Wednesday Morning, May 18, 1966

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

Ballroom

31. Selective Cardiac Vagotomy: Surgical Preparation and Techniques of Verification

T. Cooper*, W. M. Daggett*, G. G. Nugent*, and C. R. Hanlon,

St. Louis, Mo.

Bilateral cervical vagotomy in the dog produces vomiting, dyspnea, and death within five days. In addition to pulmonary and gastroesophageal malfunction, there is also severe tachycardia associated at times with cardiac decompensation. We have devised a procedure to identify a cardiac contribution to this fatal postoperative course, and to provide a chronic experimental preparation in which cardiac function can be studied in the absence of vagal influence. Preganglionic vagal denervation of the heart is performed on each side by two operations a week apart. We have transected those vagal mediastinal branches which produce cardiac deceleration on electrical stimulation. The main thoracic vagal trunks are left intact, as are those branches in which stimulation causes acceleration or no response. After bilateral denervation, tachycardia without sinus arrhythmia persists unaffected by atropine, neosynephrine, or supramaximal electrical stimulation of the cervical vagi. Vomiting is absent. The difference between selective vagal denervation and the total extrinsic denervation of cardiac autotransplantation is exemplified by persistence of response to stellate ganglion stimulation in the vagal denervation animals. The preparation should prove useful in analyzing the topography of the intrathoracic vagus and in the study of vagal effects on cardiac and coronary dynamics.

32. The Electrophysiologic Effects of Respiratory and Metabolic Alkalosis on the Heart

Robert E. Cline*, Andrew G. Wallace*, W. C. Sealy, and

W. Glenn Young, Jr., Durham, N.C.

Experiments were performed on anectinized, awake dogs to define further the effects of acute changes in acid-base balance on the heart. Chronically implanted electrodes were used to measure conduction and excitability in atrium, Purkinje tissue, and ventricle. Respiratory alkalosis was induced by three or five hours of hyperventilation. Metabolic alkalosis was produced by infusions of sodium bicarbonate or Tris. Changes in arterial pH, pCO₂, and serum potassium were monitored. During hyperventilation, conduction in Purkinje tissue was slowed and ventricular activation was prolonged. These changes were related to the fall in serum potassium. Ventricular excitability was frequently increased (average 17%) during hyperventilation. In contrast, during bicarbonate infusion there was little change in intra-ventricular conduction and a decrease in excitability (average 36%). The administration of Tris resulted in an even greater decrease in excitability (average 70%). Studies using buffered Tris (pH 7.5) produced a comparable decrease in excitability, indicating the effects of this agent were not pH dependent. Parallel studies in dogs following cardiac denervation demonstrated that reflex mechanisms did not contribute to the above changes. These experiments demonstrate certain fundamental mechanisms which may contribute to cardiac arrhythmias observed during hyperventilation and the antiarrhythmic properties of certain alkalinizing agents.

33. Controlled Atrial Hypertension: A Method for Supporting Cardiac Output Following Open Heart Surgery

Noel H. Fishman*, John C. Hutchinson*, and Benson B. Roe,

San Francisco, Calif.

Successful management of the critical post-cardiotomy patient depends upon avoidance of the "low-output syndrome." The clinical indices which are usually employed to detect an inadequate circulation do not differentiate between hypovolemia and intrinsic impairment of myocardial function as the cause of a diminished cardiac output state. The mean left atrial pressure (MLAP) was continuously monitored with a small indwelling vinyl catheter for as long as 7 days following aortic and/or mitral valve replacements in 50 patients. MLAP, a direct reflection of left ventricular filling pressure, was found to be a sensitive index of optimal blood volume, and the need for inotropic drug administration. Changes in the central venous pressure paralleled those of the MLAP but the quantitative correlation was inconstant and the response was delayed. The unreliability of arterial pressure as a guide to therapy was confirmed. Elevation of the MLAP to 25 to 30 cm H₂O by transfusion was consistently associated with improvement in skin color, peripheral pulses and urinary output. Pulmonary edema did not occur at these pressures. The inotropic effect of isoproterenol was enhanced by controlled atrial hypertension, demonstrating the importance of high filling pressures in a diseased or non-compliant left ventricle.

