Combined Valve Replacement and Coronary Bypass Surgery*

Combined Valve Replacement and Coronary Bypass Surgery* Results in 127 Operations Stratified by Surgical Risk Factors W Dudley Johnson, M.D., F.G.G.P.; Kenneth L. Kayser, M.S.; Pablo M. Pedraza, M.D.; and jerold B. Brenowitz, M.D. The results of 127 operations with both valve replacement and coronary bypass were compared with all 5,053 operations involving coronary bypass performed from August 1972 through June 1985. Both groups were stratified by the number of risk factors (age over 70 years, bad ventricle, extensive endarterectomy, and reoperation). Compared with all bypass operations, valve replacement had no effect on surgical mortality except in the group at highest risk. Conversely, valve replacementwas associatedwith reduced late survival in all but those at highest risk. Results with tissue valves were better than with mechanical, but statistical significance was lacking. Relief of angina was equal. Ischemic mitral insufficiency continues to be the greatest challenge, with 46 percent five-year survival. We conclude that combined valve replacement and bypass surgerycan be performed successfully, even in the patients at higher risk; however, this operation should be performed only by teams with demonstrated success in surgically treating advanced coronary artery disease. The purpose of this study was to assess the results of combined valvular replacement and coronary bypass surgery and to compare these results with all patients undergoing bypass surgery in a comparable period of time. Surgical mortality, late mortality, and relief of angina were evaluated. The discussion con- For editorial comment see page 312 tains a comparison with other series in the literature. To make the comparison more meaningful, we stratified all subjects according to the number of major surgical risk factors present. Among the myriad of potential risk factors one could consider, we have found four which are most significant: (1) age over 70 years; (2) reoperation; (3) requirement of extensive endarterectomy; and (4) severe left ventricular dysfunction. These factors were defined after an analysis of all patients operated undergoing bypass surgery since July 1972 and were determined before this retrospective study on combined valves commenced. Anyone of these surgical risk factors adds about 6 percent to the surgical mortality. Any two add about 12 percent. We define "extensive endarterectomy" as two or more grafts placed to coronary arteries which required endarterectomy. We have found that single endarterectomy adds nothing to the surgical risk. Two or more procedures (it does not matter how many more) add 6 percent. Severe left ventricular dysfunction is defined as two or more major walls exhibiting distinct hypokinesia. This assessment is made by the surgeon after viewing the ventriculogram. *From St. Mary's Medical Center, Milwaukee. Reprint requests: Dr. Johnson, 2315 North Lake Drive, Milwaukee 53211 All available views are taken into account. Where the ejection fraction is under 20 percent or global hypokinesia is present, we assign a double risk factor. Ejection fraction is measured by the method of Dodge. These risk factors were carefully derived from over 6,000 bypass operations; however, there is no guarantee that these four risk factors will influence the small group of patients with combined valve and bypass surgery in exactly the same way that they influenced the large group. Group under Study MATERIALS AND METHODS The group studied consisted of all 127 patients undergoing combined bypass surgery and valvular replacement from August 1972 through June 1985. The initial group of6,872 patients used for comparison contained all patients undergoing bypass surgery (combined valvular replacement procedures included) during the same period of time; however, an analysis of this group for comparison found a disproportionate number of patients who underwent surgery in the earlieryears. This resultedin a much longeraverage follow-up for the comparison group. To reduce the possibility of bias and to facilitate comparisons, we randomly eliminated one half of the comparison group for the years 1973 through 1977. The resulting comparison group contains 5,053 subjects. Compared with the studied group, the comparison group has a good year-by-year proportion match and an almost identical average follow-up time. We made no otherconcessions to match the groups. For brevity, we shall refer to the 127 patients in the studied group as "valve and bypass" and refer to the 5,053 comparison group as "all bypass." The valveand-bypass group had 36/127(28.3 percent) women; age ranged from 25 to 81 years (average, 61.2 years). The all-bypass group had 803/5,053 women (15.9 percent); age ranged from 24 to 83 years (average, 57.3 years). Reason for Valve Replacement:Etiology All disease of the natural valves was presumed to be non-ischemic except mitral regurgitation. Tobe classed as ischemic mitral regurgitation, all of the following four factors must have been present: no 338 CombinedValveReplacement and Bypass Surgery (Johnson at 81)

