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ISSN (On-line): 1678-9741 Impact Factor: 0.809
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Volume 33 Number 2, March - April, 2018

ORIGINAL ARTICLE

DOI: http://dx.doi.org/10.21470/1678-9741-2017-0157

Thrombocytopenia After Aortic Valve Replacement: Comparison Between Sutureless Perceval S Valve and Perimount Magna Ease Bioprosthesis

Syed Saleem MujtabaI; Simon LedinghamI; Asif Raza ShahI; Stephan SchuelerI; Stephen ClarkI; Thasee PillayI

IDepartment of Cardiothoracic Surgery, Freeman Hospital, Freeman Road, United Kingdom of Great Britain and Northern Ireland.

This study was carried out at the Department of Cardiothoracic Surgery, Freeman Hospital, Freeman Road, United Kingdom of Great Britain and Northern Ireland.

Correspondence To:
Syed Saleem Mujtaba
Department of Cardiothoracic Surgery
Freeman Hospital, Freeman Road Newcastle upon Tyne
NE3 1YS, United Kingdom
E-mail: saleemmujtaba@yahoo.com

ABSTRACT
Introduction: The incidence of postoperative thrombocytopenia after aortic valve replacement (AVR) with the Perceval S Sutureless bioprosthesis remains unclear. The aim of this study was to report thrombocytopenia associated with the use of sutureless AVR.
Methods: The data was collected retrospectively for patients who had isolated AVR with sutureless Perceval S valve (Group A: 72 patients) and was compared with patients who underwent isolated sutured AVR with Perimount Magna Ease Bioprosthesis (Group B: 101 patients) in our institution between June 2014 and January 2017.
Results: Cardiopulmonary bypass and cross-clamp time were significantly shorter in group A. Maximum drop in platelet count was 58% mean (day 2.3) in group A versus 44% mean (day 1.7) in group B (P=0.0001). Absolute platelet count on postoperative day 1-6 in group A was significantly less than in group B (P≤0.05). Platelet count recovered to preoperative value in 44% patients in group B versus only in 26% patients in group A at discharge (P=0.018). Moderate thrombocytopenia occurs more often in group A (41% vs. 26%) (P=0.008) while severe thrombocytopenia (<50 x 109) was observed in 6% in group A but never in group B. Platelets (P=0.007) and packed red blood cells (P=0.009) transfusion was significantly higher in the group A.
Conclusion: The implantation of sutureless Perceval aortic valves was associated with a significant drop in platelet count postoperatively with slow recovery and higher platelets and packed red blood cells transfusion requirements. A prospective randomised trial is needed to confirm our findings.

Keywords Aortic valve/surgery. Thrombocytopenia. Bioprosthesis/ Adverse Effects. Heart valve prosthesis implantation/adverse effects

ABBREVIATIONS AND ACRONYMS

AVR = Aortic valve replacement

CPB = Cardiopulmonary bypass

ECC = Extracorporeal circulation

POD = Postoperative day

TAVI = Transcatheter aortic valve implantation

INTRODUCTION

Surgical aortic valve replacement (AVR) still represents the gold standard in patients with severe aortic valve stenosis[1]. Owing to increasing age of the patient population in the Western world, there has been an increase in the prevalence of patients with valvular heart disease eligible for AVR[2]. Given the increasing number of co-morbidities and the increasing age of patients, a tendency has emerged to use biological valve implants thus avoiding the need for long-term anticoagulation therapy. Although the concept of transcatheter aortic valve implantation (TAVI) appears attractive, the calcified aortic valve is not removed during this procedure. Therefore, paravalvular leakage remains an important issue with this technique[3]. Other important concerns are access site-related problems and device malpositioning.

The recent introduction of sutureless bioprostheses may offer an additional tool in the therapeutic armamentarium as these valves do not need to be sutured into place resulting in shorter cross-clamp and cardiopulmonary bypass (CPB) durations which may be beneficial in older patients with co-morbid conditions. Moreover, due to the absence of a sewing ring, these valves exhibit favourable hemodynamic properties. Excellent outcomes have been demonstrated with sutureless AVR in minimally invasive surgical setting[4].

