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Ann Thorac Surg 1995;59:1113-1119
© 1995 The Society of Thoracic Surgeons

Double-Valve Replacement With Medtronic-Hall or St. Jude Valve

Divisions of Cardiothoracic Surgery, St. Louis University Health Sciences Center and St. Mary's Health Center, St. Louis, Missouri, and Indiana University Medical Center, Indianapolis, Indiana

	Abstract

Top Footnotes Abstract Introduction Material and Methods Results Comment Appendix 1. Preoperative... Acknowledgments References

 
To define better the performance of the bileaflet St. Jude and the tilting-disc Medtronic-Hall valves, we retrospectively analyzed 122 patients (St. Jude, 80 patients; Medtronic-Hall, 42 patients) who received simultaneous aortic and mitral replacement from May 1984 until June 1994. The two groups were not different with respect to preoperative clinical and hemodynamic parameters and New York Heart Association functional class. The hospital mortality and late mortality were not significantly different. Risk analysis identified advanced age and previous myocardial revascularization as predictors of operative death. Follow-up was complete in 96 of 103 hospital survivors (93%) and was similar in both groups. The actuarial survival, linearized rates of valve-related complications, and actuarial freedom from valve-related complications were similar in both cohorts. The presence of coronary artery disease negatively influenced the actuarial survival after simultaneous aortic and mitral valve replacement. Postoperative New York Heart Association functional class was not significantly different in either group. These data indicate that the Medtronic-Hall and St. Jude prostheses are not significantly different with respect to their clinical performance and valve-related complications for simultaneous double-valve replacement.

	Introduction

Top Footnotes Abstract Introduction Material and Methods Results Comment Appendix 1. Preoperative... Acknowledgments References

 
See also page 1119.

The bileaflet St. Jude (SJ) and the tilting-disc Medtronic-Hall (MH) valves are the most common mechanical valve prostheses currently employed in the United States. The short- and medium-term results of patients after isolated aortic and mitral replacement have been analyzed and thus far the clinical and hemodynamic performance of these two prostheses have not been different [1, 2]. It has been suggested that the simultaneous implantation of two valves might magnify differences allowing for identification of a superior prosthesis. In this report we compare the SJ and MH valves inserted simultaneously as aortic and mitral valve replacement.

	Material and Methods

Top Footnotes Abstract Introduction Material and Methods Results Comment Appendix 1. Preoperative... Acknowledgments References

 
A retrospective review was instituted at St. Louis University Health Sciences Center and Indiana University Medical Center.

Computerized cardiothoracic surgical registries were used to identify patients who had undergone simultaneous aortic and mitral valve replacement with either two SJ (St. Jude Medical, St. Paul, MN) or two MH (Medtronic, Minneapolis, MN) mechanical prostheses. The selection of the prosthesis was based on the surgeon's preference. From May 1984 through May 1994, 122 patients (80 SJ and 42 MH) were identified who had undergone double-valve replacement with like mechanical valves. Clinical data obtained from the registries and hospital records included age, sex, body surface area, and the presence of concomitant medical problems such as smoking, diabetes mellitus, and hypertension; New York Heart Association functional class also was noted. Also recorded were a history of myocardial infarction, prior valve procedure, or coronary artery bypass grafting. The preoperative administration of intravenous inotropic drugs or the need for an intraaortic balloon pump was noted.

Cardiac catheterization findings recorded included number of diseased vessels (defined as a greater than or equal to 50% obstruction of the luminal diameter in any plane on coronary angiography) and left ventricular function as quantitated by left ventricular score (abnormal segmental wall motion scoring system used by the Coronary Artery Surgery Study [3]). Additional cardiac catheterization data recorded included left ventricular end-diastolic pressure, pulmonary artery systolic and diastolic pressures, and pulmonary capillary wedge pressure. Calculated valve areas were noted as was the presence of aortic or mitral regurgitation as quantitated on a scale of 1 to 4.

Operative variables included the size of the prosthesis implanted, concomitant coronary artery bypass grafting, global ischemic time, and total cardiopulmonary bypass time.

The general conduct of all surgical procedures was similar. The operations were performed jointly by University faculty and surgical residents using a membrane oxygenator, moderate systemic hypothermia (28°C), and hemodilution. Myocardial preservation consisted of cold potassium blood cardioplegia delivered antegrade or retrograde every 20 minutes and supplemented with cold lactated Ringer's slush topically. After aortic cross-clamping, coronary artery bypass grafts were performed. If myocardial revascularization was not required, mitral valve replacement always was carried out first and aortic valve replacement then followed. Suture placement consisted of interrupted pledgeted horizontal mattress sutures placed from above downward to evert the annulus. In the mitral position, the SJ valve was oriented in the antianatomic plane whereas the disc of the MH valve was oriented to open anteriorly whenever possible. Sodium warfarin therapy was initiated within 3 days of valve implantation to maintain the international ratio at 2.5 to 3 times control.

