WEDNESDAY AFTERNOON, APRIL 18, 1973

2:00 P.M. Scientific Session

Regency Ballroom

37. Pneumothorax Complicating Continuous Ventilatory Support

MICHAEL STEIER,* NATHANIEL CHING,* ENRIQUE

BONFILS ROBERTS* and THOMAS F. NEALON JR.,

New York, New York

There has been a 35 per cent increase in the incidence of pneumothorax in our hospital in the last 3 years. The increase has been due to iatrogenic causes related to improvements in the care of critically ill patients-external cardiac massage, central venous pressure monitoring and continuous ventilatory support. The factors associated with continuous ventilatory support seemed appropriate for presentation before the Association.

In the period from January 1, 1968 to December 31, 1971,61 patients at our institution developed pneumothorax during continuous ventilatory support. The significant factors leading to the occurrence of this complication include:

1. volume-controlled ventilation

2. large tidal volumes

3. high inspiratory pressures

4. positive end expiratory pressure

5. history of chronic obstructive lung disease and previous rib fractures. These factors will be discussed in detail.

The importance of early diagnosis based on physical findings allowing immediate treatment will be stressed. Eight per cent of patients so diagnosed and treated succumbed as compared to 38 per cent of those in whom diagnosis waited confirmation with a chest x-ray due to the hazard of pressure ventilation in patients with pneumothorax.

*By invitation

38. Electronmicroscopy and Physical Chemistry of Healing in Prosthetic Heart Valves, Skirts, and Struts: Modification by Electrochemically Clean, Physiologic Surfaces

P. N. SAWYER, B. STANCZEWSKI,* N. RAMASAMY,*

G. W. KAMMLOTT,* J. G. STEMPAK* and S. SRINIVASAN,*

Brooklyn, New York

Repeated attempts have been made to decrease the incidence of valve thrombosis, infection, embolism, fibroblastic overgrowth, with orifice occlusion and/or poppet sticking. Sequential studies from this laboratory have revealed various solutions to these problems. The first problem, valve thrombosis, can be prevented by use of "electrochemically clean" oxide free negatively charged non-thrombogenic metallic surfaces. Aluminum, Starr-Edwards stellite 21, titanium and a recently developed metal surface from Howmedica seem to provide this antithrombogenic characteristic along with appropriate uniform net negative surface potentials.

Light electron and scanning electron microscopic studies of the surfaces and composition of healing characteristics of 100 valves implanted in the mitral and tricuspid annuli of calves for periods as long as 765 days have been completed. The scanning electron microscope and transmission electron microscope pictures have proven of real value in developing insight into the pathologic processes found in dysfunctioning valves.

The use of cloth around struts leads to abnormal fibrin deposition in the cloth interstices covering the metallic valve surfaces with invasive fibroblasts followed by abnormal collagen production, sequential platelet deposition and significant repetitive onion layering of fibrin on strut surfaces. This results in increasing strut diameter, poppet sticking, and increased trans-valvular pressure gradients.

Infection, fibroblastic overgrowth on the cuff, and orifice occlusion can be prevented by use of the dacron reinforced autogenous venous skirt which heals as normal autogenous tissue to the valve orifice. The remaining problems are obviated by the use of clean surfaces and appropriately designed valves as shown by flow, electrochemical, and valve surface studies before and following implantation. The characteristic photographs and surface phenomena changes found using the new techniques will be presented along with related interfacial potentials and characteristic light, electron, and scanning electron microscopic histology.

*By invitation

39. Evaluation of Aortic Valve Homograft Failures

ROBERT B. WALLACE, STEPHEN P. LONDE* and

JACK L. TITUS,* Rochester, Minnesota

Between May 1965 and June 1972, 229 patients (163 males and 66 females) had replacement of their aortic valve with an aortic valve homograft. The hospital mortality rate was 4.8% (11 patients). Of the 218 patients dismissed from the hospital, 22 have required reoperation for homograft failure 3 to 73 months after the initial operation, and 16 others have died during the follow-up period.

