The Medtronic-Hall Cardiac Valve:

Transcription

1 The Medtronic-Hall Cardiac Valve: 7?h Years' Clinical Experience Regent L. Beaudet, M.D., Normand L. Poirier, M.D., Daniel Doyle, M.D., Gisde Nakhlb, M.Sc., and Christiane Gauvin, M.T. ABSTRACT Clinical information on the Medtronic-Hall valve prosthesis was obtained by reviewing the records of 379 patients, 164 of whom had aortic valve replacement (AVR), 163 of whom had mitral valve replacement (MVR), and 52 of whom had double valve replacement over 90 months (1,225 patient-years) (mean follow-up, f 1.3 months [ f standard error]). Mean age was 53.8 t 12 years. One hundred ninety-three patients (50.9%) had some type of concomitant operation, such as tricuspid annuloplasty, coronary artery bypass grafting, or resection of ascending aortic aneurysm. Ninety-one percent were in New York Heart Association (NYHA) Functional Class I11 or IV preoperatively. Early mortality and late mortality were 7.7% (29 patients) and 13.5% (51 patients), respectively. The actuarial survival at 7% years was 74.1 t 2.7% for the total group and % for those having AVR, 81.0 f 3.2% for those having MVR, and 67.0 t 8.9% for those having double valve replacement. All patients but 2 were maintained on a regimen of chronic anticoagulation with warfarin sodium. Twenty-six thromboembolic episodes occurred ( patient-years): 13 after MVR (2.3/100 patient-years), ll after AVR ( patient-years), and 2 after double valve replacement (1.4/100 patient-years). Four thromboembolic episodes were fatal; no valve thrombosis occurred. There were no structural failures. Of the 350 late survivors, 92% were in NYHA Functional Classes I and 11. Total valve-related complications have been minimal. Our 7%-year experience with the Medtronic-Hall valve prosthesis reveals a low thromboembolic rate of patient-years in anticoagulated patients, a well-engineered and resistant valve structure, an acceptable hemolysis, and an acceptable rate of valve-related complications. Mechanical valves remain the most resistant valve substitute to date, yet they are associated with a relatively stable incidence of valve-related complications. Several reports [l-51 over the last 10 years have shown an acceptable rate of problems with the newer prosthetic models, especially of the disc and bileaflet designs. From the Cardiovascular and Thoracic Surgery Service, Notre-Dame Hospital, University of Montreal, and the Cardiovascular and Thoracic Service, Royal Victoria Hospital, Montreal, Que, Canada. Presented at the Twenty-second Annual Meeting of The Society of Thoracic Surgeons, Washington, DC, Jan 27-29, Address reprint requests to Dr. Beaudet, 1560E Sherbrooke St, Room G- 1149, Notre-Dame Hospital, Montreal, Que, Canada H2L 4K8. However, we are still looking for improvement that would influence surgeons in selecting a bioprosthetic or mechanical valve replacement. In an attempt to confirm our personal preference, we conducted a retrospective study to evaluate our results over the last 7% years in all our patients undergoing aortic (AVR), mitral (MVR), or MVR and AVR with the low-profile pivoting-disc Medtronic-Hall mechanical prosthesis (pyrolitic carbon disc with a central aperture) [6]. Material and Methods Patients Between January, 1978, and July, 1985, 379 patients received a total of 451 Medtronic-Hall prostheses for single or multiple valve replacement. There were 193 men and 186 women with a mean age of 53.8 years (* SD years). Preoperatively, 88.4% of the patients requiring AVR, 94.6% of patients requiring MVR, and 93.7% of those requiring double valve replacement were in New York Heart Association (NYHA) Functional Class I11 or IV. Concomitant procedures were performed on 193 occasions; these procedures included coronary artery bypass grafting, which was the most frequent (105 procedures), tricuspid annuloplasty (31), and others (57). Some patients underwent more than 1 concomitant procedure. Surgical Procedures Conventional techniques of cardiopulmonary bypass were used, including hypothermia to 30 C, moderate hemodilution, and a bubble oxygenator. Cold potassium cardioplegia or intermittent coronary perfusion were used for myocardial protection. The valves were anchored with an interrupted suture technique involving everting mattress