We noticed that sutureless valves are associated with greater drops in postoperative platelet counts compared to sutured valves. Albacker[5] reported this phenomenon with sutureless AVR and the aim of this study was to investigate this observation and try to find an explanation for its occurrence.

METHODS

Patients

It is a retrospective, observational study. All the patients who underwent isolated sutureless Perceval AVR between June 2014 and November 2016 were compared with patients who had isolated AVR with Carpentier-Edwards Perimount Magna Ease valve between June 2015 and January 2017. Any non-isolated AVR cases i.e.: coronary artery bypass grafting, mitral and tricuspid valve surgery, myomectomy, ascending aorta surgery were excluded. Moreover, all the redo, emergency and infective endocarditis patients were excluded.

All the sutureless AVRs were performed by the six different surgeons in our institution during that period. Data was collected on all the patients who underwent sutured AVR by the same surgeons during the same time period (101 patients) as a control group.

A total of 72 patients received isolated Perceval bioprosthesis and 101 patients had Perimount Magna Ease valve. The Percevel S valve sizes were small, medium, large and extra-large. For statistical purposes they were taken as equivalent to 19-21, 23, 25 and 27 mm Perimount Magna Ease sizes, respectively.

Severe thrombocytopenia was defined as a platelet count <50x109/Lit during the postoperative period. The platelet count was determined preoperatively, day of surgery and every day until day 5 in the postoperative period. In-hospital mortality was defined as any death occurring within first 30 days after surgery. Aspirin and clopidogrel was discontinued 7 days before surgery and warfarin was stopped 5 days before operation.

Surgical Approach

A complete median sternotomy was performed and extracorporeal circulation (ECC) with moderate hypothermia (34°C) was employed in every patient. Antegrade cold blood cardioplegia was administered after application of cross clamp. The choice of prosthesis implanted was made by the surgeon. Perioperative transesophageal echocardiogram was performed routinely to confirm correct position of the valve, exclude any paravalvular leak and evaluate valve hemodynamics.

The Perimount Magna Ease valve was rinsed with normal saline for 3 minutes before implantation while Perceval valve does not require any rinsing before implantation. Perimount Magna Ease valves were intra implanted with interrupted or semi continuous 2/0 prolene sutures.

The Perceval valve is a surgical bioprosthetic heart valve consists of glutaraldehyde-fixed bovine pericardium treated with homocysteic acid in order to remove the free aldehyde residues and prevent the calcification process. It is fixed in a metal cage made up of an alloy of nickel and titanium, known as nitinol.

Three 4/0 polypropylene guiding sutures were passed at the nadir of the aortic annulus. An appropriately sized prosthesis was collapsed in a side table and placed into the manufacturer's holder. The three guiding sutures were passed through the three green holes arising from the annular ring of the prosthesis, which was consequently seated on the debrided annulus. Once the delivery system is in position, the stent is deployed by turning the release screw and leaving the valve in place. The delivery system and the guiding sutures are removed. The field was rinsed with warm saline, and the prosthesis was dilated at four atmospheres for 30 seconds.

On first postoperative day, patients were started on aspirin 150 mg orally and low molecular weight heparin subcutaneously for deep vein thrombosis prophylaxis.

Statistical Analysis

All data has been extracted from the Dendrite PATS CS2010F SCTS v4.1.2 database. Date of data extract was 25.07.17 to cover the period from 01.06.2014 to 31.01.17. Analysis was performed using MS Excel. Numerical values were compared using an independent t-Test, with a two-tailed distribution assuming unequal variances. Categorical variables were compared using Chi Square χ2 analysis.

RESULTS

The preoperative characteristics of patients are depicted in Tables 1 and 2. There was no difference between Group A and B regarding history of preoperative renal impairment or pulmonary disease. Group A has more female patients (A=52% vs. B=31%; P≤0.004), patients with hypertension (79% vs. 60%; P=0.01), neurological dysfunction (17% vs. 7%; P=0.05) and angina (54% vs. 37%; P=0.03). In group A, patients were older (range: 54-84, mean 74 vs. 47-86, mean 70 vs. range 34-91, mean 71; P=0.001) and with higher logistic EuroSCORE (3.07 vs. 1.87; P=0.001).

