Biomedical subjects
Publications and source records attributed to A J Roberts.
The principles used to develop techniques for myocardial preservation in cardiac surgery have been successfully applied to the protection of the donor heart in transplant surgery. This article reviews the latest advances in myocardial preservation during cardiac surgery and shows how they have been adopted in current cardiac transplant techniques.
During coronary artery bypass graft operations, the saphenous vein graft and native coronary arteries in 17 patients were examined with a 1.7 mm fiberoptic catheter to determine the feasibility of the procedure and its potential for clinical application. Good to excellent visualization in 10 of 11 proximal and 10 of 10 distal coronary anastomoses was obtained promptly and consistently. Good visualization of native coronary arteries was obtained in only six of 11 vessels. Three of three coronary arteries were visualized through the completed distal anastomosis, whereas only three of eight vessels could be visualized directly through the arteriotomy site before completion of the distal anastomosis. The image quality improved with operator experience. Vessel distention by cold crystalloid solution during catheter visualization was also important for obtaining better images. Limitations of the current "state of the art" fiberoptic catheters include the large size relative to the usual dimensions of the native coronary vessels, a lack of perfusion channel, and the absence of an angulation or guiding system. Potentially, angioscopic catheters may be useful as an instructional aid during bypass operations or as a diagnostic tool in monitoring arterial status after thrombolytic intervention, balloon angioplasty, or laser therapy.
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The relative accuracy of five simplified methods of measuring glomerular filtration rate was prospectively assessed using 99mTc-DTPA. The slope of the biological clearance curve, the 3-h volume of dilution and three renal tracer uptake methods (Piepsz, Gates and Nielsen) were concurrently compared with a multiple blood sampling reference method. The volume of dilution method from a single blood sample was markedly superior to the other four simplified methods which all had a similar degree of accuracy.
An analysis of myocardial protection was performed in 45 low-risk patients undergoing coronary bypass procedures who were divided into three equal groups with similar preoperative ejection fractions and coronary artery obstructions. Group 1 (N = 15) received cold blood cardioplegia, Group 2 received cold blood cardioplegia and secondary cardioplegia, and Group 3 received cold blood cardioplegia plus warm cardioplegic induction. The aortic cross-clamp time and the number of bypass grafts were similar among the groups. The following variables were measured serially: electrocardiographic changes, serum myocardial-specific isoenzyme of creatine kinase, cardiac output, left ventricular filling pressure, ejection fraction, and left ventricular wall motion. The three methods evaluated were all effective in protecting the myocardium during global myocardial ischemia. Patients who received secondary cardioplegia (Group 2) were more likely to exhibit spontaneous defibrillation (12/15) than those in Group 1 (5/15) or Group 3 (6/15) (p less than 0.05). However, measurements of left ventricular performance and evidence of perioperative myocardial infarction were similar among all three groups. These data suggest that a standard technique of cold potassium cardioplegia alone should be the method of choice in elective, low-risk coronary bypass operations rather than this technique in combination with either of the other two more costly and complex methods evaluated in this study.
The purpose of this study was to document early mortality, perioperative complication rate, duration of hospitalization, and costs related to coronary artery bypass graft (CABG) surgery in the elderly. Arbitrarily, elderly patients were defined by age greater than or equal to 65 years; younger patients were less than or equal to 60 years old. A detailed list of specific perioperative complications was analyzed. Early (30-day) mortality was similar between groups, while 120-day mortality was higher among elderly compared with younger patients (7.6% versus 1.3%; p = 0.05). The number of elderly patients with 1 or more complications was also higher than among the younger patients (62% versus 43%; p = 0.05). When the incidences of atrial arrhythmias and transient psychoses were considered minor complications and excluded from consideration, the incidence of major complications was higher in the elderly: 41 major events among 76 younger surviving patients compared with 89 major complications in 61 older surviving patients (p = 0.001). Time spent in the intensive care unit and the duration of postoperative hospitalization were also greater in the elderly (p = 0.01 and p = 0.001, respectively). Finally, the elderly group incurred greater costs than the younger patients (p = 0.03). The likelihood of increased perioperative morbidity in elderly patients is documented in this study. Also, it appears that the increased frequency of complications in elderly patients is associated with a longer hospital stay and greater financial expense. Consequently, the careful preoperative evaluation of these patients, including cautious patient selection, assumes greater importance. After CABG procedures, the highly symptomatic elderly patient may experience dramatic relief of symptoms.(ABSTRACT TRUNCATED AT 250 WORDS)
