Imperial Ballroom

19. Carpentier's Annulus and De Vega's Annuloplasty: The End of The Tricuspid Challenge

PIERRE GRONDIN, CLAUDE MEERE*, RAYMOND LIMET*, Montreal,

Canada JUAN-LUIS DELCAN-DOMINGUEZ* and RAMIRO RIVERA-LOPEZ*,

Madrid, Spain

Acquired tricuspid insufficiency has been for years a surgical challenge. Its importance remains difficult to assess not only by clinical and hemodynamic investigations, but even at the time of surgery by digital exploration. In borderline cases, the surgeons are hesitant to use a prosthesis entailed with numerous ill-effects or to perform a Wooler-Kay annuloplasty known for its unpredictable results.

The advent of Carpentier's annulus and of De Vega's semi-circular annuloplasty has favorably altered this challenge by providing excellent immediate results. A long term evaluation was conducted by two groups of investigators (Madrid and Montreal), in 32 cases with a Carpentier's annulus and in 17 with De Vega's annuloplasty. Tricuspid function was assessed between 6 and 24 months after operation by clinical examination and by the following hemodynamic studies: atrial and ventricular pressure readings, dye dilution curves, intra-cavitary phono-cardiogram and right ventriculography.

No thrombo-embolic phenomenon, no A.V. block and no significant complication related to the surgical technique were observed. Tricuspid incompetence has completely disappeared in most instances and has been markedly reduced in all. Comparing these results to a similar study done in cases in which a Wooler-Kay annuloplasty was employed, has disclosed a notable superiority. Is this the end of the Tricuspid Challenge?

*By invitation

20. Isolated Mitral Valve Replacement With the Kay-Shiley Disc Valve-Actuarial Analysis of the Long Term Results

HARRY A. WELLONS, JR.*, ROBERT S. STRAUCH*,

STANTON P. NOLAN and WILLIAM H. MULLER, JR.,

Charlottesville, Virginia

With increasing numbers of prosthetic valves available for replacement of the mitral valve, it is vital that clinical results with each valve be carefully documented. Results should be examined in terms of operative and late mortality, quality of life, thromboembolic complications, mechanical and hemodynamic function. It is only by this method that the true value of various mechanical designs will be determined.

Between March 1967 and December 1972, the Kay-Shiley disc valve was utilized for 83 isolated mitral valve replacements. Nine patients were NYHA Class IV, 59 Class III, and 15 Class II. There were 14 early deaths (17.2% early mortality) and 29 late deaths. One of the early deaths and 14 of the late deaths were directly attributable to embolic phenomena. Survival determined by the actuarial method revealed a cumulative survival rate of 39.8% six years following operation. Thirty-three patients had a total of 55 thromboembolic events, representing a rate of 24.7 emboli/1000 months at risk. Thromboembolism was evaluated by a modified actuarial table, which revealed that 35.2% of the patients were event free at six years following operation. Of the 63 patients in whom sufficient follow up information was available, 35 had improved by one or two cardiac classes, 26 were unchanged, and two were worse.

It is our opinion, based on this experience, that this prosthesis should not be used for mitral valve replacements due to the unacceptable incidence of thromboembolism and late mortality.

*By invitation

21. The Significance of Coronary Arterial Stenosis During Cardiopulmonary Bypass

RICHARD M. ENGELMAN*, FRANK C. SPENCER and

ARTHUR D. BO YD, New York, New York

Myocardial infarction may develop during an uneventful open heart operation. In order to better understand this complication, an experimental study was undertaken. The left circumflex coronary artery of 20 dogs was narrowed to 50% of its area by a metal screw clamp, producing a localized coronary stenosis. Regional myocardial perfusion in both the (stenotic) circumflex and (normal) left anterior descending (LAD) distribution was measured by injection of a radioactive labeled microsphere (15±5µ). Circumflex coronary artery flow was measured using an electromagnetic flow probe. An epicardial electrogram was recorded in the distribution of the left circumflex and the area of the ventricle marked by a tissue stain. Measurements of regional myocardial perfusion, circumflex flow, and the epicardial electrogram were performed in each animal during the control (pre-bypass) state and during Cardiopulmonary bypass (CPB) with a beating and fibril-lating ventricle. Half the animals had CPB performed at 50mm Hg perfusion pressure and half at 100mm Hg. The animals were sacrificed at the end of the study, the hearts sectioned, weighed, and counted. A cast was made of the stenotic circumflex coronary artery, the degree of stenosis measured and percent area stenosis calculated.

