Aortic Valve Replacement

Transcription

1 Aortic Valve Replacement Russell M. Nelson, M.D., Conrad B. Jenson, M.D., and Kent W. Jones, B.S. T he development of the ball-valve prosthesis for replacement of the diseased aortic valve by Starr et al. [22] extended operability to many patients for whom palliative surgical treatment had not been previously available. Many of these patients now survive and are subject to the benefits and risks of this prosthesis, for which the long-term results are as yet incompletely assessed. Moreover, with the recent development of significant alterations in the design of prosthetic valves and the interest in the use of allografts and xenografts to replace the aortic valve, it seemed desirable to evaluate our results to date with the use of the Starr-Edwards aortic valve prosthesis. CLINICAL MATERIAL Of the total 170 patients in this series, 130 (76%) had isolated aortic valve replacement (Group I), 18 (11%) had aortic valve replacement with mitral valve repair (Group II), 17 (10%) had aortic and mitral valve replacement (Group III), and 5 (3%) had triple valve replacement or other surgery (Group TV). The series was begun in February, 1963, and includes all patients to March 31, The ages ranged from 19 to 76 years, with a mean of 46 years. There were 121 males and 49 females. Nine patients (5%) had had previous operations on the aortic valve either for implantation of Hufnagel leaflets or for decalcification and sculpturing. All patients had significant and progressive symptoms. Particular attention was paid to the history of recent major increase in the severity of symptoms. Sixty-nine percent of the patients were in New York Heart Functional Classification 111 or IV; the remaining 31% were in Class 11. Since this system of classification is less helpful for evaluating patients with aortic valve disease than it is for evaluating those with mitral valve disease, greater weight was given to the electrocardiogram, chest x-rays, hemodynamic studies, and cineangiocardiograms from right-heart and left-heart catheterizations in selecting patients for surgery. Because the operation is a palliative one and the long-term results are unknown, surgery was advised in each instance only if it was thought that the patient could not survive without it or would not represent a reasonable risk for surgery if one were to wait another year for the operation. The predominant lesion was aortic stenosis in 61 (36y0), aortic regurgitation in 63 (37%), and combined aortic stenosis and regurgitation in 46 (27%). From the Surgical Research Laboratory, Department of Surgery, Latter-Day Saints Hospital, and the Department of Surgery, University of Utah College of Medicine, Salt Lake City, Utah. Supported by grants from the U.S. Public Health Service (No. HE ) and the Utah Heart Association. Accepted for publication April 17, Address reprint requests to Dr. Nelson, Surgical Research Laboratory, Latter-Day Saints Hospital, Salt Lake City, Utah VOL. 6, NO. 4, OCTOBER,

2 NELSON, JENSON, AND JONES OPERA TI VE TECHNIQUE The operation was performed through a median sternotomy incision. In the first operations in the series, extracorporeal circulation was employed, utilizing roller pumps and a rotating disc oxygenator. We soon changed to the disposablebag bubble oxygenator* and more recently have used the lexan plastic disposable 0xygenator.t In most cases, minimal hypothermia to 93OF. and hemodilution with 5% dextrose in lactated Ringer's solution for priming were used. Continuous perfusion of the coronary arteries was employed with use of the Spencer-Malette silastic coronary cannulas. Ventricular fibrillation was induced electrically when a quieter field was desired. Electrical countershock with D.C. defibrillators was employed with uniform success. Pacemaker wires were not implanted, and tracheostomy was performed only when indicated in the postoperative period. THE PROSTHESIS The aortic valve prosthesis, as supplied commercially,$ has been employed routinely in this series. This device consists of Stellite 21, Teflon cloth, and a ball of silicone rubber. Model 1000 was used until January, 1966, when the manufacturer supplied the improved Model In October, 1967, the Model 2300 valve with cloth-covered struts and a hollow metal ball was adopted. PROPHYLACTIC ANTIBIOTICS The anti-infection regimen was initiated usually 48 hours before surgery, consisting of thorough baths with Gamophen soap. Penicillin, streptomycin, and oxacillin (or cloxacillin) were employed before, during, and after surgery as described in previous publications [15, 161. Oxygen for the heart-lung machine was sterilized by passage through a millipore filter [IS]. RESULTS There were 24 postoperative deaths (14%) (0 to 30 days postoperatively) and 21 late deaths (12%) in the total series of 170 patients. Of the 130 patients in Group I (isolated aortic valve replacement), 12 (9%) were classified as postoperative deaths and 15 (11.5%) were late deaths. Of the 18 patients in Group I1 (aortic valve replacement with mitral valve repair), 3 (17%) were postoperative deaths and 2 (11%) were late deaths. Of the 17 patients in Group I11 (aortic and mitral valve replacement), 4 (24%) were postoperative deaths and 4 (24%) were late deaths. Of the 5 patients in Group IV (triple valve replacement or other surgery), all were classified as postoperative deaths. The overall incidence of thromboembolic complications for the entire series was 22 (15%) of the 146 operative survivors. Analysis with respect to the use of Model 1000, Model 1200, and Model 2300 prostheses is shown in Table 1. The results by groups will be discussed below. GROUP I (ISOLATED AORTIC VALVE REPLACEMENT) Of the 130 patients in this group, there were 101 males and 29 females. Mortality. Analysis of operative deaths by age is shown in Figure 1. The entire group of 18 patients from 60 to 76 years of age survived surgery. The operative mortality rate in the first 35 patients was 26%. In the subsequent 95 operations done over a period exceeding three years, there have been 3 postoperative deaths for a current operative mortality rate of 3.2%. Causes of Death. The causes of death are listed in Table 2. The timing of *Travenol Laboratories, Morton Grove, Ill tbentley Laboratories, Santa Ana, Calif $Edwards Laboratories, Santa Ana, Calif THE ANNALS OF THORACIC SURGERY

