Terry L. Flanagan

Coronary revascularization rather than cardiac transplantation for chronic ischemic cardiomyopathy.

Patients with very poor ventricular function have been thought to be highly vulnerable to elective myocardial revascularization. Ischemic cardiomyopathy is now the major indication for cardiac transplantation. The 2-year survival of medically treated patients with ejection fractions less than 20%, but who are not sufficiently symptomatic for cardiac transplantation, is less than 25%. At our institution we have taken an aggressive approach by using myocardial revascularization for chronic ischemic cardiomyopathy. Between 1983 and 1988, 39 patients with preoperative ejection fractions less than 20% underwent coronary artery bypass. Patients were excluded if they had valvular heart disease other than mild to moderate mitral regurgitation, required resection of a left ventricular aneurysm, or required emergency operation for acute coronary occlusion. Mean age was 63.3 years (range, 43 to 80 years) and 31 were men. Mean preoperative ejection fraction was 18.3% (range, 10% to 20%) and the mean preoperative left ventricular end diastolic pressure was 22 mm Hg (range, 8 mm Hg to 38 mm Hg). There was one operative death (2.6%). Mean follow-up was 21 months (range, 3 to 60 months) with eight late deaths (a total mortality rate of 21%). Seven deaths were due to arrhythmias. Three patients continued to have severe heart failure, one of whom underwent successful cardiac transplantation. By life table analysis, there was a 3-year survival rate of 83%. With the present shortage of cardiac transplant donors, myocardial revascularization for ischemic cardiomyopathy is a reasonably effective means for preserving residual ventricular function.

Reducing Postischemic Paraplegia Using Conjugated Superoxide Dismutase

Paraplegia after thoracic aortic aneurysm repair has an incidence of 2.2% to 24%. Oxygen-derived free radicals after reperfusion of an ischemic spinal cord may be partly responsible for neuronal destruction. We studied the effects of polyethylene glycol-conjugated superoxide dismutase (PEG-SOD), a free radical scavenger, as a way of increasing spinal cord tolerance to ischemia. Thirty rabbits underwent 40 minutes of aortic occlusion (a known model of paraplegia). Ten of these animals received 25,000 U/kg of PEG-SOD 24 hours before aortic occlusion and two additional doses of 10,000 U/kg, one before and one subsequent to spinal ischemia. Ten animals received superoxide dismutase in the same dosages as those receiving PEG-SOD. Ten control animals received placebo. All animals were studied for 96 hours, at which time a final neurological examination was performed and the results were recorded. Of the 10 animals treated with PEG-SOD, 2 were completely paralyzed whereas 8 had less (7) or no (1) neurological impairment. Eight of the 10 control animals and 9 of the 10 animals receiving superoxide dismutase were completely paralyzed. None of the control animals or animals receiving superoxide dismutase had a normal neurological examination (p less than or equal to 0.05). Treatment with PEG-SOD before and during occlusion increased the rabbit spinal cord tolerance to a 40-minute ischemic insult. Scavenging free radicals may lessen experimental spinal cord injury.

Incidence and risk of reintervention after coarctation repair

We examined the need for intervention after coarctation repair in a retrospective study of 197 procedures performed between 1967 and 1989. Reintervention was required in 23 patients. No technique of coarctation repair was free from complications. Although there were only two stenoses in the group receiving Dacron patch angioplasty, only seven of these procedures were performed in children under the age of 1 year. The risk of stenosis was inversely correlated to the age at primary repair, with children less than 1 year old being at greater risk than those more than 1 year of age (p less than 0.05). Subclavian flap angioplasty had a lower risk of reoperation than end-to-end anastomosis (p less than 0.02). Formation of true aneurysms was confined to the Dacron patch angioplasty group. The morbidity and mortality for reintervention was low in all groups, with only one procedure-related death and no incidence of paraplegia. Although no technique is free from risk, subclavian flap angioplasty leads to fewer reinterventions in younger patients.

Coronary artery bypass grafting in patients with ventricular fibrillation

The role of coronary artery revascularization in the management of survivors of cardiac arrest remains controversial. Patients with sustained monomorphic ventricular tachycardia rarely respond to revascularization, but the response of patients with ventricular fibrillation as their basic arrhythmia has not been characterized. Coronary artery bypass grafting was performed in 8 patients with a history of cardiac arrest known to be caused by ventricular fibrillation without preceding sustained monomorphic ventricular tachycardia. All patients had critical double-vessel or triple-vessel coronary artery disease, and 7 of 8 had wall motion abnormalities from a prior myocardial infarction. After successful operation, 5 patients had no spontaneous arrhythmias and no inducible arrhythmias at a postoperative electrophysiological study. Three patients, however, had spontaneous, recurrent episodes of ventricular fibrillation unassociated with recurrent ischemia. Clinical factors were not useful predictors of response. The effect of coronary artery revascularization in patients with ventricular fibrillation is unpredictable, and full postoperative electrophysiological evaluation is necessary to judge the success of the procedure.

