019 and April 2024.

Figura 2. Extreme case of underexpansion (9%) of multiple layers of previously implanted stents.

Figura 3. . Significant stent malapposition at the proximal third of the left anterior descending ar...

Figura 4. Significant coronary dissection distal to an implanted stent.

Figura 5. Tissue protrusion through the stent struts between the 11 o'clock and 12 o'clock positions...

Figura 6. Intracoronary thrombus, with features of white thrombus due to the presence of low lumen ...

Introduction

Angiography is the standard method for assessing the coronary tree and guiding coronary angioplasty, but it has limitations, as it does not allow for the visualization of the vessel wall, exact diameters, plaque characteristics, or a detailed view of stenting results. It displays a complex three-dimensional structure in two dimensions1. These limitations have driven the development of new intravascular imaging diagnostic techniques2. Optical coherence tomography (OCT) is an interferometric optical tomographic imaging technique that offers millimeter penetration (approximately 2-3 mm into tissue), similar to conventional biopsy thickness, and axial and lateral resolution on a micrometric scale2, 3. It is an alternative to intravascular ultrasound (IVUS) for obtaining intravascular images. It measures the intensity of reflected infrared light instead of using the image generated by ultrasound3. The higher resolution of OCT compared to other intravascular diagnostic techniques allows for accurate measurement of vessel diameter and luminal area for correct stent selection. Additionally, this technique has more sensibility for detecting dissections, stent malapposition, or minimal plaque prolapses when compared to IVUS2. However, its penetration into the vascular wall is limited, so visualization of structures that are far from the lumen (near the adventitia) is compromised when there is a significant amount of atherosclerotic plaque4.

Objective

To evaluate the immediate results of OCT in a healthcare center in the city of Mar del Plata.

Material and methods

This is a observational, descriptive, and prospective study. Out of a total of 1070 angioplasties conducted between February 2019 and April 2024, researchers included 60 consecutive patients (5.6%) who underwent endovascular imaging acquisition by OCT (Figure 1). Once a decision was made to perform the procedure, patients were invited to participate in the study and asked to sign an informed consent form. For image acquisition, a Dragonfly Optis (Abbott) optical fiber catheter was used. All patients were on dual antiplatelet therapy at the time of the study and were administered a dose of at least 70 IU/kg of sodium heparin by means of an intra-arterial bolus. In cases where there were no contraindications, intracoronary nitroglycerin was also administered.

Definitions

Malapposition: separation of the stent struts from the vessel wall greater >0.4 mm and with a length >1 mm.

Underexpansion: when the ratio between the minimum stent luminal area and the average proximal and distal luminal area multiplied by 100 is < 80%.

Edge dissection: disruption of the arterial lumen surface with clear separation from the vessel wall or underlying plaque within 5 mm of one end of the stent, observed in at least two consecutive images. It was considered significant if it compromised more than 60° of the circumference, was deep (involving the media or adventitia), or had a length >2 mm.

Tissue protrusion: extrusion of tissue inside the stent.

Statistical analysis

All values are expressed as mean and standard deviation (for continuous variables) or as count and percentage (for categorical variables). Data analysis was conducted using the EPI Info 7.2.6.0 biostatistics software.

Results

During the study period, there were 60 patients were included. Their average age was 65 years (standard deviation [SD] 9.5428; range: 44-86 years), and 83.3% of subjects were men. Regarding the procedures, 88% had been scheduled beforehand while 12% were conducted as urgent.

Table 1 shows the reasons for performing OCT. The most common was ostial lesion in the anterior descending artery (21.7%), lesion in the left main coronary artery (LMCA, 20%), ostial lesion in the circumflex artery (11.7%), in-stent restenosis (11.7%), and bifurcation lesions that did not involve the left main coronary artery (11.7%).

In 85% (51/60 patients) of cases, patients underwent OCT-guided percutaneous transluminal coronary angioplasty (PTCA). Of them, 50 patients underwent stenting while one had a drug-eluting balloon implanted. Additionally, in 15% (9/60 patients) of cases a decision was made not to go forward with PTCA after OCT. Table 2 shows the type of procedure performed. The most frequent was in the left main coronary artery (33%), followed by bifurcation angioplasty not involving the LMCA (11.7%).

In the PTCA group, 11.76% (6/51 patients) of subjects underwent pre-PTCA OCT. Then, 43.14% (22/51 patients) of subjects underwent post-PTCA OCT, and 45% (23/51 patients) of subjects underwent both pre- and post-PTCA OCT.

Of the 38 patients who underwent OCT before revascularization, there was a change in approach in 47.3% (18 patients) of cases, either because a decision was made not to proceed with endovascular revascularization (9 patients) or because the stenting strategy was modified.

In the group of patients who underwent OCT after PTCA with stent implantation, the underexpansion rate was 45.5% (20 of 44 patients who underwent stenting), and the malapposition rate was 29.55% (13 of 44 patients). OCT-guided post-dilation was performed in 48% (21 of 44 patients) due to underexpansion and/or malapposition. Figures 2 and 3 show a case of stent underexpansion and stent malapposition, respectively.

There were 14 detected coronary dissections (31.8% of patients). In 92% (13 patients) of cases, that occurred after stent implantation; in 78% of cases, the dissection was significant (11 patients) and required correction with another stent. In other words, 25% (11 of 44 patients) of patients with implanted stents required correction for a significant dissection. Figure 4 shows a case of a significant coronary dissection.

Tissue protrusion was observed in 22.7% of the implanted stents (10 of 44 patients). See Figure 5.