Valves removed at reoperation or autopsy were studied grossly and morphologically, and factors possibly related to the status of the homograft were evaluated. These factors included valve preparation (92 of the valves used in this series were sterilized with (3-propiolactone and 137 were sterilized by irradiation), age and sex of the donor, condition of graft and recipient valve at time of insertion, function of graft at the time of hospital dismissal, and the relationship of graft function to the cause of death. Correlations were done in an attempt to define better those patients in whom the operation might be most appropriate and to delineate those factors that may be important in the long-term results of this procedure.

*By invitation

40. Surgical Management of Acquired Tricuspid Valve Disease

A. CARPENTIER,* A. DELOCHE,* A. HANANIA,* A. PIWNICA,"

Cl. FARCE* and Ch. DUBOST,* Paris, France

Sponsored by Dwight C. McGoon

Acquired tricuspid valve disease (A.T.V.D.) raises two questions which continue to challenge the surgeon. (1) In what circumstances the tricuspid disease should be corrected? (2) and if so, by what means? A four years experience with the Carpentier tricuspid annuloplasty (C.A.) allows us to bring new answers to these questions.

From May 1967 through September 1972, 375 A.T.V.D. have been treated at Broussais Hospital with correction of severe mitral (271) or mitroaortic (104) diseases.

Kay annuloplasty (K.A) was used in 103 cases with an hospital mortality of 39% (1967-1969). C.A. has been used in 137 cases with a mortality of 9.5% (1969-1972). Starr prosthesis has been used in 135 cases with a mortality of 37% (1967-1972).

In the first 62 C.A., follow up study (1 to 4 years) including cardiac catheterization in 30 patients has shown constant effectiveness of the repair, no recurrent insufficiency, no A.V. block, no thromboembolic complications at the site of the tricuspid valve.

These results led us to a shift in our policy concerning the treatment of A.T.V.D.:

1. All A.T.V.D. clinically detected and operatively confirmed have to be corrected.

2. The C.A. is the only method capable to physiologically correct the disease and prevent the recurrent dilatation of the annulus. It can be used either isolated or combined with a commissurotomy in 90% of the A.T.V.D., as shown by our experience.

*By invitation

41. Closed Mitral Commissurotomy on Cannulated Pump Standby Through A Sternal Split Incision-An Alternative to Routine Open Commissurotomy

VINCENT L. GOTT, ANTONIO REVILLA,* JAMES S.

DONAHOO,* EDWARD H. KLOPP,* and ROBERT K. BRAWLEY,*

Baltimore, Maryland

Open mitral commissurotomy offers several advantages over closed commissurotomy, including greater patient safety on pump bypass and easier conversion to prosthetic replacement if necessary. In some patients, however, fibrous obliteration of the commissures makes direct incision somewhat imprecise and the surgeon, in turn, may use a transventricular dilator to accomplish the commissurotomy. Engineering analysis demonstrates that a dilator used this way in the flaccid heart applies equal stress to the leaflets and commissures and not infrequently produces leaflet fracture, whereas in the beating heart, the stresses appear to be concentrated at the commissures because of the leathering mechanism of the chordae. All patients having mitral commissurotomy at this hospital since 1965 have been reviewed. One hundred patients had a standard closed commissurotomy (93% successful commissurotomies, 2% mortality) and 25 patients had open commissurotomy (40% requiring prosthesis, 4% mortality). In an attempt to combine the mechanical advantages of closed commissurotomy with the best features of open commissurotomy, we have more recently carried out all mitral commissurotomies as a "closed" procedure through a median sternotomy on cannulated pump standby with a newly designed "right angle" transventricular dilator. Eighteen patients have had this new procedure. One patient had a valve unsuited for commissurotomy and was easily converted to open cardiotomy for prosthetic replacement. The remaining 17 patients obtained excellent commissurotomies with no morbidity or mortality. This technique for mitral commissurotomy appears to offer several advantages over other currently used methods.

