Interact CardioVasc Thorac Surg 2009;8:70-73. doi:10.1510/icvts.2008.188524
© 2009 European Association of Cardio-Thoracic Surgery
Institutional report - Valves |
Differences in the recovery of platelet counts after biological aortic valve replacement
Lutz Hilkera,*,
Michael Wodnyb,
Mario Ginestaa,
Hans-Georg Wollerta and
Lothar Eckela
a Clinic for Thoracic and Cardiovascular Surgery, Klinikum Karlsburg, Heart and Diabetes Center Mecklenburg-Vorpommern, Karlsburg, Germany
b Institute of Biometry and Medical Informatics, Ernst Moritz Arndt University Greifswald, Germany
Received 16 July 2008;
received in revised form 15 September 2008;
accepted 16 September 2008
 Has been presented as a poster presentation at ‘The Houston Aortic Symposium: Frontiers in Cardiovascular Diseases’, Houston, Texas, April 4–6 2008.
*Corresponding author. Klinikum Karlsburg, Klinik für Herz-Thorax und Gefäßchirurgie, Greifswalder Straße 11, 17495 Karlsburg, Germany. Tel.: +49 38355 701330 (Ms. Schulz).
E-mail address: Ludovici{at}gmx.de (L. Hilker).
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Abstract
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Observations among Karlsburg patients in 2006 revealed that the majority of very low platelet levels inducing postoperative heparin-induced-thrombocytopenia (HIT)-diagnostics with at the end negative results appeared related to aortic valve replacement (AVR) with stentless bioprostheses. We 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]). Between February 2005 and April 2007, 209 patients received AVR with SOLO, in 137 patients a PM-prosthesis was implanted. The mean platelet levels were compared from the first up to the fifth postoperative day. A higher occurrence of platelet levels below 100 Gpt/l between the second and the fifth postoperative day was found in the SOLO-group (71.9%) compared with the other biological substitute PM (36.6%). Differences in platelet counts between SOLO- and PM-subgroups were measured for day 2 (P=0.03), day 3 (P=0.0004) day 4 (P=0.0007), day 5 (P=0.0002) and at discharge (P<0.0001). Following intervention with conventional biological AVR, differences in the postoperative recovery of platelet counts can be detected, depending on the prosthesis used. The causes for and the clinical implications of this phenomenon are not yet assessed.
Key Words: Platelets; Biological valve replacement; Stentless prostheses
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1. Introduction
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After the introduction of a new generation of pericardial stentless prostheses (Sorin Biomedica Freedom Solo [SOLO]), with extreme pliability and very satisfying clinical and hemodynamic results [1], the Clinic of Karlsburg took up the implantation of this valve in February 2005. Until April 2007, 209 of these prostheses in aortic position were implanted. During the same period, 197 stented biological prostheses were implanted (137 Carpentier Edwards Perimount [PM], 36 Sorin Mitroflow [MF] and 24 St Jude Medical Biocor [BIOCOR]). Observations of a higher number of HIT-diagnostics with negative results in terms of a postoperative decrease of platelet levels throughout 2005/2006, led to more detailed data analysis. This revealed that most of these cases were patients after aortic valve replacement with SOLO-prostheses.
Further investigations were conducted into retrospective analyses of pre- and postoperative platelet counts; this included clinical data of all patients with biological prostheses.
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2. Material and methods
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2.1. Patients
During the period of investigation 406 patients underwent biological aortic valve surgery. For further retrospective comparison data of 137 PM-patients (90 males, 47 females; mean age 71.1±6.4 years) and 148 SOLO-patients (67 males, 81 females; mean age 73.9±6.4 years), who were operated on between February 2005 and August 2006, were included (Table 1). The main diagnosis in these patients was aortic valve disease (122 with pure aortic stenosis, 148 with mixed aortic valve disease, 15 with aortic regurgitation and/or endocarditis); 157 (55.1%) of them had concomitant coronary artery disease, 5 (1.8%) had additional mitral valve pathology and one patient had tricuspid valve pathology. In 11 patients an additional epicardial radiofrequency ablation of the right atrium was performed, in 11 cases the dilated ascending aorta was either plicated (n=10) or replaced (n=1). In five cases a persistent foramen ovale or an atrial septal defect was closed by direct suture. Five simultaneous thromboendarterectomies of a carotid artery were performed. Fifteen cases were emergencies, 22 cases were reoperations. One hundred and one patients underwent isolated AVR.
