Multiple Valve Replacement: Changing Status

Multiple Valve Replacement: Changing Status Phillip N. West, M.D., Thomas B. Ferguson, M.D., Richard E. Clark, M.D., and Clarence S. Weldon, M.D.

ABSTRACT Review of our experience with multiple valve replacement over a 6-year period revealed a recent marked reduction in operative risk. Operative mortality for 62 patients operated on before 1974 was 34%; for 44 patients operated on since 1974, mortality was only 11%. In both groups, mortality was clearly related to the preoperative cardiac functional status. Several recent technical advances including myocardial protection by topical hypothermia, shortened perfusion time, and the intraaortic balloon pump may all have contributed to the reduced operative risk.

Disease of multiple cardiac valves presents a formidable challenge to the surgeon. The degree of cardiac decompensation is usually severe, and the hemodynamic alterations often result in dysfunction of other organs. Replacement of multiple diseased valves requires an extended period of cardiopulmonary bypass, and, in spite of current popular methods of myocardial "protection," some myocardial damage usually occurs during operation [ll]. These factors, combined with the technical demands of replacing or repairing major portions of the cardiac structure, contribute to the high risk of surgical treatment of multiple valve disease [6, 7, 121. In this report we analyze 106 consecutive operations for multiple valve replacement performed in 102 patients during the years 1970 through 1976. Although the population of patients undergoing this operation has changed little, a reduction in operative mortality has occurred. Multiple recent changes in operative and postoperative management have been associated with the reduced risk of operation. From the Division of Cardiothoracic Surgery, Washington University School of Medicine, St. Louis, MO. Presented at the Twenty-fourth Annual Meeting of the Southern Thoracic Surgical Association, Nov 3-5, 1977, Marco Island, FL. Address reprint requests to Dr. Weldon, 4960 Audubon Ave, St. Louis, MO 63110. 32 0003-497517810026-0107$01.25 @ 1978 by Phillip N. West

Materials and Methods All patients undergoing replacement of multiple cardiac valves at Barnes Hospital in St. Louis from January, 1970, through June, 1976, form the basis of this report. Patients who underwent double valve replacement and coronary artery bypass were excluded. The hospital charts and perfusion records of 102 patients having 106 consecutive operations for replacement of multiple cardiac valves were reviewed. Sixty-two patients were operated on before 1974, during the time when coronary perfusion was used for myocardial protection (Group 1); 44 patients were operated on after that period (Group 2), and ischemic arrest and topical hypothermia [13] were employed to provide myocardial' protection. In the 1-year period from July, 1976, through June, 1977, 15 additional patients underwent multiple valve replacement. For them cardioplegia in combination with topical hypothermia was the means of myocardial protection. Because of the small number involved, the records of these more recent patients were analyzed only for operative mortality. Preoperative characteristics identified for each patient were age, sex, functional status according to the New York Heart Association (NYHA) Functional Classification, previous cardiac operations, electrocardiographic evidence of complete heart block or previous myocardial infarction, and the roentgenographic finding of cardiomegaly. The valvular hemodynamic abnormality (stenosis, regurgitation) and an assessment of left ventricular function were determined from the report of the cardiac catheterization. Data gathered from the operative period included duration of cardiopulmonary bypass and, for patients in Group 2, the aortic cross-clamp time. In the postoperative period, the need for cardiovascular support with catecholamines or the intraaortic balloon pump (IABP) was noted, and the duration of this support was recorded. The pres-

