Safety and efficacy of frequency-domain optical coherence tomography in evaluating and treating intermediate coronary lesions

ARTICLE HIGHLIGHTS

Research background

Conventional angiography and other adjunct coronary imaging techniques such as fractional flow reserve and intravascular ultrasound have in the past been used to evaluate the anatomical and physiological significance of coronary lesions considered to fall in the intermediate category (40%-70%). However, to this date, no study has been conducted to assess the safety and efficacy of frequency-domain optical coherence tomography (FD-OCT) in the evaluation and treatment of angiographically-intermediate coronary lesions (ICL). Our interventional team wanted to explore if FD-OCT could assist us in our daily practice to better evaluate and treat this subset of coronary lesions, compared to when angiographic-guidance alone is used to guide decision making in this clinical setting.

Research motivation

The current study addresses a very important topic in interventional cardiology, as it focuses specifically on the management of ICL. Cases of coronary lesions considered to be borderline are frequently under- or over-treated, hence providing a reliable tool for the accurate assessment of these lesions is of great importance to their appropriate management. Coronary angiography has several known limitations, including a lack of correlation between the percentage of stenosis and the lesion’s physiologic importance, and considerable inter-observer variability in classifying the lesion’s severity. On the other hand, percutaneous coronary intervention (PCI) has inherent risks even in the most experienced hands. The possibility of procedural complications with PCI such as coronary dissection, no reflow phenomenon, in-stent restenosis, and stent thrombosis requires accurate stratification of patients with intermediate coronary lesions to appropriate therapy. The present study explores the use of FD-OCT as an ultra-high resolution intracoronary imaging tool with regards to its safety and efficacy to accurately assess and manage intermediate coronary lesions interventionally or medically, and will spark interest for further research in this specific setting to reinforce the concept being explores.

Research objectives

Our aim in designing this study was to demonstrate that FD-OCT is a safe and effective procedure to be performed when faced with intermediate coronary artery lesions during coronary angiography in the cardiac catheterization laboratory. As this is the first study to investigate the safety and efficacy of OCT in the setting of ICL, it will pave the way for further studies (multi-center, larger sample size, longer follow-up times) to be conducted to confirm our findings, and reinforce our conclusions and recommendations. In particular, these studies are expected to have higher statistical power, with a larger sample size and a more equal representation of patients from the different coronary artery disease (CAD) population subgroups. This paper will provide investigators from across the world a platform to improve on the study design, methodology in conducting studies with similar objectives, taking into account the difficulties we encountered in this study, and the related limitations that ensued.

Research methods

With the aim in mind of elucidating whether FD-OCT was safe and effective in treating ICL, we decided to conduct the study by including patients found to have borderline lesions on angiography in our cardiac catheterization laboratory, and who consented to the OCT procedure. Patients who presented with cardiogenic shock, acute stroke, renal dysfunction, left main stem ICL, and acute or chronic total occlusion coronary lesions were excluded from the study. Patients were assigned to either of the 2 arms of the study based on specific predetermined OCT criteria. Focusing importantly on the specific aim of our study, we clearly defined our primary efficacy endpoint (demonstration of the superiority and higher accuracy of FD-OCT compared to 2D-QCA in evaluating stenosis severity in patients with ICL), primary safety endpoint [incidence of 30-d major adverse cardiac events (MACE)] and secondary endpoints (MACE at 12 mo and other clinical events), and obtained the necessary 2D-QCA and FD-OCT measurements, as well as the follow-up statistical results on MACE and other clinical outcomes. These results generated enabled an in-depth discussion and appropriate conclusions to be made. We hope that the methodology and study design used in our study will be useful in assisting investigators to design further studies with similar objectives.

Research results

The primary efficacy endpoint of our study was fully met, with statistically significant results clearly demonstrating that 2D-QCA overestimates the stenosis severity of the ICL in both the OCT-guided PCI and OMT groups. Our primary safety endpoint was also fully met, with none of the patients in the study experiencing any MACE at 30 d post-procedure. Incidences of secondary endpoints were also found to be low in both arms, the only exception being the relatively high incidence of recurrent episodes of angina which was, however, very similar in the 2 groups. Analysis of the above results gives a clear insight into the superiority of FD-OCT compared to 2D-QCA in evaluating stenosis severity of ICL, and lays a foundation on which further studies to further reinforce this finding and implement its application in clinical practice in managing patients with angiographically-borderline lesions, owing to the efficacy of the FD-OCT in this setting. The findings of the present study also highlighted the safety of this intracoronary-imaging technique in the same setting. However, these results should be interpreted with appropriate caution, given the relatively small sample size of the study, which resulted in the study lacking statistical power. In addition, patients across the different CAD population subgroups are not equally represented in this study, especially patients presenting with an AMI. Further studies are required to address these limitations from our present study, so that the safety and efficacy of FD-OCT can be extrapolated to the management of ICL in patients presenting with different categories of CAD.

Research conclusions

To this date, the efficacy and safety of FD-OCT when specifically faced with an ICL in the cardiac catheterization laboratory irrespective of the clinical presentation of the patient, was unknown. The present study provides significant insight into the topic and successfully meets the objectives laid out by its investigators. It shows that in evaluating and treating an ICL, performing FD-OCT following coronary angiography adds significant value to the assessment and management of that lesion, and is found to be a safe and effective procedure in this setting. However, further studies are required with larger sample size and higher statistical power to determine whether this statement can be applicable to patients with ICL across the different CAD population subgroups, and if OCT is equally safe and effective in treating ICL in patients presenting with an AMI, compared to those presenting with UA or SA. It is expected that this pioneering study sparks further interest amongst researchers in the field of CAD and amongst interventional cardiologists in practice to design and conduct large, multicenter clinical trials in order to obtain more reliable data that can be used to implement guidelines and positively change clinical practice, as well as provide direction for future research in this field and in the clinical setting of ICL.

Research perspectives

This study shows that 2D-QCA leads to an overestimation of lesion severity in comparison to FD-OCT, which is a prerequisite for overtreatment. On the other hand, the results show that OCT-guided decision making seems to be safe. The population with intermediate coronary lesions is largely underrepresented across different randomized trials. Therefore, despite its relatively small sample size, this prospective single center interventional study adds a lot of important data to the topic and provides a good platform for future larger multicenter clinical trials to be conducted to further reinforce the utility of FD-OCT in evaluating and treating ICL with regards to its safety and efficacy in this specific clinical setting.