Michael D. Crittenden

Radial Artery Grafts vs Saphenous Vein Grafts in Coronary Artery Bypass Surgery: A Randomized Trial

CONTEXT Arterial grafts are thought to be better conduits than saphenous vein grafts for coronary artery bypass grafting (CABG) based on experience with using the left internal mammary artery to bypass the left anterior descending coronary artery. The efficacy of the radial artery graft is less clear. OBJECTIVE To compare 1-year angiographic patency of radial artery grafts vs saphenous vein grafts in patients undergoing elective CABG. DESIGN, SETTING, AND PARTICIPANTS Multicenter, randomized controlled trial conducted from February 2003 to February 2009 at 11 Veterans Affairs medical centers among 757 participants (99% men) undergoing first-time elective CABG. INTERVENTIONS The left internal mammary artery was used to preferentially graft the left anterior descending coronary artery whenever possible; the best remaining recipient vessel was randomized to radial artery vs saphenous vein graft. MAIN OUTCOME MEASURES The primary end point was angiographic graft patency at 1 year after CABG. Secondary end points included angiographic graft patency at 1 week after CABG, myocardial infarction, stroke, repeat revascularization, and death. RESULTS Analysis included 733 patients (366 in the radial artery group, 367 in the saphenous vein group). There was no significant difference in study graft patency at 1 year after CABG (radial artery, 238/266; 89%; 95% confidence interval [CI], 86%-93%; saphenous vein, 239/269; 89%; 95% CI, 85%-93%; adjusted OR, 0.99; 95% CI, 0.56-1.74; P = .98). There were no significant differences in the secondary end points. CONCLUSION Among Veterans Affairs patients undergoing first-time elective CABG, the use of a radial artery graft compared with saphenous vein graft did not result in greater 1-year patency. TRIAL REGISTRATION clinicaltrials.gov Identifier: NCT00054847.

Continuous perfusion of donor hearts in the beating state extends preservation time and improves recovery of function

OBJECTIVES Improving methods of donor heart preservation may permit prolonged storage and remote procurement of cardiac allografts. We hypothesized that continuous, sanguineous perfusion of the donor heart in the beating, working state may prolong myocardial preservation. METHODS We developed a portable perfusion apparatus for use in donor heart preservation. Contractile, metabolic, and vasomotor functions were monitored simultaneously in an isolated swine heart. The metabolic state was monitored by myocardial tissue pH. Vasomotor function was assessed in isolated coronary ring chambers. Hearts were randomized into 3 groups: group I (n = 5), cardioplegic arrest, 12-hour storage at 4 degrees C with modified Belzer solution, and 2-hour sanguineous reperfusion in the working state; group II (n = 6), 12-hour continuous perfusion in the beating working state, 30 minutes of arrest (to simulate re-implantation time), and 2 hours of reperfusion, as above; group III (n = 7), coronary ring control hearts. RESULTS At 2 hours of reperfusion, left ventricular developed pressure in group II was higher than in group I (mean +/- standard deviation: 90 +/- 6 mm Hg, 53 +/- 15 mm Hg, P = .005). Significantly less myocardial edema was observed in group II than in group I (73% +/- 4%, 80% +/- 1% water content, P = .01). Significantly less myocardial acidosis was noted in group II than in group I during preservation (pH 7.3 +/- 0.01, 6.1 +/- 0.03, P < .001) and reperfusion (pH 7.3 +/- 0.008, 6.8 +/- 0.05, P < .001). Coronary endothelial vasomotor function was better preserved in group II than in group I as evidenced by dose-response relaxation of coronary rings to 10(-8) mol/L bradykinin (37%, 55% delta baseline, P = .01). CONCLUSION This new method extends the current preservation limit and avoids time-dependent ischemic injury, thereby allowing for distant procurement of donor organs.