33

West et al: Multiple Valve Replacement

ence of ventricular arrhythmias requiring administration of lidocaine, procainamide, or ventricular pacing was recorded. Evidence of heart block or perioperative myocardial infarction (MI) was sought in electrocardiograms made approximately one week after operation. When available, postmortem reports were examined to determine the cause of death and to identify myocardial damage that might have been incurred at operation. Double coronary perfusion was used for myocardial protection during multiple valve replacements performed prior to 1974. Combined coronary flow of 250 to 500 ml per minute was delivered through left and right coronary cannulas during aortic and mitral valve replacement. If triple valve replacement was necessary, the tricuspid valve was usually inserted after release of the aortic cross-clamp. Mitral and tricuspid replacement was performed with intermittent aortic cross-clamping in place of continuous coronary perfusion. Details of cardiopulmonary bypass included moderate hemodilution and systemic hypothermia to 28" to 30°C. A bubble oxygenator* was used in 59 patients and a membrane oxygenatort in the remaining 3. Hypothermic ischemic arrest and substrate priming prior to ischemia were used for myocardial protection during operations performed from January, 1974, through June, 1976. Local hypothermia was achieved by the method of Griepp and associates [3], bathing the heart in cold (4°C) Ringer's lactate prior to and during the period of aortic cross-clamping. At the initiation of cardiopulmonary bypass, 100 gm of glucose, 60 units of regular insulin, and 60 mEq of potassium chloride were added to the extracorporeal circuit. Valve replacement was performed during one to three periods of aortic cross-clamping up to 90 minutes in length. Bubble oxygenators$,§ were used in 31 patients and a membrane oxygenator11 in 13. Systemic

*Temptrol Q 100, Bentley Laboratories, Inc, Irvine, CA. tModulung 3000, Travenol Laboratories, Deerfield, IL. $Galen Optiflo 42-200, Cobe Laboratories, Lakewood, CO. §Harvey H1000, William Harvey Research, Santa Ana, CA. IlTravenol TMO, Travenol Laboratories, Deerfield, IL.

hypothermia and moderate hemodilution were routine, as in the earlier group. During the operation in both Groups 1and 2, low cardiac output was treated by continued partial bypass and infusion of catecholamines. In patients operated on since January, 1974, if these measures were insufficient to improve and sustain cardiac performance, an intraaortic balloon was placed and counterpulsation was initiated. Anesthetic management was constant over the years of this study. Morphine sulfate (1.0 to 1.5 mg per kilogram of body weight) administered intravenously was supplemented by controlled ventilation with a mixture of nitrous oxide and oxygen. After operation, reduced cardiac output and arterial hypotension were treated with continuous infusion of catecholamines, including epinephrine, isoproterenol, and norepinephrine. After January, 1974, an additional agent, dopamine, was used. The IABP was used in 12 patients operated on after January, 1974, to assist in weaning from cardiopulmonary bypass and to provide hemodynamic support early after operation. Controlled ventilation for a minimum of 12 hours postoperatively was necessitated by the anesthetic management just described. Thereafter, extubation was dictated by evaluation of serial arterial blood gases. Ventricular arrhythmias were managed with continuous infusion of lidocaine, parenteral administration of procainamide, or both of these, and occasionally by ventricular pacing. A temporary epicardial electrode, routinely placed at the time of operation, was used for cardiac pacing if heart block was evident postoperatively. In general, when heart block persisted for seven days, a permanent epicardial pacemaker was placed.

Results Preoperative Characteristics Patients having multiple valve replacement before 1974 (Group 1) included 23 males and 39 females. Group 2, those operated on since January, 1974, had 11 male and 33 female patients. The mean age of patients in Group l was 45.9 k 2.3 (SEM) years and in Group 2, 49.4 f

34 The Annals of Thoracic Surgery Vol 26 No 1 July 1978

2.4 (SEM) years. Differences between groups with regard to age and sex were not statistically significant by the unpaired Student t test. The cause of multivalvular heart disease in both groups was overwhelmingly rheumatic endocarditis. However, 3 patients (all in Group 2) with atrioventricular canal defects required mitral and tricuspid valve replacement when primary repair resulted in residual atrioventricular valve insufficiency. Re-replacement of multiple cardiac valves was necessary in 5 patients (4 previously operated on at this center): 3 had known or suspected prosthetic wear and 2, prosthetic endocarditis. Debilitating congestive heart failure was the indication for operation in virtually every patient. The distribution of patients with respect to preoperative NYHA Functional Classification is remarkably similar for the two groups. In Group 1, 6 patients were in Functional Class 11, 42 in Class 111, and 14 in Class IV; in Group 2 , 3 patients were in Class 11, 27 in Class 111, and 14 in Class IV. This similarity reflects the advanced degree of cardiac decompensation characteristic of patients with multivalvular disease. The distribution of diseased valves requiring replacement was likewise similar for the two groups (Table 1). There was no difference between the groups with respect to the kinds of valve disease (stenosis or insufficiency) or the combinations of valve disease, as determined by preoperative cardiac catheterization. Left ventricular function was not routinely assessed by calculation of ejection fraction during the early years of the study, but for patients in whom this information was available, there was no difference between the two groups. The ECG demonstrated previous myocardial infarction in 3 patients in each group. In addition, recent myocardial infarction (less than six weeks previously) was present in 2 patients in Group 1 (unsuspected in 1)and in 1 patient in Group 2 (also unsuspected). Roentgenograms of the chest revealed cardiomegaly in all but 4 patients in Group l and in all but l patient in Group 2. Of interest was the cardiac surgical history of patients having multiple valve replacement. Seventeen of the 62 patients in Group 1 had