Table 1 - Preoperative summary.
  Perceval   Perimount   Chi-squared Test
Total  n=72 %  n=101 % P
Gender (male/female) 34/38 47/52% 69/31 69/31% 0.004
Cigarette smoking history 3 4% 11 11% 0.106
History of hypertension 57 79% 60 60% 0.01
Renal disease at time of surgery __ __ 1 1% 0.40
History of pulmonary disease (i.e: COPD, asthma) 16 22% 19 19% 0.61
History of neurological disease (i.e.: TIA, CVA) 12 17% 7 7% 0.05
Angina Status pre-surgery 39 54% 37 37% 0.03
    0. No angina 33 46% 63 88%  
    1. No limitation of physical activity 16 22% 18 25%  
    2. Slight limitation of ordinary activity 11 15% 11 15%  
    3. Marked limitation of ordinary physical activity 10 14% 6 8%  
    4. Symptoms at rest or minimal activity 2 3% 2 3%  
Dyspnoea status pre-surgery 65 90% 82 82% 0.13
    1. No limitation of physical activity 7 10% 18 18%  
    2. Slight limitation of ordinary physical activity 23 32% 39 39%  
    3. Marked limitation of ordinary physical activity 41 57% 40 40%  
    4. Symptoms at rest or minimal activity 1 1% 3 3%  
History of diabetes mellitus 13 18% 20 20% 0.75
Preoperative heart rhythm  
    0. Sinus rhythm 55 76% 84 87%  
    1. Atrial fibrillation/flutter 16 22% 12 12% 0.07
    2. Complete heart block/pacing 1 1% __ __ 0.24
    3. Other abnormal rhythm __ __ 1 1.0%  
Ejection fraction category  
    1. Good (LVEF > 50%) 58 81% 84 84%  
    2. Fair (LVEF 30-50%) 12 17% 15 15% 0.77
    3. Poor (LVEF < 30%) 2 3% 1 1% 0.38

COPD=chronic obstructive pulmonary disease; CVA=cerebrovascular accident; LVEF=left ventricular ejection fraction; TIA=transient ischemic attack

Table 1 - Preoperative summary.
Table 2 - Preoperative summary (continued).
  Perceval Perimount t-Test
  Range Mean Median Range Mean Median Two-Sample Assuming Unequal Variances
Age of patients at time of procedure 54-84 74 75 47-86 70 70.5 <0.001
Logistic EuroSCORE comparison 0.53-18.89 3.07 2.41 0-7.57 1.87 1.44 0.001
Height (cm) 140-185 164.1 163 138-185 167.3 169 0.029
Weight (kg) 40.3-158 82.2 80.1 50-181.6 84.90 81.1 0.387
Table 2 - Preoperative summary (continued).

Greater number of L and XL size valves was implanted in Perceval valve group, and of 23 and 25 mm prosthesis in Perimount Magna Ease group (Table 3).

Table 3 - Proportion of different valve sizes.
Perceval valve sizes N % Perimount Magna valve sizes N %
      19 1 1
Small 8 11 21 20 11
Medium 20 28 23 42 42
Large 22 31 25 29 29
X large  22 31 27 10 18
      29 __ __
Total 72     101  
Table 3 - Proportion of different valve sizes.

When Perceval valve sizes S, M, L and XL were compared with their counterpart Perimount Magna Ease valve sizes, there was more significant thrombocytopenia in Perceval group (Table 4). Haematology data is depicted in Tables 5, 6 and 7. Among the Perceval valve group, 5 (6%) patients had severe thrombocytopenia. Their peak reduction was on day 3 with 58% of their preoperative platelet value. While in Perimount Magna group none of them had severe thrombocytopenia. Their peak reduction was on day 2 with 44% of preoperative value which is significantly less then Perceval valve group. Perceval valve group required more blood (1.5 vs. 0.7 units) (P=0.009) and platelet (0.3 vs. 0.1 platelets pools; P=0.007) transfusion. No significant difference in absolute platelet count between two groups on preoperative and operation days was observed. Platelet count was significantly reduced in Perceval group from day 1-6 and 20% patients came back to preoperative level at discharge. Forty-four percent of Perimount patients came back to preoperative value at the time of discharge. Forty-one percent of Perimount group had moderate thrombocytopenia while this value was 26% in Perceval valve group.