Saphenous Vein Conduits Harvested by Endoscopic Technique Exhibit Structural and Functional Damage

BACKGROUND Injury to the saphenous vein endothelium during harvest impacts patency after coronary artery bypass graft surgery. Many centers are adopting endoscopic saphenous vein harvest (ESVH) instead of using the traditional open saphenous vein harvest (OSVH) technique. Our objective was to compare the effects of ESVH and OSVH on the structural and functional viability of saphenous vein endothelium using multiphoton imaging, immunofluorescence, and biochemical techniques. METHODS Ten patients scheduled for coronary artery bypass graft surgery were prospectively identified. Each underwent ESVH for one portion and OSVH for another portion of the saphenous vein. A 1-cm segment from each portion was immediately transported to the laboratory for processing. The vessel segments were labeled with fluorescent markers to quantify cell viability (esterase activity), calcium mobilization, and generation of nitric oxide. Samples were also labeled with immunofluorescent antibodies to visualize caveolin, endothelial nitric oxide synthase, von Willebrand factor, and cadherin, and extracted to identify these proteins using Western blot techniques. All labeling, imaging, and image analysis was done in a blinded fashion. RESULTS Esterase activity was significantly higher in the OSVH group (p < 0.0001). Similarly, calcium mobilization and nitric oxide production were significantly greater in the OSVH group (p = 0.0209, p < 0.0001, respectively). Immunofluoresence and Western blot techniques demonstrated an abnormal alteration in distribution of caveolin and endothelial nitric oxide synthase in the ESVH group. CONCLUSIONS Our study indicates that ESVH has a detrimental effect on the saphenous vein endothelium, which may lead to decreased graft patency and worse patient outcomes.

Intraoperative cerebral high-intensity transient signals and postoperative cognitive function: a systematic review

BACKGROUND Much attention in the literature has focused on the relationship between perioperative microemboli during cardiac and vascular surgery and postoperative cognitive decline. Transcranial Doppler ultrasonography (TCD) has been used to measure high-intensity transient signals (HITS), which represent microemboli during cardiac, vascular, and orthopedic surgery. The purpose of this study was to systematically examine the literature with respect to HITS and postoperative cognitive function. METHODS Systematic PubMed searches identified articles related to the use of TCD and cognitive function in the surgical setting. RESULTS The literature remains largely undecided on the role of HITS and cognitive impairment after surgery, with most studies being underpowered to show a relationship. Although the cognitive effects of HITS may be difficult to detect, subclinical microemboli present potential harm, which may be modifiable. CONCLUSIONS TCD represents a tool for intraoperative cerebral monitoring to reduce the number of HITS during surgery.

Atherosclerosis is associated with delirium after coronary artery bypass graft surgery.

Objectives: To investigate whether atherosclerosis of the ascending aorta, internal carotid arteries, and coronary arteries is predictive of postoperative delirium in subjects undergoing coronary artery bypass graft (CABG) surgery.

Multi-photon microscopic evaluation of saphenous vein endothelium and its preservation with a new solution, GALA

BACKGROUND Injury to endothelium can compromise the patency of bypass grafts harvested during coronary artery bypass graft (CABG) surgery. Maintaining structural and functional viability of endothelium in grafts may lead to improved long-term patency. The information gained from the application of multi-photon microscopy in transmission and epifluorescence mode was used to assess the structural and functional integrity of human saphenous vein segments stored in multiple preservation solutions, and to design a superior storage solution. METHODS Multi-photon microscopy was used to image deep within saphenous vein tissue harvested from patients undergoing CABG for analysis of endothelial structure and function. Endothelial cell structural viability, calcium mobilization, and nitric oxide generation were determined using specific fluorescence markers. RESULTS Within 60 minutes of harvest and storage in standard preservation solutions, calcium mobilization and nitric oxide generation were markedly diminished with more than 90% of endothelial cells no longer viable in the vein. In contrast, veins could be stored for 24 hours without substantial loss in cell viability in a newly formulated heparinized physiologic buffered salt solution containing glutathione, ascorbic acid, and L-arginine (GALA). CONCLUSIONS Standard solutions in clinical use today led to a profound decline in saphenous vein endothelial cell viability, whereas the newly designed physiologic salt solution (GALA) maintained endothelial function and structural viability for up to 24 hours. The improvements seen from using GALA as a vessel storage medium may lead to greater long-term vein graft patency following CABG surgery.

