WEDNESDAY MORNING, APRIL 19, 1967

8:30 A.M. Scientific Session: THORACIC SURGERY FORUM Imperial Ballroom

31. Fetal Cardiovascular Surgery: Experimental Pulmonary Artery Atresia and Its Repair in the Fetal Lamb

S. Z. Turkey,* and J. H. Kennedy, Cleveland, Ohio.

Pulmonary artery atresia with intact ventricular septum was produced in a series of controlled chronic experiments in fetal lambs. Techniques of fetal surgery were modified for application to the intrathoracic and intra-pericardial regions. Following laparotomy, hysterotomies were made in anesthetized ewes and fetuses delivered, preserving the placental circulation. Chronic survivals were achieved routinely utilizing micrpsurgical techniques, precise replacement of fetal blood loss by transfusion, and preservation of the integrity of the amniotic cavity postoperatively. A median sternotpmy and pericardiotomy were made in the 60 day fetal lamb (normal gestation is 143 days). The intrapericardial, preductile portion of die main pulmonary artery was dissected and ligated. During surgery ventricular and pulmonary artery pressures as well as fetal and maternal blood pH, pO₂, pW₂ and hematocrit were monitored. The imcompatibility of the same lesion in humans with long survival and the high mortality of bypass procedures in early infancy lead to investigation of repair of this experimental lesion during fetal life, with the benefit of the "extra corporeal" placental "lung". Gross and microscopic histologic study were made of the effects of this lesion on development of the right heart and pulmonary vasculature.

32. Acute and Chronic Hemodynamic Effects of Ligation of the Fetal Ductus Arteriosus

J. Alex Haller, Jr., Bradley M. Rodoers,* and

William W. Morgan,* Baltimore, Md.

Acute and chronic hemodynamic effects of ligation of the fetal ductus arteriosus have not been investigated. Occlusion of the ductus arteriosus was performed upon 17 dog fetuses; 7 were maintained as chronic intra-uterine experiments. Pulmonary artery pressure, left atrial pressure, and electrocardiographic changes were recorded before, during and after occlusion. The ductus was then permanently ligated in 7 fetuses, and their transuterine electrocardiograms were monitored for the following 5 days. Two of the 7 fetuses survived 3 and 5 days respectively. In each fetus there was an immediate rise in diastolic, systolic, and mean pulmonary artery and left atrial pressures during ductal occlusion and rapid return to normal pressures with release of the ductus. Significant alterations in the electrocardiograms did not occur. Preliminary studies on changes in pulmonary blood flow before and after fetal ligation will be presented as well as cinefluoroscopic studies of the alterations which occurred in blood flow through the heart and lungs. No histolpgical evidence of pulmonary congestion or of pulmonary vascular abnormality was noted. The technique of intra-uterine fetal ductus ligation will be presented.

33. Evaluation of Left Heart Bypass in a Standardized Experimental Situation of Acute Heart Failure

Michael L. Small,* London, England.

Sponsored by Frank Gerbodb

Despite great interest in the development, and now the clinical use, of mechanical support of circulation (either extracorporeal or with an implanted "artificial heart") after acute myocardial infarction, the value of the procedure remains in question. Poor survival after severe myocardial infarction occurs despite treatment with left heart bypass (LHBP) and may be due to two factors of previously unreported significance. These are: (1) site of perfusion, and (2) potassium requirement in LHBP after myocardial infarction. Thirty-four dogs were subjected to standardized circumflex coronary artery occlusion. Thirty-three percent of untreated animals survived. No dogs survived when treated with LHBP if perfusion was via the femoral artery. Eighty-three percent of dogs survived when treated with LHBP if perfused via the carotid artery and given supplementary potassium during the procedure. In addition to perfusion site and potassium requirement, several other factors, considered to be of critical importance in the performance of LHBP after myocardial infarction, are examined. These are: (1) type and volume of fluid requirement, (2) optimal percentage of bypass, (3) level to which left atrial pressure may safely be allowed to fall, and (4) optimal timing and duration of the procedure.

34. Acute Circulatory Support by Mechanical Ventricular Assistance Following Myocardial Infarction

David B. Skinner,* George L. Anstadt,* and Thomas F. Camp, Jr.,*

Brooks Air Force Base, Texas.

