Society of Cardiovascular Anesthesiologists

Particulate Emboli Capture by an Intra-aortic Filter Device During Cardiac Surgery

H. Reichenspurner, MD, PhD; JA Navia, MD; G Berry, MD; RC Robbins, MD; D Barbut, MD; JP Gold, MD; B Reichart, MD
J Thorac Cardiovasc Surg 2000;119:233-41.

Reviewer: Jayne C.K. Fitch, MD
University of Chicago, Illinois

Summary: This article describes a new intra-aortic filter device whose safety and efficacy were evaluated. Patients studied were undergoing cardiac surgery with CPB through standard median sternotomy. After routine anesthetic induction, the aorta was evaluated by palpation and TEE (epiaortic scanning was not specified). This new filter device was inserted through a modified 24Fr arterial cannula immediately prior to cross clamp release in 77pts. The filter was inserted through the side part of the arterial cannula. The filter is a butterfly net type filter that has a pore diameter of 120 mm and whose mesh is heparin coated. The filter remained in the aorta until the heart was fully ejecting and CPB was discontinued. The filter was also removed through the side part of the arterial cannula. The filter was assessed for safety and efficacy. The filters subsequently underwent visual inspection as well as preparation for histologic and electron microscopy examination. The results revealed that the insertion and removal were safe, easy and uneventful. Hemodynamics and CPB flow rates were normal during the filter dwell period. There were no strokes or gross neurologic defects noted. Visual inspection revealed hard or soft particles or both in 96% of the filters. The average number of particles was 5 to 10 per filter with a range of 1 to 20. The average particle size was 0.6mm, ranging from 0.1 to 6 mm. Barbut (1997) reported that 72% of particles were > 0.6 mm, 28% > 1.0 mm and 44% between 0.6 and 1.0 mm, and 27% <\<> 0.6 mm. Electron microscopy analysis of 12 filters revealed insignificant platelet adhesion on the filter surface. The SEM confirmed thromboresistance of the filter mesh. Histologic examination of 44 filters revealed that 66% had atheromatous material, 36% had platelet fibrin contents, 25% had true thrombus and /or clot, 7% had normal blood vessel wall and 2% had cholesterol aggregates or the grumous the portion of an atheromatous plaque.

Comments: Despite technologic advances relative to CPB, neurologic sequelae continue to plague our patients. Recent literature suggests that this incidence, which is underestimated, ranges from 6 to 33% (Roach 1996). Although the pathogenesis is multifactorial, particulate embolization during surgical manipulation of the aorta is significantly linked with neurologic injury. Studies by Gold (1995) and Barbut (1996) reveal that 60% of perioperative emboli are attributed to aortic clamp manipulation, especially clamp removal. These emboli have the potential to cause not only neurologic injury, but also peripheral ischemic injury as well. A criticism of the study is that it investigated a mixed population of both closed (CABG) and open (valve) chamber procedures. It has been established that incidence of neurologic injury may be different between these two populations. What is not discussed in this study is what specific neurologic examinations they performed. It is also well established that the ability to detect abnormalities depends upon the sensitivity and specificity of the test battery. In conclusion, intra-aortic filtration is a feasible method of capturing particulate emboli during CPB. However, more prospective studies are needed to further delineate its safety and efficacy.

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