sutures supported with Teflon felt pledgets. In the aortic position, the large opening was oriented so the disc would open without any tissue interference; in the mitral position, the large opening was directed more than 90% in toward the ventricular septum (anteriorly). All patients were given warfarin sodium anticoagulation, which was begun on the fourth postoperative day. Patients were released from the hospital when the prothrombin time was two to two and one-half times control. In a majority of patients, anticoagulation was regulated through our clinic. Clinical Follow-up Clinical analysis and collection of follow-up data were carried out in the summer of All patients were accounted for by personal contact, by telephone conver- 644 Ann Thorac Surg , Dec 1986

2 ~~~ ~ 645 Beaudet, Poirier, Doyle, et al: The Medtronic-Hall Cardiac Valve sation, by their local physician, or by one of us. Autopsy reports or death certificates were used to ascertain the cause of death whenever possible. Data were entered into an IBM personal computer running the R4000 data base system. They were then transmitted to a Cyber 70 for statistical analysis based on the Statistical Package for Social Sciences (SPSS), which performed actuarial analyses for all valve morbidity and mortality factors, according to the method of Berkson and Gage [7] and Lee-Desu PI. The definitions of thromboembolism, valve thrombosis, and hemorrhagic complications related to anticoagulation were those established by Karp and colleagues (91. Cerebral or occular thromboembolism was assumed to have occurred in the presence of definite transient or permanent neurological or visual deficit when cerebral hemorrhage had been reasonably excluded [9]. Results Operative Survival Operative survival was analyzed by valve type and NYHA Functional Class. Operative death was defined as death within thirty days of operation [9], and the operative deaths are summarized in Table 1. Operative mortality was higher for AVR, and no reason could be found to explain this discordance between most series and the present data [4-lo]. Long-Term Survival and Functional Improvement Long-term survival was analyzed in the 350 survivors. It totaled 14,704 months of follow-up (median, months [ f standard error or SE]; range, 1 to 90 months). No patients were lost to follow-up (Table 2; see Table 1). The late causes of deaths, cardiac and noncardiac, are summarized in Table 3. Cardiac deaths included congestive heart failure, myocardial ischemia, infection, and all sudden deaths. Although in our mind, late survival is not the dominant criterion for evaluation of performance of mechanical prostheses, it is certain that the more satisfactory the valve, the longer the observation period needed to describe its faults. Survival for the AVR, MVR, and double valve replacement subgroups was similar to that reported for other mechanical and biological valve replacement devices [l-21. At 7% years, the survival for the AVR patients was % (k SE); for Table 1. Operative and Late Deaths by Location of Valve Prosthesis MVR + Deaths MVR AVR AVR Operative Late Total An operative death was a death occurring within thirty days of operation. MVR = mitral valve replacement; AVR = aortic valve replacement Table 2. Results of Medtronic-Hall Valve Replacement in 379 Patients No. of No. of Deaths Study Prosthesis Patients Operative Late Group Aortic Isolated AVR AVR + associated procedure Mitral I8 153 Isolated MVR MVR + associated procedure Aortic + mitral Isolated AVR + MVR AVR + MVR + associated procedure Medtronic-Hall another device An operative death was one occurring within thirty days after operation. AVR = aortic valve replacement; MVR = mitral valve replacement. Table 3. Causes of Late Death Cause Unknown 7 Valve-rela ted 32 Congestive heart failure Myocardial infarction Arrhythmias Endocarditis Cerebral embolus Gastrointestinal hemorrhage Cerebral hemorrhage Digitalis intoxication Non-valve-rela ted 12 No. of Patients the MVR patients, 81 f 3.2%; and for the double valve replacement patients, % (Fig 1). Actuarial survival at 84 months for all patients after AVR, MVR, and double valve replacement with or without an associated procedure, divided into NYHA subsets, and excluding operative mortality is summarized in Figures 1 through 3 and Table 4. Survival according to age is illustrated in Figure 4. Thromboembolism During the period of the study, thromboembolism occurred in 26 patients, an incidence of 2.1/100 patientyears. Among the 11 patients in the AVR group having thromboembolic episodes, 6 were considered to have had minor episodes and 5, major episodes (2 fatal). The incidence was 2.1/100 patient-years. In the MVR group, 7 of the 13 episodes were minor and 6, major (2 fatal);

