TUESDAY MORNING, APRIL 23, 1968

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

Ballrooms 1 and 2

15. Experimental Papillary Muscle Infarction

George E. Miller,* Keith E. Gohn,* William J. Kerth,

Arthur Selzer,* and Frank Gerbode, San Francisco, Calif.

Papillary muscle contraction occurring synchronously with that of the left ventricle has been ascribed important in maintaining mitral valve competency. Loss of this function resulting from myocardial infarction has been considered a cause of acquired mitral insufficiency. This insufficiency is explained by two mechanisms: - 1. That occurring early after infarction in which the papillary muscle loses its ability to contract with resultant prolapse of the leaflet into the atrium. 2. That occurring late due to contraction and shortening of the fibrotic papillary muscle pulling the leaflet into the ventricle. In this study, the papillary muscles of dogs, six anterior and six posterior were selectively infarcted. The animals were studied at varying periods from immediately postoperative to 20 weeks post infarction, by auscultation, left atrial catheterization and cineangiograms of the left ventricle. The completeness of infarction was verified by histological section. These studies indicate that selective papillary muscle infarction does not result in mitral insufficiency.

16. Experimental Coronary Artery Surgery: Long Term Follow-up of Bypass Venous Autografts, Longitudinal Arteriotomies and End-to-End Anastomoses

Mark Dedomenico,* Abbas A. Sameh,* Knute E. Berger,*

Stephen J. Wood,* and Lester R. Sauvage, Seattle, Wash.

In 1963 we reported the early results (6 months) of direct coronary artery procedures performed upon the branches of the left coronary artery of 69 dogs. This report detailed the results observed in 11 of these animals kept for long term study and followed up to 5 years. This series consists of 5 end-to-end bypass aorto-coronary venous autografts, 3 longitudinal arteriotomies and 3 end-to-end bypass aorto-coronary venous autografts, 3 longitudinal arteriotomies and 3 end-to-end anastomoses. This long-term study has consisted of serial arteriograms and careful sacrifice studies with particular attention to healing characteristics. In brief, these studies show: 1) Persistent patency of all grafts or anastomoses. 2) Absence of stricture formation at the anastomotic site. 3) Progressive dilatation of vein grafts to true aneurysmal proportions. We believe that these studies have clinical significance to the expanding field of direct coronary artery surgery. The arteriograms, gross specimens and histologic studies will be demonstrated by slides.

17. Evaluation of Cardiac Revascularization Procedures Using Tissue Lactic Acid Determinations in Induced Myocardial Infarctions

James D. Whiffen,* Madison, Wis., and Vincent L. Gott,

Baltimore, Md.

At the present time, there is not a completely satisfactory method for the evaluation of myocardial revascularization procedures. A method has been developed by the coauthors which provides an excellent indication of the degree of new collateral channels. In this test, a small myocardial biopsy is taken in the distribution of the anterior descending artery and then this artery is occluded. After two minutes, a second biopsy is taken in the same area. The occlusion is released and then the same technique is repeated in the area supplied by the circumflex artery. The tissue is analyzed for the two-minute rise in lactic acid, thus providing an indication of hypoxia in the myocardium and direct reflection of new coronary collateral development. Fifty-five animals were studied. The average two-minute lactic acid rise in ten control dogs was 65 ± 3.6 mg.% and 56 ± 3.3 mg.%following occlusion of the anterior descending and circumflex arteries respectively. Evaluation of Vineberg's implant showed significant tissue perfusion in 75% of the animals. Other experimental operations were evaluated and the most significant collateral development was seen after chronic left pulmonary artery ligation. This "lactic acid rise test" appears to be a simple and accurate way of evaluating myocardial revascularization procedures.

18. Comparative Flow Studies of Myocardial Revascularization Grafts

Akio Wakabayashi,* and John E. Connolly, Los Angeles, Calif.

