Biomedical subjects
Publications and source records attributed to I L Kron.
Lung transplantation is now established as a clinical reality for patients with irreversible, lethal pulmonary conditions. We report the first successful application of this treatment modality in Virginia.
Sequential endocardial resection was used in 92 consecutive patients to treat ventricular tachycardia. All patients had coronary artery disease with previous myocardial infarction. All patients had repeated cycles of mapping and resection of arrhythmogenic foci in the normothermic beating heart until ventricular tachycardia was no longer inducible. Eighty-six patients (93%) survived to hospital discharge. The survival rate in patients normotensive at the time of operation was 98% and in patients in shock at the time of operation, 43%. By Cox regression analysis, preoperative shock was the significant predictor (p less than 0.001) of operative mortality. Seventy-four of the 86 operative survivors (86%) had no sustained ventricular tachycardia at initial postoperative electrophysiologic study when receiving no antiarrhythmic drugs. Eighty-three of the 86 operative survivors (97%) had no sustained ventricular tachycardia at final postoperative electrophysiologic study when using antiarrhythmic drugs as needed. After a median follow-up of 21 months (range 1 to 79 months) there were 4 sudden cardiac deaths, 12 other cardiac deaths, and 3 noncardiac deaths. There were no documented nonfatal episodes of sustained monomorphic ventricular tachycardia after hospital discharge. Use of the sequential endocardial resection technique is effective in curing ventricular tachycardia with low operative morbidity and mortality.
Aneurysms of the iliac arterial system are often difficult to approach surgically. Aortobifemoral (ABF) bypass grafting with exclusion of the aneurysms can be used as an alternative to the usually recommended approach of endoaneurysmorrhaphy. Fourteen patients with iliac artery aneurysms treated by ABF are compared to 16 patients treated by direct repair to compare the incidence of complications related to decreased pelvic blood flow or to the presence of the excluded iliac artery aneurysm. There were no differences between the two groups. Therefore, it is concluded that ABF is a reasonable alternative in the treatment of iliac artery aneurysms.
The vascular endothelium is important in the modulation of vascular tone via production of endothelium-derived relaxing and contracting factors. The abdominal aortas of five groups of rabbits were subjected to varying lengths of ischemia (0, 1, 2, 3, or 4 hours), removed, sectioned into transverse rings, and placed in tissue baths containing Krebs' buffer at 37 degrees C and aerated with 95% O2/5% CO2. After equilibration the rings were tested for endothelium-dependent vasodilation with methacholine and nonendothelium-dependent vasodilation with nitroprusside. Endothelium-dependent relaxation as elicited by methacholine was impaired at 3 and 4 hours of ischemia but was not significantly different at 1 and 2 hours as compared to control, whereas endothelium-independent vasodilation remained normal throughout the different periods of ischemia. The addition of 1 x 10(-6) mol/L rabbit hemoglobin reduced the time needed to demonstrate significant impairment of endothelial function to 2 hours. Endothelium-independent vasodilation was not affected by hemoglobin. We conclude that hemoglobin exacerbates ischemia vascular dysfunction in the rabbit aorta.
A single-donor fibrin sealant system was used in 689 thoracic and cardiovascular surgical procedures over the 4-year period between April 1, 1985, and March 31, 1989. An excellent overall success rate (646/689, 94% effective) was achieved with specific applications, including reduction of leakage of air (29/33, 88% effective), blood (595/634, 94% effective), and fluid (14/14, 100% effective), as well as positioning of anatomical structures such as coronary bypass grafts (8/8, 100% effective). Application methods included use of spray bottles (477/497, 96% effective), syringes (165/186, 89% effective), and a Silastic cannula through the flexible fiber-optic bronchoscope (4/6, 67% effective). The system was used in a wide variety of cardiac, pulmonary, esophageal, and vascular procedures to seal staple lines, suture lines, anastomoses, conduits, fistulas, and raw surfaces. No complications with this single-donor system secondary to blood-borne disease have been documented. Overall infection occurred at a nominal rate (16/689, 2%). Thus, fibrin sealant has been a useful tool to control the leakage of air, blood, and fluid during a wide variety of thoracic and cardiovascular procedures and may be of benefit to other surgeons.
Myocardial ischemia may ensure after coronary artery translocation during the arterial switch operation. We report the successful use of a right internal mammary artery to right coronary artery bypass graft in an infant with angiographic documentation of persistent graft patency 6 months postoperatively.
The effects of chronic denervation on pulmonary vasculature are not well understood. Three groups of young pigs were prepared: (1) those receiving sham thoracotomy, (2) those having left upper lobectomy alone (innervated left lower lobe), and (3) those receiving left pneumonectomy followed by reimplantation of the left lower lobe (denervated left lower lobe). At 10 weeks after operation, animals were anesthetized and instrumented for study. No changes in baseline pulmonary artery pressure, pulmonary capillary wedge pressure, cardiac output, or pulmonary vascular resistance were observed. With diversion of the entire cardiac output to the left lung or lobe, however, the group with reimplanted lobes had a significantly higher pulmonary artery pressure and pulmonary vascular resistance than the other groups. This may result from chronic denervation of the pulmonary vasculature and receptor upregulation.
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.