Postoperative complications recorded included low cardiac output (defined as a cardiac index less than 2 L • min^-1 • m^-2 or the need for intravenous inotropic drugs or intraaortic balloon support for more than 24 hours postoperatively), reoperation for bleeding, renal failure requiring dialysis, perioperative myocardial infarction (defined by the presence of new Q waves on the electrocardiogram or cardiac enzyme analysis), respiratory insufficiency (defined as the need for reintubation or mechanical ventilatory support for more than 48 hours), and the presence of new postoperative ventricular or atrial arrhythmias. Operative mortality was defined as any death during hospitalization or within 30 days of the surgical procedure.

Determinations of valve-related morbidity and mortality were based on the ``Guidelines for Reporting Morbidity and Mortality After Cardiac Valvular Operations'' developed by The Society of Thoracic Surgeons [4]. All operative mortality was considered valve-related.

Follow-up information on survivors was obtained by mailed questionnaire, office visit, or by telephone contact with the patient or their physician. Follow-up was complete in 96 of 103 hospital survivors (93%). Five patients in the SJ and 2 in the MH group could not be located. The total number of patient-years of follow-up was 354.1 (SJ, 228.1; MH, 126 patient-years). The mean follow-up time was similar in both groups (SJ, 34.2 ± 34.9 versus MH, 36 ± 37.3 months; not significant).

Data were analyzed with the Statview II statistical software package (Brainpower, Inc, Calabasas, CA). A ² test or Fisher's exact test was used to determine significance for discrete variables. Continuous variables were analyzed by an unpaired two-tailed Student's t test. A p value of less than 0.05 was considered significant, and a value of 0.05 or greater but 0.10 or less was considered marginally significant.

Actuarial curves were computed by the method of Berkson and Gage and compared using a log-rank analysis [5]. The actuarial analysis considered all events, early and late. Linearized rates, expressed as events per 100 patient-years of follow-up, were computed from late events (beyond 30 days) in order not to violate the constant risk of assumption. The significance of valve-related events was obtained from a comparison of the actuarial estimates. Mean values are expressed as plus or minus the standard deviation except as noted.

All variables that were significant or marginally significant were entered into a Cox step-wise logistic regression model for a multivariable analysis (Appendix 1). Variables that were not available in at least 95% of the patients were omitted from analysis to avoid loss of statistical power.

	Results

Top Footnotes Abstract Introduction Material and Methods Results Comment Appendix 1. Preoperative... Acknowledgments References

 
Clinical Profile
The cohorts were similar with respect to age, gender, New York Heart Association functional class, degree of angina pectoris, and risk factors for coronary artery disease (Table 1). Patients receiving two MH valves had a greater incidence of coexisting coronary artery disease, previous myocardial revascularization, and concomitant coronary artery bypass grafting. Preoperative myocardial infarction was nearly fourfold higher in this group. The hemodynamic parameters and the degree of valve stenosis or insufficiency were similar in both groups (Table 2). The majority of patients had elevated left ventricular end-diastolic pressure with mild left ventricular dysfunction. The prosthesis size and the time on the extracorporeal circuit were similar (Table 3). A greater percentage of patients in the SJ group had previous valve replacement.

The most common cause of operative death was multiorgan system failure, which occurred in 9 patients of whom 6 had had a previous cardiac operation (5 valve, 1 coronary artery bypass grafting). In all cases, death was associated with the need for prolonged ventilatory support, inotropic support, and hemodialysis.

Three patients died in the operating room of low cardiac output secondary to biventricular failure. In 2 patients who had had previous cardiac operations (1 valve, 1 coronary artery bypass grafting) low cardiac output developed secondary to prolonged global ischemic times. An additional intraoperative death was associated with a perioperative myocardial infarction and uncontrolled hemorrhage.

One patient who received two MH valves died in the intensive care unit of a cardiac arrest when the left atrial line catheter entrapped the disc of the mitral prosthesis in the closed position.

Two patients died of gram-negative sepsis secondary to ischemic bowel on the 2nd and 12th postoperative days. The remaining death occurred from uncontrolled gastrointestinal hemorrhage on the 70th postoperative hospital day. Three patients who required concomitant myocardial revascularization had severe left ventricular dysfunction and experienced sudden unexplained deaths at home on the 13th, 16th, and 21st postoperative day.

