Patient-Specific Hemodynamics of New Coronary Artery Bypass Configurations.

PURPOSE: This study aims to quantify the patient-specific hemodynamics of complex conduit routing configurations of coronary artery bypass grafting (CABG) operation which are specifically suitable for off-pump surgeries. Coronary perfusion efficacy and local hemodynamics of multiple left internal mammary artery (LIMA) with sequential and end-to-side anastomosis are investigated. Using a full anatomical model comprised of aortic arch and coronary artery branches the optimum perfusion configuration in multi-vessel coronary artery stenosis is desired. METHODOLOGY: Two clinically relevant CABG configurations are created using a virtual surgical planning tool where for each configuration set, the stenosis level, anastomosis distance and angle were varied. A non-Newtonian computational fluid dynamics solver in OpenFOAM incorporated with resistance boundary conditions representing the coronary perfusion physiology was developed. The numerical accuracy is verified and results agreed well with a validated commercial cardiovascular flow solver and experiments. For segmental performance analysis, new coronary perfusion indices to quantify deviation from the healthy scenario were introduced. RESULTS: The first simulation configuration set;-a CABG targeting two stenos sites on the left anterior descending artery (LAD), the LIMA graft was capable of 31 mL/min blood supply for all the parametric cases and uphold the healthy LAD perfusion in agreement with the clinical experience. In the second end-to-side anastomosed graft configuration set;-the radial artery graft anastomosed to LIMA, a maximum of 64 mL/min flow rate in LIMA was observed. However, except LAD, the obtuse marginal (OM) and second marginal artery (m2) suffered poor perfusion. In the first set, average wall shear stress (WSS) were in the range of 4 to 35 dyns/cm2 for in LAD. Nevertheless, for second configuration sets the WSS values were higher as the LIMA could not supply enough blood to OM and m2. CONCLUSION: The virtual surgical configurations have the potential to improve the quality of operation by providing quantitative surgical insight. The degree of stenosis is a critical factor in terms of coronary perfusion and WSS. The sequential anastomosis can be done safely if the anastomosis angle is less than 90 degrees regardless of degree of stenosis. The smaller proposed perfusion index value, O(0.04 - 0) × 102, enable us to quantify the post-op hemodynamic performance by comparing with the ideal healthy physiological flow.

Epidural anesthesia versus general anesthesia in patients undergoing minimally invasive direct coronary artery bypass surgery.

OBJECTIVE: Minimally invasive direct coronary artery bypass (MIDCAB) surgery in the awake patient with epidural anesthesia had been previously reported. However, there is no prospective randomized study comparing MIDCAB surgery with epidural anesthesia versus general anesthesia. METHODS: The study was conducted as a prospective and randomized study. Between January 2002 and May 2003, 76 patients were randomly assigned into either MIDCAB under general anesthesia (GA Group) or MIDCAB under epidural anesthesia (EA Group). The EA Group patients did not receive concomitant general anesthesia and they were conscious throughout the procedure. All patients had a left internal thoracic artery to left anterior descending coronary artery bypass using the same MIDCAB techniques. There were 42 patients in the GA Group and 34 patients in the EA Group. For statistical analysis, unpaired t-test for independent samples was used for comparison of continuous variables, and Pearson Chi-Square test was used for comparison of discrete variables. RESULTS: The demographic characteristics of the groups were similar. There was no mortality or major morbidity in both groups. The EA Group patients had lower arterial oxygen saturations (93.3+/- 3.2% versus 97.4+/- 1.3%, p<0.001) and higher partial carbon dioxide pressures (45.8+/- 3.6 mmHg versus 41.5+/- 2.5 mmHg, p<0.001), but these were not clinically significant. The EA Group patients had significantly less intensive care unit (ICU) (5.5+/- 6.5 hours versus 18.2+/- 4.8 hours, p<0.001) and hospital stay periods (31.4+/- 20.7 hours versus 58.6+/- 17.9 hours, p<0.001), as well as significantly less postoperative pain (visual analog score 1.06+/-0.6 versus 2.3+/-0.6, p<0.001) and blood loss (184.2+/- 169.0 ml versus 371.7+/- 315.3 ml, p<0.001). There was no any difference in regard to patient satisfaction after the procedure between the two groups. Long -term results were equally satisfactory in both groups. CONCLUSION: It can be concluded that, similar surgical results can be achieved by MIDCAB surgery with general or epidural anesthesia. Although epidural anesthesia has no impact on the degree of patient satisfaction after the procedure, it yields significantly shorter ICU and hospital stay periods, which may result in more efficient use of hospital resources.

