Impact of Valvular Prosthesis Type on Cardiova cular Out omes in Patients on Chronic Dialysis

.يولكلا ليس�غلاب نولجاعي نيذلا يولكلا لس�فلا ىس�رم في ليدبلا مامس�لا رايتخإا لىإا ةدس�رلما تانايبلا في ض�راعت دجوي :ض�خللما تاس�ارد 9 ةعوممج .نمزلما يولكلا ليس�غلا ىس�رم في مامس�لل ليدب لس�فأا نع ،ةروس�نلما ةقلعتلما تاس�اردلا ةعجارم دعب ،ثحبلا انررق ليس�غلا ىس�رم في ةيجولويبلا تامامس�لا مادختس�إا نامآا تزربأاو ةهباس�تم جئاتن ترهظأا ،تامامس�لا نم ينعون جئاتن تنراق ةيداعتس�إا ض�لكتلل عس�خت ةجس�نألا تامامس� نأا دقتعي ناك ةليوط ةترفل ،نمزلا برع ةليدبلا تامامس�لا رايتخإا يرياعم تيرغت دقل .نمزلما يولكلا تامامس�لاب ةقلعتلما تافعاس�لما ثركأا ناك فزنلا .ةرخأاتلما لحارلما في يولكلا لس�فلا ىس�رم في مويس�لاكلا بلاقتس�إا للخ ببس�ب ركبلما لوطأا رمعل ءاقبلا ةزيم هل ناك ةيكيناكيلما تامامس�لا عرز نأا ناتس�ارد تحس�وأا .ةيكيناكيلما تامامس�لا مادختس�إل روس�ق بركأا لثيمو تلاح برتعي تامامس�لا هذه فلت نأل ةيجولويبلا تامامس�لا عرز في اوددتري لأا بجي بلقلا ينحارج نأاب جاتنتس�إلا نكيم .ىس�رملل ىس�رلما ىلع ةقبطلما يرياعلما ض�فن ىلع ىنبم نوكي نأا بجي ليدبلا مامس�لا رايتخإا .ىس�رلما نم ةعومجلما هذه في شر�تنم يرغو ةيدرف .يولكلا لس�فلا نم نوناعي ل نيذلا .ليلتح ،تاس�رغو تلدب ،ةيجولويب تلدب ،يبلقلا مامس�لا تلدب ،يولك ليس�غ :تاملكلا حاتفم


T
he best valve substitute in patients on chronic dialysis undergoing valve replacement surgery is still a matter of ongoing debate.When choosing a mechanical valve, the preservation and durability of the biological components of a bioprosthesis should be weighed against the risk of life-threatening bleeding or major thrombo-embolism generally linked to the use of life-long anticoagulants.

Methods
The standards of valve selection have changed over time.It has long been believed that tissue valves undergo premature degeneration due to the derangements in calcium metabolism in patients with end-stage renal disease.This is based on a report by Lamberti who described two patients with accelerated degeneration of their bioprosthetic valves. 1 In 1998, American College of Cardiology/ American Heart Association (ACC/AHA) guidelines recommended the use of mechanical valves in patients on dialysis.][4][5][6][7][8][9][10] Recently, accumulating data supporting the very low incidence of rapid tissue valve degeneration in dialysis patients has been taken into consideration, and the 2006 ACC/AHA practice guidelines do not specify the best choice for valve replacement in dialysis patient.
To provide the best evidence to address this issue, a literature review of the most relevant studies was performed using PubMed.The most relevant papers treating this problem are listed and summarised in Table 1.