Table 1 . Distribution of 106 Valves Requiring Replacement Valve Group

AIM

MIT

AIT

AIMIT

Group 1

41a 26“ 67

7 6 13

lb

0 1

13 12 25

Group 2 Total

“One patient had tricuspid commissurotomy. bMitral commissurotomy also was performed. “Onepatient had tricuspid annuloplasty. A = aortic valve; M = mitral valve; T = tricuspid valve.

previously undergone cardiac operation, but only 3 of 62 (5%)had had an open-heart procedure (2, open mitral commissurotomy; 1, valve replacement). Fourteen of the 44 patients in Group 2 had had previous cardiac surgery; 5 of these had undergone two or more procedures. Thirteen patients (30%) had had at least one previous open-heart procedure (10, valve replacement; 1, mitral commissurotomy; 2, repair of atrioventricular canal).

Duration of Cardiopulmonary Bypass The mean perfusion time for all patients having multiple valve replacement using topical hypothermia was 149 f 8 (SEM) minutes. This was significantly less ( p < 0.001) than mean pump time for patients undergoing operation with coronary perfusion, 190 _+ 7 (SEM) minutes. When examined in subgroups according to the valves replaced, duration of cardiopulmonary bypass was significantly shorter for Group 2 patients having aortic and mitral or triple valve replacement. No difference in bypass time was evident for mitral and tricuspid replacement between the two groups. In Group 2, mean cross-clamp time for patients having aortic and mitral replacement was 99 f 5 (SEM) minutes and for mitral and tricuspid replacement, 101 t 19 (SEM) minutes. Triple valve replacement required 130 k 9 (SEM) minutes of aortic cross-clamping. Postoperative Cardiac Performance Pharmacological support was necessary in 48 of the 62 patients (77%) in Group 1. Five of those 48 patients died in the operating room and 8

35 West et al: Multiple Valve Replacement

died in the postoperative period of low cardiac output unresponsive to catecholamines. Pharmacological or mechanical (IABP) support or both were used in 30 of the 44 patients (68%) in Group 2. Four of these 30 patients died intraoperatively of low cardiac output in spite of catecholamine and IABP support. Thus, the proportion of patients requiring postoperative hemodynamic support was similar for the two groups. The length of time of pharmacological or mechanical cardiovascular support or both for patients leaving the operating room was also similar in both groups. In Group 1, mean time of catecholamine support was 35 k 7 (SEM) hours. If patients who died in the postoperative period are excluded (12 patients, of whom 8 died of low cardiac output), this figure is 26 k 6 (SEM) hours. In Group 2, mean duration of pharmacological or mechanical support or both was 25 k 4 (SEM) hours. Ventricular arrhythmias requiring continuous infusion of lidocaine, parenteral administration of procainamide, or ventricular pacing occurred less frequently in Group 2. Thirty-four of 53 patients (64%) in Group 1 compared with only 17 of 39 patients in Group 2 (44%) ( p = 0.05) had such arrhythmias. Perioperative MI was found at postmortem examination or was diagnosed by the appearance of new Q waves in the postoperative ECG in 5 of 53 patients (9.4%) in Group 1and 3 of 30 patients in Group 2 (10%) for whom this information could be obtained. The development of complete heart block prevented electrocardiographic diagnosis of infarction in some patients. Four of the 5 patients in Group l who sustained perioperative MI died, but none of the 3 in Group 2 died.

Complete heart block requiring the placement of a pacemaker complicated multiple valve replacement 8 times in Group 1 and 10 times in Group 2. This difference was not statistically significant. Heart block was most frequent after procedures that included tricuspid replacement.