Analyses of myocardial revascularization grafts were made on long-term animals including an internal mammary graft with (No. 1) or without (No. 2 and 3) in situ communicating intercostal arteries, a modified Vineberg graft with ascending aorta origin (No. 4), autologous arterial (No. 5 and 6) or reversed saphenous vein (No. 7, 8, and 9) bypass grafts implanted between ascending aorta and coronary artery. Four normal dogs were controls. Indirect revascularization grafts (No. 1-4) did not show any long term increase in mean flow and failed to respond to levarterenol, isoproterenpl, and nitroglycerin, although the implant developed collaterals with the coronary arterial system and flow pattern changed from to-and-fro to coronary artery type. Contrarywise, all bypass grafts (No. 5-9) had high mean flows which were markedly increased by drugs like the normal coronary artery. Arterial grafts showed negative flow corresponding with ejection phase explained by Phot's principla. Venous grafts did not show this pattern, probably because valves were blocking retrograde flow. These studies indicate that an ascending aorta-coronary artery bypass graft can assume the function of the coronary artery, quantitatively and qualitatively, but an indirect revascularization graft can carry only a small amount of blood and cannot respond physiologically, even after it develops direct communicating collaterals.

19. The Use of Fluorescein for Determining the Site of Internal Mammary Artery Implantation

Ciro Armellini,* Walter L. Mersheimer,* and Sheldon O. Burman,*

New York, N.Y.

Sponsored by George J. Magovern

Selection of the proper site for implantation is said to be important in determining the success of the Vineberg revascularization procedure. However, the recognition of poorly vascularized or marginally ischemic areas of myocardium is often difficult at the operating table especially when these areas appear to be at variance with the patient's electrocardiogram or coronary arteriogram. Twelve dogs underwent coronary artery ligation, the left anterior descending was ligated in four, the left posterior circumflex in three, the right coronary in three, and the right coronary and left anterior descending in two. Fluorescein 5 cc. was injected into a peripheral vein and under ultraviolet light the demarcation between vascular and avascular myocardium was clearly seen and photographed. One or two internal mammary arteries were implanted into the avascular areas and the chest closed. Thoracotomy was repeated after six months and fluorescein again given peripherally. Fluorescence of the previously avascular areas of myocardium occurred in all except two animals whose implants were thrombosed. The technique is now routinely employed to determine the site for implantation in all patients undergoing myocardial revascularization procedures. Photographs and a movie will be shown which clearly document these phenomena.

20. The Effects of Epicardiectomy on Ventricular Function

R. L. Reis,* L. P. Enright,* H. Hannah, III,* and A. G. Morrow,

Bethesda, Md.

The effects of epicardiectomy on the function of the ischemic ventricle were determined. Left ventricular function curves were inscribed at fixed heart rate and constant aortic pressure in 18 dogs. In nine animals (Group I) a control curve (a) was inscribed. The left anterior descending coronary artery (LAD) was occluded and a repeat curve performed (b). The occluding clamp was removed, epicardiectomy performed and 30 minutes thereafter the LAD reoccluded and a third curve inscribed (c). LAD flow was restored and a fourth curve (d) performed. In nine dogs (Group II) curves were inscribed in an identical fashion but epicardiectomy was not performed. In four group I dogs and three group II dogs curve (b) could not be inscribed because of ventricular fibrillation. In the four group I animals curve (c) could be inscribed after epicardiectomy. Ventricular fibrillation prevented the inscription of curve (c) in the three group II dogs. In the remaining animals, curve (b) demonstrated severe depression. In group I, curve (c) showed moderate improvement in four dogs and slight improvement in one dog. In group II animals, curve (b) and (c) were identical. In all animals curve (d) and (a) were similar, dp/dt measurements corroborated these findings. These data indicate that epicardiectomy significantly improves the function of the acutely ischemic left ventricle.

21. Evaluation of an Everting Esophageal Anastomosis in the Puppy

Conrad W. Wesselheoft, Jr.,* Donald H. Glew, Jr.,*

Judson G. Randolph, and Brian Blades, Washington, D.C.

In an attempt to improve the anastomotic problems of leak and stricture in the treatment of esophageal atresia, many variations in suture technique have been proposed. Recent reports describing satisfactory healing and improved lumen size in everting anastomoses of the intestine prompted our evaluation of this technique in the thoracic esophagus. Following segmental resection of the esophagus, 1) a standard two layer end-to-end, 2) the Haight anastomosis, and 3) a single layer everting anastomosis were evaluated in three groups of ten, using eight week old puppies. All surviving animals were studied at three weeks, six weeks and three months after surgery by esophagoscopy and barium esophagram. At the end of four months, all remaining animals were sacrificed. The three methods were evaluated for elapsed operating time in constructing the repair, defects in healing with the occurrence of anastomotic leak, the presence of stricture, growth of the suture line, and histology of the healed anastomosis. The results of this experience demonstrate that the everting anastomosis is simpler to perform and that operating time is shortened. Mucosal healing is quite satisfactory, there is no increased incidence of anastomotic leakage, and stricture is definitely reduced. The results of this study have been translated into clinical usage in six patients with esophageal atresia and tracheo-esophageal fistula.