3 Aortic Valve Replacement TABLE 1. THROMBOEMBOLIC COMPLICATIONS (TEC) IN ENTIRE SERIES OF 146 SURVIVORS OF AORTIC VALVE REPLACEMENT Starr-Edwards Valve Total Model 1000 Model 1200 Model 2300 Patients TEC % late deaths from the date of surgery is shown in Table 3 along with the number of operations and the operative and late mortality rates for each year. Follow-up Beyond Six Months. Although the 13 patients operated upon since October, 1967, are doing well, the late follow-up data will be considered only for those operated upon before October 1, 1967, to allow for a minimum of six months of follow-up. Of the 105 patients surviving and available for six months or longer of follow-up, 78 (74%) are now well without clinical evidence of any complications. Thrombus at the valve or peripheral embolization has been diagnosed in 19 patients; 7 episodes were fatal (7%), 10 were minor with quick and complete recovery (lo%), and 2 were major with persistent disability (2%). Of the patients sustaining thromboembolic complications, 8 (42%) were known to be off anticoagulants or not in the desired range of prothrombin time (under 30%). Six 2 I -Em AGE DISTRIBUTION Number of Patients OP DEATHS RANGES Ao Stenosis 28-76(0) Ao Regurgitation 19-67tR) Ao S.tR ts) FIG. 1. Postoperative deaths and age distribution of patients in Group I (isolated aortic ualve replacement). TABLE 2. CAUSES OF DEATH IN ISOLATED AORTIC VALVE REPLACEMENT Postoperative Death Late Death Cause Number Cause Number.~ - Myocardial failure 7 Thromboembolic 7 Pulmonary embolism 1 Congestive failure after MVR 1 Cerebral ischemia 1 Ball variance 1 Myocardial infarct (arterio- 1 Myocardial infarct 1 sclerosis) Leakage from aortotomy 1 Leakage from aorta 1 + arrhythmia Anesthetic death 1 Unknown (autopsy negative, 3; 4 no autopsy, 1) VOL. 6, NO. 4, OCTOBER,