In one patient who underwent PTCA for STEMI, there was an intracoronary thrombus attached to the stent (Figure 6).

We can conclude that, in patients who underwent OCT after PTCA with stent implantation, the procedure had to be optimized in 59% of the cases (26 of 44 patients), by means of post-dilation and/or new stent implantation to correct coronary dissection, underexpansion, or malapposition. There was no need to correct the tissue protrusion, as its size was small.

There were no complications related to the use of OCT.

Discussion

Of the total number of angioplasties performed, only a small percentage used OCT (5.6%), due to lack of availability of the method mainly driven by its high cost. While in developed countries, such as the US, the rate of use of intravascular imaging remains low, a report places it at 16.6%5.

Procedures were most frequently scheduled, although this technique was also used and proved useful in urgent situations.

Regarding the reason for performing OCT, most cases were due to lesions in the left main coronary artery lesions or involving the trunk (ostial lesions in the anterior descending or circumflex artery), reaching 53%. European cardiology guidelines recommend intravascular imaging for complex coronary lesions, particularly for left main coronary artery lesions, true bifurcation lesions, and long lesions, with an IA level of evidence6. It should be noted that OCT is not useful for the assessment of aorto-ostial lesions. In these cases, there is an advantage with IVUS7. The method was used in all cases to assess left main coronary artery lesions that involved the middle third or bifurcation.

The importance of pre-PTCA assessment with OCT was evidenced in the ILUMIEN I study, where pre-PTCA images resulted in a change in strategy in 57% of the cases8. There was a strategy change after pre-revascularization OCT in 47.3% of cases, either because a decision was made not to continue with PTCA based on the findings or due to a change in strategy regarding stent implantation.

Underexpansion is the greatest predictor of stent failure9, as it is associated with stent thrombosis and restenosis10, 11. In the CLI-OPCI study, there was a 31-% underexpansion rate, with an increase in major cardiovascular events (MACE) during follow-up12. We detected a high percentage of sub-expanded stents (45.5%) using OCT. Had it not been for this method, if we had only used angiographic assessment, underexpansion would have gone unnoticed, potentially increasing the rate of MACE.

The observed stent malapposition rate was close to 30%, lower than the 41% found in the ILUMIEN III study13. Currently, the impact of stent malapposition on future events remains unclear9.

The incidence of coronary edge dissection was 31.8%, similar to the 39.1% found in the study by Daniel Chamié et al.14. There is a correlation between large dissections and stent thrombosis14, 15. Average large dissections are characterized by their depth, lateral extension (>60º), and length (>2 mm)9. Dissections >200 µm from the distal (not proximal) end of the stent are associated with higher rates of MACE15. The widespread consensus is that small dissections at the edges of the stent, which are very frequently detected with OCT, should not be treated4. In our registry, 25% of patients who underwent stenting and post-procedure OCT had a significant dissection that required intervention. In other words, we can say that, of all dissections, 78% required stenting, in contrast to Daniel Chamié’s study where only 22.6% required a stent14.

Tissue protrusion was a frequent event, reaching almost 23%. Mild tissue protrusion within the stent (thrombus or plaque), as found in our registry, does not require specific treatment4.

Regarding the use of post-PTCA OCT, it allowed us to optimize the stent or correct anomalies—either due to underexpansion, significant malapposition, or post-stent implantation dissection—in 59% of patients. Multiple studies show that OCT-guided stent optimization is performed in between 27% and 52.2% of lesions, mainly driven, as in our study, by malapposition, underexpansion, or edge dissection1. In the ILUMIEN I study, the post-PTCA strategy change rate was 27%.

All of the above leads us to conclude that OCT was useful both before and after PTCA, as it allowed us to choose a more suitable strategy and correct anomalies that were not detected by angiography alone.

There is evidence showing that OCT was superior to IVUS in detecting plaque rupture or thrombus, tissue protrusion, stent edge dissection, and malapposition16.

It has been shown that OCT is safe in routine clinical practice17, with a low rate of major complications, such as ventricular fibrillation (1.1%), air embolism (0.6%), or coronary dissection (0.2%)2. In our registry, we did not observe complications related to its use, which confirmed it to be, in our experience, a very safe method for the angioplasty planning and evaluation.

Due to its high cost, using endovascular imaging acquisition in all PTCA procedures is not feasible. However, it is very important to clearly determine which cases should include it, as it provides valuable information with prognostic implications superior to the use of angiography only.

Limitations

This is an observational study. Since it was conducted at a single center, results may not be generalizable to other populations. It assesses immediate outcomes; its lack of follow-up limits the analysis of long-term results, particularly regarding major adverse cardiovascular events (MACE). Additionally, due to the high cost of the assessed method, the number of patients was limited in relation to the total number of PTCA procedures.

Conclusions

OCT proved to be a useful and safe method, especially in complex lesions involving the LMCA, in its middle and distal segments, for planning therapeutic management and evaluating its outcome, allowing for the correction of potential stent failure.

Summary of key points

• OCT is an intravascular imaging method with very low risk for complications, which allows for precise determination of anatomical features that may not be visible on angiography.

• It is highly useful for both planning and optimizing percutaneous interventions.

• In many cases, it leads to changes in the approach planned based solely on angiographic evaluation.

We thank Dr. Guillermo Migliaro for his advice and collaboration in drafting this article.

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Immediate results of Coronary Optical Coherence Tomography use in complex lesions: experience from a center in Mar del Plata

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