22. Esophageal Function After Successful Repair of Esophageal Atresia and Tracheoesophageal Fistula: A Manometric and Cinefluorographic Study

John N. Buroess,* Harley G. Carlson,* Charles F. Code,* and

F. Henry Ellis Jr., Rochester, Minn.

Esophageal dysfunction has been reported in patients surviving repair of esophageal atresia and tracheoesophageal fistula. The nature of this dysfunction has not been clearly defined, though some have interpreted it as congenital esophageal achalasia. In order to more clearly define the condition, 9 patients were studied by esophageal motility and cinefluorography 14 to 19 years after successful repair in infancy of this congenital abnormality. None of these patients were symptomatic when studied. All showed abnormal esophageal motility characterized by absent or feeble simultaneous postdeglutitive contractions in the body of the esophagus beginning above the anastomotic site and extending to a variable level distally in the lower esophagus. Normal peristalsis returned at this level, and there was normal sequential relaxation and contraction of the inferior esophageal sphincter in which resting pressures were normal in length and amplitude. It is postulated that the abnormal esophageal motility noted in these patients was the result of injury to the esophageal branches of the vagus nerve at the time of operation. The integrity of the vagal nerve trunks was confirmed by positive Hollander tests performed in 8 of the 9 patients, and there was no evidence of esophageal achalasia.

23. Prosthetic Replacement of Esophageal Segments

Joseph N. Laguerre,* Henry Schoenfeld,* William S. Calem,*

Francis E. Gould,* and Bernard S. Levowitz, Brooklyn, N.Y.

A non-toxic, non-reactive hydrophilic polymer, hydron, has been developed and investigated in dogs for use as an esophageal substitute. Through a right thoracotomy, molded pliable, non-collapsible tubes up to 10 cm. in length and sleeved by teflon felt were used to replace segments of the mid thoracic esophagus. Postoperatively the animals were maintained on blended liquid feedings and weighed weekly. There are presently 6 long term survivors ranging from 1½to 5 months, all of which have exceeded or maintained their preoperative weight. Interval esophagoscopy and barium esophagrams have demonstrated patent hydron conduits without proximal dilatation. Among 3 postoperative deaths one resulted at 1½ months from barium aspiration during an x-ray study and two occurred at 1 and 3 weeks because of leakage at the distal anastomosis and empyema. After two months one animal regurgitated the prosthesis and succumbed 3 weeks later with complete esophageal stenosis. At postmortem examinations the inner surfaces of the clear plastic tubes have remained free of epithelial coverage. There has been minimal fibrous ingrowth of surrounding tissues into the teflon felt. To promote more rapid and secure tissue adherence esophageal hydron cylinders sleeved with Ivalon and velour fabrics are currently being studied and the results will be reported.

24. A Technique for the Use of Autologous Fresh Blood Following Open-Heart Surgery

Robert L. Hardesty,* William Bayer,* and Henry T. Bahnson,

Pittsburgh, Pa.

The present investigation concerns a technique in which fresh autologous blood is utilized as a source of platelets, factor V and factor VIII following cardiopulmonary bypass. As bypass is initiated twenty-five percent of the patient's estimated blood volume is withdrawn from the venous line into a plastic container, and simultaneously an equivalent volume is delivered from the reservoir to the patient via the arterial line. After bypass, this procedure is reversed, and the patient receives a transfusion of his own fresh blood kept at room temperature. Evaluation of this technique is favorable as judged by platelet counts and platelet adhesiveness. After withdrawal into the plastic storage container, platelet adhesiveness was normal and platelet count was fifty-one percent of the patient's circulating platelets pre-bypass. Storage during the operative procedure altered neither platelet count nor adhesiveness. Re-infusion of the autologous fresh blood at the con-operative blood loss for these patients was less than that encountered in a random series of patients undergoing extracorporeal circulation prior to utilization of this technique.

25. Perfusion-Induced Myocardial Injury

Euoene H. Blackstone,* Richard E. Evans,* Friedrich A. O. Eckner,*

Allan Drake,* and Peter V. Moulder, Chicago, Ill.