4 NELSON, JENSON, AND JONES TABLE 3. ISOLATED AORTIC VALVE REPLACEMENT (FEBRUARY, I96%MARCH, 1968): TIMING OF LATE DEATHS Year Number of Patients (3 mo.) 9 Totals 130 Postoperative Deaths 3 (21%) 6 (21%) 1(3%) 2 (9%) 0 (0%) 0 (0%) 12 (10%) Late Deaths 4 (29%) 4 (14%) 4 (11%) 1 (4%) 2 (10%) 0 (0%) 15 (12%) Timing of Late Deaths (yr. postop.) (32%) were known to be in the 20 to 30% range of prothrombin time, and prothrombin time data at the time of the embolus were not available in 5 (26%). The fate of the 105 survivors is summarized in Figure 2. There was no statistically significant relationship of the thromboembolic complication to the preoperative lesion or to the size of the prosthesis employed. Study of the timing of thromboembolic complications revealed that 9 (48%) occurred in the first year, 8 (42%) came in the second year, 2 (10%) occurred in the third year. Each of these last 2 patients had sustained a previous episode in the first year postoperatively. There has been no occurrence of bacterial endocarditis postoperatively. In fact, surgery was done in one patient with aortic regurgitation because of active subacute bacterial endocarditis which could not be controlled with medical therapy. He is now well and off antibiotics. The excellent clinical benefit to the survivors is indicated by the fact that 84% of them are able to live with no restriction (Functional Class I), 10% have only mild limitation (Functional Class II), while 6% have moderate disability (Functional Class 111). Digitalis glycosides are now used in 40% of these patients postoperatively, and diuretics are employed in 15%. The occurrence of a diastolic blowing murmur of aortic regurgitation has been noted in 19 (23%) of 84 patients who responded to the call for reexamination six or more months postoperatively. The clinical progress of these patients thus far has not been significantly different from those individuals without a murmur. None has required reoperation for regurgitation. Seventeen (89%) are in Func- 48% in 1st year 42% in 2nd year *I/3 known to be in Pro time range 20-30% FIG. 2. ment). Fate of operative surwivors in Group Z (iso!ated aortic valve replace- 346 THE ANNALS OF THORACIC SURGERY

5 Aortic Valve Replacement tional Class I with no limitations, while 2 (11%) are in Class 11. Eleven (58%) of the 19 patients with aortic regurgitation murmur have a decrease in the size of the left ventricle as determined by electrocardiogram and cardiothoracic ratio on chest x-ray, while 3 (16%) have an increase. Electrocardiogram. Seventy-eight patients had electrocardiograms taken preoperatively and six or more months postoperatively. As a means of quantitating the degree of left ventricular hypertrophy, the sum of the voltage of the Sv-2 wave and the RV-5 wave was calculated from the preoperative and most recent postoperative electrocardiograms (calibration: 1 millivolt = 1 centimeter). A decrease in this voltage figure was found in 69 (88%), an increase was found in 6 (8%), and there was no change in the remainder. The average preoperative voltage measured 56 mm., while the postoperative calculation averaged 35 mm., for an average reduction of 21 mm. In those patients with increased voltage, all had good clinical relief. One patient sustained the complication of complete heart block, but a pacemaker has not been required. Chest x-ray. The cardiothoracic ratio was calculated from the preoperative and the most recent x-rays of the chest (taken six or more months postoperatively in 79 patients). The average diameter of the cardiac silhouette was 162 mm. preoperatively and 151 mm. postoperatively, for a mean reduction of 11 mm. A decrease was measured in 58 (7379, while an increase was measured in 8 (10%); the remainder showed no significant change. GROUP 11 (AORTIC VALVE REPLACEMENT AND MITRAL VALVE REPAIR) As in Group I, the anatomical lesion found at the aortic valve was about equally distributed between predominant stenosis and predominant regurgitation. The mitral valve lesion required either annuloplasty for regurgitation or commissurotomy for stenosis, with about equal distribution; some required both. The ages ranged between 26 and 59, with a mean of 43 years. In contrast to Group I, there was 2:l predominance of females to males in this group of 18 patients. Mortality. The causes of the 3 hospital deaths were myocardial failure, air embolism, and thromboembolism, respectively. One late death was due to thromboembolic complication, and the cause of the other is unknown. Both of the late deaths occurred in the second year postoperatively. There have been no early or late deaths in this group in the past two years (7 patients). Morbidity and Fate. Thromboembolic complications occurred in 3 of the 15 operative survivors (20%). One complication was fatal, 1 caused severe disability, and the third caused no permanent disability. GROUP 111 (AORTIC AND MITRAL VALVE REPLACEMENT) This group was comprised of 11 males and 6 females ranging in age from 34 to 57 years, with a mean of 47 years. All were Functional Class I11 or IV preoperatively and all survivors are Class I or I1 now. In the first 8 cases, 4 survived (50%); whereas in the last 9 cases (July, 1966, to date), all have survived the operation. One of these latter cases was a patient with Marfan s syndrome. Mortality. The 4 hospital deaths were due to myocardial failure, hepatic failure, myocardial infarction caused by atherosclerosis, and thromboembolic complication, respectively. The causes of 3 of the 4 late deaths were known to be bleeding esophageal varices from cirrhosis, cerebral hemorrhage from Coumadin overdosage, and methanol poisoning, respectively. The cause of the fourth late death is unknown. All occurred within the first year postoperatively. Morbidity and Fate. Thromboembolic complication has been detected in only 1 patient, and this was minor, occurring in the first year with complete re- VOL. 6, NO. 4, OCTOBER,

