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Eur J Cardiothorac Surg 2003;23:299-304
© 2003 Elsevier Science NL
Department of Thoracic and Cardiovascular Surgery, J.W. Goethe University Frankfurt am Main, Theodor Stern Kai 7, 60599 Frankfurt am Main, Germany
Received 26 September 2002; received in revised form 30 November 2002; accepted 3 December 2002.
* Corresponding author. Tel.: +49-69-6301-6141; fax: +49-69-6301-5849
e-mail: mirkodoss{at}aol.com
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Abstract |
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 Top Abstract 1. Introduction2. Methods3. Results4. DiscussionAppendix A. Conference...References |
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Key Words: Aortic valve replacement • Stentless bioprosthesis
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1. Introduction |
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TopAbstract1. Introduction2. Methods3. Results4. DiscussionAppendix A. Conference...References |
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Stented bioprosthetic valve substitutes are commonly employed in the elderly. In the age group 65 years and above they display an incidence of structural valve deterioration of 6% at 15 years postoperatively [2]. The obstructive nature of the stent and sewing ring or patient prosthesis mismatch have been held accountable for persistently elevated transvalvular gradients. In the late 1980s stentless bioprostheses were introduced to circumvent these problems by offering a maximal orifice area for flow and eliminating the valvular sewing ring and stent. Thus, stentless valves seem to be the optimal choice for patients eligible for biological AVR.
The following study was designed to determine the effects of valve type on clinical and hemodynamic outcome, by means of a randomized trial in an elderly patient population.
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2. Methods |
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TopAbstract1. Introduction2. Methods3. Results4. DiscussionAppendix A. Conference...References |
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All patients provided written informed consent before inclusion in the study. The consent form was approved by our ethical committee.
2.1. Inclusion and exclusion criteria
Eligible patients included those with isolated aortic stenosis (maximum transvalvular gradient >50 mmHg or aortic valve area <0.8 cm2) in which preoperative evaluation indicated the need for an isolated AVR. Only patients expected to survive the surgery and expected to be available to return to the study site for all follow-up examinations were included in the study.
Patients who specifically chose to have a mechanical valve substitute were not suitable for enrolment. Patients that required repair or replacement of an additional heart valve and those that had prior implantation of a bioprosthetic, mechanical valve or annuloplasty device were excluded from the study. Other exclusion criteria included active endocarditis, emergency operation and a history of myocardial infarction.
Intraoperatively patients were excluded from the study if their aortic root and surrounding tissues had severe calcifications that could not be completely removed surgically and if their valve anatomy indicated an abnormally dilated aortic root or would require excessive trimming of the bioprosthesis.
2.2. Echocardiography
At our institution, only two operators performed all the echocardiograms for the study. A single echo machine (Wing Med, System Five) was used. All data collected were entered in a central database.
Apart from the standard imaging views, preoperative echocardiography also included the measurement of the diameter of the annulus and the size of the native aorta at the level of the sinotubular junction. This was necessary to identify a possible mismatch between the annulus and the sinotubular junction, which in turn would make the patients unsuitable for the implantation of a stentless valve.
2.3. Surgical technique
A total of four surgeons performed all operations. All patients had retrograde cold blood cardioplegia and carbon dioxide insufflation of the open thorax for organ protection. Access to the aortic valve was gained via a hockey stick aortotomy. After complete resection of the native aortic valve and debridement of the aortic annulus, accurate sizing was carried out using the respective CE sizers for the Prima Plus stentless and CE Perimount stented valves.
The Prima Plus stentless valves were implanted in the subcoronary position. The commissures were positioned 120° apart, with the muscular shelf corresponding to the right coronary sinus. Care was taken to suture the base of the valve subannularly, to ensure that the coaptation line of the leaflets was at the height of the native annulus. Single interrupted unpledgeted 4-0 Ethibond sutures were used for the proximal end, and the rims of the valve commissures were sutured to the native aorta using 4-0 Prolene running sutures. For the CE Perimount stented valve implantation, interrupted mattressed pledgeted 2-0 Ethibond sutures were placed circumferentially from below the annulus. The vales were implanted in the supra-annular position, with the stent positioned so as not to interfere with the coronary ostia.
2.4. Anticoagulation regime
Our anticoagulation regime was the same for both groups. It included subcutaneous low molecular heparin for the first days and parallel oral anticoagulation with vitamin K antagonists. As soon as the International Normalized Ratio (INR) levels reached the therapeutic range of 2.5–3.5, heparin was stopped. Oral anticoagulation was continued for 3 months. INR levels were monitored by the patient's general practitioner. After 3 months oral anticoagulation was stopped.