In 20 patients undergoing cardiac catheterization, usually involving balloon-catheter dilation or streptokinase infusion, catheter-induced coronary artery intimal damage resulted in severe chest pain, electrocardiographic evidence of obstruction or dissection of a major coronary artery. These patients were surgically revascularized within 8 hours after the onset of the acute chest pain syndrome. Our experience with pharmacological and catheter-related manipulations to improve coronary blood flow after the ischemic episode but before operation suggested that the additional time spent in the catheterization laboratory was worthwhile. The injured coronary artery was the left anterior descending in 10 patients, the right in 8, the left main in 1 patient, and an obtuse marginal branch of the circumflex in 1. The average number of grafts per patient was 2.5; only 6 patients had single bypass grafts. In 5 patients, intraaortic balloon pumping was used either preoperatively or postoperatively. Inotropic support was used postoperatively in 5 patients, and 7 patients received lidocaine for ventricular irritability. Abnormal elevation of the serum isoenzyme of creatine kinase (CK-MB) was seen in 8 patients, and new Q waves were noted in 4 patients; 3 of these 4 patients with new Q waves also had abnormal serum CK-MB levels. Global ejection fraction obtained by the equilibrium-gated blood pool scan postoperatively was 60 +/- 3%, which was similar to the 62 +/- 3% obtained from the contrast-determined ventriculogram done preoperatively prior to the catheter-related injury. There were no early or late deaths, but morbidity was much higher in the group who had emergency coronary artery bypass grafting (CABG) compared with those who had elective CABG.(ABSTRACT TRUNCATED AT 250 WORDS)
Basic scientific research has provided the impetus to develop cardioplegic solutions that offer excellent myocardial preservation. Future research will continue to develop methods for better delivery of cardioplegia to all myocardial regions. In addition, earlier detection of evolving ischemic damage during aortic cross-clamping might provide a basis for earlier intervention to reverse developing myocardial injury. At the present time, the cardiac surgeon has many cardioplegic solutions and delivery systems from which to choose. Only by understanding the principles involved in myocardial preservation will the surgeon be able to develop a system that will work best in his or her clinical practice.
This article provides an overview of the current status of coronary venous interventions for myocardial protection. It reviews the histories, principles, and techniques of the interventions as well as the challenges for the future.
Anti-idiotype sera, raised in rabbits against anti-acetylcholine receptor (AChR) (idiotype) purified from the serum of three myasthenia gravis patients, inhibited binding of homologous idiotype to the AChR by up to 80%. The expression of idiotype in the three individuals changed very little over a period of several years, during which they showed a declining trend in overall anti-AChR antibody. Only one of the four anti-idiotype sera inhibited the binding of anti-AChR from a number of other patients. Our results indicate a consistency of idiotype expression within an individual, and fail to show substantial idiotype sharing between individuals.
Thirty-four patients with stable angina underwent coronary artery bypass surgery with supplemental intraoperative coronary artery balloon-catheter dilatation. Coronary dilatation was performed on 35 vessels at 50 sites. The balloon catheter could not be passed through one stenotic site. Intimal dissection occurred at two sites, as noted on early postoperative angiographic studies, with resolution on follow-up studies. There was one perioperative myocardial infarction, 100% early relief of angina, and one operative death. Of 25 distal arterial narrowings studied early by angiography (mean, 10 days), 15 (60%) were unchanged, two (8%) were worse, and eight (32%) were improved. Discrete narrowings improved more than diffuse narrowings; in 46% of the former there was an increase in luminal diameter, in comparison to only 17% of the latter. During a maximal 34-month follow-up period, two patients developed recurrent angina and one died of congestive heart failure. Of 13 distal coronary narrowings studied late (mean, 1 year), six (46%) were unchanged, three (23%) were worse, and four (31%) were improved. Postoperative serial catheterization (early and late) of 10 distal narrowings revealed that nine were unchanged and one was worse. Adjunctive intraoperative coronary balloon-catheter dilatation can be performed safely with acceptable clinical results. The procedure may also allow more complete revascularization of the myocardium.
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Controversy exists concerning the most appropriate sequence of anastomoses in coronary artery bypass grafting (CABG) procedures. While the more commonly employed method of distal coronary anastomoses first has withstood a long clinical experience, a recent study and several cardiac surgical groups have suggested that construction of the proximal anastomoses first offers certain advantages. In 30 patients undergoing CABG, we performed a prospective, randomized trial comparing both techniques. Relative efficacy was assessed by hemodynamic, radionuclide, electrocardiographic, enzymatic, thermographic, and clinical evaluation. The length of cardiopulmonary bypass was longer in the group having the distal anastomoses done first. Myocardial temperature mapping was similar between groups. Hemodynamic changes, including cardiac output, ejection fraction, and regional wall motion, were nearly identical between the groups. The incidence of myocardial damage reflected by levels of myocardial-specific isoenzymes (serum CK-MB) and electrocardiographic changes was also similar. In conclusion, the sequence of anastomoses is not critical in routine CABG operations. However, we speculate that each technique may have certain advantages under different clinical circumstances found on occasion. Ideally, each method should be part of the coronary surgeon's armamentarium.