Risk analysis for hospital death is shown in Table 4. Univariate analysis of discrete variables demonstrated that age, extent of coronary artery disease, and previous myocardial revascularization correlated significantly with hospital death. Multivariable analysis using a Cox stepwise logistic regression model eliminated extent of coronary artery disease as a predictor of hospital mortality. Advanced age and previous myocardial revascularization were significant predictors of operative death.

Four non–valve-related deaths occurred due to progressive congestive heart failure. Two patients (1 SJ, 1 MH) had end-stage ischemic heart disease and died at 58 and 62 months postoperatively having undergone myocardial revascularization with simultaneous double-valve replacement. One patient died at 22 months with a congenital cardiomyopathy. The remaining non–valve-related death occurred at 57 months in a patient with rheumatic cardiomyopathy who had undergone two previous double-valve replacement operations.

Patient Survival
The actuarial survival curve for the two groups is shown in Figure 1. At 5 years the survival rates were nearly identical, but at 8 years there appeared to be a survival advantage in the SJ group although the difference was not significant. The actuarial survival was better for those patients receiving two valves without coexisting coronary artery disease regardless of the valve type (Fig 2). The postoperative New York Heart Association functional class in the 84 survivors was improved equally in both cohorts (SJ, 1.5 ± 0.7 versus MH, 1.3 ± 0.6; not significant).

View larger version (23K): [in this window] [in a new window]   Fig 1. . Actuarial survival rates after simultaneous aortic and mitral valve replacement with the St. Jude and Medtronic-Hall (Med-Hall) valves. Hospital and late deaths are included. (NS = not significant.)

View larger version (24K): [in this window] [in a new window]   Fig 2. . Actuarial survival rates after simultaneous aortic and mitral valve replacement for patients with and without coronary artery disease (CAD). Hospital and late deaths are included.

In 2 patients in the MH group transient ischemic attacks developed at 22 and 32 months postoperatively. Embolic strokes occurred in 9 patients (8 SJ, 1 MH) from 23 days to 49 months postoperatively. The linearized rate of thromboembolism was slightly higher in the MH group (SJ, 3.2 ± 1.2; MH, 4.0 ± 1.8). Actuarial freedom from thromboembolism is shown in Figure 3.

View larger version (23K): [in this window] [in a new window]   Fig 3. . Actuarial freedom from thromboembolism after simultaneous aortic and mitral valve replacement with the St. Jude and Medtronic-Hall (Med-Hall) valves. (NS = not significant.)

View larger version (24K): [in this window] [in a new window]   Fig 4. . Actuarial freedom from anticoagulant-related hemorrhage after simultaneous aortic and mitral valve replacement with the St. Jude and Medtronic-Hall (Med-Hall) valves. (NS = not significant.)

Paravalvular Leak
In 2 patients (1 MH, 1 SJ) aortic prosthetic paravalvular leak developed, which required reoperation at 2 months and 26 months postoperatively. Both patients are long-term survivors. The linearized rate of paravalvular leak was higher in the MH group (SJ, 0.5 ± 0.5; MH, 1.6 ± 1.1).

	Comment

Top Footnotes Abstract Introduction Material and Methods Results Comment Appendix 1. Preoperative... Acknowledgments References

 
The two most common mechanical cardiac valve prostheses used in the United States are the bileaflet SJ and the MH pivoting-disc prosthesis. These devices have undergone virtually no alteration in design since their development in 1977 and 1978.

It was our hypothesis that simultaneous implantation in the aortic and mitral position might magnify potential performance advantages of one valve over the other. This study has several handicaps that affect this desired goal. The small number of patients in each group and retrospective acquisition of data could reduce the validity of the conclusions drawn. The relatively short follow-up of 4 years, unequal distribution of patients favoring insertion of the SJ valve, and a total of only 354 patient-years of prostheses observation are all relative disadvantages. These limitations notwithstanding, these data represent two populations of patients whose clinical, hemodynamic, and operative characteristics are similar. Comparisons between groups are reported in an actuarial manner with a high rate of follow-up (93%), which we believe support the conclusions reached.