Table I-Surgical Procedures" Table 2-Type o/prosthesis Used Data Valve and Bypass All Bypass Data Aortic Mitral Total Mean No. of grafts 2.8 4.2 TIssue Endarterectomy Carpentier-Edwards 10 24 34 Single 22 (17) 1,192 (23.6) Ionescu-Shiley 5 2 7 Multiple 15 (12) 871 (17.2) Angell-Shiley 2 4 6 Left system 26 (20) 1,481 (29.3) Hancock 7 29 36 Valvular replacement Total tissue 24 59 83 Aortic 54 (43) Mechanical Mitral 67 (53) Starr- Edwards 4 4 8 Double 6 (5) Bjork-Shiley 1 2 3 St. Jude 30 9 39 *Numbers within parentheses are percentages. history of rheumatic fever, no mitral stenosis, no aortic disease, and severe left ventricular dysfunction. Scarring of the papillary muscles, aneurysm formation and annular dilation were frequently present. There were 42 patients with mitral regurgitation of ischemic origin. Eight previously placed prostheses (in seven patients) were explanted and replaced. Two aortic valves were replaced due to injury of the valve during endarterectomy of the left main coronary. Twenty four of the 50 patients with severe left ventricular dysfunction required aneurysm resection. No additional risk factors are assigned for aneurysm resection. Our experience indicates that in patients with similar degrees ofventricular dysfunction, aneurysm resection neither increases nor decreases early or late mortality. All of the patients undergoing extensive endarterectomy were operated after 1979. Surgical Techniques and Procedures Car14':opulmonary Bypass. Since the early 1970s, we have attempted to perfuse patients in the most physiologic way. Our target range for arterial oxygen tension (PaOJ is between 70 and 160 mm Hg and for arterial carbon dioxide tension is between 35 and 45 mm Hg. Arterial pressure is kept over 70 mm Hg, preferably over 80 mm Hg whenever possible. This usually requires pump flow in the range of 70 to 100 ml/kg, Deviations from normal physiology include totalbody hypothermia of 30 C to 34 C and maintenance of the hematocrit reading at 20 to 28 percent, preferably over 22 percent. Myocardial Protection. For aortic valvular replacement, different methods have been used. Intermittent ischemic arrest, cold crystalline cardioplegia, and, currently, blood cardioplegia have been used. For all other procedures, including mitral valvular replacement and all coronary procedures, intermittent ischemic arrest was used. We use this technique becauseit affords superiorprotection to Total mechanical 35 15 50 Total 59 74 133 the patient with severe disease. Following are important factors in our technique of myocardial preservation: hematocrit reading over 20 percent; cross-clamp time limited to 25 minutes; at least five minutes of reperfusion with a beating heart; arterial pressure during reperfusion over 60 mm Hg: and Pa0 2 under 160 mm Hg. All prostheses are implanted with interrupted suture. When replacing the aortic valve, every effort is made to implant the largest prosthesis possible. When replacing the mitral valve, it is essential to preserve as much of the natural mitral mechanism as possible, especially the posterior leaflet. Unless calcification is severe and extensive, the posterior leaflet is left in place. Figure-of-eight sutures completely encompass the leaflet and then are inserted through the cuff of the valve. Surgical Procedures Performed. Table 1 demonstrates the procedures performed. The valve-and-bypass group had significantly less grafting and coronary endarterectomy. The proportion of aortic, mitral, and double valves replaced is unremarkable. Table 2 illustrates the valvular prostheses used. TIssue valves were used more often for mitral replacement. Many of these patients had poor left ventricular function, and it was believed that the tissue valve would lower the chances for embolic problems. RESULTS Surgical and Late Mortality Figures 1 to 3 demonstrate the surgical and late mortality of the valve-and-bypass group compared with the all-bypass comparable group described previously. In the group at lowest risk (0 risk factors), 33 valve-and-bypass patients had no 30-day mortality, 100 --------------------------.........-_._._------ o o 80.-.-. All Bypass.---. Valve and Bypass lone S.E. 70 +----..---------------------------+ o 234 5 ALIVE AT BEGINNING OF INTERVAL All Bypass 2344 2020 1895 1765 1566 FIGURE 1. Survival curves from patients with no Valve and presurgical risk factors. Bypass 33 26 23 22 18 CHEST I I 3 I SEPTEMBER, 1986 339