Results
Lucke et al. reviewed 19 consecutive patients with end-stage renal disease from a single institution who had undergone aortic, mitral or aortomitral valve replacement. 2The mechanical valve patients (n = 10) had a significantly higher rate of postoperative cerebrovascular events or bleeding complications than the bioprosthetic patients (n = 9).No subsequent reoperations were required for biological valve failure.The overall estimated Kaplan-Meier survival was 42 ± 14% at 60 months.Kaplon et al., from the Cleveland Clinic Foundation, found comparable results for both types of valves when reviewing 42 patients on preoperative dialysis undergoing valve replacements; 3 17 received mechanical valves and 25 received a bioprosthesis.Of the 25 fitted with bioprosthetic valves, 4 required reoperation with one admitted for mitral bioprosthesis degeneration.Prosthetic valve-related complications and survival were similar for both mechanical and bioprosthetic valves.
Herzog et al. reviewed the US Renal Data System database.Dialysis patients (n = 5,858) hospitalised for heart valve replacement surgery were the subjects of the study. 4Tissue valves were used in 881 patients (15%).Aortic valve replacement was performed in 58%, mitral valve replacement in 32%, and combined aortic and mitral valve replacement in 10%.There was no significant difference in survival related to type of valve.The two-year survival rate was 39.7 ± 3.5% with tissue valves versus 39.7 ± 1.4% for non-tissue valves.
Brinkman et al. found that the choice of valve substitute used in dialysis patients did not influence early and late survival; however, with a mechanical valve there were a six-fold higher incidence of late bleeding or stroke in patients on dialysis. 5han et al. investigated the results of 69 valve replacements in patients with end-stage renal disease. 6One case of structural valve deterioration (SVD) occurred in the bioprosthesis group, requiring reoperation at 95 months after surgery.A survival advantage was observed in favour of mechanical prostheses at 5 years.Nevertheless, composites of complications were similar between the two groups.
Toole et al. reviewed 50 dialysis patients undergoing left-sided valve replacement. 7The tissue valve group had significantly higher Kaplan-Meier freedom from valve-related morbidity and mortality at three years.Freedom from reoperation was not significantly different.
Filsoufi et al. analysed data from 155 patients with renal failure who underwent left-sided valve surgery, of whom 108 patients were on chronic dialysis. 8Regarding the type of prosthesis, hospital mortality and freedom from reoperation were similar in patients with mechanical and biological valves.
Umezu et al. analysed data from 63 consecutive dialysis patients who underwent valvular surgery. 9he mechanical group had a higher rate of bleeding events but there was no SVD up to the 5-year followup.However, both mechanical and bioprosthetic valve patients had similar survival and event-free rates.
Tanaka et al. performed a retrospective review on 73 aortic valve replacements for dialysis patients. 10o SVD of the bioprosthesis was seen in this series.Valve-related complications were documented in 12 of 44 patients in the mechanical valve group and in 2 of 21 patients in the bioprosthesis group.The all-cause survival rate of patients with bioprosthesis was significantly worse than that of patients with mechanical valves.

Discussion
A major concern of cardiovascular surgical teams when implanting a bioprosthesis in a patient on dialysis is SVD, and many papers have been written on the subject.However, none of the studies have been randomised controlled trials.][4][5][6][7][8][9][10] Of note, the mean follow-up of each study was relatively short; therefore, definite conclusions about the longterm performance of tissue valves in this patient population cannot be drawn.
Bleeding was the most common valve-related complication, representing a major drawback of mechanical valves.Thromboembolic events were reported in 35 patients, of whom 31 received mechanical prostheses.A total of 7 of the 9 studies did not demonstrate a survival difference according to prosthesis type.The remaining two studies demonstrated a survival advantage in favour of mechanical prostheses. 6,10However, patients who received bioprosthetic valves were older and more likely to have had a previous myocardial infarction or to have received concomitant coronary artery bypass grafting.
Recently, Chan et al. performed a systematic review and meta-analysis of valve replacement in patients on dialysis. 11In 9 studies published from 1997 to 2010, no difference in survival was observed between the valve types (bioprosthesis versus mechanical prosthesis; hazard ratio 1.3, 95% CI 1.0-1.9,P = 0.09).However, bioprosthetic valves were associated with fewer valve-related complications compared with mechanical prostheses (odds ratio 0.4, 95% CI 0.2-0.7,P = 0.002).They concluded that there was no survival difference following valve replacement with either bioprosthesis or mechanical prosthesis in patients on dialysis.
More recently, Pai et al. published their review on the same subject.They found 8 relevant retrospective studies and concluded that there was no significant difference in the results and survival between patients receiving a mechanical and those receiving a bioprosthetic valve. 12However, bleeding complications were more common with mechanical valves.

Conclusion
It can be concluded that dialysis patients after cardiac valve replacement suffer poor midterm and long-term survival rates.Therefore, due to the limited life expectancy of these patients, physicians should not hesitate to implant bioprosthetic valves because SVD will be uncommon in this patient population.Prosthesis selection should be based on the same criteria used for non-dialysis patients.
Impact of Valvular Prosthesis Type on Cardiovascular Outcomes in Patients on Chronic Dialysis