The overall hospital mortality of 15% was higher than observed by other investigators reporting on isolated double-valve replacement [6, 7]. In our series 24% of the patients had either undergone previous or received concomitant coronary artery bypass grafting, and one-third of our population had reoperative double-valve replacement procedures. Operative death was associated primarily with multiorgan system failure and low cardiac output. These patients represent an increased operative risk because of prolonged extracorporeal circuit time and a longer period of myocardial global ischemia. Current methods of myocardial protection may be inadequate in the presence of ventricular hypertrophy secondary to chronic valvular and coronary artery disease. Finally, we believe the mortality in the MH group was higher because this cohort had a greater incidence of ischemic heart disease and required concomitant myocardial revascularization at the time of double valve replacement.

Age has been identified as a risk factor for isolated aortic and mitral valve replacement, and in this series age proved to be a risk factor for hospital death after double-valve replacement. This observation is supported by the work of Christakis and associates [8], who demonstrated increased ventricular dysfunction in older patients and established a negative correlation between advanced age and cardiac index. In addition to age, previous myocardial revascularization strongly correlated with operative death, whereas the presence of coronary artery disease negatively influenced the actuarial survival of patients undergoing simultaneous double-valve replacement (see Fig 2). Similar findings were noted in the recent work of Jones and co-workers [9], who observed a detrimental influence of age and coronary artery disease on the actuarial survival of patients undergoing isolated aortic or mitral valve replacement.

Sudden unexplained death was the most common cause of late mortality in our experience, occurring in 8 patients (3 early, 5 late) all of whom had known coronary artery disease. In the absence of a postmortem examination, sudden deaths such as these are considered valve-related in accordance with the published guidelines. Recently investigators have challenged this aspect of the guidelines for reporting morbidity and mortality after cardiac valvular operations [10]. Rooney and associates [11] investigated the sudden or unwitnessed deaths in 69 patients with valvular prostheses, 48 of whom (70%) underwent autopsy. There were no sudden deaths directly attributed to the prosthesis itself. Eighty percent of the deaths were due to coronary artery disease or left ventricular dysfunction, whereas 10% were due to intracranial hemorrhage. These findings have been confirmed by the work of Burke and colleagues [12] and Butchart [13]. In the light of these findings, it has been suggested that the categorization of sudden death be reappraised and revised.

Survival itself usually is regarded as an insensitive measure of overall valve performance and relates mainly to the underlying disease and the perioperative status of the myocardium. Another measure of valve performance can be the incidence of thromboembolism, which is a major risk factor for patients having mechanical prostheses. The incidence of thromboembolic complications in the third-generation valvular devices is very similar. This is predominantly due to improved hemodynamic design resulting in a better flow velocity profile, less turbulence, and reduction of stagnant areas, all of which are known to affect the thrombogenicity of the prosthesis. In the MH valve, a more central position of the disc in the open position enlarged the minor orifice, thus reducing stagnation of blood and turbulence. The central-flow design of the bileaflet SJ valve may contribute to its low incidence of thromboembolic events. In this report, actuarial 8-year freedom from thromboembolic complications was nearly identical in both groups (see Fig 3). Of the 11 patients in whom nonfatal thromboembolic complications developed, 7 (64%) had chronic atrial fibrillation. Dipyridamole (300 mg daily) was added to the anticoagulant regimen in all cases. There were no instances of valve thrombosis in this series. The overall rates of thromboembolic complications compared favorably with those reported by Armenti and associates [14] and Vallejo and co-workers [15] for double-valve replacement with the SJ and the MH valves, respectively.

In the MH cohort, the actuarial freedom from anticoagulant-related hemorrhage compared favorably with that reported in other series [16]. Anticoagulant-related hemorrhage was observed more frequently in the SJ group.

The results of this study indicate that in the first years after simultaneous implantation in the aortic and mitral position, the performance of the SJ and the MH prostheses are comparable in this patient population. The operative risk is not dependent on the type of prosthesis selected but rather is related to the age of the patient and the presence of previous myocardial revascularization. No documented advantage exists for either valve with regard to actuarial survival, freedom from valve-related complications, and overall improvement in New York Heart Association functional class.

This study suggests that neither valve is superior with regard to performance or safety and either may be recommended confidently for simultaneous double-valve replacement. The choice of prosthesis should not be made on the basis of unsupported promotional claims but rather should be based on surgeon's experience, ease of insertion, availability, and cost.