100 ------------------------r en.5 CJ) '80 70.---. All Bypass......--_._------- 60 -----. Valve and Bypass I One S.E. 50 +---r-o-..,----r----r----,r---r---.,----..._-_t_ o 234 ALIVE A T BEGINNING OF INTER VAL All Bypass 1936 1345 1088 880... I... 654 5 Vlve and Bypass 60 39 32 27 21 FIGURE 2. Survival curves from patients with one presurgical risk factor. en.5 :5 CJ) 100 80 70 60 =.:. ::::.. 1 ----.---- ---.-. 50-40.-----. Valve and Bypass 30 I One S.E. 20...---r-o--...--.----..----.----,,..---...---...--...--...-..-+ o 2 3 4 5 ALIVE AT BEGINNING OF INTERVAL All Bypass 773 421 322 223 136 FIGURE 3. Survival curves from patients with two or Valve and more risk factors. Bypass 34 18 14 10 7 compared to 98. 7 percent survival for the all-bypass group; however, late survival was much lower in the valve group, ie, 85.8 percent and 81.6 percent at three and five years, respectively, compared to 95.7 percent and 92.5 percent for the all-bypass group. Where one risk factor was present, 3O-day survival was 91.7 percent, valve and bypass vs 93.9 percentfor all bypass. Late survival was better in the all-bypass group: 84.2 percent and 76.9 percent at three and five years vs 77.3 percent and 60.5 percent for valve and bypass. The least differences were observed where two or more risk factors were present; 30-day survival was 83.8 percent, all bypass vs 76.5 percent valve and bypass. Late survival differed little if any when the difference in 30-day survival is removed. Five-year survival of those who survived 30 days was 68.1 percent in each group. ReliefofAngina Table 3 illustrates relief of angina. The valve-andbypass group had significantly lower prevalence of angina before surgery. After surgery, relief of angina was quite similar. In those with preoperative angina, the all-bypass group had a 2 percent edge in no angina and total improved; however, this difference is well within expected limits of statistical variation. Average follow-up was 53.4 months in the valve-and-bypass group and 56.6 months in the all-bypass group. Tissue vs Mechanical Prostheses Figure 4 shows survival curves divided by type of Table 3-BeliefofAngina Data Valve and Bypass All Bypass Presenting with angina 37/00 (62) 2,09412,775 (75.5) Postoperative statust Total improved 32 (87) 1,856 (88.6) No angina 23 (62) 1,354 (64.7) Less angina 9 (24) 502 (24.0) Not improved 5 (14) 212 (10.1) No answer 0 26 (1.2) Average follow-up, mo 53 57 *Data are numbers of patients; numbers within parentheses are percentages. tor patients presenting with angina. 340 CombinedvatveReplacement and BypassSurgery (Johnson et aj)

100 C).s 80 70 en 0 60 0 50 40 0 ALIVE A T BEGINNING 2 3 OF INTERVAL 4 Tissue 78 54 49 42 38 Mechanical after 1973 41 All Mechanical 47 22 15 28 19 12 16 5 FIGURE 4. Survival curves from patients receiving tissue mechanical prostheses. Groups were cornpa 7 rable in other respects. prosthesis used. All patients are included except the two double valvular replacements with mixed tissue and mechanical prostheses. Three patients had double tissue prostheses and one patient double mechanical. If any precomparison bias exists, it would seem to favor the mechanical valves. The average number of risk factors was almost equal (mechanical valves, 1.04; tissue valves, 1.02); however, tissue valves predominated as a mitral replacement (Table 2). In this series, as in most others, late mortality following mitral replacement exceeds that after aortic replacement. The first six cases were all Starr-Edwards mechanical valves. To eliminate this possible bias unfavorable to mechanical prostheses, we recalculated the mechanical group eliminating these first six cases. The overall actuarial four-year postoperative survival was 50 percent with all mechanical valves and 58 percent when the early Starr-Edwards valves were excluded (not significant). Four-year survival with tissue valves was 77 percent. Because of the observed discrepancy between tissue and mechanical prostheses, we compared tissue valves alone to a comparable "all-bypass" group. Because the numbers are small, we did not stratify by risk factors. Instead, we compared all tissue valves with a group of 3,052 patients undergoing bypass with the same proportion of risk factors (28 percent, no risk factors; 47 percent, one risk factor; and 25 percent, two or more risk factors). The "comparable all-bypass" group was formed by randomly excluding 1,495 patients with no risk factors and 506 with one risk factor from the 5,053 in the "all-bypass" group. The results are shown in Figure 5. These survival curves demonstrate a 3 percent higher surgical mortality for tissue valves but no apparent difference in late mortality. Mitral Regurgitation ofischemic Origin This group is included because many other authors discuss these patients separately and because the prognosis is exceptionally poor in all published reports. There were 42 patients with ischemic mitral insufficiency. Thirty-day survival was 85 percent, three year survival was 61 percent; and five-year was 46 percent. Twenty patients were alive at the beginningof 100 "..