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Factors associated with early and late graft patency related to aorta-coronary artery bypass grafting with a reversed segment of saphenous vein are clinically important. The present investigation examines the biochemical and electron microscopic integrity of this venous conduit intraoperatively with regard to pharmacologic manipulation with papaverine. Portions of saphenous vein were analyzed in 22 patients undergoing coronary artery bypass operations. Levels of a stable derivative of prostacyclin, 6-keto-PGF1 alpha, were measured by radioimmunoassay. Scanning as well as transmission electron microscopy was also performed. In particular, the efficacy of local vein treatment with papaverine, a phosphodiesterase inhibitor, was evaluated. We found that levels of 6-keto-PGF1 alpha in venous effluent showed a biphasic response with initial elevation followed by a relative depression after papaverine exposure. There were no such changes observed in veins subjected to a balanced electrolyte solution (Plasma-Lyte). In addition, levels of the platelet-inhibitory substance 6-keto-PGF1 alpha in venous tissue were less in papaverine-treated veins than those found in veins treated only with the balanced electrolyte solution (Plasma-Lyte). Furthermore, evidence for ultrastructural damage was also somewhat greater in the papaverine-treated group. An alternative method of dilating the saphenous vein after harvesting, which involves the creation of the proximal aorta-coronary anastomosis first and gentle finger manipulation subsequently, appeared to minimize venous injury. Under present clinical conditions, it appears that some amount of injury is inevitable during harvesting and suturing of the human saphenous vein during coronary bypass grafting.
Hymenoxon inhibition of brain hexokinase resulted in inhibition of glucose utilization evidenced by a decrease in pyruvate and the accumulation of free glucose in the brains of the in vivo treated rats. Inhibition of cerebral energy processes, resulting from inhibition of glycolysis, eventuated the coma and death of one rat at 13 hr. It also accounted for the depression, observed to increase with hymenoxon exposure time, in the treated rats. The increased sulfhydryl group concentration in the brains of the treated rats suggested that increased concentration of reduced glutathione may have resulted from a decrease in its oxidation caused by hymenoxon interaction with sulfhydryl of endogenous brain constituents.
Strict electrocardiographic, enzymatic, scintigraphic, and hemodynamic criteria for perioperative myocardial infarction (MI) were defined and related to serial assessments of left ventricular performance during rest and exercise in patients seen early and late after coronary artery bypass graft operation. Global left ventricular performance was determined by radionuclide ventriculography from which changes in the pattern of serial postoperative ejection fractions (EF) were obtained. Patients were divided into two groups based on the presence or absence of perioperative MI, and were matched in pairs on the basis of preoperative EF and extent as well as location of coronary artery obstructions. The results indicate that neither short- nor long-term depression in resting EF occurred subsequent to perioperative MI. However, an exercise-related increase in EF eight months postoperatively was depressed in patients who had perioperative MI compared with those who did not. Patients with new Q waves and abnormal postoperative elevation in serum levels of the myocardial isoenzyme of creatine kinase (CK-MB) had a greater early decrease in EF compared with patients without evidence of perioperative MI. However, seven days after operation, the EF in both groups returned to preoperative levels. Patients with abnormal technetium 99m-pyrophosphate scintigrams had changes in perioperative EF similar to those in patients without MI. The presence of low cardiac output syndrome immediately after operation was associated with immediate and short-term decreases in EF, which were not seen in any of the other patient subgroups.
Sixty patients with symptomatic coronary artery disease undergoing coronary artery bypass graft operation were prospectively randomized into one of six equal groups based on the intraoperative method of left ventricular venting and venous drainage. Group 1 had bicaval venous drainage without snaring and left ventricular venting through the superior pulmonary vein; Group 2, two-stage venous drainage and venting as in Group 1; Group 3, bicaval venous drainage without snaring and no left ventricular vent; Group 4, two-stage venous drainage and no left ventricular vent; Group 5, bicaval venous drainage without snaring and with ascending aortic venting through a catheter; and Group 6, two-stage venous drainage and venting as in Group 5. Left ventricular performance was determined by radionuclide ventriculography from which global ejection fraction and regional wall motion were determined. Cardiac output was obtained by the thermodilution technique. Myocardial temperature was assessed by a needle thermistor during aortic cross-clamping. Serial electrocardiograms and levels of myocardial-specific isoenzymes (serum CPK-MB) were also analyzed. Each of the techniques tested was equally effective as determined by an analysis of intraoperative myocardial cooling and postoperative hemodynamic profiles, radionuclide ventriculography, and ECG or enzymatic evidence of myocardial damage. However, we maintain that this conclusion is valid only if adequate ventricular decompression is provided intraoperatively.