Both map-guided endocardial resection (ER) and the automatic implantable cardioverter defibrillator (AICD) are currently used for surgical treatment of patients who have sustained ventricular tachyarrhythmias. Some authors have preferred AICD implant due to a lower published operative mortality rate. To determine if there is a discrepancy in mortality rates between the two techniques, we analyzed hospital survival in 46 patients undergoing ER and in 44 patients undergoing AICD implantation during the same 3-year period. Two ER patients (4%) died before hospital discharge. Two patients (4%) died after AICD implantation. At predischarge electrophysiologic study five patients (11%) had inducible ventricular tachycardia and received antiarrhythmic drug therapy after ER. In contrast 35 of 42 patients surviving AICD placement received chronic long-term antiarrhythmic therapy (p less than 0.05 compared to ER). Our experience shows that ER and AICD placement may be carried out with similar procedure-related mortality and morbidity rates. Lower operative risks should not be a reason for choosing the AICD over ER for surgical treatment of ventricular tachyarrhythmias. The AICD may actually improve the results of ER by offering an alternative to ventriculotomy in poor-risk surgical candidates.
Patients with aortic valve stenosis (AS) and left ventricular (LV) dysfunction may dramatically improve after aortic valve replacement, but operative risk is high. In an earlier study, all patients with low preoperative wall stress and low ejection fraction, or with low aortic valve gradient, died or had persistent heart failure after operation. Because wall stress is difficult to calculate, we reassessed its effect and the effect of other preoperative characteristics on outcome in 66 consecutive catheterization patients with predominant aortic stenosis referred for valve replacement. Despite ejection fraction that was inordinately low compared with afterloading wall stress in nine patients, seven patients improved with surgery. All three patients with ejection fraction less than 20% improved after surgery. Two of three patients with mean aortic valve gradients of less than 30 mm Hg improved. Mortality was 33% in patients with mean gradient less than 30 mm Hg and 19% with mean gradient less than 50 mm Hg. In the 54 patients with calculated aortic valve areas of less than or equal to 0.8 cm2, 1 (2%) had continuing heart failure, while 6 of 12 (50%, P less than .01) patients with aortic valve areas of 0.9-1.2 cm2 had continued symptoms of or died of heart failure. Patients who died or failed to improve after operation were older (71 +/- 9 years) than those who improved (65 +/- 9 years, P = .02). We conclude that wall stress calculations do not predict which patients with aortic stenosis will benefit from aortic valve replacement and that poor left ventricular function and low mean aortic valve gradient do not absolutely preclude operation. On the other hand, low gradient, non-critical valve area, and advanced age are all relative contraindications to aortic valve replacement in aortic stenosis.
A 51-year-old woman underwent a transhiatal esophagectomy for a failed antireflux procedure. She did well for 15 months, when she developed evidence of hemoptysis followed by tracheogastric fistula. She underwent operative repair with the use of a pericardial patch to replace the membranous trachea and interposition of a latissimus dorsi flap to isolate the stomach from the tracheal suture line. She has done well after this operation.
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.
The approach to muscular ventricular septal defect has been controversial. Traditional approaches have included pulmonary artery banding or right ventriculotomy. Left ventriculotomy has been employed in older children because of the ease of exposure in the absence of trabeculations, but concern has been raised regarding potential loss of left ventricular function. Four infants less than 4 months of age underwent repair of a large muscular ventricular septal defect by left ventriculotomy. One infant had no associated defects; 2 had undergone previous coarctation repair (1 with pulmonary artery banding); and 1 had a large secundum atrial septal defect. All had congestive heart failure refractory to maximal medical management. All patients survived, and there was no myocardial dysfunction. Echocardiographic indices of ventricular function 3 to 24 months postoperatively were normal (mean shortening fraction, 32.5%). Left ventriculotomy with patch closure of the ventricular septal defect provides a simple approach to a large muscular ventricular septal defect in infants with heart failure.
Endothelial-derived relaxing factor is an important modulator of vascular relaxation, and its production is very sensitive to endothelial injury. The abdominal aortas of five groups of rabbits were subjected to Fogarty balloon catheterization via the femoral artery. Some rabbits were killed immediately (time 0), and others were killed at weekly intervals. At time 0, isolated vascular rings sectioned from the abdominal aortas and suspended in tissue baths failed to exhibit any endothelial-derived relaxing factor dependent vascular relaxation. Vascular relaxation progressively returned but was not normal until 4 weeks after the initial injury. Morphologic changes studied by means of Evans blue dye and by scanning electron microscopy with silver staining corresponded well with these functional changes. At time 0, the delicate endothelium was completely denuded, but it progressively regenerated over the subsequent 4 weeks. This severe injury to the vascular endothelium and the resultant vascular dysfunction may result in an increased risk of early postoperative spasm and thrombosis after the use of a Fogarty balloon catheter.
Pulmonary artery (PA) banding to reduce pulmonary blood flow was described by Muller and Dammann in 1952. This review describes the outcome of 170 children who had PA banding at the University of Virginia Medical Center between 1955 and 1988. One hundred and one of the patients were banded between 1958 and 1970; fewer bands were placed in later years because early total correction was feasible for certain conditions. When analyzed by preoperative diagnoses, the data reveal that children with a single ventricle undergoing banding had a significantly lower 30-day mortality rate of 12% compared to other preoperative diagnoses, including atrioventricular canal, truncus arteriosus, and ventricular septal defect (VSD) at 30% (p less than 0.05). The late overall mortality for all patients was approximately 10%, an attrition rate of 1% per year. PA banding still has a role in management of patients with congenital heart disease, particularly for infants with a single ventricle. Actuarial survival at 10 years for patients with this condition is 92%. Interestingly, this indication for pulmonary banding is the same one cited in the original report.
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.
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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 in 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.