3 646 The Annals of Thoracic Surgery Vol 42 No 6 December LEGEND: AVR I ALMVR 10 ( ) Number of Patients/ Interval MONTHS POST OP Fig 1. Probability of survival according to location of valve prosthesis. (AVR = aortic valve replacement; MVR = mitral valve replncement. ) * 40- c - # lsoloted Valve Replacement Valve Replacements +Ass. proc. ( ) Number of Common Point - s * 40- s\o ~ NYHA Class 1,II.III NYHA Class IV ( ) Number of Common Point -~.,,,,.,....

4 647 Beaudet, Poirier, Doyle, et al: The Medtronic-Hall Cardiac Valve Table 4. Survival at 84 Months" Variable % Survival p Value All follow-up 74.1 f 2.7 Isolated valve replacement All 82.4? 3.3 AVR f 6.2 MVR 91.09? 3.2 AVR + MVR f 10.6 Valve Replacement + associated procedures All f 4.2 AVR f 6.4 MVR f 5.7 AVR + MVR f 12.9 Functional Class t 3.0 IV 62.7 f 5.8 >.05 >.05 >.001 'The probability of survival is significantly lower (p <,001) when the group having valve replacement and associated procedures is compared with the group having isolated valve replacement. AVR = aortic valve replacement; MVR = mitral valve replacement. incidence, patient-years. In the group having double valve replacement, 2 were minor and none, major (none fatal); incidence, patient-years. Thromboembolism includes all major and minor cerebrovascular or peripheral arterial symptomatology; repeated visual abnormalities were also considered embolic events. The actuarial freedom from thromboembolism (major and minor) did not reveal any significant difference among the three groups (Fig 5). At 84 months, the percentage of patients free from thromboembolism in the AVR group was 86.7%; in the MVR group, 89.4%; and in the double valve replacement group, 84.6% at 72 months Fig 4. Probability of survival according to age is statistically significant (p <.05) for the group 60 years old and older compared with the other age groups. [ll]. There was no valve thrombosis, per the definition established by Karp and co-workers [9]. Hemorrhagic Complications Some morbidity can be attributed to the use of anticoagulation. Each time a patient had a major or a minor bleeding episode resulting in any change in medication, hospitalization, or serious morbidity or mortality, it was recorded. Fifteen patients sustained some problems related to the use of chronic anticoagulation, and 4 had a fatal hemorrhage (2, gastrointestinal tract and 2, cerebral), an incidence of 1.2/100 patient-years. Actuarial freedom from anticoagulation-related complication is seen in Figure 6 for the three study groups [12, 131. No statistical difference could be established. Functional Class More than 90% of the patients were in NYHA Class III or IV preoperatively, 262 in Class III and 86 in Class IV. Ninety-two percent of the survivors were in Classes I and I1 in the postoperative period. Although there were more deaths among patients in Classes I11 and IV, since the majority of patients were in those classes, the 17 deaths in the 74 Class IV patients showed a significant relationship between Class IV and death (p <.001) (see Table 4). Although valve location does not affect survival, patients in the 60 years and older subgroup have shown a lower survival than the other subgroups, 0 through 39, 40 through 49, and 50 through 59 years of age. Survival in the oldest group is 61.4% compared with 83.5% in patients 0 through 49 years old and 77.1% in those 50 through 59 years of age (p <.05) (see Fig 4). Comment With the improvements in valve design over the last decade, the period of observation needed to point out weaknesses should be much longer. However, little information on the Medtronic-Hall valve is available, and we believe that our observations will be meaningful when comparing various prostheses. We [14] have reported on the hernodynamic perfor e d \ LEGEND : A ( ) Number of patients/ interval 8 Common point n.1 t4.5 ) ~ 2 i & i 2 i w ~ ~ 8 4 ~ MONTHS POST OP