34. Ultrastructural Evaluation of Myocardial Preservation During Cardiopulmonary By-Pass: The Mitochondrion

C. A. Kottmeier*, and M. W. Wheat, Jr., Gainesville, Fla.

The mitochondria are the "power plants" that produce the energy necessary for muscle contraction. They are also one of the most sensitive indicators of cell injury. Myocardial samples were taken every 30 minutes, prepared, and viewed in an electron microscope. Controls consisted of dogs with open thoracotomy and heparinized, cardiopulmonary by-pass at normothermia, and the initial samples in each animal prior to by-pass. Experimental animals were subjected to hypothermia to 20 C., normothermic coronary artery perfusipn, anoxic arrest, and myocardial arrest with "slush." Thoracotomy, heparinization, and cardiopulmonary by-pass for two hours produced no significant changes in the mitochondria. Hypothermia, "slush" arrest, and anoxic arrest produced increasingly severe degrees of injury evidenced by fragmentation, lysis, and transformation of mitochondria into large vacuoles and chondriospheres. Since the crests of the mitochondrion contain most of the enzymes involved in the respiratory chain, the dissolution of the inner structure of significant numbers of mitochondria, as seen in anoxic arrest, provides an ultrastructural basis for the poor return of myocardial function following anoxic arrest.

35. Origin of Left Coronary Artery from Pulmonary Artery: Successful Correction in Two Patients Using Dacron and Vein Grafts

Denton A. Cooley, Grady L. Haixman, and Robert D. Bloodwell*,

Houston, Texas

Anomalous origin of the left coronary artery from the pulmonary artery usually causes death during infancy from myocardial ischemia and infarction. Survival depends upon formation of adequate collateral connections between right and left coronary arteries. This may produce a significant left-to-right shunt from the right to the left coronary and thence into the pulmonary artery. Under these circumstances standard treatment has been ligation of the left coronary artery to eliminate the shunt and raise coronary perfusion pressure. Unfortunately this pressure is less than that in the systemic circuit, since there is an interposed collateral bed. Moreover, this operation leaves the patient with a single source of inflow into the coronary system. These disadvantages were recently overcome in 2 children ages 4 and 5 years, by anastomosing the anomalous left coronary artery to the ascending aorta using a Dacron tube graft in one patient and a segment of autogenous saphenous vein in the other. Patency was confirmed by postoperative angiography. We believe these are the first patients to be successfully treated in this manner. This presentation will include physiologic, diagnostic, and technical considerations of this challenging surgical problem.

36. Myocardial Revascularization: Use of Intercostal Artery

Charles Pearce, and Oscar Creech, Jr., New Orleans, La.

The site of implantation of the internal mammary artery for myocardial revascularization is limited by the artery's position and length in relation to the anterolateral portion of the left ventricle. For revascularization of other parts of the myocardium, a technic has been developed with use of an intercostal artery. The fifth rib was resected in 15 dogs, and a pedicle, based posteriorly, was formed of the intercostal muscle and fascia, periosteum of the resected rib, and intercostal nerve, vein, and artery. Anteriorly the artery was dissected free from other tissues for a distance of 3 cm. and was then implanted, freely bleeding, into the left ventricular myocardium. In addition, ameroid constrictors were placed around the left anterior descending and circumflex coronary arteries, or major branches of the arteries were ligated directly. Twelve of the 15 dogs survived three to seven months, whereas five control dogs with only ameroid constrictors on the anterior descending and circumflex arteries died within two to four weeks after operation. Arteriograms four to six months after operation showed proliferation of small arteries from the implanted artery into the myocardium and communication with coronary vessels. The operation has resulted in notable relief in a patient with angina pectoris.

