One-Year Clinical Outcomes in Acute ST-Segment Elevation Myocardial Infarction Patients Undergoing Optical Coherence Tomography-Guided Primary Percutaneous Coronary Intervention: A Comparative Study

Background

Acute myocardial infarction (MI) remains a leading cause of global morbidity and mortality [1]. MI disrupts the heart’s blood supply, exceeding a critical threshold and overwhelming the heart’s cellular repair mechanisms during ischemia [2]. Early effective reperfusion, achieved through thrombolytic therapy or primary percutaneous coronary intervention (PPCI), is essential to minimize ischemic damage and reduce the size of the MI [1,3]. Over the past two decades, advancements in early reperfusion therapies and pharmacotherapy have significantly improved outcomes for patients with ST-elevation myocardial infarction (STEMI) [4,5]. The timing of PPCI is critically linked to mortality risk, regardless of the time elapsed since symptom onset or the patient’s baseline mortality risk [6]. Optical coherence tomography (OCT) is a notable intracoronary diagnostic tool, providing highly detailed vascular images and superior structural detail, compared with intravascular ultrasound [7]. OCT, standing at the forefront of current intravascular imaging technology in clinical practice, excels in identifying calcified plaques and post-stent implantation, offering 3-dimensional reconstruction and real-time alignment with coronary angiographic images, thereby guiding PCI with its distinguished ability to provide high-resolution, exceptionally clear visualizations of vessel morphology [8–11]. Although OCT is gaining prominence in STEMI management during PPCI, its impact on clinical outcomes in this context is not fully established. Therefore, we aimed to compare outcomes in 75 patients from a single center with acute STEMI who underwent OCT-guided primary PCI with 163 patients with acute STEMI who underwent PCI without OCT guidance from February 2019 to July 2021.

Material and Methods

PATIENTS AND GROUPS:

Between February 2019 and July 2021, we enrolled 75 patients with acute STEMI who underwent OCT-guided PPCI, forming the OCT group. In addition, 163 patients with acute STEMI, who did not undergo OCT-guided PPCI, were selected as the control group. The exclusion criteria included patients with a critical status, those requiring supportive devices, such as extracorporeal membrane oxygenation or intra-aortic balloon pump support, and those in need of emergent coronary artery bypass graft surgery.

ETHICS STATEMENT:

This retrospective study received approval from the Institutional Review Committee of Kaohsiung Chang Gung Memorial Hospital, under approval number 201801078B0. It adhered to the ethics guidelines set forth in the 1975 Declaration of Helsinki.

OCT-GUIDED PCI PROCEDURAL STEPS:

OCT is an intravascular imaging modality that uses near-infrared light to provide high-definition, cross-sectional, and 3-dimensional images of the vessel microstructure during PCI (Figure 1). The OCT imaging system consists of 3 main components: the software, system, and catheter. The procedure’s steps are listed in Figure 2. In this study, the evaluation consisted of 6 steps, which included assessments of morphology, length, diameter, medial dissection, and expansion criteria. First, we performed an OCT pullback, in which an OCT catheter is inserted into the vessel and an infrared laser is used to scan the vessel wall in a spiral-like manner. The laser beam penetrates the tissue 2 to 3 mm deep, is reflected from there and returned to the OCT device via the catheter for evaluation. Second, we interpreted OCT images via the system, which can be done before PCI and is designed to help inform the treatment strategy, such as morphology, length, and diameter. Third, we detected the medial dissection, apposition, and expansion after PCI to optimize stent placement and outcome.

DEFINITIONS:

The definitions of MI in this study conformed to the most recent universal MI definition [12]. The Killip classes 1 to 4 were defined in 1967, when Killip and Kimball described the outcome of 250 patients with acute MI admitted to a coronary care unit, with 4 categories according to patient hemodynamic status [13]. Killip class 1 indicates without heart failure, Killip 2 indicates pulmonary rales less than half of lung field, Killip 3 indicates acute pulmonary edema, and Killip 4 indicates cardiogenic shock [14,15]. Cardiovascular mortality was defined specifically as death due to conditions including myocardial infarction, cardiac arrhythmia, and heart failure. Conversely, all-cause mortality included deaths from any cause. Target lesion revascularization was identified as any occurrence of PCI on a target lesion or coronary artery bypass graft surgery involving a target lesion.

STUDY ENDPOINTS:

This study was designed to evaluate a range of clinical endpoints over a 1-year follow-up period after treatment. Key among these endpoints was the incidence of MI, which signified a critical event in the cardiovascular health of the patients. Additionally, we closely monitored instances of target lesion revascularization, a significant indicator of the need for additional intervention at the site of the original cardiac event. The occurrence of heart failure was also a crucial endpoint, as it directly impacted patient quality of life and long-term health outcomes. Moreover, we assessed all-cause mortality rates within this period. This holistic approach allowed us to gain a thorough understanding of the treatment’s efficacy, encompassing both cardiac-specific and overall health outcomes in patients who underwent PPCI, with and without the guidance of OCT.

