Pharmacodynamics of fentanyl citrate in patients undergoing aortocoronary bypass

The pharmacodynamics of fentanyl citrate were studied in two groups of patients. One group underwent surgery with cardiopulmonary bypass (CPB) and the other group had surgery without CPB; the latter group represented the controls. Apneic periods were considerably longer (2.70 +/- 0.90 hr) for the CPB patients than for the control patients (1.75 +/- 0.75 hr). The total plasma fentanyl concentration at which apnea ceased was not statistically different between the two groups. Minor differences were attributed to the massive dilution of plasma proteins after the adding of priming fluid to the heart-lung machine. This prolongation of apnea is of considerable clinical importance because it means that CPB patients must remain mechanically ventilated for longer periods.     

Platelet regeneration time and late occlusion of aortocoronary saphenous vein bypass grafts.

The half-time for platelet regeneration was estimated in 16 patients with aortocoronary vein grafts by the use of a non-radioisotopic technique based on the permanent inhibition by acetylsalicylic acid of lipid peroxidation by platelets. Ten patients had patent grafts after 6 years; in the other six at least one graft had become occluded between 2 and 6 years after the operation as shown by serial angiography. The mean half-time (+/- the standard error) for platelet regeneration was reduced to 2.5 +/- 0.2 days (P less than 0.002) in the group with occluded grafts as compared with 3.3 +/- 11 healthy volunteers. These results suggest a relation between late graft occlusion and platelet turnover and support the idea that patients with aortocoronary vein grafts could benefit from platelet suppressive therapy. Finally, the method employed appears to be a useful and simple way of evaluating platelet function in vivo.     

CD68 expression in aortocoronary saphenous vein bypass grafts

Atherosclerosis commonly affects the arteries harvested from patients 70 years of age or older. Saphenous vein grafts appear to maintain a higher patency rate after coronary artery bypass grafting in these subjects. The infiltration of macrophages is an early step in saphenous vein graft atherosclerosis; however, little is known regarding the underlying mechanisms of infiltration. The objective of the present report is to evaluate the presence of CD68-positive cells in the saphenous vein wall and correlate initial CD68-positive infiltration to specific clinical and biochemical parameters and the graft patency rate as estimated in patients undergoing coronary artery bypass grafting. A total of 309 patients were allocated into two groups: A1 patients, who were between 50 and 70 years of age, and A2 patients, who were 70 years or older at the time of vein harvesting. CD68 expression was evaluated by immunohistochemistry. There were no significant differences between A1 and A2 patients regarding macrophage expression within any of the analyzed vascular regions. Saphenous vein macrophages were never present in the tunica intima unless they were also expressed in the media or the adventitia. The patients with CD68-positive cells in the tunica intima had a significantly higher number of bypass stenoses when compared with the subjects who did not have CD68-positive cells in this layer. These findings suggest that the CD68-positive cells (those that have not yet developed into foam cells) present in the intima of saphenous vein grafts might serve as a very early marker of graft occlusion.     

Giant aneurysm of an aortocoronary venous bypass graft compressing the right ventricle

A 69-year-old man with a history of coronary artery bypass grafting and a recent inferoposterior myocardial infarction presented to the hospital for diagnostic coronary angiography. Physical examination, laboratory analyses, coronary angiography, echocardiography, and CT scan were performed. A giant aneurysm of the aortocoronary venous bypass graft, associated with compression of the right side of the heart, was revealed. After surgical resection and replacement of the venous graft the patient died due to right ventricular failure. (Neth Heart J 2007;15:252-4.)     

Influence of preoperative variables upon the results of coronary artery bypass surgery

One thousand ninety-six consecutive patients who received aorta-to-coronary artery bypass vein grafts were followed up to 4 years postoperatively. The early mortality was 1.7%; the 4-year survival rate, computed by actuarial methods, was 93.1%; the incidence of peri-operative myocardial infarction was 1.9%. After 4 years, 94.4% of the patients were free of peri- and postoperative infarcts. Angina pectoris was relieved in 85.7% and eliminated in 62.8% of the survivors. An analysis of the effects of ten preoperative variables on operative results showed that operative risk (early mortality, perioperative myocardial infarction) was not influenced by any of the variables. Late results (4-year mortality, 4-year infarction rate), however, were negatively affected by impaired ventricular function. Symptomatic improvement was more pronounced in men than in women.     

Helical flow as fluid dynamic signature for atherogenesis risk in aortocoronary bypass. A numeric study

The main purpose of the study was to verify if helical flow, widely observed in several vessels, might be a signature of the blood dynamics of vein graft anastomosis. We investigated the existence of a relationship between helical flow structures and vascular wall indexes of atherogenesis in aortocoronary bypass models with different geometric features. In particular, we checked for the existence of a relationship between the degree of helical motion and the magnitude of oscillating shear stress in conventional hand-sewn proximal anastomosis. The study is based on the numerical evaluation of four bypass geometries that are attached to a simplified computer representation of the ascending aorta with different angulations relative to aortic outflow. The finite volume technique was used to simulate realistic graft fluid dynamics, including aortic compliance and proper aortic and graft flow rates. A quantitative method was applied to evaluate the level of helicity in the flow field associated with the four bypass models under investigation. A linear inverse relationship (R = -0.97) was found between the oscillating shear index and the helical flow index for the models under investigation. The results obtained support the hypothesis that an arrangement of the flow field in helical patterns may elicit damping in wall shear stress temporal gradients at the proximal graft. Accordingly, helical flow might play a significant role in preventing plaque deposition or in tuning the mechanotransduction pathways of cells. Therefore, results confirm that helical flow constitutes an important flow signature in vessels, and its strength as a fluid dynamic index (for instance in combination with magnetic resonance imaging flow visualization techniques) for risk stratification, in the activation of both mechanical and biological pathways leading to fibrointimal hyperplasia.     

Late results of aortocoronary bypass grafts in 100 patients with stable angina pectoris

From March 1969 to December 1972, 314 patients underwent elective aortocoronary saphenous vein bypass graft surgery at the Toronto General Hospital for the relief of stable disabling angina refractory to medical management. Inhospital mortality was 2.5%. Of these patients 100 agreed to return for follow-up hemodynamic and angiographic assessment at a mean interval of 19.7 months after operation. Seventy-four percent of patients were asymptomatic or had angina only with strenuous exertion at the time of follow-up. Seventy-five percent of the 142 grafts were patent, though a few had significant narrowings. Clinical improvement could be correlated with successful myocardial revascularization. Myocardial infarction was diagnosed by the presence of new Q waves after operation in 15% of patients. Many of these patients had patent grafts at follow-up and all were improved. Dyslipoproteinemia was not found to be a factor affecting late graft patency. Total left ventricular function was not shown to be improved by segmental revascularization. The trend toward improved survival in the intervening period for the total operated group is encouraging.     

Severe peripheral neuropathy following gastric bypass surgery for morbid obesity.

Severe weakness in the limbs developed in a young woman 3 1/2 months after successful gastric bypass surgery for morbid obesity. Electromyography confirmed the clinical impression of generalized axonal polyneuropathy. Vitamin B replacement therapy was started. The gastric bypass was not reversed, and the patient continued to lose weight while undergoing rehabilitation. After 10 months she had almost fully recovered. Her total weight loss was 76 kg. Neuropathy is an uncommon but serious complication of semistarvation that should be preventable by routine administration of vitamin B complex.