6 NELSON, JENSON, AND JONES covery. One patient was reoperated upon for angina, requiring removal of endothelial pannus from the orifice of the left coronary artery and the metal base of the aortic prosthesis. All survivors are clinically improved. GROUP IV (TRIPLE VALVE REPLACEMENT AND MISCELLANEOUS OPERATIONS) Operation was attempted in 4 patients, all of whom were in Functional Class IV and in congestive heart failure at the time of surgery. All died in the postoperative period of intractable congestive heart failure. One additional patient died at reoperation for repair of recurrent atrial septa1 defect and aortic stenosis. DISCUSSION The operative mortality rate for the 130 isolated aortic valve replacements in this series is 9%, which is similar to the 12% of 276 cases reported by Starr [21] and 13% of 538 cases reported by Cooley [7]. Our current mortality rate of 3.2% in the past three years indicates a more favorable rate with increasing surgical experience. This decline has been reported by several other groups [6, 8, 12, 14, 231. Thus, it is apparent that after the operative technique is thoroughly learned, surgery can be done at an acceptable mortality rate. The fate of the operative survivors is overcast by the incidence of late deaths, some of which, of course, are related to the prosthesis. Our late death rate of 12% for the isolated aortic valve replacement and 14% for the entire series is remarkably similar to the experience of McGoon, Ellis, and Kirklin [ll], who reported 14% late deaths of 133 cases, and of Starr 12 11, who reported 13% late deaths in all patients with valvular prostheses. This is not necessarily an argument for the use of homografts, however, as these figures are quite similar to the 11% incidence of late deaths in 353 aortic valve homografts reported by Barratt-Boyes and associates [l, 21. The occurrence of calcification in the cusps and root of aortic homografts has led Ross to autotransplantation of the pulmonic valve to the aortic position with implantation of an aortic homograft into the pulmonic position [19, 201. Heterografts have been implanted with early good results [17] but were associated with a 33% mortality in 39 patients according to Binet et al. [3, 41. The 19% rate of thromboembolic complications in our series of 105 survivors of isolated aortic valve replacement beyond six months is comparable to Starr s report of 19% in 216 survivors [21]. His report indicated that the rate was 23% (38 of 158) with the Model 1000 valve but was only 6% with the Model 1200 valve (4 of 58 cases). Our results, too, corroborate the lower incidence with the newer model valves; there has been only one minor thromboembolic complication in all survivors of isolated aortic valve replacement since January, 1966, when the Model 1200 became available, compared with 26% post- 348 THE ANNALS OF THORACIC SURGERY

7 Aortic Valve Replacement operative thromboembolic complications with the Model 1000 valve. No emboli have occurred in the six months that the Model 2300 valve has been used. The incidence is apparently smaller in those patients well managed with Coumadin, but adequate controls are not present to be certain. Others have reported benefits from the use of anticoagulants. The incidence decreases even further, according to evidence from Bonchek and Braunwald [5], when the bare metal is covered with Dacron cloth, allowing complete encapsulation of the prosthesis with a smooth neointima. The incidence of ball variance has not as yet been ascertained in our series. One fatal case has occurred, and minor variance has been seen in one other valve examined at postmortem for other reasons. Herr et al. [lo] estimate the current incidence at 10% in their series of 261 survivors followed more than one year postoperatively. This should be less of a problem now with a metal ball in the prosthesis. No persistent difficulty with hemolytic anemia has become apparent in any of our survivors. However, red blood cell survival and iron studies have not been done. The clinical improvement in the great majority of our patients is striking. It is apparent that this operation has offered significant palliation to a group of patients whose outlook otherwise was hopeless. SUMMARY Our clinical experience with aortic valve replacement using the Starr-Edwards prosthesis from February, 1963, to March, 1968, has been reviewed. The overall operative mortality was 14% for the entire series. The late mortality rate was 12%. The operative mortality rate for isolated aortic valve replacement over the last three years has now been reduced to 3.2%. Thromboembolic complications in the entire series occurred in 15%, but since the newer model valves have been employed, the incidence is now less than 2%. Over 85% of the operative survivors have returned to full activity and are clinically well without significant limitation. Yet, because of the uncertainty of the long-run results, we continue to advise this operation only in those patients with far-advanced disease of the aortic valve. REFERENCES 1. Barratt-Boyes, B. G., Lowe, J. B., and Cole, D. S. Homograft valve replacement for aortic valve disease. Thorax 20:495, Barratt-Boyes, B. G. Quoted by Kirklin, J. W., The Use of Homografts for Aortic Valve Replacement. Presented at Third Annual Postgraduate Seminar on Frontiers of Cardiovascular Surgery, 40th Annual Session, American Heart Association, San Francisco, Calif., Oct. 19, VOL. 6, NO. 4, OCTOBER,