STATISTICAL ANALYSIS:

Data are presented in 2 forms: for continuous variables, we report means along with standard deviations to reflect the central tendency and variability of the data. Categorical variables are expressed as counts and percentages, providing a clear representation of their distribution across different categories. To rigorously compare continuous variables, we used 2 distinct statistical tests depending on the nature of the data distribution: the independent sample t test was used for data following a normal distribution, whereas the Mann-Whitney U test was used for data not adhering to normal distribution patterns. For the analysis of categorical variables, we conducted comparisons using the chi-square test, a robust method for assessing the significance of differences between categorical groups. All statistical analyses were performed using SPSS version 22.0 (IBM Corp, Armonk, NY, USA). A P value of less than 0.05 was set as the threshold for determining statistical significance, with values below this cutoff considered statistically significant and indicative of non-random patterns in the data.

Results

BASELINE CHARACTERISTICS:

Between the OCT and control groups, there was no significant difference in average age (OCT: 59±10.7 years; control: 60±12.2 years; P=0.208) or in the prevalence of male sex (OCT: 62.7%; control: 65.0%; P=0.331; Table 1). Both groups had a similar body mass index and systolic blood pressure at presentation. However, the control group had a higher prevalence of diabetes (OCT: 26.7%; control: 42.3%; P=0.020) and hyperlipidemia (OCT: 46.7%; control: 78.5%; P<0.001). Hemoglobin A1c levels were also notably higher in the control group (OCT: 6.5±1.4%; control: 6.9±1.8%; P=0.020). No significant differences were observed between the groups in terms of white blood cell count, creatinine levels, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, or peak troponin-I levels.

PROCEDURAL CHARACTERISTICS BETWEEN GROUPS:

The location of the infarction was similar in both groups, with most patients experiencing anterior wall STEMI (OCT: 57.3% vs control: 54.0%; P=0.872), as shown in Table 2. The severity of the condition, measured by Killip class, was also comparable, with most patients classified as Killip class 1 or 2 (OCT: 89.3% vs control: 91.4%; P=0.236). However, a notably higher percentage of patients in the control group were transferred from other hospitals (OCT: 26.7% vs control: 48.5%; P=0.002). While reperfusion times were similar between the groups, the procedure time was significantly longer in the OCT group (OCT: 50.45±21.75 min vs control: 33.80±14.44 min; P<0.001). The use of thrombectomy was similar in both groups (OCT: 74.7% vs control: 65.6%; P=0.164), but the OCT group had a higher usage of glycoprotein 2b/3a inhibitors than did the control group (OCT: 46.7% vs control: 27.6%; P=0.004). Furthermore, there were no significant differences in the incidence of slow flow and/or no reflow between the groups (OCT: 4.0% vs control: 5.5%; P=0.325).

FINDINGS OF OCT IMAGING:

The OCT findings are summarized in Table 3. In the OCT group, thrombus was present in 18.7% (14 out of 75) of patients, with 10.7% (8 out of 75) exhibiting white thrombus, and 8.0% (6 out of 75) showing red thrombus. Plaque rupture and erosion were observed in 32.0% (24 out of 75) of patients. A calcified nodule was noted in 2.7% (2 out of 75), and an intact fibrous cap (small protruding thrombus) was identified in 6.7% (5 out of 75) of cases.

POST-MI ECHOCARDIOGRAPHIC PARAMETERS AND 1-YEAR CLINICAL FOLLOW-UP CLINICAL OUTCOMES:

Table 4 shows the 1-year clinical follow-up results and echocardiography parameters. After PPCI, the control group exhibited a significantly lower left ventricular ejection fraction than the OCT group (OCT: 53.4±10.5% vs control: 47.8±12.4%; P<0.001). The prevalence of reduced and mildly reduced ejection fraction was comparable between the groups. Similarly, the incidence of mitral regurgitation grade exceeding 2 was not significantly different (OCT: 2.7% vs control: 7.2%; P=0.168). There were no significant differences in the rates of in-hospital mortality and 1-year target lesion revascularization. However, the OCT group demonstrated a lower incidence of post-myocardial infarction heart failure (OCT: 2.7% vs control: 11.0%; P=0.030). Importantly, the 1-year mortality rate was significantly lower in the OCT group than in the control group (OCT: 1.3% vs control: 8.0%; P=0.043).

Discussion

LIMITATIONS:

First, it is crucial to acknowledge that this study was conducted as a retrospective cohort study and did not incorporate randomization to reduce potential bias. The potential confounders influenced the study’s results and conclusions. Second, the study was limited by a relatively small number of enrolled patients and the exclusion of individuals requiring extracorporeal membrane oxygenation or intra-aortic balloon pump support. Third, our analysis could not establish a correlation between OCT findings and clinical outcomes, due to the limited number of clinical events observed in the OCT group. Fourth, it may be beneficial to include a group undergoing intravascular ultrasound-guided PCI to compare results. This could help in highlighting the differences and potential advantages of OCT-guidance PCI. Despite these limitations, our study, which was prospective and observational in nature, still provides valuable insights. Notably, OCT-guided PCI did not increase the incidence of distal embolism, especially in STEMI cases characterized by a high thrombus burden.

Conclusions

During the 1-year follow-up, patients who received OCT-guided PPCI experienced a notably lower rate of post-MI heart failure than did those who underwent PPCI without OCT guidance. Importantly, the application of OCT in PPCI procedures did not result in a higher incidence of distal embolism, even in cases with a significant thrombus burden.