----------------------- C).= 80 -------- en -..--... All Bypass 70.-----. Valve and Bypass I! One S.E. 60 0 234 5 ALIVE A T BEGINNING OF INTERVAL All Bypass 3052 2188 1878 1592 1288 FIGURE 5. Survival curves from patients receiving tissue prostheses vs comparable "all-bypass" group Valve and with comparable risk factors. Bypass 78 54 49 42 38 CHEST / / 3 / SEPTEMBER, 1986 341

Table 4-Coronary Bypass and Mitral Valve Replacement in This Report and Other Recent Reports Late Survival, 30-Day percent Prosthesis Reference and No. of Mortality, Years of Surgery Group* Subjects percent 3-Year 5-Year Majority Type Percent Czer et af (69-82) EFO.55 88 10.2 80.0 64.0 EF<O.56 18.8 55.0 33.0 Mechanical 54 Lytle et al" (70-83) t 300 7.3 76 61 TIssue 54 Geha et al' (77-82) 106 22.0 61.0 Tissue 87 Kay et al (71-83) Nonischemic 70 9.0 66.0 55.0 Ischemic 28 14.0 50.0 43.0 Mechanlcalt Johnson et al (72-85) No risk factors 14 0.0 85.3 76.4 1 risk factor 54 15.1 64.2 51.9 TIssue 79 *EF, Ejection fraction. texcluding reoperation, valvular reconstruction, aneurysmectomy, and carotid surgery. :l:entire series, percent caged ball, with remainder not specified. the third year and 13 the fifth year, DISCUSSION Valve Replacement Philosophy Essential Total Revascularization with Valve Replacement When Necessary. As stated previously, in a total of 6,872 operations for bypass, we have replaced 133 valves in 127 patients (1.8 percent). We replace valves only when significant malfunction exists. The use of rings to correct mitral insufficiency due to coronary disease is an area that needs development. A few were done (not included in the valve-and-bypass group), butfailure was too common, and the technique has not been used for sixyears. Mitral insufficiency due to severe damage to the inferior wall has been seen many times.' This type of insufficiency can nearly always be corrected without valvular replacement, and the valve-and-bypass group does not include these patients. In four cases (not included in the valve-and-bypass group), mitral insufficiency has been corrected with bypass grafts alone. This rare event is most likely to occur in a patient with a dilated hypokinetic ventricle with minimal scat; usually associated with severe angina and critical ischemia in the posterior and inferior wall. Comparison with Other Published Studies Comparing results from different centers is approximate at best. Most authors divide the mitral and aortic replacements and eliminate the multiple replacements. Every report has certain qualifications, some have exclusions, and the authors divide the series according to criteria they think best. No one (including us) reports what proportion of patients they (or their referring cardiologists) reject for surgery. Many other studies consider the combined procedures as primarily valvular with some bypass grafting added. Our service is primarily coronary. We view the subjects in our study as patients with advanced coronary disease who also had valvular dysfunction. The differences in our aortic, mitral, or double valve replacements were small enough that we could combine them. For the sake of uniformity, however, we did divide our group for Tables 4 and 5. These tables contain data from recent reports where the main topic was combined valvular and bypass surgery and where data from life tables were included. Tables 4 and 5 Table 5-Coronary Bypass and Aortic Valve Replacement in This Report and Other Recent Reports 30-Day Late Survival, percent Prosthesis Reference and No. of Mortality, Years of Surgery Subjects percent 3-Year 5-Year Majority Type Percent Geha et al (77-82) 82 9 78 TIssue 68 Kouchoukos et al ll (78-82)* 54 2 87 80 TIssue 54 Nunley et al" (69-75) 96 16 70 62 Mechanicalt 92 (76-81) 101 5 82 72 Lytle et al 1J (67-81):1: 500 6 79 72 t\1echanical 55 Johnson et al (72-85) 15 0 85 85 3811 1 75 62 Mechanical 60 *Excluded all cases where problems with aorta were encountered. tspecified 92 percent, caged ball; remainder were not specified. :l:excluded all reoperation, other combined procedures, and grafting for other than atherosclerosis. No risk factors present. "One or more risk factors present. 342 CombinedValve Replacement and BypassSurgery (Johnsonat 81)

