Friday Morning, May 13, 1960

9:00 A.M. Scientific Session: REGULAR PROGRAM Napoleon Room

30. A Five Year Follow-up Study of Closed Mitral Valvulotomy.

J. Gordon Scannell, John F. Burke (by invitation), and

Farrokh Saidi (by invitation), Boston, Mass.

In the past there have been a number of reports on the technique and immediate post operative results following closed mitral valvulotomy. These reports as a rule have not discussed the long term results which can be expected following closed operation. Evaluation of the closed operation is clearly important in establishing the present indications of open-heart procedures in mitral stenosis.

In order to gain a clear picture of long term results that might allow prediction of an unsatisfactory outcome, the present status of 100 consecutive patients, who survived mitral valvulotomy at the Massachusetts General Hospital more than five years ago, has been reviewed Particular attention has been given to those patients who have required reoperation, suffered late emboli and had reactivation of rheumatic heart disease.

Preliminary survey indicates a five year recurrence rate of 5% - 10% and excellent long term results in two-thirds of the patients. There have been a certain number of late emboli. The problem of recurrence is particularly important since at the present time this has become an indication for open-heart repair.

31. Valvuloplasty for Acquired Aortic Stenosis.

Donald G. Mulder (by invitation), Albert A. Kattus (by invitation),

and William P. Longmire, Jr , Los Angeles, Calif.

Notable advances have been made in the past few years in the surgical treatment of heart diseases. Satisfactory techniques are available for the correction of most cardiac lesions. Although many procedures have been advocated for the treatment of patients with acquired aortic stenosis, none has been consistently successful. Any operation which does not restore mobility to the heavily calcified and relatively fixed aortic valve will be of limited value.

A new technique is presented by which the major obstructing and immobilizing encrustations of calcium can be removed from the valve cusps. This valvuloplasty not only increases the size of the aortic valve orifice, but even more important from the functional standpoint, it restores mobility to the valve cusps.

Eleven patients with acquired aortic stenosis have been operated upon using this technique. There have been no operative or late deaths. Several patients had been in congestive failure and all had been symptomatic prior to operation. The systolic gradient across the aortic valve preoperatively ranged from 36 mm. Hg. to 190 mm. Hg. with an average of 89 mm. Hg. The gradient was completely abolished by operation in eight patients, with an average residual gradient in the entire group of 7 mm. Hg. One patient with associated severe aortic insufficiency has two prosthetic cusps reinforcing and replacing his degenerated valve tissue. All patients have been symptomatically improved and, except for those most recently operated upon, have returned to work. The duration of follow-up is from two to eleven months

The early results of the treatment of acquired aortic stenosis by the technique of valvuloplasty have been most encouraging. Until such time as a suitable aortic valve prosthesis is available, we feel this procedure warrants further trial.

32. Partial and Complete Aortic Valve Prostheses in Advanced Aortic Insufficiency.

Dwight E. Harken, Warren J. Taylor (by invitation),

Harry S. Soroff (by invitation), Armand A. Lefemine (by invitation),

Sushil K. Gupta (by invitation), and Steven Lunzer (by invitation),

Boston, Mass.

Aortic insufficiency associated with minor degrees of left ventricular chamber enlargement has had encouraging correction with partial and elsewhere even complete valve prostheses at open operation.

The problem of prostheses and open correction of aortic insufficiency when the ventricle is markedly dilated and in failure presents a very difficult and much more formidable challenge. A primary consideration is that the increased chamber diameter aggravates the failure promptly if any resistance is added at the valve site La Place's law (P = T/r⁴)explains this difficulty when any valve resistance (a function of P) markedly increases intramural tension (T) due to a large chamber radius (r). Thus prompt failure can be expected to follow some of the currently described plastic techniques and our experience supports this. This knowledge and experience influences the type of prostheses, be they partial or complete. It has particular relevance to the technique of extending cusps with Teflon and the hinge at the base.