Facile stabilization and exposure techniques in off-pump coronary bypass surgery.

Off-pump coronary artery bypass grafting can not be performed without adequate stabilization and exposure techniques. Although most of the commercially available systems provide effective stabilization and exposure, their use were generally deemed time consuming and cumbersome. Achieving the same and even better results with simple traction sutures has led to the abandonment of commercially available systems. Although not a primary concern, the radial suture traction technique is also extremely cost efficient.

Oxidative stress is decreased in off-pump versus on-pump coronary artery surgery.

Oxidative stress occurs in patients undergoing coronary artery bypass operation. The aim of this study was to investigate the difference in oxidative stress in off-pump versus on-pump coronary artery bypass surgery. In the present study, in serial blood samples, plasma malondialdehyde (MDA) as index of lipid peroxidation, red blood cells glutathione peroxidase (GPx) and superoxide dismutase (SOD) were measured to compare the extent of oxidative stress in 30 patients undergoing OPCAB (off-pump coronary artery bypass grafting), 12 patients undergoing CABG (on-pump coronary artery bypass grafting) and 18 healthy controls. In CABG group, MDA levels increased significantly from 2.87 +/- 0.62 nmol/mL before anesthesia and 2.87 +/- 0.65 nmol/mL after anesthesia to 3.05 +/- 0.66 nmol/mL after ischemia (p < 0.05). Similarly, SOD levels also elevated significantly from 661.58 +/- 78.70 U/g Hb before anesthesia and 659.42 +/- 81.21 U/g Hb anesthesia induction to 678.08 +/- 75.80 U/g Hb after ischemia (p < 0.01, p < 0.01, respectively). In OPCAB group, only SOD levels increased from 581.73 +/- 86.24 U/g Hb anesthesia induction to 590.90 +/- 88.90 U/g Hb after reperfusion (p < 0.05). Glutathione peroxidase levels were not changed according to blood collection times in both of CABG group or OPCAB group (p > 0.05). Our results show that only mild signs of oxidative stress is found after reperfusion in OPCAB operation compared with CABG operation. Further studies are needed in order to confirm this hypothesis.

Coronary artery bypass grafting in the awake patient: three years' experience in 137 patients.

OBJECTIVE: Our experience with 137 patients operated on without general anesthesia is reviewed to explore the validity of our surgical strategy. METHODS: Between October 1998 and January 2002, 137 patients underwent coronary artery bypass grafting with high thoracic epidural anesthesia. There were 47 female and 90 male patients, ranging in age from 37 to 92 years (mean, 68 +/- 12 years). Two patients underwent reoperation. Nineteen patients had contraindications for general anesthesia. Target vessels involved were the left anterior descending artery in 122, the right coronary artery in 6, the left anterior descending artery plus right coronary artery in 7, and the left anterior descending artery plus circumflex artery in 2 patients. Coronary artery bypass was performed through limited access in 74 patients (H-graft in 42 and rib cage lifting in 32 patients) and through a median sternotomy in 63 patients. Cardiopulmonary bypass was not used. RESULTS: In 39 (28.4%) patients pneumothorax was observed during surgical intervention. There was no mortality. Of the 137 patients, 132 (96.3%) completed the procedure awake. In 58 patients the intensive care unit was not used. Eight patients were discharged from the hospital on the day of their operation. Mean length of hospitalization was 1 day (range, 0-3 days). One hundred thirty-one patients were followed up for a period of 3 months and 3 years after their operations, and 94.7% of the patients were symptom free. Control angiograms were obtained in 41 patients. Graft patency was 100%, with one radial artery graft spasm. CONCLUSIONS: Our initial experience confirms the feasibility and safety of performing coronary artery bypass grafting in the conscious patient without general anesthesia. Further study is required to define the possible extent and limitations of this strategy.