contain no data on double valve replacements, which are discussed below Other Reports, Combined Mitral Valve Replacement and Bypass Surgery Czer et al" reported on 174 subjects, with ejection fraction data. Sixty-three percent had three vessel disease. These authors concluded that where concomitant valvular and coronary disease exist, it is essential to bypass the coronary disease. DiSesa et al", reporting on 100patients, found the greatest predictor of surgical survival to be preoperative NYHA functional class. Thirty-six patients in class 3 had no death; 64 patients in class 4 had 18 (28 percent) surgical deaths. Surgical mortality on "emergency" patients was 60 percent. These investigations concluded that earlier intervention and better methods of myocardial protection would lead to lower mortality. Geha et al," reporting on 106 patients, compared isolated valvular replacement with combined procedures and found that the combined procedures had slightly higher surgical mortality but no increased late mortality. This seems to corroborate results in our study. In the groups at lower risk, most of the late mortality seems to be associated with the prosthesis or the valvular disease. Kay et al" reported on 98 patients. They divided the group into groups with "nonischemic" and "ischemic" valvular disease. These authors present the longest follow-up. Ten-year survival with isolated mitral valve disease was 63 percent, compared to 43 percent with combined bypass surgery. They found ischemic mitral regurgitation to have a very poor prognosis; only 50 percent of the patients survived one year. Kabbani et al" reported on 40 patients. Surgical mortality was 29 percent in patients with three-vessel disease and 43 percent with ejection fraction under 50 percent. These investigators recommend caution where extensive coronary disease or ventricular dysfunction exists. Reed et af reported 66 aortic, 28 mitral, seven double, and four triple combined valvular "procedures." All patients with "acute dissection of the ascending aorta, infected prosthesis, acute myocardial infarction, and cardiac arrest" were excluded. The number of patients excluded was not stated. These investigators reported the best overall surgical mortality (3.5 percent); however, the series of 28 mitral "procedures" includes seven annuloplasties, leaving only 21 mitral replacements. An average of 2.4 grafts were placed. Late mortality was about 1 percent per month in an average 15-month follow-up. The proportion of mitral replacements (21) vs aortic (66) seems low, suggesting, perhaps, that these authors were somewhat selective when mitral dysfunction is present. Lytle et al" reported the findings from 300 patients undergoingsurgeryfrom 1970throughJuly 1983. They excluded patients undergoing cardiac reoperation, mitral valve reconstruction, concomitant aneurysmectomy, or carotid operation. They had early mortality of 7.3 percent, with 76 percent for three-year survival and 61percentfor five-year survival. Patients receiving a tissue prosthesis without anticoagulants had the best survival. Yadov et al" reported the findings from 62 patients undergoing combined mitral replacement and bypass grafting. Mortality during hospitalization was 13 percent for disease of ischemic origin and zero for rheumatic, 20 percent for mitral regurgitation, and zero for stenosis. Mattila et apo reported on 15 procedures with two early deaths (13 percent). Recent Reports on Combined Bypass Surgery and Aortic Valvular Replacement. Table 5 lists five recent reports on bypass surgery combined with aortic valvular replacement. Geha et al' concluded that combined aortic replacement and bypass surgery had results comparable to isolated aortic replacement. Kouchoukas et all! reported excellent survival but reported only the later patients and excluded all patients requiring repair or replacement of the ascending aorta. All operations were done with cold cardioplegia. Nunley et al" showed a marked difference in mortality by year of surgery; surgical mortality dropped to one third in the later period. These investigators concluded that bypass surgery added nothing to the surgical or late mortality of aortic valvular replacement. Reed et al' reported on 66 aortic replacements with only two surgical deaths; however, as stated earlier, they excluded an unknown number of subjects from their series. An average of3. 