2.5. Follow-up
Follow-up examinations were scheduled for discharge from the hospital at 6 months and 12 months after operation. All patients had evaluation of their clinical status including New York Heart Association (NYHA) classification blood data including signs of hemolysis and coagulation profile, occurrence of early and late complications and echocardiographic data.
Our special emphasis was focused on the evaluation of LV mass regression. Both completeness and rate of LV mass regression were assessed. Additional endpoints were changes in LV function and hemodynamics including effective orifice area (EOA) and changes in postoperative transvalvular gradients.
2.6. Statistical methods
Data were compiled and analyzed using Microsoft Access, Microsoft Excel (Redmond, WA) and Stat view (Cary, NC). The baseline characteristics and hospital outcomes for the two groups were compared using chi-square or Fisher's exact test for categorical data and unpaired t-tests for continuous variables. Results are reported as the mean±standard deviation in text and tables. Statistical significance was defined as a P value less than 0.05.
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3. Results |
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TopAbstract1. Introduction2. Methods3. Results4. DiscussionAppendix A. Conference...References |
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EOAs improved significantly in both groups over time. Again, there were no differences between the groups at 6 and 12 month postoperatively. However, no significant differences in mean gradients were noted between the groups at 6 and 12 month postoperatively.
Echocardiographically determined EF did not improve or increase significantly over time in both groups. Although there was a slight decrease in EF at 12 months in the Perimount group and a slight increase in the Prima Plus group, overall no significant differences were found in the groups at 6 and 12 months, respectively.
NYHA classification improved over time in all patients. Most patients were in NYHA class I and II at 6 months and remained in it at 12 months, regardless of which valve substitute they had received. All clinical results over time are summarized in Table 3.
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4. Discussion |
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TopAbstract1. Introduction2. Methods3. Results4. DiscussionAppendix A. Conference...References |
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Nonetheless despite such promising findings, few randomized comparative trials exist with which to confirm the favorable results associated with stentless valve implantation. Especially in the elderly, where exercise-related gradients do not play a predominant role, due to their reduced physical activity, it would be helpful to have reliable randomized data.
Our study compared the performance of the CE Perimount stented with the CE Prima Plus stentless bioprosthesis in a prospective randomized setting. From our understanding of the pathophysiology of aortic valve stenosis, we would expect a significant difference in the regression of LV mass between bioprostheses, if their implantation results in significant differences in transvalvular gradients.
Jin et al. [12] evaluated the regression of LV mass in a large number of patients after AVR with different types of valve substitutes (the mean age of their patients was 76±16 years). They found that patients with stentless valves or homografts had a greater reduction of LV mass than patients who received a stented bioprosthesis or mechanical valve. They also found that LV mass regression had been completed at 6 months postoperatively in patients with stentless valves, whereas LV mass regression had not been completed after 12 months in patients with stented valves.
We found that all our patients operated on for aortic stenosis had a significant reduction in LV mass, irrespective of the valve substitute they received. The rate of LV mass regression was similar in both groups at 6 and 12 months, respectively. Unlike most other studies our patients were randomized to receive a specific valve. Cohen et al. [13] also conducted a prospective randomized trial. Ninety-nine patients were randomly assigned to receive a Toronto stented porcine valve or a CE pericardial valve. The mean age was 71.8±7.1 years.
Interestingly they shared our findings and reported no difference in the rate and completeness of LV mass regression after 3 and 12 months, respectively. Furthermore, they compared the transvalvular gradients based on the actual valvular internal diameters and found no statistically or clinically significant differences between the groups. Similarly there were no statistically significant differences between stented and stentless valves in our study. To explain these results, which are somewhat different to what we expected, from our knowledge of current literature, we first of all inquired whether 1 year of follow-up is sufficient to assess the regression of LV hypertrophy in patients after AVR. Jin et al. [12] found no differences in LV mass or ventricular function between 6 months and 3 years of follow-up. Monrad et al. [14] demonstrated that regression of LV hypertrophy is maximal within the first year of follow-up and that more than 8 years are necessary to detect a further reduction in ventricular mass.
We therefore assume that our follow-up period of 12 months should be suffice to detect all relevant changes in LV mass.
Apart from the changes in transaortic pressure gradients there are a number of additional independent factors influencing the rate of LV mass regression. Patients with advanced severe aortic stenosis often present with a specifically altered collagen matrix, which does not show remodeling within the first postoperative years despite relief of LV pressure overload due to AVR [15].
