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Biomedical subjects

L W Stephenson

Publications and source records attributed to L W Stephenson.

At least 109 records · Page 6Linked to original sources
PubMed1981

Replacement of ventricular myocardium with diaphragmatic skeletal muscle: short-term studies.

A pedicled diaphragmatic skeletal muscle graft was used to replace a portion of resected right ventricle in 35 dogs. The graft contracted when electrically stimulated directly or via the phrenic nerve before and after insertion. The electrical pacing threshold was lower for phrenic nerve stimulation (0.9 +/- 0.20 mamp) than for direct graft stimulation (2.3 +/- 1.19 mamp). The heart could be captured and paced by stimulating the muscle graft with higher current (16.2 +/- 4.49 mamp). The delay from pacing stimulus to muscle graft contraction when the graft was paced directly was 10 msec. The epicardial activation time delay when the heart was paced through the muscle graft was 27.0 +/- 9.08 msec. When the muscle graft pedicle was transected, the graft lost its ability to contract. The heart, however, could still be captured electrically through the graft for up to 4 hours. Strain gauge studies of the nonstimulated muscle graft showed tension development during pre-ejection ventricular contraction identical to that of the right ventricle. In the ejection phase, muscle graft tension slowly declined. The stimulated muscle graft developed active tension and echographically demonstrated muscle thickening during contraction. This study demonstrates that a vascularized, neurally innervated diaphragmatic muscle graft can be placed into the right ventricle. The graft retains its ability to contract in response to direct or phrenic nerve stimulation. It can be made to contract during any phase of the cardiac cycle. Thus diaphragmatic muscle grafts may provide a method to augment ventricular cavity size with synchronously contracting muscle.

Animals↗
PubMed1981

Subclavian--left coronary artery anastomosis (Meyer operation) for anomalous origin of the left coronary artery from the pulmonary artery.

Six patients, ages 2--76 months, had subclavian--coronary artery anastomosis (the Meyer operation) through a left thoracotomy without cardiopulmonary bypass for anomalous origin of the left coronary artery. Five of the six had congestive heart failure and ischemic abnormalities on the ECG. All six had cardiomegaly by chest x-ray. Preoperative left ventricular rejection reactions averaged 0.46 +/- 0.171. In three patients in whom peak systolic pressure was measured in the left coronary artery at operation, pressure increased by a mean of 26 mm Hg when the anastomosis was unclamped. One patient died. Five patients are alive 8--92 months postoperatively and four of the five anastomoses were patent at postoperative cardiac catheterization. Postoperative ECGs were normal or showed reduced T-wave abnormalities in all patients, and heart size by chest x-ray has decreased or is normal. Postoperative ejection fractions increased by a mean of 0.12 in four of the five patients (p = 0.01). On patient had a normal ejection fraction preoperatively and it remained unchanged postoperatively. No patient receives cardiac medications or is symptomatic at late follow-up. The Meyer operation can be performed at an early age, establishes a two-coronary-artery system, has growth potential, requires one vascular anastomosis, and in this series, resulted in reversal of left ventricular ischemic changes and improvement in left ventricular contractility.

Child, Preschool↗
PubMed1981

Effect of electrical stimulation on diaphragmatic muscle used to enlarge right ventricle.

The effect of chronic electrical stimulation on muscle mass of pedicled diaphragmatic muscle grafts (DMGs) implanted into the right ventricle was studied in 21 dogs. Nineteen dogs, followed up to 70 days (mean, 34 days), were divided into three groups. In six dogs (control) the DMG was not stimulated. In six other dogs the DMG was stimulated at 50 stimuli/min with a fixed-rate unipolar pacemaker. In seven animals the graft was paced 1:1 with the dog's own rhythm with an R-wave synchronous pacemaker. Surface area of the DMG decreased 34% to 43% (P less than 0.05) in all dogs. DMG thickness increased in all dogs (P less than 0.05). The increase was 29% for control animals and 132% and 134% for the two paced groups. The volume of the DMG decreased 24% in the nonpaced animals but increased 29% and 51% in the two paced groups. Histologic studies showed some degree of muscle degeneration and atrophy in all grafts. However, morphometric studies showed relatively normal fiber diversity in paced grafts. Fiber size decreased in nonpaced grafts, indicating muscle atrophy. Perfusion studies with labeled microspheres and silicone injections demonstrated collateral circulation with the host ventricle as early as 28 days. However, total blood flow to DMGs implanted for 4 to 6 weeks averaged only 32% of the blood flow to normal ventricular myocardium. Chronic electrical stimulation of DMGs reduces muscle degeneration and atrophy and is associated with an increase in graft thickness and volume.

