Optical coherence tomography-guided approach in diagnosing and managing spontaneously recanalized coronary thrombus

Abstract

Recanalized coronary thrombus is a rare and under-recognized condition in interventional practice, however its incidence is steadily increasing with the use of endo-coronary imaging. It has been initially described by pathological studies in approximately one-third of chronic coronary occlusions. It is described as a chronic occlusion that constitutes several endothelium-covered channels separated by septa that converge into a single lumen. In angiographic studies, it is often misidentified as fresh thrombus, spontaneous coronary artery dissection or severe calcification. Hence the interest of intracoronary imaging, particularly optical coherence tomography, to conclusively establish its diagnosis and identify the related mechanism in order to guide the optimal therapeutic strategy.

In this report, we describe our experience with a case of recanalized thrombus diagnosed using intracoronary optical coherence tomography imaging with successful percutaneous coronary intervention.

Introduction

Spontaneously recanalized coronary thrombus (SRCT) is an entity initially diagnosed on histopathological studies. It is a chronic coronary occlusion that has revascularized spontaneously via multiple endothelialized channels separated by thin septa and converging to a central lumen. As such, it has an aspect of “honeycomb” or “Swiss cheese”. The exact etiology is still not identified, but certain theories have explained the spontaneous recanalization of the thrombus by plaque erosion, plaque rupture, embolism or as a consequence of vasculitis. It appears angiographically as a fuzzy, hazy intraluminal coronary lesion, usually without significant stenosis. The angiographic presentation is neither specific nor sensitive, as it might relate to different pathological entities, including fresh thrombi, calcification, plaque rupture, dissection and aneurysms. Hence the importance of high-resolution intracoronary imaging, particularly the optical coherence tomography (OCT), which is used to confirm the diagnosis and identify the underlying mechanism in order to guide percutaneous intracoronary intervention.

In this report, we describe our experience with a case of recanalized thrombus diagnosed using intracoronary OCT imaging with successful percutaneous coronary intervention (PCI).

Case presentation

A 54-year-old male patient was admitted for management of an acute coronary syndrome. His cardiovascular risk factors included active smoking, dyslipidemia and arterial hypertension. He had a history of hematemesis related to ruptured esophageal varices (grade II) secondary to alcoholic cirrhosis. He was treated with Ramipril 5 mg/day and Carvedilol 5 mg/day.

He reported an atypical chest pain, associated with exertional dyspnea class III of NYHA (New York Heart Association). The physical examination was unremarkable with hemodynamic and respiratory stability. The 12-lead electrocardiogram showed a regular sinus rhythm with signs of anterolateral subendocardial ischemia. Biological analysis objectified High-sensitivity Troponin 4 times higher than the reference range, anemia with 11 g/dL hemoglobin, and chronic renal failure with a glomerular filtration rate (GFR) of 81 mL/minute/m². Transthoracic echocardiography identified severe apical septal hypokinesia with decreased left ventricular ejection fraction (LVEF) of 48%. A diagnostic coronary angiography was performed via the right radial artery, which identified a right dominance system, without significant stenosis or aneurysm, however an intraluminal haziness with multiple linear filling defects was visualized in the mid-segment of the left anterior descending coronary artery (LAD), with Thrombolysis in Myocardial Infarction (TIMI) flow grade 3 beyond it (Fig. 1). The other coronary arteries were free of significant lesions. Therefore, the decision was made to perform coronary evaluation by intracoronary imaging. OCT was performed using MEDTRONIC LAUNCHER 6F CORONARY GUIDE CATHETER EBU 3.75. The analysis of resulting images showed several venules separated by fine septa with high signal intensity and low attenuation of optical signal, providing the typical “Swiss cheese” appearance (Fig. 2), which is consistent with a recanalized thrombus, thus ruling out other differential diagnoses. A percutaneous coronary intervention was performed, after predilatation with balloon angioplasty, a drug-eluting stent (ORSIRO SIROLIMUS STENT 3.5×22M) was deployed. Postangioplasty OCT analysis showed an optimal deployment of the stent with complete stent apposition to the vessel wall (Fig. 3).

Fig. 1.

Coronary angiogram. The left anterior descending coronary artery (LAD) showed an intraluminal haziness and preserved distal flow (TIMI 3).

Fig. 2.