Impairment of Vascular Endothelial Function by High-Potassium Storage Solutions

High-potassium cold storage solutions are currently used to preserve myocardial function during heart transplantation. However, the effects of high potassium concentration on vascular endothelial function are not well known. We therefore tested vascular rings for endothelial-dependent and endothelial-independent relaxation during storage in normokalemic, normothermic buffers and then in buffers supplemented with 10 to 110 mmol/L KCl. Maximal endothelial-dependent relaxation was significantly reduced at all high potassium concentrations. Endothelial-independent relaxation was impaired only with 80 and 110 mmol/L KCl buffers. Both endothelial-dependent relaxation and endothelial-independent relaxation returned to normal values after washout of excess potassium. Similarly, endothelial-dependent relaxation and endothelial-independent relaxation were assessed in rings after 24 hours of hypothermic storage in normokalemic Krebs buffer, and in buffers containing 20 and 110 mmol/L KCl. Maximal endothelial-dependent relaxation was significantly reduced after preservation in the high-potassium solutions, whereas endothelial-independent relaxation was not impaired. We conclude that there is significant impairment of endothelial function after cold storage in a high-potassium buffer. Inadequate washout of potassium during normothermic conditions may lead to further functional impairment of vascular responsiveness. A low-potassium storage medium is recommended for improved vascular protection.

The effect of hyperemia on spinal cord function after temporary thoracic aortic occlusion

Nineteen mongrel dogs had 30 minutes of thoracic aortic occlusion to determine the effects that blockade of the renin-angiotensin system may have on preserving spinal cord blood flow and function during a period of temporary spinal cord ischemia. Cross-clamping of the thoracic aorta causes renal ischemia and activates the renin-angiotensin system with resulting increased production of angiotensin II. Angiotensin II is a potent peripheral constrictor and elevated levels may constrict collateral spinal cord circulation. At the time of aortic cross-clamping, 10 dogs received 100 mg/kg of MK422 (intravenous enalapril maleate), a converting enzyme inhibitor, and nine animals served as controls. The blockade of the renin-angiotensin system had no preserving effects on spinal cord flow as measured by microspheres and on spinal cord function as graded with the Tarlov scale. However, the paraplegic animals all had significantly increased lower thoracic and lumbar spinal cord flows 30 minutes after clamp release when compared with those animals that remained neurologically intact. In conclusion, marked hyperemia occurring after a period of hypoperfusion may lead to spinal cord edema and compartment syndrome with resulting paraplegia.

Successful treatment of postoperative chylothorax using an external pleuroperitoneal shunt

We report 3 patients with chylothorax who were successfully managed as outpatients using external pleuroperitoneal shunts. This external shunt has the advantage over subcutaneously placed shunts of pumping large volumes of fluid with each compression of the pumping chamber, of not causing the discomfort associated with pumping a subcutaneous chamber, of not becoming difficult to find in the subcutaneous space, and of being constructed of larger components which do not kink or become easily clogged with fibrinous debris.

Weight is not an accurate criterion for adult cardiac transplant size matching

Owing to the limited availability of donor hearts, standard donor criteria for heart size matching need to be reexamined. The current practice at most centers is to match the donors body weight to within +/- 20% of the recipients. Our hypothesis was that minimal differences exist in heart sizes of the adult donor population, and therefore, the donor pool could be expanded for any given patient. M-mode echocardiographic measurements of left and right ventricular internal dimensions, left ventricular mass, and percent fractional shortening were reviewed in 235 normal adult subjects (101 men, 134 women). Low correlation coefficients and a high degree of variance were consistently observed between cardiac parameters and body size. There were no significant differences in left ventricular internal dimension when women weighing 40 to 109 kg were compared with men statistically different among men weighing 50 to 99 kg. No difference was noted in right ventricular size among men and women. Echocardiography is a simple and accurate technique to assess cardiac dimensions. Body weight does not correlate well with adult cardiac size and should not be used as an exclusion criterion for a donor heart.

Transhiatal esophagectomy: A safe alternative for selected patients

One hundred one consecutive patients underwent an esophagectomy with gastric interposition for benign and malignant processes from January 1982 through July 1990. Seventy-seven underwent transhiatal esophagectomy and 24, transthoracic esophagectomy. Multivariate analysis was performed comparing the hospitalization experience of the two groups. There was no significant difference found between the mean intraoperative blood loss for transhiatal esophagectomy (770 +/- 105 mL) and that of transthoracic esophagectomy (700 +/- 175 mL). There was a significant difference between operative time, with transhiatal esophagectomy averaging 5.4 hours and transthoracic esophagectomy averaging 7.3 hours. Postoperative stay was not significantly different although there was a wide range of values for the transthoracic esophagectomy group. An 8% operative mortality was experienced by both groups. There were a significant number of minor anastomotic leaks at the cervical anastomotic level for the transhiatal esophagectomy group, but all responded to nonoperative management. The highest morbidity and mortality were seen in the subgroup of transhiatal esophagectomies done for laryngocervical malignancies. The lowest morbidity and mortality were seen in the subgroup of 12 patients who underwent transhiatal esophagectomy for nonmalignant esophageal conditions. Transhiatal esophagectomy appears to be a safe alternative for early intrathoracic esophageal malignancies at any level, for bulky distal esophageal lesions, and for benign conditions requiring total esophagectomy.

Morphological and Functional Techniques for Assessing Endothelial Integrity: The Use of Evans Blue Dye, Silver Stains, and Endothelial Derived Relaxing Factor

Abstract The endothelium is an important aspect of vascular function and pathology. Simple and reliable methods for assessing the presence or absence of endothelium in vascular specimens are presented. Intravenous Evans blue dye that stains endothelial denuded vessel walls is recommended for the macroscopic visualization of endothelial injury in gross intact arterial specimens. Scanning electron microscopy (SEM) is often used for investigating microscopic endothelial injury, but the differentiation of endothelial cells from underlying vessel wall structures can be difficult. By demarcating endothelial cell borders, silver stains allow for better endothelial identification by SEM. A third technique describes assessing endothelial integrity by how well it functions and involves the selective production of endothelium derived relaxing factor. As cardiovascular surgeons become more involved in basic vascular research, a review of these techniques should be appropriate and helpful.