Saturday Afternoon, May 4, 1957

2:00 P.M. Scientific Session: REGULAR PROGRAM-Grand Ballroom.

7. Rigid Plastic Prostheses in Vascular Surgery.

F. X. Byron, Josh Fields (by invitation), Augustus Foster (by invitation)

and Richard Hood (by invitation), Beverly Hills, Calif.

Our interest in the use of rigid plastic prostheses in vascular reconstruction was stimulated by Hufnagel's demonstration that such prostheses can be tolerated for a period of years and his multiple point method of fixation has made their use practical, investigating these rigid plastic tubes we have found numerous situations in which they are applicable. They permit restoration of flow within a very short time minimizing the period of cross-clamping. When used as shunts continuity may be restored rapidly permitting leisurely anastomosis, eliminating multiple time consuming sutured shunts. These techniques, together with their several modifications, will be presented and a new method of treating dissecting aneurysms will be demonstrated. Clinical cases showing the application of these techniques will be presented, including a case of reconstruction of the aortic arch. A short motion picture will demonstrate the versatility and rapidity with which these prostheses may be employed.

8. Diagnostic and Physiologic Measurements Using Left Heart Catheterization.

W. S. Blakemore (by invitation), T. G. Schnabel (by invitation)

P. T. Kuo (by invitation) and H. B. Conn (by invitation), Philadelphia, Pa.

The original technique of left heart catheterization of Bjork, Blakemore, and Malmstrom, has been modified to permit: 1. simultaneous pressure readings from the left atrium, ventricle, and ascending aorta; 2. the estimation of cardiac output determination of central mixing volumes, and quantitative estimates of mitral re-gurgitation by the use of radioactive potassium dilution curves; and 3- correlation of phonocardiographic and electrocardiographic recordings with the changing intra-cardiac pressures. This preoperative study permits: 1. quantification of the degree of mitral and aortic stenosis and mitral insufficiency; 2. calculation of the left ventricular work load with instantaneous and peak ventricular ejection rates, and 3- interpretation of the mechanism of production of the changing quality of the first heart sound, the opening snap, and gallop sounds in patients with mitral valvular disease. The data have been supplemented by animal studies and mtracardiac measurements at the time of operation for which especially designed explosion-proof equipment has been built, including a new stable sensitive manometer which can measure the differential pressure across the valve. Criteria for selecting patients for preoperative study have been established and during more than two years of its use the test has been found to be a valuable diagnostic aid in forty seriously ill patients with atypical or multivalvular rheumatic lesions. The complications are few but may be fatal and the indiscriminatory use of this test solely for the purpose of obtaining data should be discouraged.

9. Effect of Exercise on the Diastolic Atrio-Ventricular Gradient in Mitral Stenosis.

Robert S. Litwak (by invitation), Philip Samet (by invitation), W. H. Bernstein

(by invitation), Leonard Silverman (by invitation), Hyman Turkewitz

(by invitation) and Milton E. Lesser (by invitation), Miami, Fla.

Three factors determine the magnitude of the diastolic atrio-ventricular gradient across the stenotic mitral valve. These are (1) severity of the stenosis, (2) flow across the valve, and (3) cardiac rate. These data can best be obtained by simultaneous combined left and right heart catheterization in the supine position. The purpose of this report is to present data relative to these three parameters both at rest and during exercise.

Fifty-two simultaneous combined left and right heart catheterizations have been performed to date. In 15 of these, the effect of exercise on the diastolic atrio-ventricular gradient, pulmonary artery pressure, cardiac rate and calculated flow across the valve (cardiac output) was studied.

Right heart catheterization is performed by the standard technique. Left heart catheterization is performed by a modification of the Fisher technique in which two No. 17 thin-walled 7-inch needles are inserted into the left atrium. A polyethylene catheter is then passed through each needle into the left atrium and left ventricle. The needles are then removed leaving the catheters in situ. Following this the patient is rotated back into the supine position and steady-state pressure, flow and cardiac rate determinations are made at rest and exercise.

Preoperative mean diastolic gradients at rest varied from 7 to 25 mm. mercury. On exercise, these gradients uniformly rose. Postoperatively, there was either a marked reduction or total obliteration of the gradient at rest. In those cases where a measurable resting gradient could not be demonstrated after surgery, exercise still resulted in the production of small gradients. In the postoperative group where only a reduction in gradient had been achieved, exercise was almost invariably accompanied by expansion of the gradient.

The significance of these data will be discussed with reference to (a) selection of patients for commissurotomy, and (b) physiological evaluation of the results of the surgery.

10. Surgical Treatment of Transposition of the Aorta and Pulmonary Artery.

Thomas G. Baffes (by invitation), William L. Riker (by invitation),

Arthur DeBoer (by invitation) and Willis J. Potts, Chicago, Ill.

About a year ago, a new method for partially correcting transposition of the aorta and the pulmonary artery was described, and successful application of this method to one patient was reported. This method involved redirection of blood from the right pulmonary veins to the right atrium and, by means of a homologous aortic graft, simultaneous redirection of blood from the inferior vena cava to the left atrium.

Since that initial report, the method has been applied to thirty-two clinical cases, with fourteen immediate postoperative deaths and eighteen survivors. Two of the survivors died after leaving the hospital, of causes unrelated to the operative procedure. The remaining survivors have shown satisfactory clinical improvement. Their oximetric readings have risen from 35%-60% preoperatively, to 75%-91% postoperatively. Generally, a rise of 30%-50% oxygen saturation has been recorded after operation. In addition, the patients have shown significant alleviation of clinical symptoms.