5 648 The Annals of Thoracic Surgery Vol 42 No 6 December Ly L 30- s\ LEGEND:. AVR m MVR A A(LMVR ( Number of Patients/ Interval 0 Common point y !$ 20- t 10-8\0-0 LEGEND: I AVR 0 MVR A+MVR ( 1 Number of Potients lnteivol 0 Common mint MONTHS POST OP Fig 6. Probability offreedom from hemorrhagic complications in patients with a mechanical prosthesis and anticoagulation. (AVR = aortic valve replacement; MVR = mitral valve replacement.) mance of the Medtronic-Hall valve, and others [5] have described its performance. Although we are not specifically commenting on hemolysis, during this whole period, no patient has been treated with any form of replacement therapy unless there was a perivalvular leak, at which time the increased turbulence was responsible for the phenomenon [14]. This report summarizes the 7%-year experience with a low-profile disc valve replacement device. This is an allinclusive experience, unless anticoagulation was a significant risk factor or advanced age made it unlikely that a reoperation would be entertained, at which time a bioprosthesis was used. However, some patients in their 80s had mechanical valve implantation. In younger patients, we believe the mechanical valve should be used unless a desire for pregnancy is strongly expressed or the patient's occupation precludes the use of anticoagu- lation. The choice of valve is definitely influenced by the surgeon's preference. Noted in this series is the extremely important determinant role on operative and late survival after valve replacement of the existence of coronary disease, NYHA Functional Class, and age associated with the valvular pathology [l]. Coronary artery bypass grafting was by far the most frequent associated procedure with the valve replacement, and coronary disease is associated with a higher operative and late mortality. Reoperation for valve thrombosis is rare but is often associated with a tragic outcome [9]. This condition did not develop in this series, although some patients were reoperated on because of disc malfunction attributed to clot formation and confirmed at the time of reoperation. This condition can occur in spite of well-maintained anticoagulation. However, there was no valve dysfunction that could be related to structural abnormalities. The incidence of thromboembolism is lower than in most reported series with mechanical valves [3, 10, 151. We think that a very close surveillance of anticoagula-

6 649 Beaudet, Poirier, Doyle, et al: The Medtronic-Hall Cardiac Valve tion plays a major role in the prevention of clot formation on mechanical devices. Also, the enlarged small orifice of the Medtronic-Hall valve diminishes the turbulence and formation of eddies in the outflow surface of the disc, and permits better washout in that area [6]. The overall valve-related morbidity and mortality do not stand comparison with bioprostheses used in a similar time frame, for structural failure of bioprosthetic valves would begin to show at a somewhat later time. However, if the actual trend for reoperation in patients with bioprostheses is maintained, the curves will start separating [l-31. The present report indicates equal or superior performance in the intermediate follow-up of the Medtronic- Hall valve. Problems do exist in relation to thromboembolism, and a late follow-up analysis will be necessary to delineate survival and valve-related morbidity as an indication of valve performance. Nevertheless, our follow-up shows that the Medtronic-Hall valve is durable, that the prosthesis is associated with a moderately low incidence of valve-related complications, and that it can be expected to perform well on a long-term basis. References Cohn LH, Allred EN, Cohn LA, et al: Early and late risk of mitral valve replacement. J Thorac Cardiovasc Surg 90:872, 1985 Marshall WG Jr, Kouchoukos NT, Karp RB, Williams JB: Late results after mitral valve replacement with the Bjork- Shiley and porcine prostheses. J Thorac Cardiovasc Surg 85902, 1983 Martinell J, Fraile J, Artiz V, et al: Long-term comparative analysis of the Bjork-Shiley and Hancock valves implanted in J Thorac Cardiovasc Surg 90:741, 1985 Nicoloff DM, Emery RW, Arom KV, et