2 grafts were placed. Lytle et al" reported on 500 patients with combined aortic replacement undergoing surgery from 1967 through 1981. They excluded all cardiac reoperation, other combined procedures, and bypass grafting for reasons other than atherosclerosis. Mortality during hospitalization was 5.9 percent; survival was 79 percent at three years and 72 percent at five years. These investigators found excellent late survival in patients with biological prostheses and no anticoagulants. Nugent et ap4 reported the findings from 11 patients undergoing aortic replacement in the presence of severe left main stenosis. There were three deaths in the first five patients and none in the next six when a double clamping technique was used. Watson et aps reported the findings from 50 patients with bypass and aortic replacement. Thirty-day mortality was 10 percent, with approximately 79 percent as 30 month survival. Mattila et al" are unusual. They used all mechanical prostheses. In 39 patients, there were two early and two late deaths. Multiple Valve Replacement. Akins et ap6 reported 33 consecutive double replacements with four deaths during hospitalization (12.1 percent). They reported 70 percent survival at 16 months and 60 percent at 40 CHEST / / 3 / SEPTEMBER, 1986 343

Table 6-1schemic Mitral Insufficiency in This Report and Other Recent Reports Late Survival, 30-Day percent No. of Mortality, Reference Subjects percent 3-Year 5-Year Czer et af 27 80 60 41 DiSesa et ap 55 82 Ceha et al' 57 72 Kay et ap 28 84 50 43 Kabbani et all) 14 79 Lytle et af* 47 89 71 52 Johnson et al 42 86 61 46 *Excluding aneurysmal resection. months. There were no deaths after 40 months. Reed et af reported on seven double and four triple "procedures." Most of these were single replacements with repair of the other valve(s). These investigators had one surgical and two late deaths in an average I5-month follow-up. Akins et al" reviewed the literature for double replacement and found an average surgical mortality of 18.8 percent. Of the six double replacements in this series, there was one early death (17 percent) and no late deaths in the eight-year follow-up period. Ischemic Mitral Insufficiency. Table 6 compares the results of combined mitral replacement and bypass surgery where the primary cause was ischemia. Because this entity is always associated with severe left ventricular dysfunction, early mortality and late mortality are high. The best results are reported by the Cleveland Clinic," but they excluded all patients with aneurysm. Ofour 42 patients, 21 required aneurysmal resection with a closure of 6 em or more. Kay et al" showed the highest mortality, with a 50 percent one year survival. Comments on All Comparisons Although comparisons are, at best, very approximate, it is apparent that mitral replacement carries a higher mortality than aortic and that mitral regurgitation of ischemic origin has the worst prognosis. Gleaning what information we can from our study and others, especially the two from the Cleveland Clinic, tissue prostheses appear to be superior in the first five years following surgery. When one considers the other advantages of tissue (no anticoagulation; quiet; slow failure mode), it would seem to be the valve of choice in most instances; however, there are very few data after the first five years. It is very possible that tissue prostheses will fail at increasingly higher rates as time passes. CONCLUSION The results of this study and those of the cited studies indicate that valve replacement in the presence of significant coronary arterial disease must be approached with caution. When patients with combined valve replacement and bypass surgery were compared with a time-matched group of all patients with bypass surgery, the following was observed: Best risk group: valve replacement was associated with an elevated late mortality; five-year survival was 82 percent; Moderate risk: valve replacement was associated with an elevated late mortality, five-year survival was 60 percent; High risk: valve replacement was associated with a slightly elevated surgical mortality, five-year survival was 52 percent. When considering tissue prostheses alone, valve replacement was associated with no increase in late mortality compared to the all bypass group and fouryear survival was 77 percent. However, it must be stressed that there are few data after five years and that this pattern could change substantially. Many other series report greatly elevated surgical mortality in the presence of ventricular dysfunction, especially when associated with severe mitral regurgitation of ischemic origin. Surgery can be successfully performed in high risk patients, but only surgical teams with