Table 4 - Comparison of different sizes of valves in respect of drop in platelet count %.
Perceval valve Size  % Perimount Magna valve Size % P value
Small 66.11% 19-21 mm 48.36% 0.0001
Medium 56.28% 23 mm 43.25% 0.0003
Large 59.41% 25 mm 44.85% 0.0003
X large 56.89% 27-29 mm 39.3% 0.0005
Table 4 - Comparison of different sizes of valves in respect of drop in platelet count %.
Table 5 - Haematology data.
  Perceval valve
N=72
Perimount Magna
N=101
P
Maximum drop in platelet count: "which day" Mean 2.3
Median 2
Range 0-5
Mean 1.7
Median 2
Range 0-6
0.0005
Maximum drop in platelet count: "what %" Mean 58.0%
Median 58.3%
Range 35-84%
Mean 44.3%
Median 45.0%
Range 14-64%
<0.0001
Blood transfusion: units Mean 1.5
Median 0.5
Range 0-10
Mean 0.7
Median 0
Range 0-8
0.0091
Platelet transfusion: pool of platelets Mean 0.3
Median 0
Range 0-4
Mean 0.1
Median 0
Range 0-2
0.0075
FFP Transfusion: units Mean 0.2
Median 0
Range 0-4
Mean 0.1
Median 0
Range 0-3
0.21
Table 5 - Haematology data.
Table 6 - Haematology data (continued).
Patients having postoperative thrombocytopenia Perimount Magna valve Perceval valve P value
Moderate thrombocytopenia: <100 x 109 N=26 (26%) N=34 (41%) 0.008
Severe thrombocytopenia: <50 x 109 __ N=5 (6%)  
Patients whose platelet level returned to preoperative level following surgery/did not return to preoperative Perimount Magna valve
N=44/57 (44/56%)
Perceval valve
N=20/56 (26/74%)
0.018
Table 6 - Haematology data (continued).
Table 7 - Absolute platelet count on preoperative, operative and postoperative days.
Platelet count on days Perimount Magna valve Perceval valve P value
Preoperative platelet count 244 239.8 =0.73
Operation day platelet count 158.6 144.6 =0.07
Postoperative day 1 platelet count 158.7 132.8 =0.0007
Postoperative day 2 platelet count 145.9 112.8 <0.0001
Postoperative day 3 platelet count 158.4 111.4 <0.0001
Postoperative day 4 platelet count 183.5 130.0 <0.0001
Postoperative day 5 platelet count 216.4 157.5 <0.0001
Postoperative day 6 platelet count 260.3 174.4 <0.0001
Postoperative day 7 platelet count 254.6 205.7 =0.23
Table 7 - Absolute platelet count on preoperative, operative and postoperative days.

Intraoperative and early postoperative variables are summarized in Tables 8 and 9. Cross clamp (range 23-76 min, mean 39 min vs. 24-133 min, mean 54 min; P=0.001)) and bypass time (range 25-119 min, mean 59 min vs. range 19-175 min, mean 71 min; P=0.001) were shorter in isolated Perceval valve group (Group A1) compared to isolated conventional valve group (Group B1).