37. Experimental and Clinical Results of Myocardial Revascularization with "Arterialized" Autogenous Vein Graft

Randolph M. Ferlic*, Frank Quattlebaum*, and

C. Walton Lillehei, Minneapolis, Minn.

For patients with advanced occlusive coronary artery disease, a revascularization operation must fulfill two criteria to be effective: 1) bring in new arterialized blood, and 2) distribute this blood immediately to the ischemic areas. Clinical experience with the Vineberg operation has indicated several limitations; viz, small size and limited length of this vessel, frequent involvement by atherosclerotic disease, and arbitrary site of placement. Experience in more than 200 dogs has established the feasibility of utilizing an autogenous vein to shunt blood from the aorta directly into myocardial tunnels by a variety of objective measurements. These dogs were studied by angiography, flowmeter measurements, distribution of injected micro-spheres, vinyl acetate injections, dependency upon shunts induced by coronary ligations, and direct observation at autopsy. Eight patients with angina at rest and advanced disease by arteriography have been operated upon. One patient died 12 hours postoperatively; autopsy indicated a large posterior infarct that had occurred 10 days preoperatiyely (shunt was anterior). One patient succumbed from massive mitral insufficiency secondary to rupture of a papillary muscle and another died from technical problems during the operation. The other five (one with two previous revascularization procedures without relief) have had dramatic improvement in follow-up to 13 months.

38. Flowmeter Studies of Internal Mammary Artery Function After Implantation into the Left Ventricular Myocardium

J. L. Provan*, G. L. Hammond*, and W. Gerald Austen, Boston, Mass.

A sine wave electromagnetic flowmeter was used to study internal mammary artery implant flow in thirty dogs. Pulsatile and mean blood flows were measured before dissection of the artery and immediately after implantation into the myocardium. Gradual anterior myocardial ischemia was produced by the simultaneous application of an ameroid constrictor to the origin of the anterior descending artery. Implant flow was again measured three weeks to eight months after implantation. Flow was determined in the resting state, during anoxia and after the administration of various drugs. Changes in blood pressure and femoral flow were also recorded. Immediately after implantation, 5 ml. of blood per minute entered the myocardium. The pulse wave was markedly altered in that maximal flow in the artery occurred during diastole. After eight months, resting flows of 20 ml. per minute were recorded. Anoxia and drug administration increased implant flow significantly; the increase in flow was not dependent on increased blood pressure and was associated, in all instances, with a decrease in mean systemic arterial flow. These results indicate that the internal mammary artery implant functioned like a coronary artery and after eight months carried an amount of blood equivalent to a normal anterior descending artery.

39. Experimental Tricuspid Valve Replacement: Evaluations of Anticoagulants and Graphite-Benzalkonium-Heparin Coating

Constantine J. Tatooles*, Nina S. Braunwald

Andrew G. Morrow, Bethesda, Md.

The fate of Starr-Edwards valves utilized for tricuspid replacement was determined in 36 calves. Anticoagulants were not given to 10 animals with standard valves, nor to 13 with valves coated with graphite-benzalkonium-heparin (GBH). Thirteen additional calves with standard valves received daily intramuscular warfarin. Twenty-four calves died or were sacrificed within 6 months. All of 7 standard valves revealed thrombus, and 2 were totally occluded. Thrombus was evident on 7 of 9 GBH valves, and 3 were occluded. No thrombus occurred in any anticoagulated calf, but in one fibrous tissue bound the cage to the ventricular wall, preventing descent of the ball. All valves examined after one year were free of thrombus and functioned satisfactorily. The metal rings of GBH valves were not covered by tissue, but fibrous overgrowth of variable degree was evident on standard valves in both control and anticoagulated groups. The study indicates that early thrombosis of Starr-Edwards valves in the tricuspid position may be prevented by warfarin, but not by GBH coating. After 6 months no fatal thrombus formed on any valve, but the significance of the different patterns of tissue growth on coated and uncoated valves remains uncertain.

40. Comparative Study of Prosthetic Heart Valves

Edward A. Smeloff*, David F. Smith*, Trevor B. Davey*,

Boris Kaufman*, Sacramento, Calif., and Frank Gerbode,

San Francisco, Calif.