*By invitation

42. The Open Approach to Mitral Commissurotomy

JAMES O. FINNEGAN,* HORACE MacVAUGH, III, DENNIS C.

GRAY,* CLAUDE R. JOYNER* and JULIAN JOHNSON,

Philadelphia, Pennsylvania

Of the 1005 operations on the mitral valve (380 open) done at the Hospital of the University of Pennsylvania from 1961 to 1971, 592 (317 open) consisted of mitral commissurotomy only.

As the first half of the 10 year period progressed the closed technic was used less and less, being reserved for the more favorable valves, but still constituted 50% for the period. For that 5 year period the mortality was 4% closed and 11% open-combined 7.5%. During the second 5 year period, the open technic was used exclusively, with a single death-less than 1% mortality.

The improved results for mitral commissurotomy in the second 5 year period was no doubt due to better selection of patients for the procedure, the freer replacement of the badly diseased valves, and improvements in postoperative care. These will be described, along with pre and postoperative complications.

The operative and late (5.3%) deaths in the open group have been analyzed. Of the surviving patients all but one have been followed and 73% have been restored to Class I (NYHA).

*By invitation

43. Mitral Valve Replacement with Beall Mitral Valve Prosthesis

N. P. ROSSI, C. KONGTAHWORN* and J. L. EHRENHAFT,

Iowa City, Iowa

To evaluate the function of the Beall valve, 100 consecutive cases of single valve replacements in the mitral position with a Beall prosthesis were analyzed. The procedures were performed from November 1967 to January 1972 allowing a followup of at least one year and up to five years. Eighty percent were performed for rheumatic disease and 20% for mitral incompetence due to nonrheumatic causes. Sixty-five percent of patients were in New York Heart Association Class IV, 26% in Class III and 9% in Class II. We found a 2% incidence of thromboembolism, 2% of paravalvular leak, and 19% of hemolysis. The problems relating to hemolysis were encountered early and were resolved within six months. Twenty-four percent had a previous mitral commissurotomy. Mortality was confined to patients in functional Classes III and IV (17% hospital and 7% late). Of 65 patients who were in functional Class IV, 59 showed improved functional classification, 25 out of 26 patients in functional Class III had changed to Class I or II postoperatively, and six out of nine patients in functional Class II had improved to Class I.

The results of analysis suggested satisfactory clinical improvement after replacement with Beall valve mitral prosthesis. There was a low incidence of thromboembolism but a high initial incidence of hemolysis.

*By invitation

44. Mitral Valve Replacement with Cloth-Covered, Composite Seat Prostheses: The Case for Early Operation

LAWRENCE I. BONCHEK* and ALBERT STARR,

Portland, Oregon

Operative and late complications of prosthetic valves have usually limited mitral valve replacement (MVR) to functional class (FC) III or IV patients refractory to medical management.

146 patients have undergone MVR with cloth-covered, composite seat prostheses (models 6310, 6320). 129 were FC III or IV. Operative mortality was 2% (3/146), and late mortality was 9% (13/146). Only two late deaths were valve related (one leak, one infection). Nine patients had emboli (6%) two with significant residuals, in 2,216 months of patient followup.

110 patients were FC I or II postoperatively. Since this improvement did not correlate with preoperative FC, a new prognostic classification was introduced to correlate preoperative duration of symptoms and response to medical therapy with postoperative result. 75% (15/20) survivors with unsatisfactory functional results postoperatively were in the worst prognostic classification (C2).

The striking reduction in valve related complications, and the minimal operative mortality, indicate that MVR with the current prosthesis should be offered early to patients with recent deterioration who respond to medical treatment (prognostic class Al). The poor functional results seen after MVR for neglected mitral disease may thus be avoided.

*By invitation