Table 8 - Intraoperative and early postoperative data.
  Perceval Perimount t-Test: Two-Sample Assuming Unequal Variances
  Range Mean Median Range Mean Median P
Cumulative cross-clamp time (min) 23-76 39.2 38 24-133 54.1 48.5 <0.001
Cumulative bypass time 25-119 59.3 56.5 19-175 71.6 63.5 <0.001
Post operative blood loss @ 12 hours 15-2000 304 212.5 100-2000 359.7 300 0.197
ITU stay in days 1-13 3.2 2 1-17 1.9 1 0.005

ITU=intensive care unit

Table 8 - Intraoperative and early postoperative data.
Table 9 - Intraoperative and early postoperative data (continued).
  Perceval   Perimount   Chi-squared Test
Total n=72 % n=100 % P
Reoperation for bleeding, tamponade 2 2.78% 2 2.00% 0.738
Patient status at discharge (mortality) 1 1.39% __ 0.00% 0.237
Table 9 - Intraoperative and early postoperative data (continued).

Perceval valve patients spent more time in ICU compared to Perimount Magna patients (3.2 days vs. 1.9 days; P=0.005). No significant difference in postoperative neurological dysfunction, renal impairment, atrial fibrillation, permanent pacemaker requirement or mortality could be observed.

DISCUSSION

Our retrospective study showed that there is a relationship between Perceval S valve implantation and severe thrombocytopenia. Severe thrombocytopenia in our study was not associated with higher mortality and morbidity, and none of these deaths was related to severe thrombocytopenia.

Sánchez et al.[6] compared the incidence of thrombocytopenia after AVR with Perceval S Sutureless Bioprosthesis (n=27) and Mitroflow prostheses (n=50). The incidence of severe thrombocytopenia was significantly higher (P=0.046) in Perceval S patients than in Mitroflow patients. The platelet count recovered in all patients with severe thrombocytopenia.

The biological structure of the Perceval S valve and Freedom Solo stentless bioprosthesis are very similar[6].

Hilker et al.[7] compared the postoperative courses of platelet counts in patients having had AVR with stentless prostheses (Sorin Biomedica Freedom Solo [SOLO]) or stented prostheses (Carpentier Edwards Perimount [PM]). A higher occurrence of platelet levels below 100 Gpt/l between the second and the fifth postoperative day (POD) was found in the SOLO-group (71.9%) compared with the other biological substitute PM (36.6%).

Miceli et al.[8] evaluated the postoperative evolution of platelet count and function after AVR in 116 patients undergoing isolated stentless biological AVR with Freedom Solo and compared with 206 patients who received stented biological valves. Freedom Solo implantation was associated with a higher incidence of thrombocytopenia compared with the control group (24.1% vs. 4.4%, P<0.0001).

Piccardo et al.[9] also studied the incidence and clinical impact of thrombocytopenia in patients receiving AVR with Freedom Solo bioprosthesis and Carpentier-Edwards Perimount pericardial prosthesis. They reported that severe thrombocytopenia occurred in 25% and 3% of patients with Freedom Solo and Perimount bioprostheses, respectively (P<0.0001).

Yerebakan et al.[10] compared platelet counts within 2 weeks after implantation of either a stentless (Sorin Freedom Solo) or a stented (Sorin Mitroflow) bovine pericardial bioprosthesis. In the Mitroflow group, the mean platelet count moderately dropped to a minimum of 60% of the initial value on 3rd POD and fully recovered on 8th POD. In the Freedom Solo group, platelet loss was significantly more severe (minimum relative value 25% on 4th POD) with no recovery during follow-up. However, there were no other complications reported in association with thrombocytopenia related to the use of these Freedom Solo valves and the phenomenon was transient and resolved without clinical consequences or hemodynamic dysfunction[9,10].

Platelet count decrease has also been reported after percutaneous coronary intervention[11]. Gallet et al.[12] studied the effect of transcatheter (via femoral artery) aortic valve implantation (TAVI) on platelet count. They observed that platelet count systematically decreased after TAVI, with an average decrease of 34±15%, and a decrease in platelet count reported to be associated with in-hospital major adverse cardiovascular events and strongly influenced patient outcome. In the setting of TAVI procedures platelet activation can be caused by endothelial damage caused by prosthesis implantation, fibrinogen binding on metallic armatures, and shear stress modifications due to prosthesis implantation[13].