Sponsored by Richard H. Hood, Jr.

Since many deaths from myocardial infarction occur within hours, acute mechanical support of circulation might permit increased survival following infarction and more satisfactory initiation of long-term therapy. A pump has been developed to provide direct mechanical assistance to the ventricles without requiring circulation of blood outside the intact cardiovascular system. This simple, reliable device can be applied to the heart as quickly as open cardiac massage can be instituted. No cannulations are necessary. During induced ventricular fibrillation in dogs, cardiac output, blood pressure, regional blood flow to vital organs, coronary artery flow, and arterial pH were well maintained by this method. Experimentally in dogs, the mortality of left circumflex coronary artery division was reduced from 75% when standard supportive treatment was given to 35% by electively inducing ventricular fibrillation after coronary interruption, and supporting the circulation by mechanical ventricular assistance for six hours. Ventricular fibrillation was reversed without difficulty. The comparative extent of myocardial infarction and collateral coronary circulation was evaluated by coronary angiography, serum enzyme measurements, electrocardiograms, and autopsy studies. Problems encountered and clinical applications of this method will also be presented.

35. An Implantable Left Ventricular-Aortic Assist Device

R. M. Filler,* W. F. Bernhard, T. Robinson,* M. Bankole,*

and C. G. lafaroe,* Boston, Mass.

A new method of assisted circulation is under investigation employing an implantable, double valved pump directly interposed between die left ventricular apex and descending aorta. The device accepts blood from the biologic ventricle during systole, and ejects it into the aorta in diastole. Outflow from the left ventricle to the pump is provided by a short, thin-walled, silastic covered tube (1.0 centimeters in diameter) inserted through a stab wound in the apical myocardium. Placement of the tube is such that it passes through the endocardium, but does not project into the body of the ventricle. Chronic experiments, performed in dogs and miniature swine, indicate firm myocardial fixation of the outflow tube without any interference in left ventricular function. The distal pump connection consists of a segment of dacron graft sutured to the side of the descending aorta. Hemodynamic and metabolic studies demonstrate an 85% average reduction in left ventricular peak pressure along with maintenance of normal systemic pressure and blood flow. Myocardial energy requirements were also markedly reduced. The left ventricular-aortic assist device utilized in this investigation proved to be superior to other implantable, in-series and parallel flow pumps studied.

36. Experimental Allotransplantation of the Lung

David A. Bluhenstogk, Oscar V. Grosjean,* and

Henri P. Otte,* Cooperstown, New York.

Prolonged survival and function of allotransplants of the lung have been obtained in 8 dogs using a variety of treatment programs. Rejection occurred in 2 to 4 years in 5 animals. Three animals are living with a functioning lung transplant as tested by differential bronchospirometry 2, 3 and 5 years after transplantation. They retain one autologous lung. No drug or other therapy has been given for the past year. The methods used to suppress rejection and the implication of the prolonged presence of a living allograft upon the donor-recipient relationship will be discussed.

37. Regression of Intrinsic Nerves and Other Sequellae with Lung Reimplantation

S. L. Nioro, E. Hamouda,* J. Rams,* E. F. Hirsch,* and

W. E. Adams, Chicago, Ill.

Dogs maintained on replanted lung tissues have been reported to have markedly reduced oxygen uptake, reduced pulmonary ventilation, pulmonary hypertension and normal respiratory cycles. The nervous tissues at that time were not examined. Recently our detailed studies have confirmed an extensive autonomic innervation of the lungs, apparently with preponderance of the vagal component, and largely afferent. Sensory end-organs are distributed extensively in the respiratory passages as thick terminal fibers and their branches; rounded encapsulated or free glomerular structures; and curved segments composed of thick sinuous argyrophilic fibers. Reimplantation of a lung or a lobe divides the nerves at the hilum. Regression of the intrinsic afferent and efferent axons and their terminals occurs. These changes are progressive and are associated with an indurative pneumonia and other sequellae. The hilar nerves 5 ½ years after reimplantation had some evidence of remyelinization, but without restoration of the peripheral structures. The results observed in twenty dogs with these and other nerve ablations will be presented and discussed.