Operative Mortality Twenty-one of the 62 patients in Group 1 (33.9%) died within thirty days of operation and 5 of the 44 patients in Group 2 (11.4%) ( p < 0.01). Two late hospital deaths in Group 2 were related to complications from operation: wound infection in 1 and anoxic brain damage in the other. No late hospital deaths occurred in Group 1. Only 1 operative death (6.7%) occurred in the 15 patients who underwent multiple valve replacement between July, 1976, and June, 1977, when cardioplegia and topical hypothermia were used for myocardial protection. Thirteen patients in Group 1and 4 patients in Group 2 died of low cardiac output unresponsive to supportive measures. This was the most frequent cause of death in both groups. Only catecholamines were available for postoperative hemodynamic support in Group 1; in contrast, the IABP was used in 12 of the 44 patients of Group 2. However, of 9 patients treated with the IABP who left the operating room, 4 did not require concurrent infusion of catecholamines. Therefore, a critical role for the IABP can be inferred in only 5 patients. Technical errors were less often the cause of death. One patient in each group died of hemorrhage from the posterior atrioventriculargroove following operations that included mitral valve replacement.

Table 2 . Operative Mortality with Regard to Valve Replaced Valve Group

AIM

M/T

AIMIT

AIT

Group 1 Group 2 p Value

11/41 (27%) 3/26 (12%) p < 0.2”

417 (57%) 1/6 (17%) p < 0.2a

5/13 (38%) 1/12 (8%) p < 0.1”

111 (100%)

“Comparison of Groups 1 and 2 by unpaired t test. A = aortic valve; M = mitral valve; T = tricuspid valve.

36 The Annals of Thoracic Surgery Vol 26 No 1 July 1978

Table 3 . Operative Mortality by Preoperative N e w York Heart Association Functional Class Functional Class

Group

I1

Group 1 Group 2 Total

0/6 (0%) 13/42 (31%) 0127 (0%) 113 (33%) 1/9 (11%) 13/69 (19%)

111

IV 8/14 (57%) 4/14 (29%) 12/28 (43%)

Mortality according to valves replaced is illustrated in Table 2. A reduction in mortality for every subgroup is evident in those patients operated on since 1974. These differences only approach statistical significance because of the size of the population. Risk of operation correlated with preoperative NYHA Functional Class (Table 3). Of special interest, in Group 2, all 4 patients who died of low cardiac output had Class IV cardiac disability before operation. Previous cardiac operation did not increase or decrease the risk of multiple valve replacement. One of 3 patients in Group 1 and 2 of 13 patients in Group 2 who had undergone a previous open heart procedure died following multiple valve replacemen t .

Comment We cannot implicate any single factor as the cause of the reduced operative mortality that was observed in these very ill patients. The technique of myocardial protection during operation was used to retrospectively identify patient Groups l and 2. However, at the same time that topical hypothermia was adopted for use, substrate priming of the extracorporeal circuit with glucose, insulin, and potassium became our standard practice. The IABP became available for use in our institution in late 1973; as a result, it was used only in patients of Group 2. Increasing experience of the surgeons may have contributed to the lower operative mortality observed in more recent years. The two groups we have compared retrospectively were very similar in preoperative characteristics. Comparison of patients in Groups 1 and 2 with regard to preoperative functional status suggests that our cardiologists

are not referring patients for operation at an earlier stage of disease. The case for surgical intervention before irreversible deterioration of ventricular function was well stated by McGoon [9]. Our recent experience supports this theory since all deaths due to low cardiac output in Group 2 occurred in patients with Class IV cardiac disability preoperatively. The only apparent difference between the groups preoperatively was the cardiac surgical history. Only 3 of 62 patients in Group 1, but 13 of 44 patients in Group 2 had undergone previous open-heart surgery. To some degree, no doubt, this reflects the evolution of cardiac surgical practice. It was our expectation that the history of a previous open-heart procedure would have a negative effect on operative mortality; in fact, neither a positive nor a negative effect was observed in either group. A significant reduction in cardiopulmonary bypass time was observed in patients of Group 2, reflecting markedly shorter perfusion times for the subgroups having aortic and mitral or triple valve replacement. We believe that shortening of pump time is a result of the technical simplicity of myocardial protection by topical hypothermia, and this conclusion is supported by the observations of others [8, 111. The incidence of perioperative MI in our series is similar to that reported by others for patients having valve operations [ l , 8, l l ] and is likely an underestimate of the true incidence of myocardial ischemic injury due to the limitations of the diagnostic methods employed. Topical hypothermia for myocardial protection, substrate priming prior to ischemia, and shortened perfusion time did not result in improved cardiac performance in the immediate postoperative period. A significant reduction in the incidence of serious ventricular arrhythmias was observed in Group 2, and although 2 deaths in Group 1 resulted from intractable arrhythmias, none occurred in Group 2 from this cause. Two other crude indexes of postoperative cardiac performance-namely, the proportion of patients in each group requiring pharmacological or mechanical hemodynamic support and the duration of that support-failed to detect any difference between the two groups. Karp and Lell [5] reported no difference in the