Furthermore, age is known to be an independent factor of LV hypertrophy [16]. Lindroos et al. [17] who evaluated the amount of LV hypertrophy in an old patient population found that the increase of LV mass is due partly to age-related disease but also partly to an independent effect of age. The LV mass was often found to exceed 70% of the standard limits in the oldest patient cohort (85 years old). As all of our patients were 75 years and older age in itself could not influence outcome significantly between the groups. Gender is also worth consideration, as LV mass, when indexed to BSA, has been found to be greater in men than woman [18]. However, female patients show greater increase in LV mass with advanced age. As our patients were well comparable with regards to gender, this again could not influence the outcome significantly between the groups.
Hypertension is often present in elderly patient populations and might significantly influence the rate of LV mass regression [19]. In our study the hypertensive patient distribution was even between the groups and could therefore not influence outcome significantly.
All these considerations indicate that in an elderly population with reduced physical activity that often has hypertension and has had aortic stenosis for a great number of years, it might be difficult to observe a complete regression of LV mass and ascribe it to the type of valve substitute. Furthermore, we were not able to detect significant hemodynamic differences between the stented and stentless valve groups.
Therefore, as no significant differences in transvalvular gradients were detected it is not surprising that no differences in the rate and completeness of LV mass regression resulted. Overall, the complexity of stentless valve implantation with its prolonged cross-clamping times might under these circumstances not be justifiable if, as we found, the same results can be achieved with a standard stented bioprosthesis. Our findings were obtained from evaluating valves of sizes 21–27 mm. As we did not implant valves of size 19 mm, we can not extend our conclusions to patients with small aortic annuli.
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Footnotes |
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Appendix A. Conference discussion |
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TopAbstract1. Introduction2. Methods3. Results4. DiscussionAppendix A. Conference...References |
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Dr Doss: Number one, we looked at the hypertensive population in our study, and, as I showed in the slide, there were about four hypertensive patients in one and five in the other group, and also postoperatively when patients came for follow-up, these hypertensive patients tended still to have slight hypertension, with systolic gradients of up to 150. But as the percentage was matched in both groups we didn't find it as a significant factor to influence the overall results. And when you say echocardiography is unreliable, that is, unfortunately, the way everybody did it in all these studies, so that is how we did it as well.
Dr W.-P. Kloevekorn (Bad Nauheim, Germany): Did you do a septal resection prior to valve implantation?
Dr Doss: We looked at whether there was septal hypertrophy in the patients, that was part of the standard protocol, and all patients that would have any, let's say, subannular stenosis were actually excluded from the study. So in these patients there was no septal resection done.
Dr C. Yankah (Berlin, Germany): My question relates to the left ventricular function of these patients. You didn't measure any functional parameters like systolic and diastolic function by echo which I believe are useful and important parameters to predict postoperative cardiac morbidity and mortality. Did you have any figures or data on these patients to predict their outcome? Both valves, the stented or stentless, are differently designed and are hemodynamically different in behavior. However, in this age group valve-related risk factor and the effect on the cardiac performance is insignificant.
Dr Doss: Yes, I agree. First of all, in this group of patients, all patients that had a myocardial infarction preoperatively were excluded. That means we did not have patients with a low ejection fraction in this group.
Secondly, we did not look at the diastolic cardiac function. We didn't look at the systolic. We looked at fractional shortening, and that actually matched the results of the ejection fraction that I had shown, which showed no differences between the groups.
Dr G. Luciani (Verona, Italy): We have been involved with stentless surgery for 10 years now, and I am a bit disturbed by several findings in your report. The first one, how do you go about randomizing stented and stentless bioprostheses? There are certain anatomical contraindications with stentless surgery and how do you exclude these patients? A second question, I noticed all your patients had normal ventricular function, but you have a mortality in the stented group which is 10%. Could you comment on that mortality estimate, which is quite high?
And the third question is, did you correct for effective orifice area after the implant of the valves to compare the functional performance?
Dr Doss: Well, the first question, how do we randomize the patients regarding anatomical implant considerations, we had a protocol, and if you had a patient that was not suitable for implantation of a stentless valve, then he was also not included in the study and he did not also receive a stented valve, number one.
Number two, we had a 10% mortality in the stented group, but, as I said, it was not valve-related. Actually one patient had a pneumonia, the other patient died of septicemia, and the third patient, which was a late complication, actually had a ruptured aortic aneurysm which was not treated and they found it in the long run. So it was not actually valve-related. I cannot say it was valve-related.
Dr Luciani: And did you match for effective orifice area after the operation to compare the regression of LV mass?
Dr Doss: We looked at the effective orifice area and we found no significant difference between effective orifice area. Actually these are also findings that were found by the other randomized trial that I had mentioned from the Cleveland Clinic. So, again, there we didn't have any differences I have to say.
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References |
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TopAbstract1. Introduction2. Methods3. Results4. DiscussionAppendix A. Conference...References |
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