38. Esophageal Motility Dysfunction After Ischemia of Ganglion Cells of Lower Esophagus and Cardia of the Dog

Richard J. Earlam,* and F. Henry Ellis, Jr., Rochester, Minn.

Although the cause of esophageal achalasia is unknown, decreased number or absence of ganglion cells in Auerbach's plexus is a common finding in the disease. In an effort to reproduce this disease experimentally, selective destruction of these nerve cells by a 4-hour period of ischemia was attempted in 14 dogs by perfusing an intact but isolated segment of the lower esophagus and cardia with Tyrode's solution. The results of this procedure were observed during the next 9 months by esophagoscopy, cinefluoroscopy, esophageal motility studies, and histologic studies of postmortem specimens with special staining techniques. Esophagoscopy excluded the presence of a stricture. Cinefluoroscopy demonstrated esophageal dilatation and weak, incoordinated contractions in the lower esophagus. Esophageal motility studies disclosed a variable pattern including decreased resting sphincteric pressure and increased pressures in the body of the esophagus, which returned toward normal values. The swallowing patterns included premature simultaneous contractions in the body of the esophagus, absence of relaxation at the sphincter, and premature sphincteric contractions. Histologic studies demonstrated decreased numbers of ganglion cells and changes in their morphology.

39. Experimental Study of a New Operation for the Treatment of Reflux Esophagitis

Nicholas J. Demos,* and Joseph J. Timmes, Jersey City, N. J.

Surgical technics for correction of reflux esophagitis associated with a sliding hiatal hernia are established. Considerably more difficult is the surgical correction or prevention of reflux esophagitis associated with wide diaphragmatic, especially lateral, defects, or with congenitally short esophagus, recurrent sliding hernias, or reflux caused by esophagogastrostomy. An operation has been devised which cures reflux esophagitis through the use of a viable intercostal muscle pedicle containing intact the corresponding nerve and vessels. Reflux was produced in 45 dogs by two methods: (1) myomectomy of the lower esophagogastric area, and (2) esophagogastrostomy. The reflux and the consequent esophagitis were verified by fluoroscopy, esophagoscopy, cinefiberoscopy and histologic examination. At a second operation, the reflux was abolished by the intercostal pedicle method. The consistent absence of reflux and esophagitis was verified postoperatively using the above methods for over 18 months. The advantages of the new procedure are: (1) ease of performance at any level in the chest, (2) contraction of the pedicle simultaneously with the diaphragm, (3) easily available and bilaterally present pedicles, (4) a living functional sphincter whose tightness may be adjusted at will, (5) usefulness in any type of reflux and particularly in the difficult and recurrent cases, and (6) interposition of intestinal segments is avoided.

40. Mechanical Augmentation of Coronary Circulation in the Ischemic Heart, Angiographic and Hemodynamic Correlation with Prolonged Survival

Jacob Rosensweig,* and Shekhar Chatterjee,* Montreal, Quebec.

Sponsored by Edouard D. Gagnon

Experiments were carried out to determine the functional capacity of mechanically induced collateral circulation in dogs with proximal stenosis of the anterior descending and circumflex arteries. Earlier studies indicated prolonged survival of 80% of treated animals. The SIMAS pump was used for diastolic augmentation for one hour, fourteen days after placement of constrictors. Twelve dogs were operated upon. Coronary blood flow was monitored by implanted flow probes. The animals were observed for one month, then sacrificed. Flow in the anterior descending artery fell from 50 c.c. per minute to 25 by the seventh day, with little change thereafter. During diastolic augmentation, the flow rose rapidly to 65. After discontinuation of pumping, it dropped gradually over several days, then maintained at 45 c.c. per minute. Circumflex artery flow fell from 90 to 45, rose to 100 during diastolic augmentation, then settled at 80 c.c. per minute. At autopsy, both arteries were completely occluded proximally, but prominent intercoronary communicating vessels were demonstrated angiographically arising from either the right coronary or the septal artery. The findings suggest that prolongation of survival following diastolic augmentation results from opening of potential intercoronary channels which become functional, perfuse the occluded coronary artery and restore near normal blood flow.