	Appendix 1. Preoperative Variables for Univariate Analysis

Top Footnotes Abstract Introduction Material and Methods Results Comment Appendix 1. Preoperative... Acknowledgments References

 

• Age
  
• Sex
  
• New York Heart Association class
  
• Angina pectoris class
  
• Body surface area
  
• Aortic stenosis
  
• Aortic regurgitation
  
• Mitral stenosis
  
• Mitral regurgitation
  
• Left ventricular function
  
• Number of diseased coronary vessels
  
• Double-valve replacement and coronary artery bypass
  
• Smoking
  
• Hypertension
  
• Insulin-dependent diabetes mellitus
  
• Myocardial infarction
  
• Previous valve repair
  
• Previous valve replacement
  
• Previous double-valve replacement
  
• Previous coronary artery bypass
  
• Preoperative intraaortic balloon
  
• Preoperative inotropic drugs
  
• Operative priority
  
• Type of valve
  

	Acknowledgments

Top Footnotes Abstract Introduction Material and Methods Results Comment Appendix 1. Preoperative... Acknowledgments References

 
We gratefully acknowledge Terri Wriley for her assistance with preparation of the manuscript.

	Footnotes

Top Footnotes Abstract Introduction Material and Methods Results Comment Appendix 1. Preoperative... Acknowledgments References

 
Address reprint requests to Dr Fiore, Department of Surgery, Cardiothoracic Division, St. Louis University Health Sciences Center, 3635 Vista Ave at Grand Blvd, PO Box 15250, St. Louis, MO 63110-0250.

	References

Top Footnotes Abstract Introduction Material and Methods Results Comment Appendix 1. Preoperative... Acknowledgments References

 

1. Antunes MJ. Clinical performance of St. Jude and Medtronic-Hall prostheses: a randomized comparative study. Ann Thorac Surg 1990;50:743–7.[Abstract]
2. Arom KV, Nicoloff DM, Kersten TE, Northrup W III, Lindsay WG, Emery RW. Ten years' experience with the St. Jude Medical valve prosthesis. Ann Thorac Surg 1989;47:831–7.[Abstract]
3. Principal Investigators of CASS and Their Associates. The National Heart, Lung, and Blood Institute Coronary Artery Surgery Study. Circulation 1981;63(Suppl 1):1–81.[Free Full Text]
4. Edmunds LH Jr, Clark RE, Cohn LH, Miller DC, Weisel RD. Guidelines for reporting morbidity and mortality after cardiac valvular operations. Ann Thorac Surg 1988;46:257–9.[Medline]
5. Berkson J, Gage RP. Calculation of survival rates for cancer. Proc Meet Mayo Clin 1950;25:270–86.
6. Kratz JM, Crawford FA Jr, Sade RM, Crumbley AJ, Stroud MR. St. Jude Prosthesis for aortic and mitral valve replacement: a ten-year experience. Ann Thorac Surg 1993;56:462–8.[Abstract]
7. Lindblom D, Lindblom U, Aberg B. Long-term clinical results after combined aortic and mitral valve replacement. Eur J Cardiothorac Surg 1988;2:347–54.[Abstract]
8. Christakis GT, Weisel RD, Fremes SE, et al. Can the results of contemporary aortic valve replacement be improved? J Thorac Cardiovasc Surg 1986;92:37–46.[Abstract]
9. Jones EL, Weintraub WS, Craver JM, Guyton RA, Shen Y. Interaction of age and coronary disease after valve replacement: implications for valve selection. Ann Thorac Surg 1994;58:378–85.[Abstract]
10. Hwang MH, Burchfiel CM, Sethi GK, et al. Comparison of the causes of late death following aortic and mitral valve replacement. J Heart Valve Dis 1994;3:17–24.[Medline]
11. Rooney SJ, Moreno de la Santa P, Lewis PA, Butchart EG. Sudden death in a large prosthetic valve series based on a single prosthesis: experience with the Medtronic-Hall valve. J Heart Valve Dis 1994;3:5–9.[Medline]
12. Burke AP, Farb A, Sessums L, Virmani R. Causes of sudden cardiac death in patients with replacement valves: an autopsy study. J Heart Valve Dis 1994;3:10–6.[Medline]
13. Butchart EG. The significance of sudden and unwitnessed death after heart valve replacement. J Heart Valve Dis 1994;3:1–4.[Medline]
14. Armenti F, Stephenson LW, Edmunds LH Jr. Simultaneous implantation of St. Jude Medical aortic and mitral prostheses. J Thorac Cardiovasc Surg 1987;94:733–9.[Abstract]
15. Vallejo JL, Gonzales Santos JM, Albertos J, et al. Eight years' experience with the Medtronic-Hall valve prosthesis. Ann Thorac Surg 1990;50:429–36.[Abstract]
16. Keenan RJ, Armitage JM, Trento A, et al. Clinical experience with the Medtronic-Hall valve prosthesis. Ann Thorac Surg 1990;50:748–53.[Abstract]

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