al: Clinical and hemodynamic results with the St. Jude Medical cardiac valve prosthesis. J Thorac Cardiovasc Surg 82674, 1981 Nitter-Hauge S, Semb B, Abdelnoor M, Hall KV: A five year experience with the Medtronic-Hall disc valve prosthesis. Circulation 68:Suppl 2:169, 1983 Hall KV, Kaster RL, Wsen A An improved pivotal disctype prosthetic heart valve. Oslo City Hosp J 29:3, 1979 Berkson J, Gage R Calculation of survival rates for cancer. Proc Mayo Clin, 25:270, 1950 Lee E, Desu M: A computer program for comparing K samples with right-censored data. Comput Programs BioMed 2:315, Karp RB, Cyrus RJ, Blackstone EH, et al: The Bjork-Shiley valve: intermediate-term follow-up. J Thorac Cardiovasc Surg 81:602, 1981 Bjork VO, Henze A: Ten years experience with the Bjork- Shiley tilting disc valve. J Thorac Cardiovasc Surg 78331, 1979 Hetzer R, Topalidis R, Borst HG: Thromboembolism and anticoagulation after isolated mitral valve replacement with porcine heterografts. In Cohn LH, Gallucci V (eds): Cardiac Bioprostheses. New York, Yorke Medical, 1982, pp St. John MG, Sutton G, Miller AH, et al: Anticoagulants and the Bjork-Shiley prosthesis: experience of 390 patients. Br Heart J 40:558, Chesebro JH, Fuster V, Elveback LR, et al: Trial of combined warfarin plus dipyridamole or aspirin therapy in prosthetic heart valve replacement: danger of aspirin compared with dipyridamole. Am J Cardiol51:1537, Beaudet RL, Poirier N, Guerraty A: Four years experience with an improved tilting disc valve (Medtronic-Hall). In Kaplitt M, Borman J (eds): Concepts and Controversies in Cardiovascular Surgery. New York, Appleton-Century- Crofts, 1983, pp Miller O.C., Oyer PE, Stinson EB, et al: Ten to fifteen-year reassessment of the performance characteristics of the StamEdwards Model 6120 mitral valve prosthesis. J Thorac Cardiovasc Surg 85:1, 1983 Discussion DR. JOHN c. ALEXANDER (Evanston, IL): My colleagues and I have used the Medtronic-Hall valve for 3% years, and my remarks will be based on that experience. We are in general agreement with the authors on the major points presented. This is an important paper because it adds to our knowledge about the Medtronic-Hall valve. The main thrust of the paper concerns the performance of the valve. Hemodynamic performance, although not commented on today in detail, has been shown by the authors and others to be very good. Thromboembolic events and anticoagulation complications have been discussed today. The rates of these events are well within an acceptable range. Thromboembolic complications with current technology are probably unavoidable. This series documents a very acceptable low incidence of this complication. I think the most important statement that the authors made relates to the structural integrity of the valve. They have reported no known structural failures of this valve, and to my knowledge there are none. I hope this record will continue and the structural integrity of this valve will hold up. In summary, we agree with the authors that the Medtronic- Hall valve is a very good valve. It is our valve of choice. I thank the authors for allowing me to review the manuscript prior to this presentation. DR. JACK J. CURTIS (Columbia, MO) I congratulate the authors for this lucid presentation, which assures us that the theoretical structural advances incorporated into the manufacture of this prosthesis are translating into dependable clinical performance. My associates and I had an experience with the Medtronic- Hall prosthesis, which can be summarized as phantom positional malfunction. A 29-mm mitral prosthesis was inserted without difficulty into a 55-year-old man. Free excursion of the tilting disc was confirmed using a cotton-tip applicator prior to left atrial closure. On the morning of the first postoperative day, the patient experienced acute and severe shortness of breath and sat bolt upright in bed to relieve it. He remained in sinus rhythm but slight beat-to-beat variation in blood pressure was observed on inspection of the radial artery trace. Each time the patient tried to recline, two or three ECG complexes would occur without an ejection. The patient underwent urgent reoperation. We expected to find a chordae tendineae, a suture, a calcium spicule, or a papillary muscle tip interfering with the excursion of the tilting disc. The relationship of the malfunction to the position of the patient was mystifymg. To our surprise, no mechanical impedance was apparent. Free excursion of the tilting disc was assured. In an attempt to float up any offending chordae, the left ventricle was filled with saline