Microemboli are not associated with delirium after coronary artery bypass graft surgery

Delirium is an acute change in cognition which occurs frequently after coronary artery bypass graft (CABG) surgery. Cerebral microemboli, from plaque, air, or thrombus, have been hypothesized to contribute to delirium and cognitive decline after CABG. The purpose of this study was to determine if there was an association between cerebral microemboli and delirium after cardiac surgery. Non-delirious patients (n=68) were prospectively enrolled and underwent intraoperative monitoring of the middle cerebral arteries with transcranial Doppler (TCD). TCD signals were saved and analyzed postoperatively for microemboli manually, according to established criteria. Postoperatively, patients were assessed for delirium with a standardized battery. Thirty-three patients (48.5%) developed delirium after surgery. Microemboli counts (mean ± SD) were not significantly different in those with and without delirium (303 ± 449 vs. 299 ± 350; p=0.97). While intraoperative microemboli were not associated with delirium after CABG, further investigation into the source and composition of microemboli can further elucidate the long-term clinical impact of microemboli.

Intraoperative metabolic monitoring of the heart: I. Clinical assessment of coronary sinus metabolites.

Numerous clinical studies have corroborated the ability of intraoperative sampling of coronary sinus blood to measure changes in myocardial metabolism induced by ischemia and reperfusion. Among other changes, cardiac arrest induces a period of obligate myocardial lactate production that persists for an indeterminate amount of time after reperfusion. Coronary sinus lactate assays have been established as a standard method to compare various myocardial protection strategies. Current methodology requires detailed sample processing, precluding real-time feedback in the operating room. Newer devices hold promise in allowing the online assessment of myocardial metabolism; however, these methods await precise validation.

Cerebral Hemodynamics during Coronary Artery Bypass Graft Surgery: The Effect of Carotid Stenosis

Carotid stenosis is a frequent coexisting condition in patients undergoing coronary artery bypass graft (CABG) surgery. The impact of carotid stenosis on cerebral perfusion is not fully understood. The purpose of this study was to determine the impact of carotid stenosis on cerebral blood flow velocity in patients undergoing CABG. Seventy-three patients undergoing CABG were prospectively recruited and underwent preoperative Duplex carotid ultrasound to evaluate the degree of carotid stenosis. Intraoperatively, transcranial Doppler ultrasound was used to record the mean flow velocity (MFV) within the bilateral middle cerebral arteries. In addition, during the period of cardiopulmonary bypass, regulators of cerebral hemodynamics such as hematocrit, partial pressure of carbon dioxide and temperature were recorded. The ipsilateral middle cerebral artery mean flow velocity was compared in arteries with and without carotid stenosis using a repeated measures analysis. Seventy-three patients underwent intraoperative monitoring during CABG and 30% (n=22) had carotid stenosis. Overall, MFV rose throughout the duration of CABG including when the patient was on cardiopulmonary bypass. However, there was no significant MFV difference between those arteries with and without stenosis (F=1.2, p=.21). Further analysis during cardiopulmonary bypass, demonstrated that hemodilution and partial pressure of carbon dioxide may play a role in cerebral autoregulation during CABG. Carotid stenosis did not impact mean cerebral blood flow velocity during CABG. The cerebrovascular regulatory process appears to be largely intact during CABG.

Costs and quality of life associated with radial artery and saphenous vein cardiac bypass surgery: results from a Veterans Affairs multisite trial.

BACKGROUND In coronary artery bypass grafting (CABG) surgery, there is uncertainty about whether the radial artery affects quality of life or costs relative to the saphenous vein. This study compared the cost and quality of life for patients randomized to either radial artery or saphenous vein grafts. METHODS We analyzed the duration and cost of the index surgery and costs and quality of life (Seattle Angina Questionnaire and Health Utility Index) at 1 year for 726 participants. RESULTS The 2 treatment groups had similar baseline characteristics. Using the radial artery added approximately 31 minutes to the surgery (from skin incision to skin closure; P < .001) compared with a saphenous vein graft. There were no significant differences in terms of costs and quality of life after the index hospitalization or at 1 year. CONCLUSIONS Coronary artery bypass grafting with the radial artery lasts approximately 31 minutes longer than with the saphenous vein. However, costs and the quality of life were not statistically different.