37 West et al: Multiple Valve Replacement

need for catecholamine support in two groups vances, including topical hypothermia for myoof patients having aortic valve replacement, one cardial protection, shortened perfusion time, group having coronary perfusion and the other, and use of the IABP have all contributed to the hypothermic ischemic arrest for myocardial reduced risk of multiple valve replacement. protection. A prospective randomized study from the same institution had previously References shown no advantage for either method of myo- 1. Bercot M, Deloche A, Piwnica A, et al: Selective hypothermia versus coronary perfusion. J Carcardial protection with regard to postoperative diovasc Surg (Torino) 16:232, 1975 cardiac performance or operative mortality [ll]. 2. Cooley DA, Bloodwell RD, Beall AC, et al: Total The contribution of the IABP to the reduction cardiac valve replacement using SCDK-Cutter prosthesis: experience with 250 consecutive paof operative mortality since January, 1974, cantients. Ann Surg 164:428, 1968 not be separated from beneficial effects of other changes in operative and postoperative man- 3. Griepp RB, Stinson EB, Shumway NE: Profound local hypothermia for myocardial protection duragement introduced at the same time. Five ing open heart surgery. J Thorac Cardiovasc Surg patients were successfully supported after oper66:731, 1973 ation only with the combination of catechol- 4. Hurley EJ, Angel1 WW, Dor V, et al: Multiple valve replacement. Arch Surg 94:163, 1967 amine infusion and IABP support, suggesting a 5. Karp RB, Lell W: Evaluating techniques of myocritical role for the latter in their survival. cardial presentation for aortic valve replacement: Reported series of multiple valve replacement operative risk. J Thorac Cardiovasc Surg 72:206, are relatively infrequent, perhaps in part be1976 cause of the high mortality associated with the 6. Kirklin JW, Pacific0 AD: Surgery for acquired valvular heart disease. N Engl J Med 288:194, 1973 operation. Our results before 1974 are similar to 7. Kittle CF, Dye WS, Gerbode F, et al: Factors inthose reported by Starr and associates [12] and fluencing risk in cardiac surgical patients: Cooley and co-workers [21 in small, early series cooperative study. Circulation 39,4O:Suppl1:169, and later by a cooperative study which included 1969 several cardiac surgical centers [71. More favor- 8. Lee SJK, Millan M: Result of aortic valve replaceable results were reported in two larger series, ment with and without coronary artery perfusion. Ann Thorac Surg 17:122, 1974 one in which topical hypothermia was used for myocardial protection [4] and the other in 9. McGoon DC: Valvular replacement and ventricular function. J Thorac Cardiovasc Surg 72:326, which coronary perfusion was used [lo]. The 1976 operative mortality we have experienced since 10. Midell AI, DeBoer A: Multiple valve replacement: 1974 is similar to that reported recently by Beran analysis of early and late results. Arch Surg 104:471, 1972 cot and co-workers [l]. Griepp and associates [3] performed 31 multiple valve replacements 11. Sapsford RN, Blackstone EH, Kirklin JW, et al: Coronary perfusion versus cold ischemic arrest without a death. during aortic valve surgery: a randomized study. In conclusion, we have observed a reduction Circulation 49:1190, 1974 in operative risk for patients undergoing multi- 12. Starr A, McCord CW, Wood J, et al: Surgery for ple valve replacement. Recent technical admultiple valve disease. Ann Surg 160:596, 1964