Comparative study of flow patterns and pressure pulse contours has been made, utilizing the Smeloff-Cutter, Starr-Edwards, Kay-Suzuki, Gott, and Roe valves, comparing them with the homologous human valves in a specially constructed pulse simulator designed so that both mitral and aortic valves can be studied simultaneously. This has been standardized so as to obtain as normal pressure and flow characteristics as is feasible in an artificial system. Flow has been studied utilizing aluminum particles suspended in a solution approximately the viscosity of blood and photographed with high-speed equipment with slit lighting in a three-dimensional chamber. Pressure and flow contours have been made like those found in normal circulation by providing physiologic atrial pressures, a passive diastolic ventricular phase, a simulated aortic root, and an artificial arteriolar system. Pertinent comparisons of the full-orifice ball valve (Smeloff-Cutter), the orifice-seating ball valve (Starr-Edwards), the tri-leaflet valve (Roe), the discoid valve (Kay-Suzuki), and the hinged-leaflet valve (Gott) were made. Discussion of the practical and theoretical advantages and disadvantages of the various valves will be included, especially in regard to the minimizing or elimination of thrombo-embolic tendencies.

41. Autogenous Pericardium in the Mitral Valve. Findings in the Human at 56 Months with Review of Principles of the Leaflet Advancement Operation

Lester R. Sauvage, Stephen J. Wood*, and Knute E. Beroer*,

Seattle, Wash.

Cumulative experience with prosthetic replacement of the mitral valve suggests that, if other means will suffice, they should be considered. We have used the leaflet advancement operation employing autogenous pericardium for contracted insufficient valves that are not heavily calcified. The question as to what happens to the pericardial grafts can now be answered since we have recently examined a 3 x 2 cm. graft which had been implanted for 56 months. The patient was killed in an automobile accident. The graft was moderately thickened, pliable, beautifully healed, and glistening. It was satisfactory in all obvious respects. On the basis of the observations in this patient we suggest that the leaflet advancement operation using autogenous pericardium could, and perhaps should, be used for more patients who would otherwise need a prosthetic valve for effective correction. The principles of the procedure will be reviewed in this light.

42. Canine Mitral Valve Replacement with Preserved Homologous Aortic Valves

Malcolm B. McKenzie*, George Pappas*, J. L. Titus*, and

F. Henry Ellis, Jr., Rochester, Minn.

Experience with four technics of preserving homologous aortic valves for canine mitral valve replacement forms the basis of this study. The methods of preservation used include Hank's solution, B-propriolactone, freeze-dry, and liquid nitrogen. A total of 28 dogs, more or less evenly divided among the various methods, were followed up to two years after insertion. The overall results did not differ significantly among the four groups. There were 20 long-term survivors, of which 8 lived from 6 to 24 months. All animals eventually died, the majority from bacterial endocarditis, dehiscence of the grafted tissues, or fibrocartilaginous stenosis at the annulus region. In most instances, the dehiscence occurred at the annulus or the root of the aortic homograft. The valve leaflets, although often covered with fibrin, were only slightly thickened but pliable. When compared with the results obtained from fresh homologous grafts previously reported, the overall survival was poorer with the preserved grafts. This was due to a higher incidence of mitral incompetence and a slightly higher incidence of bacterial infection. The incidence of fibrocartilaginous mitral stenosis was similar in both groups. Detailed histologic studies of necropsy specimens will be reported.

43. Heterotransplantation of the Human Pulmonic Valve to the Calf Pulmonic Area

Ronald J. Nelson*, Hitoshi Mohri*, David H. Dillard*, and

K. Alvin Merendino, Seattle, Wash.

The remarkable course of homotransplanted aortic leaflets together with the problems of their procurement and failure to fit dilated annuli stimulated investigation of heterotransplantation. Human and calf pulmonary valves were transplanted to the pulmonic area of 22 calves using cardio-pulmonary bypass. Twelve calves survived 48 hours or more. The mortality rate declined from 60 percent in the first ten, to 20 percent in the second ten. Contributing factors will be discussed. Of ten calves with heterografts, two were electively sacrificed, one died early, and six died of severe pulmonary stenosis from 6 to 22 weeks postoperatively with massive thrombus containing gram positive cocci. Evidence that this does not necessarily represent breaks in operative technique but their natural fate in this model will be presented. Fragmented but recognizable leaflet was seen in the animal surviving 22 weeks. The gross and microscopic pathology will be presented. One animal is still alive with a pulmonary systolic murmur at six months. The two homo-transplants died at five weeks with similar stenosis. A possible explanation will be given and a critique presented regarding the use of the calf as an experimental animal in such work.

*By Invitation