Optical Coherence Tomography (OCT) showing a typical “Swiss cheese” appearance, which is consistent with a recanalized thrombus in proximal left anterior descending (LAD).

Fig. 3.

(A): Postangioplasty OCT showed an optimal deployment of the stent with complete stent apposition to the vessel wall. (B) and (C): Coronary artery angiogram after percutaneous coronary intervention.

Follow-up and outcomes

No complications during or after the procedure were noted. The patient was discharged from the hospital within 24 hours.

Discussion

Recanalized thrombus is a natural long-term evolution of chronic intracoronary occlusion. Multiple channels are formed through the thrombus to establish the downstream coronary flow. This phenome was initially described on histopathological studies and was frequently observed in about one third of thrombotic occlusions [1]. However, the prevalence and incidence of recanalized thrombus remains unknown.

The pathological mechanism remains poorly elucidated; some hypotheses have suggested that thrombus recanalization is potentially the result of plaque erosion, plaque rupture, dissection, coronary thromboembolism, or coronary vasculitis such as occurs in Kawasaki disease [2,3]. Histologically, the septa are formed by the interposition of bilateral endothelial layers separated by connective tissue containing collagen and elastin fibers [4].

The angiographic appearance is a fuzzy coronary lesion with irregular filling defects that can be diagnosed as plaque ulceration, plaque rupture, dissection or thrombus. Coronarography is therefore neither specific nor sensitive in diagnosing this entity.

Intracoronary imaging, in particular OCT, is the most appropriate modality in this case, it identifies the coronary lesion and specifies its characteristics to better guide and optimize the percutaneous coronary intervention. OCT provides high resolution intracoronary images based on near infrared interferometry [5]. It has neatly identified the typical features of recanalized thrombi in vivo, described in the literature as a “Swiss cheese”, “spider web”, “lotus root” or “honeycomb” appearance. The pathognomonic aspect consists of several different sized channels separated by fine septa, thus differentiating it from dissection, which is characterized by true and false intraluminal channels which are in communication. This appearance results from signal-rich, diaphragm-like protrusions with high backscatter, dividing the light into multiple small channels separated by fibrous septa composed of high signal intensity and low signal attenuation, suggesting elastin and collagen fibers [2]. The deepest area showed a low signal, conforming to a proteoglycan-rich region. Meanwhile, the areas approximating to the light were brighter, indicating regions that are rich in collagen and smooth muscle cells. OCT is advantageous over IVUS in this case, due to its 10-fold higher spatial resolution (10 µm), thus allowing an accurate diagnosis of the ambiguous angiographic appearance.

Hemodynamically, several studies have reported that downstream blood flow through channels is generally insufficient to restore adequate myocardial perfusion [6]. This is explained by the fact that channels constitution takes several weeks or even months, thus the short-term contribution of revascularization in the postmyocardial infarction period is insignificant. It has been reported that invasive functional tests revealed inducible ischemia in majority of cases regardless of the degree of angiographic stenosis [7].

The complexity and variability of this structure is a real challenge during percutaneous coronary intervention. Among the difficulties encountered, we cite: severe tortuosity, extensive calcifications, severe stenosis or subtotal occlusion. Treatment is essentially based on stenting, namely a drug-eluting stent and a bioresorbable vascular scaffold [8]. Different therapeutic strategies have been reported in order to better prepare the lesion to optimize PCI, such as balloon dilation, atherectomy devices or intravascular lithotripsy; the choice of which must be made on a case-by-case basis [2]. Good shot-term results have been reported, in particular satisfactory apposition, as well as good medium-term results (a follow-up of seventeen months) with 9.1% of major adverse cerebrovascular and cardiovascular events (MACCE) [9].

The long-term prognosis of recanalized coronary thrombus remains unclear. Ultimately, additional studies are called for with long-term follow-up to better understand the natural history of this under-diagnosed intracoronary lesion in order to improve the therapeutic strategy.

Conclusion

Recanalized thrombus is an under-diagnosed entity in current practice. OCT can be used to diagnose and guide percutaneous coronary intervention. Although, further studies are needed in this way to better clarify this unusual lesion.

Patient consent

I hereby confirm that informed consent has been obtained from the patient for the publication of their case in this article. The consent was provided voluntarily and after a thorough explanation of the potential risks and benefits. This statement will be included in the article.