Amaurosis

Objectives: Elective carotid stent implantation using a distal protection is increasing. In this article we describe an observation method for carotid plaque debris collection during carotid stent ing.

Methods: Endovascular stenting for the right internal carotid artery (ICA) stenosis was performed under distal balloon protection. During balloon protection, 30 ml of blood containing debris was aspirated followed by vigorous saline irrigation flushing any residual debris out into the ipsilateral external carotid circulation. Post-operatively, the aspirated blood was filtered and the debris remained on the membrane. The membrane was stained with hematoxylin-eosin (HE) solution and then mounted onto a glass slide for visualization.

Results: Microscopic observation of the slide revealed several debris such as atheromatous plaques and intimal strips. HE staining facilitates the characterization of the debris composition. In addition to the histological evaluation, this technique revealed the particle size as well as the quantity of debris. The resulting HE slide is also suitable for permanent storage. In addition to the qualitative and quantitative qualities, this simple technique requires neither specific instrumentation nor equipment.

Discussion: Carotid plaque debris aspirated during carotid artery stenting under distal protection can be filtered and visualized on a permanent glass slide. This simple method allows us to better understand quantity, particle size, and composition of debris. [Neurol Res 2005; 27: 22-26]

Keywords: Carotid plaque debris; microscopic observation; hematoxylin-eosin (HE) stain; filteration

INTRODUCTION

Percutaneous endovascular intervention is a well-accepted technique for treating atherosclerotic stenosis of carotid arteries. The results of several studies indicate that balloon angioplasty effectively resolves stenosis of the carotid arterial bifurcation1. Stents provide an effective means of ensuring good results and long-term patency of peripheral and coronary arteries as compared with percutaneous transluminal angioplasty (PTA). The distal embolism is always a feared complication during endovascular procedures in carotid arteries2. This high propensity for embolie plaque debris led to the development of distal protection techniques to be used during endovascular procedures performed for lesions of the carotid bifurcation3"5. It is generally accepted that aspirated blood samples contain plaque debris, but due to their microscopic size they are difficult to visualize and assess. We have developed a quantitative and qualitative debris observation technique using filtration and hematoxylin-eosin (HE) staining.

case REPORT

A 71-year-old man visited our hospital due to transient left amaurosis. Angiography demonstrated left internal carotid artery (ICA) occlusion. The left cerebral hemisphere is fed by the collateral flow from the right ICA via the anterior communicating artery. High-grade stenosis was revealed in origin of right ICA (Figure IA). Endovascular stenting for right ICA stenosis was performed. Under local anesthesia, a 9F-guiding catheter was introduced to the right common carotid artery via the 9F sheath, which was placed in the right femoral artery. Pre-dilatation was performed using a 4 mm × 2 cm balloon catheter. Intravascular ultrasound demonstrated a hyperechoic plaque. A 10 mm × 4 cm SMARTstent delivery device was advanced over the guide-wire to the angioplasty site, where the self-expanding stent was deployed. After removal of the stenting device, the coaxial blocking balloon catheter was introduced to the distal portion of the stenosis. Post-dilatation was performed with a 5 mm × 2 cm PTA balloon under distal blocking. After deflation of PTA balloon catheter the guiding catheter was advanced just proximal to the occlusion balloon and 30 ml of blood containing debris was aspirated using a 30 ml syringe. Vigorous saline irrigation through the guiding catheter flushes any residual thrombus and plaque debris retrograde through the ICA and into the ipsilateral external carotid circulation. 500 units of heparin were added to the aspirated blood to avoid blood coagulation. The post-operative angiogram showed a satisfactory opening of the ICA (Figure TB). There were no periprocedural complications.

TECHNICAL NOTE

The aspirated blood was poured into a filter cup (pore size 40 µm Cell Strainer 2340 FALCON, NJ) commonly used for cell culture (Figure 2A). The blood cells passed through by gravity filtration leaving the remaining debris on the filter. Larger pieces of debris were visible by the naked eye. After briefly washing with phosphatebuffered saline, the filter was placed in 1 ml Mayer's hematoxylin solution for 1 minute (Figure 2B), and then placed in 1 ml eosin for another 1 minute in 35 mm dishes with a brief wash in between procedures. Subsequently, the filter was dehydrated in 100% alcohol for 3 minutes, then in xylene for 3 minutes. Finally, the bottom of the filter was cut off from the cup and mounted onto a glass slide using paramount (Figure 2C). The HE-stained debris on the filter could be visualized using light microscopy. Figure 3 shows aspirated debris on the filter. Thrombotic debris with cellular components and endothelial stripes were observed. The particle size was measured from 40 to 500 µm and the number of debris pieces was 24 in this case. The debris-containing slides are suitable for long-term storage. Furthermore, this simple technique required neither specific instrumentation nor equipment.