A second cardinal problem is that of circulatory support while the heart is resuming function after the repair. The conventional constant flow arterial pump return results in the fragile dilated ventricle having to work against ("buck") the pump. Left auricular "sumping", coronary perfusion, etc., have made it possible to correct the aortic incompetence associated with some of the more severe grades of myocardial insufficiency The "bucking" problem can only be overcome by a combination of complete surgical correction of valvular incompetence and coordinated pulsatile arterial pump return. Such a pump is available in the Davol Birtwell pump. Experimental and clinical application of this type of pump-oxygenator and valve prostheses in advanced grades of myocardial dilatation and failure constitute the basis of this communication.

33. The Results of Surgical Treatment for Ventricular Septal Defect.

John W. Kirklin, Dwight C. Mcgoon, and James W. DuShane

(by invitation), Rochester, Minn.

By the date of the meeting of the Association, five years of experience with the surgical treatment of ventricular septal defect will have been had at the Mayo Clinic. At the time of submission of this abstract, this comprises an experience with 355 cases.

In this study all cases are reviewed except those in which the ventricular septal defect was a part of the tetralogy of Fallot or of the complete form of common atrioventricular canal. Classification is into the following groups:

1. Ventricular septal defect with mild pulmonary hypertension.

2. Ventricular septal defect with moderate pulmonary hypertension.

3. Ventricular septal defect with severe pulmonary hypertension.

a. high pulmonary blood flow/systemic flow ratio

b. moderately elevated pulmonary blood flow/systemic flow ratio.

c. low pulmonary blood flow/systemic flow ratio (one or less).

The clinical and hemodynamic criteria for classification are discussed in detail. Sixty per cent of the cases in this series had severe pulmonary hypertension.

Over-all data on hospital mortality rate are presented. In the year 1955, the hospital mortality rate was 20.0 per cent for all cases of ventricular septal defect repaired while in the year 1959 (until November 1), it was 5.3 per cent. Factors contributing to the reduction in hospital mortality are analyzed.

Complications following the repair of ventricular septal defect include the development of complete heart block and the persistence of residual shunt after repair. Their incidence and methods by which their occurrence can be minimized, are detailed.

34. The Closure of Atrial Septal Defects Utilizing General Hypothermia: The Effectiveness of Treatment as Determined by Cardiac Catheterization.

Andrew G. Morrow, Joseph W. Gilbert, Jr. (by invitation),

R. Robinson Baker (by invitation), and N. Ferryman Collins

(by invitation), Bethesda, Md.

Thirty-six patients were operated upon at the National Heart Institute during the period in which general hypothermia was employed to permit the repair, by direct suture, of atrial septal defects. Cardiac Catheterization was carried out postoperatively in 32 patients and the hearts of three others, who died in the early postoperative period were examined at autopsy. Of these 35 patients, 10 were demonstrated to have residual or recurrent left-to-right shunts into the right atrium.

The repair was found to be incomplete in all of the four patients who had sinus venosus defects with associated partial anomalous pulmonary venous drainage. Five patients with residual shunts had ostium secondum defects 4 cm. in diameter or larger. In the remaining patient an unsuspected incomplete A-V canal was present.

The brevity of the period of circulatory interruption permitted by hypothermia, even with coronary perfusion, was found to impose severe technical limitations It is considered that in the patients with ostium secundum defects the failures of surgical treatment could have been obviated had sufficient time been available for the insertion of a prosthesis, permitting closure of the defects without tension. In the patients with sinus venosus defects the pulmonary venous drainage could have been diverted into the left atrium in this manner.

This high incidence of incomplete repair has led to the abandonment of hypothermia and the adoption of cardiopulmonary bypass in the surgical management of all patients with atrial septal defects. The value of detailed postoperative studies in assessing the effectiveness of a cardiac surgical procedure is also illustrated

35. Elective Cardiac Arrest Using Selective Cardiac Hypothermia.

David M. Long, Jr. (by invitation), Laurence P. Sterns (by invitation),

Vincent L. Gott (by invitation), Robert H. Deriemer (by invitation),

and C. Walton Lillehei, Minneapolis, Minn.