41. Direct Coronary Artery Surgery Employing Retrograde Coronary Sinus Perfusion

Allen L. Davies,* Graeme L. Hammond,* and W. Gerald Austen,

Boston, Mass.

Prerequisites for successful coronary artery surgery include a dry operative field and a method of maintaining myocardial viability for the time periods necessary to perform endarterectomy and patch graft or direct anastomoses. A method of retrograde perfusion of the left coronary artery via the coronary sinus has been investigated and appears to fulfill these requirements. Twenty-three dogs underwent total cardiopulmonary bypass and one hour of left coronary artery occlusion while oxygenated blood was perfused retrogradely via the coronary sinus. Perfusion pressure if kept below 60 mm Hg. did not produce venule or capillary damage and permitted flows up to 40 cc/min. Blood oxygen determinations during retrograde perfusion demonstrated oxygen uptake by the left ventricle. EKG changes of ischemia during perfusion reverted to near normal post-operatively. Comparison of preoperative with postoperative left ventricular function curves demonstrated only minimal depression of left ventricular reserve. Seventeen additional dogs underwent either direct left coronary artery to left subclavian artery anastomosis or left coronary artery patch graft utilizing this method. Postoperative left ventricular function curves demonstrated only minimal depression. Postoperative EKG showed minor changes. This technique and its clinical applications will be discussed.

42. Local Coronary A-V Blood Gas, Carbohydrate, and Enzyme Gradients Following Acute Coronary Occlusion Before and After Selective Elimination of Preliminary Indirect Myo-cardial Revascularization

Hilary H. Timmis,* and Patrick H. Lehan,* Jackson, Miss.

Sponsored by James D. Hardy

Although indirect myocardial revascularization procedures have been evaluated extensively by survival studies, there is little information concerning the metabolic protection afforded the experimental animal following acute coronary occlusion. Ten adult mongrel dogs were subjected to internal mammary artery implantation, application of a pedicle graft of pericardial fat and simultaneous ligation of a tributary of the longitudinal descending artery in the region of the implant. Following angiographic demonstration of arborization from the implant, thoracotomy was repeated for sampling of blood from the great cardiac vein and the left coronary artery. Coronary arterial-venous gradients of O₂ saturation, pCO₂, bicarbonate, glucose, lactate, pyruvate, lactic dehydrogenase and glutamic oxalacetic transaminase were measured (1) before and after ligation of the anterior longitudinal descending artery, (2) following occlusion of the arterial implant, (3) following division of all peripheral connections of the pericardial fat pad, (4) following removal of the pericardial fat pad and (5) before and after occlusion of the anterior longitudinal descending artery in animals not protected by myocardial revascularization. The results of these determinations and an appraisal of the cumulative and selective effect of techniques of myocardial revascularization listed above will be presented.

43. Relief of Posterior Myocardial Ischemia by Splenic Artery Implantation

Robert J. Gardner,* Benjamin L. Plybon,* David D. Glass,*

and Herbert E. Warden, Morgantown, W. Va.

The internal mammary artery when implanted intramyocardially has been found capable of increasing blood flow to the adjacent heart muscle. Prolonged patency and the development of numerous anastomoses between the implanted vessel and the coronary system have been demonstrated experimentally and clinically such implants have benefited selected patients with myocardial ischemia. The internal mammary artery has been employed to revascularize the antero-lateral aspect of the left ventricular myocardium. This report concerns the experimental development and evaluation of the splenic artery as a source of blood for revascularization of the posterior myocardium. Either the isolated splenic artery or a pedicle consisting of the splenic artery and vein were implanted in the diaphragmatic myocardium in more than fifty dogs. The effectiveness of the implant was assessed in long term survivors by in vivo arteriograms and flow rate determinations. Further evidence of patency and splenic coronary anastomoses was obtained by additional arteriograms, histologic examination, and corrosion cast demonstrations on material obtained at autopsy. Patency rates ranged from 75-90% depending in part on the technique of implantation. In vivo flow rates ranged from 15-65 ml per minute. The factors influencing the results will be emphasized and discussed in detail.

*By invitation