Van Straten et al.[14] compared thrombocytopenia after AVR with mechanical and biological valves. They concluded that patients undergoing AVR with the Carpentier-Edwards Perimount bioprosthesis or a Medtronic Freestyle stentless bioprosthesis had a lower minimum platelet count within the first five POD, compared to patients receiving ATS and St. Jude Medical mechanical prostheses.

In our study, the drop-in platelet count started to occur during the 3rd POD with very slow recovery toward the 7th to 10th POD. The lowest drop in platelet count was down to 22% of the preoperative baseline level and occurred in patients implanted with the Perceval valve. As shown in other studies, there were no other clinical consequences associated with thrombocytopenia that was transient but resulted in more transfusion requirements.

The bovine pericardium leaflets of both Perceval S valve and Mitroflow bioprosthesis are fixed in a process using gluteraldehyde. The Mitroflow prosthesis is stored in a solution of gluteraldehyde and needs rinsing before it is used. On the other side, the Perceval S prosthesis and Freedom Solo prosthesis are detoxified with homocysteic acid to eliminate any residual aldehyde and then stored in an aldehyde free solution; so, it does not require rinsing prior to use. Homocysteic acid can have a damaging effect on vessel endothelial cells and can precipitate platelet aggregation resulting in both thrombocytopenia and thrombotic complications[15]. These valves are carefully washed after detoxification with a homocysteic acid-free solution and then stored in jars filled with a homocysteic acid-free storage solution. Consequently, the residual amount of homocysteic acid, which could be transferred to the patient during the valve implantation, is negligible and the resulting concentration in blood is extremely low, so cannot be blamed for the postoperative thrombocytopenia. Moreover, the same solution is used for other bioprosthesis[16], without causing higher incidence of thrombocytopenia.

Mechanical stress and hemodynamic turbulence have also been proposed as a cause of thrombocytopenia after Freedom Solo prosthesis[10].

Small valve sizes have been described as causing some turbulence across the valve resulting in platelet activation or destruction, and consequently postoperative thrombocytopenia[7,9,14]. However, sutureless valves are well known for their superior hemodynamic performance and this hypothesis is quite unlikely.

Non-specific activation of platelets leading to diffuse consumption and thrombocytopenia after AVR with both mechanical and bioprosthetic aortic valves was suggested by Leguyader et al.[17]. Platelet activation could also result from valve manipulation or the presence of the metal stent.

The Perceval S valve has metal structure that serves as an anchoring system to the aortic valve, which could be the cause of turbulent flow, platelet rupture and mechanical structure. The metal stent may play a role in platelet activation and the possibility of paravalvular leaks may also trigger platelet activation and consumption. Moreover, the metal stents of these valves could interfere with the quality of images and could conceal or underestimate the degree of some paravalvular leaks[5].

Long CPB duration has been suggested by other studies to be associated with postoperative thrombocytopenia[14]. In our study the CPB durations were shorter in the sutureless group than the sutured one so it cannot be responsible for post-operative thrombocytopenia.

Severe thrombocytopenia is a common complication in patients who undergo cardiac surgery with ECC. It occurs as result of structural changes and activation of platelets, hemodilution, platelet aggregation and bleeding[18].

Limitations

The main limitation of our study is due to its observational, non-randomized and retrospective characteristics. Heparin induced thrombocytopenia was not investigated as a possible cause of thrombocytopenia, as it appears after the 5th postoperative day[18].

CONCLUSION

It seems to be an association between sutureless Perceval valve and severe thrombocytopenia, although it does not affect patient's mortality and morbidity. These patients had also higher rate of blood and platelets transfusion. A prospective randomised trial is needed to confirm our findings.


REFERENCES

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3. Martens S, Sadowski J, Eckstein FS, Bartus K, Kapelak B, Sievers HH,et al. Clinical experience with the ATS 3f Enable® suturelessbioprosthesis. Eur J Cardiothorac Surg. 2011;40(3):749-55.

4. Santarpino G, Pfeiffer S, Concistrè G, Fischlein T. Perceval Saortic valve implantation in mini-invasive surgery: the simple suturelesssolution. Interact Cardiovasc Thorac Surg. 2012;15(3):357-60.