Selective cardiac hypothermia has been employed successfully experimentally and clinically as a method for providing routine elective cardioplegia and as a method for providing maximum protection to the myocardium during aortic valvular surgery. Only short periods of anoxic arrest or chemical cardioplegia are tolerated without the production of myocardial insufficiency or necrosis. Uneven distribution of the coronary perfusate and certain technical factors limits the usefulness of continuous retrograde and antegrade coronary perfusion. Extensive clinical experience has demonstrated by objective measurements the significant superiority of selective cardiac hypothermia as compared with the above methods

The method is simple. Gardiopulmonary bypass is employed using the bubble oxygenator and Sigmamotor pump. A separate line from the bottom of the oxygenator is used to pump oxygenated blood through a disposable cooling unit which will be described. The temperature of the arterial blood is lowered to 5° to 12° C. After clamping of the ascending aorta, cold blood is perfused through the coronary arteries. The exact method utilized depends upon the lesions present and these will be described. The myocardial temperature is decreased to 15° to 17° C within 3 to 5 minutes

Animal experiments were designed to evaluate the tolerance of the myocardium to coronary perfusion with cold blood and to test effects of interruption of the coronary flow of the hypothermic heart for intervals up to one hour. Combinations of selective cardiac hypothermia and chemical cardioplegia were also studied. Comparisons of these methods were made by measuring coronary venous pH and lactic acid levels before and after hypothermia. The methods were also compared with regard to survival of the dogs and histologic changes in the myocardium.

Selective cardiac hypothermia has been employed to date in 100 patients with a wide variety of cardiac lesions. Myocardial biopsies of human hearts subjected to potassium citrate arrest and selective cardiac hypothermia have been analyzed for lactic acid, glucose, adenosine tri-phosphate and phosphocreatine levels before and after cardioplegia.

36. Open Heart Surgery Using Deep Hypothermia Without an Oxygenator.

Archer S. Gordon (by invitation), Bertrand W. Meyer, and

John C. Jones, Los Angeles, Calif.

The ultimate goal in extracorporeal circulation for intracardiac surgery is to reduce and simplify the mechanical equipment to its barest essentials. We have accomplished this by performing all types of prolonged open heart surgical procedures using only two mechanical pumps and a heat exchanger (no oxygenator or special monitoring equipment is required). Using temperatures down to 10° C., this has allowed us to operate in a completely quiet, bloodless field for periods up to one hour on such lesions as ventricular septal defects, tetralogy of Fallot, total anomalous pulmonary venous drainage, aortic stenosis, etc.

The advantages of this technique include the following: (1) Requires a minimum amount of equipment (only two pumps and heat exchanger), (2) Requires only 1200 cc. of blood to prime the system; (3) Cardiac arrest results from cold - neither cardioplegic drugs nor anoxic arrest are used; (4) Circulatory standstill is used during the intracardiac surgery and provides an absolutely quiet, bloodless field; (5) Periods up to several hours can be used safely, if required, for intracardiac repairs.

Laboratory and clinical studies reveal freedom from problems associated with hemolysis, acidosis, perfusion rates, clotting mechanisms, and blood volume balance. Blood aspirated from the open heart is minimal and may be discarded or reused.

Studies of oxygen utilization have provided a determination of the safe period of circulatory occlusion at any given temperature. Thus, the temperature can be selected for each patient on the basis of the time requirements for his case. If it becomes necessary for circulatory occlusion to exceed the time allowable at the temperature selected, brief reperfusion allows prolonged extension of this period.

This simple, versatile, safe procedure appears to provide the best approach for the correction of most intracardiac lesions.