Abstract

Carotid Artery Diameter, Plaque Morphology, and Hematocrit, in Addition to Percentage Stenosis, Predict Reduced Cerebral Perfusion Pressure during Cardiopulmonary Bypass: A Mathematical Model

Address correspondence to: Michael Poullis, The Cardiothoracic Centre, Thomas Drive, Liverpool L14 3PE, UK. E-mail: Mike.Poullis@ctc.nhs.uk

Received: 25 March 2008
Accepted: 11 February 2009

Abstract

Cerebral complications after cardiac surgery are a significant cause of morbidity, mortality, and financial cost. Numerous risk factors have been proposed to explain the risk of cerebral damage. Carotid artery disease has an important role. Percentage carotid artery stenosis is the only measure of carotid artery disease that is used by cardiac surgeons to determine the need for either a carotid endarterectomy and/or a higher pump perfusion pressure. Identification of patients through their carotid plaque morphology who might benefit from higher pump perfusion pressures or concomitant carotid endarterectomy may reduce cerebral morbidity and mortality. A mathematical model using finite element analysis was created to model the carotid artery vessel and its stenotic plaque. Analysis showed that the degree of carotid artery stenosis, the length of the carotid artery plaque, the diameter of the carotid artery, and the blood hematocrit all independently significantly affect the required pump perfusion pressure to main tain adequate cerebral perfusion during cardiopulmonary bypass (CPB). The results from a mathematical model showed that carotid artery dia meter, carotid artery plaque length, and hematocrit, in addition to percentage stenosis, should be included in any thought process involving carotid artery stenosis and cardiac surgery. Estimating cerebral risk during CPB should no longer rely on only the percentage stenosis.