7 650 The Annals of Thoracic Surgery Vol 42 No 6 December 1986 solution. Nothing was found. The valve was rotated 90 degrees, the atrium was closed, and bypass was discontinued. Again we observed prosthesis malfunction. Bypass was reestablished, and the prosthesis was replaced with a porcine valve prosthesis. Subsequently the patient had an uneventful recovery. In the process of replacing the valve and to the present, no satisfactory explanation for the malfunctioning of the prosthesis has become apparent, and the relationship of function to patient position remains unexplained. I have heard of two similar cases and ask the authors if they have had experience with phantom malfunction of this prosthesis or are aware of similar occurrences. DR. BEAUDET: I thank Dr. Alexander and Dr. Curtis for their comments. I will begin by discussing Dr. Curtis s question. The valve itself opens freely when you take it in your hand. Consequently, once it is in place and is not functioning properly, then something is interfering with its motion. We have had this happen in the past, but it was not a ghost interference. This type of interference is usually related to two aspects: (1) the long chordae tendineae can interfere with the opening and closing of the disc by being squeezed between the disc and the housing, thereby preventing its opening by a lowpressure system in the left atrium; and (2) the sizing has to be appropriate to fit in a valve that is not too large for the ventricular cavity. When the problem is related to the presence of a long chordae tendineae, the hemodynamic appearance is almost pathognomonic of this problem where we have an intermittent normal electrocardiogram, an absence of blood pressure curve, and an elevation of left atrial pressure. To prevent this, the chordae are always cut short with the tip of the papillary muscle to prevent any free-floating pieces that could interfere with the disc motion. In your patient, I have to assume that the valve was slightly too large for the annulus or the left ventricular cavity, and either an appropriate orientation or a smaller size could have prevented this happening. This is something that has to be judged at the time of the operation. Dr. Alexander confirms our own data, and I congratulate him on the excellent results he reported. Notice from the American Board of Thoracic Surgery The American Board of Thoracic Surgery began its recertification process in Diplomates interested in participating in this examination should maintain a documented list of the cardiothoracic operations they performed during the year prior to application for recertification. They should also keep a record of their attendance at thoracic surgical meetings, and other continuing medical education activities pertaining to thoracic surgery and thoracic disease, for the two years prior to application. A minimum of 100 hours of approved CME activity is required. In place of a cognitive examination, candidates for recertification will be required to complete both the general thoracic and cardiac portions of the SESATS 111 Syllabus (Self-EducatiodSelf-Assessment in Thoracic Surgery). It is not necessary for candidates to purchase SESATS 111 booklets prior to applying for recertification. SESATS 111 booklets will be forwarded to candidates after their applications have been accepted. Diplomates whose 10-year certificates will expire in 1989 may begin the recertification process in This new certificate will be dated 10 years from the time of expiration of the original certificate. Recertification is also open to any Diplomate with an unlimited certificate and will in no way affect the validity of the original certificate. The deadline for submission of applications is July 1, A recertification brochure outlining the rules and requirements for recertification in thoracic surgery is available upon request from the American Board of Thoracic Surgery, One American Plaza, Suite 803, Evanston, IL