5. Albacker TB. Thrombocytopenia associated with Perceval suturelessaortic valve replacement in elderly patients: a word of caution. Heart SurgForum. 2015;18(3):E093-7.

6. Sánchez E, Corrales JA, Fantidis P, Tarhini IS, Khan I, Pineda T, etal. Thrombocytopenia after aortic valve replacement with Perceval S suturelessbioprosthesis. J Heart Valve Dis. 2016;25(1):75-81. [MedLine]

7. Hilker L, Wodny M, Ginesta M, Wollert HG, Eckel L. Differences inthe recovery of platelet counts after biological aortic valve replacement.Interact Cardiovasc Thorac Surg. 2009;8(1):70-3.

8. Miceli A, Gilmanov D, Murzi M, Parri MS, Cerillo AG, Bevilacqua S,et al. Evaluation of platelet count after isolated biological aortic valvereplacement with Freedom Solo bioprosthesis. Eur J Cardiothorac Surg.2012;41(1):69-73. [MedLine]

9. Piccardo A, Rusinaru D, Petitprez B, Marticho P, Vaida I,Tribouilloy C, et al. Thrombocytopenia after aortic valve replacement withfreedom solo bioprosthesis: a propensity study. Ann Thorac Surg.2010;89(5):1425-30.

10. Yerebakan C, Kaminski A, Westphal B, Kundt G, Ugurlucan M, SteinhoffG, et al. Thrombocytopenia after aortic valve replacement with Freedom Solostentless bioprosthesis. Interact Cardiovasc Thorac Surg.2008;7(4):616-20.

11. De Labriolle A, Bonello L, Lemesle G, Roy P, Steinberg DH, Xue Z, etal. Decline in platelet count in patients treated by percutaneous coronaryintervention: definition, incidence, prognostic importance, and predictivefactors. Eur Heart J. 2010;31(9):1079-87.

12. Gallet R, Seemann A, Yamamoto M, Hayat D, Mouillet G, Monin JL, etal. Effect of transcatheter (via femoral artery) aortic valve implantation onthe platelet count and its consequences. Am J Cardiol.2013;111(11):1619-24.

13. Nobili M, Sheriff J, Morbiducci U, Redaelli A, Bluestein D. Plateletactivation due to hemodynamic shear stresses: damage accumulation model andcomparison to in vitro measurements. ASAIO J. 2008;54(1):64-72. [MedLine]

14. van Straten AH, Hamad MA, Berreklouw E, ter Woorst JF, Martens EJ,Tan ME. Thrombocytopenia after aortic valve replacement: comparison betweenmechanical and biological valves. J Heart Valve Dis.2010;19(3):394-9.

15. Piccardo A, Rusinaru D, Petitprez B, Marticho P, Vaida I,Tribouilloy C, et al. Thrombocytopenia after aortic valve replacement withfreedom solo bioprosthesis: a propensity study. Ann Thorac Surg.2010;89(5):1425-30.

16. Santarpino G, Pfeiffer S, Fischlein T. Thrombocytopenia afterfreedom solo: the mystery goes on. Ann Thorac Surg.2011;91(1):330.

17. Leguyader A, Watanabe R, Berbé J, Boumediene A, Cogné M, Laskar M.Platelet activation after aortic prosthetic valve surgery. Interact CardiovascSurg. 2006;5(1):60-4.

18. Weerasinghe A, Taylor KM. The platelet in cardiopulmonary bypass.Ann Thorac Surg. 1998;66(6):2145-52.

Article received on july 31, 2017.

Article accepted on september 6, 2017.

No financial support.
No conflict of interest

Authors' roles & responsibilities

SSM Drafting the work or revising it critically for important intellectual content; final approval of the version to be published

SL Drafting the work or revising it critically for important intellectual content; final approval of the version to be published

ARS Drafting the work or revising it critically for important intellectual content; final approval of the version to be published

SS Drafting the work or revising it critically for important intellectual content; final approval of the version to be published

SC Drafting the work or revising it critically for important intellectual content; final approval of the version to be published

TP Drafting the work or revising it critically for important intellectual content; final approval of the version to be published

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