Myocardial perfusion prebypass distal to the circumflex stenosis was 151ml/100g/min compared to 144 in the LAD distribution. Thirty min of CPB at 50mm Hg (beating ventricle) reduced perfusion distal to the stenosis to 92 and distal to the LAD to 114 while 30 mm CPB at 100mm Hg increased perfusion distal to the stenosis to 190 and distal to the LAD to 215ml/100g/min. The epicardial electro-gram showed ischemic changes in 2 of 10 animals at 50mm Hg and none at 100mm Hg. During CPB at 50mm Hg in the beating ventricle, the already depressed myocardial perfusion was unchanged by 30 min fibrillation. At 100mm Hg, however, regional circumflex perfusion decreased from 190 to 154 and LAD perfusion decreased from 215 to 164ml/100g/min after 30 min fibrillation.

This study shows that the effect of a 50% coronary stenosis in reducing distal flow is only apparent during CPB at reduced pressure. The mechanism whereby a myocardial infarction develops during CPB could evolve from the development of a "critical" stenosis out of a mild to moderate one at a reduced perfusion pressure during CPB.

*By invitation

22. A New Method for Temporary Left Ventricular Bypass: Preclinical Appraisal

WILLIAM F. BERNHARD, VICTOR POIRIER*, JAMES G. CARR*,

and C. G. LAFARGE*, Boston, Massachusetts

Surgical patients who cannot be weaned from cardiopulmonary bypass during operation, or who develop balloon dependent left ventricular failure postoperatively, are now considered irretrievable. However, in those with potentially reversible ventricular dysfunction, recovery might be possible if an improved means of temporary (maximum 30 days) circulatory support were available. Toward this end, a pneumatically actuated, left ventricular assist pump was developed and evaluated in 12 consecutive calf experiments. The device, containing a flexible, polyurethane pumping chamber (80ml stroke volume), was positioned on the chest wall and connected to the left ventricular apex (inflow) and descending thoracic aorta (outflow) by two Dacron conduits containing porcine xenograft valves. All animals survived the 30-day pumping interval, and five underwent successful removal of the device by dividing the Dacron conduits below skin level. During pumping, cardiac catheterization (six animals) revealed no systolic transvalvular pressure gradients at a continuous flow of 5.0 L/min, and die absence of blood trauma was confirmed by hematologic studies, including erythrocyte survival (30 ± 4.0 days), platelet survival (5.3 ± 1.2 days) and fibrinogen clearance (4.5 ± 1.0 days). After animal sacrifice, examination of pump surfaces revealed firm attachment of a fibrin and collagenous layer to the underlying matrix of flocked Dacron fibrils. The xenograft valves also remained free of loose thrombus.

As a prelude to human investigation, pumps were implanted during a series of routine autopsies through a midline sternotomy incision. The device was positioned on the right antero-lateral chest wall, with two valved conduits traversing the mediastinum to connect the pump to the left ventricular apex and ascending aorta.

Recently, the blood-prosthetic interface and implantation method has been evaluated in a patient with severe diffuse hypoplasia of the aortic valve annulus and ascending aorta. A single-valved left ventricular-aortic bypass prosthesis was inserted and has functioned satisfactorily for six months.

3:30 P.M. Executive Session (Limited to Active and Senior Members)

Imperial Ballroom

*By invitation

TUESDAY EVENING, APRIL 15, 1975

7:00 P.M. President's Reception

Georgian Ballroom

8:00 P.M. President's Dinner and Dance

Georgian Ballroom

Attendance open to all physicians and their ladies. Tickets must be purchased at the registration desk by 5:00 P.M. on Monday, April 14.

Dinner dress preferred.