Preliminary to the development of a disposable coronary perfusate for cardiopulmonary bypass is a knowledge of potential perfusion induced myocardial injury. Arrest, arrest with distension, and graded hypoxic perfusion experiments were performed and resulting injury assessed. Groups: 12 experiments: Graded hypoxic blood perfusion (closed circuit heart preparation), constant flow rate, 37°C. 10 experiments: Oxygenated low molecular weight dextran, dual perfusion (heart, body), 28°C and 37°C. 5 experiments: Coronary circulatory arrest with induced distention, 30-45 minutes at 30°C and 37°C. Methods: Serial full thickness myocardial biopsies (frozen-dried) for histology and histochemical glycogen and enzyme studies; cross-coronary bed lactate, pyruvate, glucose, and oxygen extraction; acid-base balance; and hemodynamics. Compartmental water-electrolyte concentrations were studied on the right and left myocardium. Abnormalities noted: Instances of generalized glycogen depletion and/or patchy loss; a reversal to lactate production when O₂ availability dropped below 5-8 vol. O₂/minute delivery; a rapid (less than 10 minutes) development of edema, hemorrhage, and imbalance of intracellular myocardial cation concentrations (especially magnesium) with severe oxygen depletion. When compared to previously reported arrest alone experiments, these studies suggest that an inadequate coronary perfusate is worse than arrest, and indeed may lead rapidly to irreversible myocardial injury.

26. The Effect of Profound Hypothermia on Preservation of Cerebral ATP Content During Circulatory Arrest

Richard S. Kramer,* Aaron P. Sanders,* Alan M. Lesage,*

Barnes Woodhall,* and W. C. Sealy, Durham, N.C.

Development of an improved method for instantaneous freezing (-196°C) of sequential cerebral biopsies permits the accurate determination of ATP (adenosine triphosphate) disappearance during complete circulatory arrest and recovery. Control cerebral ATP concentrations in biopsies from 30 normothermic dogs equalled 2.32 ± .17 mcM/g (S.D.). Simultaneous aortic and vena caval occlusion, for periods of 4, 6, or 8 minutes, resulted in a 50% decrease of cerebral ATP within 3.78 minutes. Electroencephalographic silence occurred at 20.9 ± 3.1 seconds, coincident with the loss of < 8% of control ATP content. Reappearance of brain ATP after resumption of flow correlated inversely with the duration of circulatory arrest. Eleven dogs were cooled to 5-11°C (esophageal) using high-flow extra-corporeal perfusion for 50 minutes with attendant reduction of cerebral ATP to 88.7 ± 7.4% of normothermic control levels. EEG silence occurred at 16.8 ± 3.50° (esophageal), coincident with the loss of <7% of control ATP concentrations. Circulatory arrest resulted in a 50% reduction in cerebral ATP after 13.3 minutes. Recovery of ATP with re-warming was observed after 30 and 60, but not 90, minutes of hypothermic arrest. EEG recovery was associated with return of ATP concentrations to 89% of normothermic control levels. Profound hypothermia results in a 4- to 5- fold increase in survival of cerebral ATP during circulatory arrest.

27. A Non-Polarizing Electrode for Endocardial Stimulation of the Heart

V. Parsonnet,* L. Gilbert,* G. Lewin,* G. Myers,*

and I. R. Zucker,* Newark, N.J.

Sponsored by Irving A. Sarot

A new electrode was developed which has negligible polarization, is biologically non-reactive, and permits pacing of the heart with one-twentieth of the power required with ordinary metal electrodes. When the heart is stimulated with standard metal electrodes, energy is wasted in polarization at the electrode tip. Epicardial, myocardial and endocardial electrodes were designed. The endocardial form of the electrode consists of a plastic dielectric cylinder with a hole at the end of area 1.8 mm containing a metal cylinder whose area is 3 cm. The plastic cylinder is the entire tip of a standard cardiac catheter electrode, is filled with saline, and the hole is placed in contact with the endocardium. All of the current leaving the metal passes through the small hole to the tissue, thus providing high current density at the tissue but low current density at the metal. The device thus acts as a current-density transformer, or a "differential-current-density" (DGD) electrode. The electrode has been used successfully in humans for three months, with chronic stimulus thresholds of less than one microjoule. These electrodes have been consistently superior to standard metal electrodes in animals and man, and are suitable for long-term implantation.

*By Invitation