DISCUSSION

Emboli are known to be associated with a high neurological complication rate and are also recognized as a potential cause of periprocedural stroke during PTA or stenting5. It seems to be commonly accepted that embolization occurs most often during post-dilatation. Currently, to avoid embolization, the distal trapping technique using balloon or filter device has been developed3'5'6. Using the distal protection balloon during carotid artery stenting it is possible to collect particulate debris that initially was thought to bring vessel occlusion in a high percentage of cases. Only a few studies give a detailed morphological evaluation of the material retrieved during percutaneous intravascular procedures4'7. Debris observation is not easy because most of the debris pieces are

We used a cell strainer for debris filtration, which is used to isolate astrocytes from infantile rat brains in our laboratory. Three pore sizes (40, 70, and 100 µm) are available; however, the 40 µm pore size is the best choice for debris. A smaller pore size is preferred to catch smaller debris but requires a vacuum system for filtration in addition to the force of gravity. The filter was cup shaped, making it convenient for washing and staining. A 35 mm diameter dish is best for the filter staining. Only 1 ml of liquid, such as hematoxylin or eosin solution is enough for staining when using a 35 mm dish. After staining or dehydration, the filter membrane is removed and then mounted on a glass slide for permanent storage. The filter grid allows for quantitative determination of the debris size. The time required for performing the procedure is short, taking only 30 minutes, and is economical. Furthermore, no special tool is needed excluding the filter, which is commercially available and inexpensive. To avoid contamination, materials must be kept clean and fresh buffers used for each wash.

Using this method, the character or size of debris is measured and the debris number is counted under a microscope. Qualitative analysis of embolized material showed debris dislocated during the percutaneous intervention from atheromatous plaques. Collected debris consisted predominantly of thrombotic material, acellular and amorphous material in this observation. Angelini et al. reported the pathological examination of debris collected during the use of filter protection device4. Microscopic evaluation revealed that particles could be detected in filters and that they were adherent mostly to the filter device. Manninen et al. identified the composition of filtered material to be clusters of unspecified cells, atherosclerotic plaques and intimai stripes8. The latter are also seen in this observation and are considered to be the cause of embolism, which appear even in diagnostic angiography. The balloon angioplasty or stent deployment was not necessarily the reason for the visualized strips, but rather the guide-wire and/or catheter manipulation may have been the causative factor. These are also found in experimental atheablations of lower limb arteries with Kensey atherectomy catheters6. In other reports, foam cells or cholesterol clefts are also observed in debris samples. To a minor degree, calcium particulate and platelets entrapped in fibrin strands were also present. The debris samples size was in the range of 40-500 µm in this case. Larger debris, >1 mm, can be observed and may induce massive cerebral infarctions4.

Composition of debris should be compared with imaging studies such as carotid echo, intravascular ultrasound, or angiographical appearance. Recognition of the imaging features corresponding to the histopathologic constituents of carotid plaques associated with increased risk of distal embolization during endovascular intervention would be very useful before deciding on therapy options in individual cases. The presence of histopathologic intraplaque hemorrhage and/or remarkable neovascularity was associated with greater abundance of lipid-filled foam cells in the embolie filtrate. Intraplaque hemorrhage indicates an unstable lesion, which is prone to spontaneous rupture9. Distal protection is not always guaranteed because of possible fatty shower embolism. Carotid endarterectomy should be recommended for an unstable, lipid-rich plaque rather than stenting.

Carotid plaque debris aspirated during carotid artery stenting under distal protection can be filtered where, upon processing in a permanent glass slide, visualization is possible. This simple method allows us to better understand the quantity, particle size, and also composition of debris.

REFERENCES

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Kentaro Hayashi, Naoki Kitagawa and Minoru Morikawa*

Department of Neurosurgery and *Radiology, Nagasaki University Graduate School of Medicine, Nagasaki, Japan

Correspondence and reprint requests to: Kentaro Hayashi, MD, Department of Surgery/Neurosurgery, University of Kentucky Medical Center, 800 Rose Street, Lexington, KY40536-0298. [kenkunijp@ yahoo.co.jp] Accepted for publication July 2004.

Copyright Maney Publishing Jan 2005
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