In order to illustrate the various types of transposition encountered, a study of seventy-five autopsy specimens of this anomaly is also presented. It is pointed out that "transposition" represents a basic type of heart, on which may be superimposed almost any other well-known congenital cardiac anomaly. Comments are made regarding the operability of the various types of transposition described.

Finally, the causes of immediate operative mortality following this procedure are discussed. These deaths have emphasized a number of unusual physiological aspects of transposition of the great vessels, which create operative hazards not encountered with other forms of cyanotic congenital heart disease. A number of changes have been made in the originally described operative procedure in order to avoid these unusual operative hazards. These changes are described.

11. The Use of a Mechanical Bypass during Cross-Clamping of the Aorta.

Harold King (by invitation) and Harris B. Shumacker, Jr., Indianapolis, Ind.

The experimental work was performed on mongrel dogs. The thoracic aorta was simultaneously occluded just distal to the left subclavian and at the level of the diaphragmatic hiatus. In a control group of 11 dogs with aortic occlusion for one hour there were 2 instances of paraplegia, 8 deaths, and only one normal survival.

In 23 animals, blood was shunted from the superior vena cava to the distal aorta during an hour's interval of aortic clamping. Plastic catheters were inserted through the jugular vein and femoral artery and connected with plastic tubes running through one pumping head of a sigmamotor pump. No blood reservoir was used. No blood was needed to "prime the pump". No oxygenator was used. Preliminary observations indicate that under the conditions of the experiment, the superior vena caval blood is well oxygenated. Of these 23 animals, 22 survived without paraplegia and one died. An additional animal in which the aorta was clamped for 90 minutes survived without difficulty.

The usefulness of the method in clinical cases will be illustrated by 4 experiences. The cathetenzation of the jugular vein and femoral artery is easily performed prior to thoracotomy. The shunt appears to protect from paraplegia.

12. Elective Cardiac Arrest: An Adjunct to Open Heart Surgery.

Donald B. Effler, Laurence K. Groves (by invitation), Harold F. Knight, Jr.,

(by invitation), Wilhelm J. Kolff (by invitation) and F. Mason Sones, Jr.,

(by invitation), Cleveland, Ohio

Open heart surgery that employs the now conventional by-pass technique does not provide the ideal surgical field. There is an appreciable blood return to the right side of the heart from the coronary sinus, the thebesian veins, and retrograde flow from the pulmonary arteries, the left heart receives blood from bronchial vessels and any collaterals that might be present. The total blood loss in a so-called heart by-pass may be measured in liters under certain conditions. In addition to the imperfect hemostasis, the beating heart may also impair surgical exposure and hamper operative technique.

The adjunct of elective cardiac arrest coupled with the now conventional by-pass technique approaches the ideal in open heart surgery. It offers the surgeon a field that is relatively dry (although bleeding from collaterals is still present), free of motion and easily visualized With elective cardiac arrest there is no coronary circulation; the paralyzed heart muscle has minimal metabolic needs and for this reason requires no perfusion even for prolonged periods. In the authors series the longest period of induced cardiac arrest has been 58 minutes without interruption.

The Melrose technique of inducing elective cardiac arrest utilizes potassium citrate solution. Details of this method will be presented. In 1956, the authors have employed elective cardiac arrest in 51 of 55 open heart procedures employing extracorporeal circulation. A detailed report of the results and the physiologic observations will be presented.

Advantages of the Melrose technique are readily apparent. True cardiac arrest is obtained; as yet no time limit for safe arrest has been established; no supplementary drugs or techniques (e.g. hypothermia) are used; the method is basically simple and quickly reversible. In the cases presented the shortest period of arrest has been ten minutes and the longest fifty-eight minutes. A satisfactory heart rhythm has been reestablished in every case to date.

13. Experiences with the Use of Cardioplegia (Induced Cardiac Arrest) in the Repair of Interventricular Septal Defects.

Conrad R. Lam, Thomas Geoghegan (by invitation), Charles K. Sergeant

(by invitation) and Edward Green (by invitation), Detroit, Mich.

The advantages of a quiet heart in addition to a relatively bloodless field during certain intracardiac operations are obvious. Such a situation is most nearly obtained if the heart is stopped during the cardiotomy. After a series of experiments using the agents potassium chloride and acetylchohne, we elected to use the latter in operations for the closure of interventricular septal defects in humans. A pump-oxygenator of the bubble type has been used during the cardiac by-pass. Following the closure of the caval snares around their cannulas, the aorta has been clamped and 10 mg. per kilogram of body weight has been injected into the aorta and thence into the coro-naries. Prompt cessation of the heart results. Following the intracardiac procedures, resuscitation is obtained by removing the aortic clamp which results in a washing out of the drug.

At the time of submission of this abstract, 30 patients having interventricular septal defects have had surgical repair under induced cardiac arrest. The resumption of the heartbeat has been of regular occurrence. Ventricular fibrillation occurred in one patient both before and after the repair. There have been two instances of permanent and fatal atnoventricular block.

The possible cause of this complication will be discussed.

6:30 P.M.-8:30 P.M. COCKTAIL PARTY-INFORMAL

PALMER HOUSE-RED LACQUER ROOM