Animals↗
PubMed1980

External stent for repair of secondary tracheomalacia.

Tracheomalacia was created in anesthetized piglets by submucosal resection of 3 to 5 tracheal cartilages. Measurements of airway pressure and flow showed that expiratory airway resistance is maximal at low lung volumes and is significantly increased by creation of the malacic segment. Cervical flexion increases expiratory airway resistance, whereas hyperextension of the neck reduces resistance toward normal. External stenting of the malacic segment reduces expiratory airway resistance, and the combination of external stenting and hyperextension restores airway resistance to normal except at low lung volume. Two patients with secondary tracheomalacia required tracheostomy and could not be decannulated after the indication for the tracheostomy was corrected. Both were successfully decannulated after external stenting of the malacic segment with rib grafts. Postoperative measurements of expiratory pulmonary resistance show a marked decrease from preoperative measurements. External stenting of symptomatic tracheomalacia reduces expiratory airway resistance by supporting and stretching the malacic segment and is preferable to prolonged internal stenting or tracheal resection.

Airway Resistance↗
PubMed1980

Propranolol for prevention of postoperative cardiac arrhythmias: a randomized study.

Two hundred twenty-three patients were randomly selected to receive propranolol, 10 mg orally every 6 hours, or to serve as controls after coronary artery bypass grafting. The study began at the time of discharge from the intensive care unit. Patients were ineligible if they had cardiac arrhythmias while in the intensive care unit, low cardiac output requiring catecholamine support, or bradycardia requiring a pacemaker. In the control group, cardiac arrhythmias for which treatment was necessary developed in 31 of 136 patients (23%), atrial fibrillation or flutter in 24 patients (18%), and ventricular arrhythmias in 7 (5%). In the group receiving propranolol, cardiac arrhythmias requiring treatment developed in 9 of 87 patients (10%), atrial fibrillation or flutter in 7 (8%), and ventricular arrhythmias in 2 (2%). The difference in frequency with which cardiac arrhythmias occurred between the two groups is significantly different (p less than 0.05). We conclude that propranolol is effective in the prevention of cardiac arrhythmias following coronary artery bypass grafting.

Arrhythmias, Cardiac↗
PubMed1980

The intraaortic baloon pump: an analysis of five years' experience.

During a five-year period, 178 patients had the intraaortic balloon pump (IABP) inserted for circulatory support. The IABP was used most frequently as an adjunct for weaning patients from cardiopulmonary bypass. Seventy-seven of 103 patients (75%) were successfully weaned from cardiopulmonary bypass with the IABP, and 36 of them (35%) ultimately survived hospitalization. Other indications for the IABP included circulatory support before cardiac operation (16 patients), operative prophylaxis in high-rish patients (13), and postoperative hemodynamic support (23). Additionally, the IABP was placed in 23 patients who did not undergo cardiac operation. The incidence of IABP-related complications was significantly less when the IABP was inserted through the ascending aorta (4%) intraoperatively compared with the femoral or iliac artery (25%) (p less than 0.05). This was due primarily to vascular complications and groin wound infections that occurred with the femoral or iliac artery approach. IABP-related spinal cord paralysis developed in 3 patients (1.7%). We conclude that the IABP is an effective support device for treating patients with left ventricular failure particularly when weaning them from cardiopulmonary bypass. However, the risk of complications, including paraplegia, must be carefully weighed when use of the IABP is considered, especially in situations in which its efficacy is less clear.

Adult↗
PubMed1980

Coarctation resection in children with Turner's syndrome: a note of caution.

Eight children were recognized to have Turner's syndrome, among 353 patients over 1 year of age who had undergone surgical treatment for coarctation of the aorta. Of these eight children, three developed a significant perioperative hemorrhage from aortic rupture, resulting in one death and one instance of paraparesis related to a period of prolonged hypotension. In two of the other five patients with Turner's syndrome, a decision was made to perform an angioplasty rather than a resection of the coarctation because of apparent friability of the aortic wall. In contrast, only one of the 345 patients without Turner's syndrome died as a result of surgical treatment, and none developed spontaneous perioperative aortic rupture or neurologic deficit. This experience suggests that the operative risk for coarctation of the aorta in this subgroup of patients is considerably greater than that in patients without Turner's syndrome (p < 0.001). Special precautions should include use of rubber-jaw vascular clamps, choice of technique to avoid tension at the anastomotic suture line, and careful control of systemic blood pressure intraoperatively and postoperatively. Indications for surgical treatment of coarctation as well as the type of operative procedure must be individualized cautiously in patients with Turner's syndrome.

