Ann Thorac Surg 2007;84:e17-e18
© 2007 The Society of Thoracic Surgeons
Case Reports
Breakdown of Atheromatous Plaque Due to Shear Force From Arterial Perfusion Cannula
Ikuo Fukuda, MD, PhDa,*,
Masahito Minakawa, MD, PhDa,
Kozo Fukui, MD, PhDa,
Satoshi Taniguchi, MD, PhDa,
Kazuyuki Daitoku, MD, PhDa,
Yasuyuki Suzuki, MD, PhDa,
Hiroshi Hashimoto, MD, PhDb
a Department of Cardiovascular Surgery, Hirosaki University School of Medicine, Hirosaki, Aomori, Japan
b Department of Anesthesiology, Hirosaki University School of Medicine, Hirosaki, Aomori, Japan
Accepted for publication June 5, 2007.
* Address correspondence to Dr Fukuda, Department of Cardiovascular Surgery, Hirosaki University School of Medicine, 5 Zaifu-cho, Hirosaki, Aomori, 036-8562, Japan (Email: ikuofuku{at}cc.hirosaki-u.ac.jp).
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Abstract
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Breakdown of an atheromatous plaque in the aorta due to jet from the arterial cannula is reported. The patient underwent mitral valve replacement under ventricular fibrillation because of severe atheromatous change in the ascending aorta, transverse aortic arch, and descending aorta. A dispersive arterial perfusion cannula was inserted into the middle portion of the ascending aorta where the atheromatous change was minimal. Postoperative epiaortic ultrasonography revealed a breakdown of the atheromatous plaque in the lesser curvature. In view of this complication, further study of the effects of shear stress to the diseased aorta should be done by clinical and flow dynamics investigation.
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Introduction
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Causes of stroke after cardiac surgery are multifactorial. One of the major causes is atheroembolism due to manipulation of a severely atherosclerotic aorta. The most hazardous procedure that induces detachment of atheromatous debris is application of a side biting or aortic clamp and insertion of arterial perfusion cannula into a diseased aorta [1]. Breakdown of a thickened posterior aortic wall caused by aortic clamp is well documented in the literature [1–3]. However, the role of jet flow from the arterial cannula had not been clearly documented. We herein report a breakdown of atheroma caused by jet lesion from a dispersion arterial perfusion cannula.
A 66-year-old man who had a history of bifurcated graft replacement for an abdominal aortic aneurysm 8 years ago was admitted to our hospital due to congestive heart failure. Cardiac catheterization revealed severe mitral valve regurgitation and pulmonary hypertension. Echocardiography demonstrated thickening of the anterior mitral leaflet and massive mitral regurgitation. The patient underwent mitral valve replacement using a bioprosthesis. Before institution of cardiopulmonary bypass, the ascending and descending aorta was assessed using direct epiaortic echogram and transesophageal ultrasonography. There was severe atheromatous change over the descending aorta and aortic arch. There was severe atheroma on the lesser curvature of the transverse aortic arch (Fig 1). Severe atherosclerotic thickening on the orifices of arch vessels was also noted. Because the anterior aspect of the ascending aorta had normal thickness and no calcification, the arterial perfusion cannula was inserted into the middle portion of the ascending aorta. Dispersive flow arterial cannula, RMI DCT21A (Research Medical Inc, Midvale, UT) was used as arterial perfusion cannula. The nose of the cannula tip was oriented toward the aortic arch. Mitral valve replacement was performed under ventricular fibrillation using cardiopulmonary bypass with moderate hypothermia. No arterial clamps were applied on the ascending aorta. After the patient was weaned from cardiopulmonary bypass, epiaortic echogram was performed again to evaluate any morphological change within the atheroma. It revealed a breakdown of the atheromatous cap with pendulous motion in the aortic lumen (Fig 2). Although no embolic complication occurred after surgery, the patient temporally exhibited cognitive dysfunction such as restlessness and recent memory disturbance. Finally, the patient was discharged without any neurologic sequela. The patient had no embolic episodes in 2 years after the mitral valve replacement.
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Fig 1. Epiaortic echogram before arterial cannulation. Note there was thick atheromatous plaque on the lesser curvature of the proximal aortic arch.
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Fig 2. Epiaortic echogram after arterial decannulation. Breakdown of the atheromatous plaque was evident.
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Comment
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The incidence of stroke after cardiac surgery has been reported in the literature as high as 2% to 8% in the elderly population [4]. The major causes of stroke are hypoperfusion in an atherosclerotic cerebral circulation during cardiopulmonary bypass and atheroembolism caused by manipulation of the diseased aorta. Ura and colleagues [2] observed an aortic intimal lesion caused by aortic manipulation using preoperative and postoperative intraoperative echocardiography [2]. They pointed out that the jet from a straight end-hole cannula may cause intimal injury that can frequently result in stroke. In this situation, modification of cardiopulmonary bypass is necessary. An alternative site other than the femoral artery or the ascending aorta for arterial perfusion is the axillary artery [5]. It is useful for patients with extensive peripheral vascular and ascending aortic disease. However, in this patient there were severe atherosclerotic changes on the ostia of the arch vessels. Flow velocity through the axillary artery may be very swift and is directed to the lesser curvature of the aortic arch in our clinical observation (unpublished data). Several types of dispersion cannulas were developed to attenuate the jet lesion on the aortic wall. The RMI DCT21A arterial cannula was excellently designed to reduce shear stress due to fanlike flow from the crooked cannula tip. However, the role of mechanical stress on the fragile atheromatous plaque due to arterial jet flow is not clearly understood. In our patient, the atheromatous plaque was partially broken after extracorporeal circulation. As there was no manipulation of the ascending aorta other than arterial cannulation, the broken atheroma was most likely due to the jet flow from the arterial cannula. As the sandblast effects of swift flow from the arterial cannula are not clearly known, further study of the effects of shear stress to the diseased aortic wall should be done by clinical and flow dynamics investigation.
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References
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- Wareing TH, Davila-Roman VG, Barzilai B, Murphy SF, Kouchoukos NT. Management of the severely atherosclerotic ascending aorta during cardiac operations J Thorac Cardiovasc Surg 1992;103:453-462.[Abstract]
- Ura M, Sakata R, Nakayama Y, Goto T. Ultrasonographic demonstration of manipulation-related aortic injuries after cardiac surgery J Am Coll Cardiol 2000;35:1303-1310.[Abstract/Free Full Text]
- Calafiore AM, Di Mauro M, Teodori G, et al. Impact of aortic manipulation on incidence of cerebrovascular accidents after surgical myocardial revascularization Ann Thorac Surg 2002;73:1387-1393.[Abstract/Free Full Text]
- Eagle KA, Guyton RA, Davidoff R, et al. ACC/AHA 2004 guideline update for coronary artery bypass graft surgery: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (Committee to Update the 1999 Guidelines for Coronary Artery Bypass Graft Surgery) Circulation 2004;110:e340-e437.[Free Full Text]
- Sabik JF, Lytle BW, McCarthy PM, Cosgrove DM. Axillary artery: an alternative site of arterial cannulation for patients with extensive aortic and peripheral vascular disease J Thorac Cardiovasc Surg 1995;109:885-890discussion 890–1.[Abstract]
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Abstract
Introduction