8 NELSON, JENSON, AND JONES 3. Binet, J. P. Heterograft Replacement of the Aortic Valve. Presented at Postgraduate Course in Cardiovascular Surgery, 53rd Annual Clinical Congress, American College of Surgeons, Chicago, Ill., Oct. 6, Binet, J. P., Duran, C. G., Carpentier, A., and Langlois, J. Heterologous aortic valve transplantation. Lancet 2: 1275, Bonchek, L. I., and Braunwald, N. S. Thrombus resistant rigid prosthetic heart valves covered with porous synthetic fabric. Trans. Amer. SOC. Artif. Intern. Organs 13: 101, Cohen, M., Barwinsky, J., and Cases, J. M. Total prosthetic valve replacement: Clinical experience in 70 cases. Canad. J. Surg. 9:131, Cooley, D. A. New Aortic and Mitral Valve Prostheses: Experimental and Clinical Experience. Presented at Third Annual Postgraduate Seminar on Frontiers of Cardiovascular Surgery, 40th Annual Session, American Heart Association, San Francisco, Calif., Oct. 19, Fishman, N. H., Roe, B. B., and Hutchinson, J. C. Control of the hazards of cardiac valve replacement. Arner. J. Surg. 112:218, Gadboys, H. L., Litwak, R. S., Niemetz, J., and Wisch, N. Role of anticoagulants in preventing embolization from prosthetic heart valves. J.A.M.A. 202:282, Herr, R. H., Kloster, F. E., Sezai, Y., and Starr, A. Diagnosis and Management of Ball Variance Following Aortic Valve Replacement. Presented at 40th Annual Session, American Heart Association, San Francisco, Calif., Oct. 22, McGoon, D. C., Ellis, F. H., Jr., and Kirklin, J. W. Late results of operation for acquired aortic valvular disease. Circulation 31 (Suppl.): 108, McGoon, D. C., Pestana, C., and Moffitt, E. A. Decreased risk of aortic valve surgery. Arch. Surg. (Chicago) 91:779, Mortensen, J. D., Hurd, G., and Hill, G. Bacterial contamination of oxygen used clinically-importance and one method of control. Dis. Chest 42: 567, Mulder, D. G., Mazzei, E. A., and MacAlpin, R. N. Ball valve replacement for aortic valvular disease. J. Thorac. Cardiovasc. Surg. 52:76, Nelson, J. C., and Nelson, R. M. The incidence of hospital wound infection in thoracotomies. J. Thorac. Cardiovasc. Surg. 54:586, Nelson, R. M., lenson, C. B., Peterson, C. A., and Sanders, B. C. Effective use of prophyla& antibiotics in open heart surgery. Arch. Surg. (Chicago) 90:751. ~-.--, O Brien, M, F., and Clareborough, J. K. Heterograft aortic valve replacement. Lancet 1:929, Pierie, W. R., Hancock, W. D., Koorajian, S., and Starr, A. Materials and Heart Valve Prostheses. Presented at the New York Academy of Sciences, Materials in Biomedical Engineering Conferences, New York, June, Ross, D. N. Aortic valve replacement. Lancet 2:461, Ross, D. N. Homograft Replacement of the Aortic Valve. Presented at Postgraduate Course in Cardiovascular Surgery, 53rd Annual Clinical Congress, American College of Surgeons, Chicago, Ill., Oct. 6, Starr, A. Clinical and Laboratory Experience with the Ball Valve Prostheses. Presented at Third Annual Postgraduate Seminar on Frontiers of Cardiovascular Surgery, 40th Annual Session, American Heart Association, San Francisco, Calif., Oct. 19, Starr, A., Edwards, M. L., McCord, C. W., and Griswold, H. E. Aortic replacement: Clinical experience with a semi-rigid ball-valve prosthesis. Czrculation 27:779, Wheat, M. W., Jr., Linhart, J. W., Bartley, T. D., Taylor, W. J., Crevasse, L. E., and Green, J. R., Jr. Aortic ball-valve (Starr-Edwards) prostheses: A follow-up evaluation. Ann. Thorac. Surg. 2: 166, THE ANNALS OF THORACIC SURGERY