Adolescent↗
PubMed1979

Effects of nitroprusside and dopamine on pulmonary arterial vasculature in children after cardiac surgery.

The hemodynamic effects of nitroprusside and dopamine were studied in 28 children early after intracardiac repair. Children were placed in six groups, five according to their anatomic lesion and one made up of those who had postoperative pulmonary artery hypertension, to evaluate the possible differences in response of the pulmonary arterial vasculature to the drugs. Seven children had repair of an atrial septal defect; six, repair of tetralogy of Fallot; four, repair of ventricular septal defect; five, surgery for pulmonary stenosis; one, closure of a left ventricular to right atrial tunnel; and five, postoperative pulmonary artery hypertension. Dopamine was infused at 8 microgram/kg/min, and nitroprusside at 3 microgram/kg/min. With dopamine, the heart rate increased an average of 10% and the cardiac index 11%; both increases were statistically significant. Changes in systemic and pulmonary vascular resistance, however, were not. With nitroprusside, the heart rate increased an average of 9% and the cardiac index 5%, while there was a significant decrease in both systemic (-20%) and pulmonary (-27%) vascular resistance. With the combination of dopamine and nitroprusside, both the cardiac index (+13%) and heart rate (+20%) increased significantly while systemic vascular resistance fell an average of 23% from control, and the pulmonary vascular resistance decreased 21%. Drug response among all five anatomic subgroups tended to be similar. We conclude that an afterload-reducing agent, such as nitroprusside and an inotropic drug such as dopamine, may have potential clinical advantages when used together in children providing heart rate does not become excessive.

Adolescent↗
PubMed1979

Tricuspid valvular incompetence and rupture of the ventricular septum caused by nonpenetrating trauma.

A young adult involved in an automobile accident had tricuspid valvular incompetence and rupture of the ventricular septum owing to blunt trauma. He had a successful repair of the ventricular septal defect and replacement of the tricuspid valve. Tricuspid valvular incompetence owing to nonpenetrating trauma is uncommon. Blunt trauma resulting in rupture of the ventricular septum is rare. Rupture of the membranous portion of the ventricular spetum is extremely rare. This is the first report of a patient having a combination of these lesions.

Adult↗
PubMed1978

Surgery using cardiopulmonary bypass in the elderly.

This study included 89 patients, 70-82 years (mean 72.8 years), who had procedures using cardiopulmonary bypass since 1955. Twenty-six patients had elective aortic valve replacement (AVR), with two hospital deaths. One patient who underwent emergency AVR for bacterial endocarditis died of septic shock. Ten patients had AVR and coronary artery bypass surgery (CABG), with one hospital death (10%). Fourteen patients had mitral valve replacement (MVR), with eight hospital deaths (57%). Two died of left ventricular rupture after leaving the operating room, and the remainder died of low cardiac output. Twenty-five patients had CABG with no early deaths. Seven patients had aneurysms of the thoracic aorta, with two early deaths. Six patients had other procedures with one death, making a total of 16 operative deaths in the 89 patients. Eighty-four of the patients (94%) were New York Heart Association (NYHA) Functional Class III or IV for congestive heart failure and/or angina, preoperatively. Of these, 12 were in extremis immediately before surgery, and six survived. There were 10 late deaths. The actuarial survival rates for one, two and five years for all patients were 69% (40 patients), 47% (20 patients) and 21% (seven patients), respectively. At recent follow-up (mean 20 months) 84% of the hospital survivors were symptomatically improved at least one NYHA Functional Class. We conclude that CABG and/or AVR can be performed in elderly patients with a low hospital mortality and with symptomatic improvement. However, MVR in the elderly carries an unusually high mortality (7.3 times greater than patients less than 70, in our experience), and this risk must be weighed when considering MVR in these patients.

Aged↗
PubMed1978

Staged surgical management of tetralogy of Fallot in infants.