demonstrated success in treating severe coronary disease should attempt them. No definite conclusion can be drawn from our data comparing mechanical with tissue prostheses (see addendum). However, the data presented herein, combined with data from the Cleveland Clinic, are sufficient to convince us to favor tissue valves in this type of surgery. ADDENDUM Since the manuscript was prepared, we have obtained additional data on four patients with mechanical prostheses and three with tissue prostheses. All four with mechanical valves are alive and two of three with tissue valves have expired at 31 and 25 months. Three offour mechanical valves were aortic. Twotissue valves were mitral and one double. We added these additional data to those used to generate Figure 4. The resulting five-year survival is as follows: Tissue valves 0.66, SE 0.06 Mechanical valves 0.5542, SE 0.09 Later Mechanical valves 0.6288, SE 0.09 The additional followup data have caused the difference between tissue valves and mechanical valves to diminish. REFERENCES 1 Johnson WD, Pedraza PM, Kayser KL. Preservation and restoration of the mitral mechanism during inferior wall aneurysmectomy. In: Recent progress in mitral valve disease. London: Butterworths, 1984:410-15 2 Czer LS, Gray RJ, DeRobertis MA, Bateman TM, Stewart ME, 344 Combined Valve Replacement and BypassSurgery (Johnson at al)

Chaux A, et al. Mitral valve replacement: impact of coronary artery disease and eterminants of prognosis after revascularization. Circulation 1984; 70(suppl 1):1198-207 3 DiSesa VJ, Cohn LH, Collins JJ, Koster JK, VanDevanter S. Determinants of operative survival following combined mitral valve replacement and coronary revascularization. Ann Thorac Surg 1982; 34:482-89 4 Geha AS, Francis CK, Hammond GL, Laks H, KopfGS, Hashim SW. Combined valve replacement and myocardial revascularization. J Vasc Surg 1984; 1:27-35 5 Kay PH, Nunley DL, Grunkemeier GL, Pinson CW, Starr A. Late results of combined mitral valve replacement and coronary bypass surgery. J Am Coll CardioI1985; 5:29-33 6 Kabbani SS, Bashour T'I, Hanna ES, Ellertson D. Risk of combined coronary artery bypass and mitral valve replacement. Tex Heart Inst J 1984; 11:348-51 7 Reed GE, Sanoudos GM, Pooley R Moggio RA, McClung JA, Somberg ED, et al. Results ofcombined valvular and myocardial revascularization operations. J Thorac Cardiovasc Surg 1983; 85: 422-26 8 Lytle B\V, Cosgrove DM, Gill CC, Stewart RW, Golding LA, Goormastic M, et ai. Mitral valve replacement combined with myocardial revascularization: early and late results for 300 patients, 1970 to 1983. Circulation 1985; 71:1179-9 Yadav KS, Ross JK, Monro JL, Shore DF: Study of risk factors related to early mortality following combined mitral valve replacement and coronary artery bypass grafting: factors influencing early and late results. Thorac Cardiovasc Surg 1985; 33: 16-9 10 Mattila S, Harjula A, Jarvinen A, Kyllonen KEJ, Tala P Combined valve replacement and myocardial revascularization. Scand J Thorac Cardiovasc Surg 1984; 18:49-52 11 Kouchoukos N'I, Lell WA, Rogers WJ. Combined aortic valve replacement and myocardial revascularization: experience with a cold cardioplegic technique. Ann Surg 1983; 197:721-27 12 Nunley DL, Grunkemeier GL, Starr A. Aortic valve replacement with coronary bypass grafting: significant determinants of ten-year survival. J Thorac Cardiovasc Surg 1983; 85:705-11 13 Lytle B Cosgrove DM, Loop FD, Taylor PC, Gill CC, Golding LA, et al. Replacement of aortic valve combined with myocardial revascularization: determinants of early and late risk for 500 patients, 1967-1981. Circulation 1983; 68:1149-62 14 Nugent WC, Weintraub RM, Thurer RL, Levine FH. Aortic valve replacement and coronary bypass in patients with severe stenosis of the left main coronary artery. Ann Thorac Surg 1983; 35:562-64 15 Watson DR, Osborn C, Bush C. Aortic valve replacement with concomitant myocardial revascularization. Ohio State Med J 1985; 81:112-16 16 Akins CW, Buckley MJ, Daggett WM, Hilgenberg AD, Austen WG. Myocardial revascularization with combined aortic and mitral valve replacements. JThorac Cardiovasc Surg 1985; : 272-77 Advanced Cardiac Life Support Provider Course Advanced Cardiac Life Support Instructor Course The University of Kansas Medical Center will present the Life Support Provider Course November 5-6 at the Student Center, Fransisco Lounge, UKMC, and the Life Support InstructorCoursein the same location, November7. For information, contact David S. Baldwin, MPA, University of Kansas Medical Center, Office of Continuing Education, 39th and Rainbow Blvd, Kansas City, Kansas 66103 (913:588-4488). CHEST / / 3 / SEPTEMBER, 1986 345