A cohort of 61 consecutive patients 24 months of age of younger had palliative shunts for symptoms of tetralogy of Fallot during a 12-year period. Thirty-six of these patients have been followed through definitive intracardiac repair or to death. For analysis palliative operations were separated into two six-year periods, 1965--1970. During the first period seven of 30 infants operated on died; all 31 infants operated on during the second period survived. The Waterston anastomosis was performed most frequently (67%) during the first period; the Blalock-Taussig anastomosis was performed in 68% of infants during the second period. Of 54 hospital survivors, three died before definitive intracardiac repair. Two of the three interim deaths were related to heart disease. Twenty-six of the remaining 51 patients have had definitive intracardiac repair with two deaths (8%). Twenty-four in this group had intracardiac repair since 1973 with one hospital death (4%). The cumulative mortality for the entire cohort is 25%, but more recent experience (1971--77) indicates a cumulative mortality near 5%. The recent mortality rate for staged management is less than the 14% rate reported by others for primary intracardiac repair of tetralogy of Fallot in 205 infants. We conclude that primary intracardiac repair has important advantages for infants with tetralogy of Fallot who have favorable anatomic features and no other associated cardiac lesions or medical problems. Staged management of tetralogy of Fallot is still recommended for infants with unfavorable anatomy, additional lesions or associated medical problems.

Age Factors↗
PubMed1977

Radical resection for periampullary carcinomas: results in 53 patients.

Radical pancreaticoduodenectomy for periampullary cancer was performed in 53 patients over a 22-year period. All tumors were adenocarcinomas: 35 patients had adenocarcinoma involving the head of the pancreas, nine, the Vater ampulla, seven, the distal common bile duct, and two, the duodenum. There were nine hospital deaths (17%). The postoperative course was classified as uneventful in 33 patients (62%). Thirty of the 39 patients who left the hospital died later, with evidence of recurrent carcinoma. The actuarial survival rate for the 53 patients was 51% +/- 6.9% at one year, 12% +/- 4.6% at five years, and 7% +/- 3.9% at ten years. Patients surviving 3.5 or more years appeared to have a decrease in their cancer mortality. We discuss actuarial survival rates, according to the location of the tumor. This experience suggests that radical pancreaticoduodenectomy id indicated to remove small, localized periampullary carcinomas in patients who are otherwise in good health.

Adenocarcinoma↗
PubMed1977

Triple-valve replacement: an analysis of eight years' experience.

The total experience with combined aortic, mitral, and tricuspid valve replacement in 38 patients during an eight-year period ending in December, 1974, is reviewed. The hospital mortality was 23.7% (9 patients) and was influenced by the preoperative New York Heart Association Functional Class: 18%(5 of 28 patients) in Class III and 40%(4 of 10) in Class IV. Intraoperative myocardial injury was the other important factor affecting hospital mortality. The majority of late deaths were related to cardiac causes. The five-year survival was 53% (20 patients) for the entire group and 62% (17 patients) for the Class III patients. At latest follow-up (mean, 44 months), 22 (76%) of the hospital survivors had improved by at least one functional class. It appears that surgical intervention before patients reach Class IV status should give better early and long-term results. Our current indications for tricuspid valve replacement as opposed to repair are presented.

Adult↗
PubMed1976

Bullet emboli to the pulmonary artery: a report of 2 patients and review of the literature.

Bullet embolization to the pulmonary artery is a rare event. The purpose of this study is to report our experience with 2 patients and to review the 15 patients reported in the literature, with special emphasis on a rather peculiar complication that has occurred in 4 of the 9 patients who underwent bullet embolectomy: dislodgment of the missile during the surgical procedure and migration to the down-side lung, for which a second thoracotomy was required in 3 of those patients. The usual untoward effects of foreign bodies in the vascular system were seen in this series: embolization with thrombosis, sepsis, erosion and hemorrhage, and vascular occlusion with infarction. This review suggests that operative removal of a bullet in the pulmonary artery is necessary. The operation is safe and uncomplicated if precautions are taken to prevent the missile from migrating during manipulation of the lung.

Abdominal Injuries↗
PubMed1976

Indications for and resluts of tricuspid valve replacement.

A review of our experience with tricuspid valve replacement over a 7.5-year period is presented. Isolated disease of the tricuspid valve was encountered infrequently [8 of 87 patients] and was due to a variety of causes. In the remaining cases, the tricuspid disease was associated with rheumatic valvular disease of the mitral and/or aortic valves. The hospital mortality for the entire group of patients was 22%, and the late mortality during a mean follow-up of 32 months was 16%. Operative and late mortality were clearly affected by the severity of myocardial dysfunction present preoperativley. Problems related to the prosthetic valves and to anticoagulant therapy were relatively few. Our present indications for replacement of the tricuspid valve and presented. Earlier operative intervention in patients with tricuspid valvular disease should improve the early and long-term results.

Adolescent↗