2.2. Implantation technique
In all patients a complete median sternotomy was performed followed by the cannulation of the ascending aorta and the right atrium for standard normothermic extracorporeal circulation with cardioplegic arrest induced by warm blood cardioplegia (Calafiore) and repeated every 10 to 15 min. If necessary, any concomitant procedures were performed. Then, after transverse incision of the aorta, the mostly degenerated aortic valve was excised. The annulus size was measured using specific obturators.
The choice of prosthesis used was only influenced by the surgeon's individual decision. The size of the stentless prosthesis was chosen according to the size of the sinotubular junction, the size of the other prostheses depended on the diameter of the annulus.
SOLO was implanted as stentless prosthesis completely supra annular with a 4-0 Prolene running suture interrupted at each commissure in routine fashion. A special detoxification technique (glutaraldehyde fixation, treatment with homocysteic acid) eliminated the need for rinsing before implantation as recommended by the SORIN company.
The stented prostheses (PM) were implanted intra-annular with standard 3-0 Ethibond single pledgeted mattress sutures.
The aortotomy was closed with a 4-0 Prolene suture in two layers. If necessary, the proximal anastomoses of aortocoronary bypasses were performed. Cardiopulmonary bypass was then discontinued and the chest closed in routine fashion.
2.3. Postoperative management
If there was no bleeding six hours postoperative, all patients were treated with intravenous heparin (PTT 60''). After the second postoperative day we began an anticoagulation regime with Marcumar (INR 2.0–3.0) for three months to prevent early valve thrombosis. Heparin treatment was finished when the aimed INR was reached.
Furthermore, patients with concomitant coronary heart disease were treated with 100 g Acetylsalicylic acid per day. Before discharge a transthoracic echocardiography was performed.
2.4. Data assessment
Platelet levels were measured preoperatively, directly after the operation and daily from the first to the fifth postoperative day. The blood samples were analyzed in an authorized hematological laboratory.
2.5. Data analysis
Demographic data and platelet levels are presented as mean±S.D. Statistical analysis was performed using Wilcoxon–Mann–Whitney rank sum test (Software from SAS Institute Inc., Cary, NC, USA). A P-value <0.05 was considered to be statistically significant.
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3. Results
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Fig. 1 shows the postoperative course of the mean platelet levels for all patients receiving a SOLO- or PM-prostheses between February 2005 and August 2006. No significant level differences were detected neither preoperatively nor directly postoperative.
The commonly observed first decrease down to the half of the initial level (due to dilution and ECC technique) was seen for every prosthetic intervention. A slight regeneration of the platelet counts occurred on the first postoperative day, with higher incidence in the PM-group. On day two, a second decrease occurred and from here on significant differences between the platelet courses were observed. In patients with SOLO-prostheses, the second decrease was more intensive and lasted up to the third day. 71.9% of the SOLO-patients reached platelet levels below 100 Gpt/l. After day three – in most cases – a slow secondary regeneration of platelet counts was found. A slight second decrease with minimum on day two was observed among the majority of patients with PM-prostheses. Only 36.6% of the PM-patients reached platelet levels below 100 Gpt/l between day two and day five. After that a continuous increase was observed.
3.1. Subgroup comparison
Following the primary observations, the analyses continued by investigating and comparing subgroups of the numerous patients with SOLO- and PM- aortic valve replacement (AVR) in order to achieve a better description of this phenomenon (data relating to period between February 2005 and August 2006, Table 2).
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Table 2 Patient characteristics, patients treated between February 2005 and August 2006 with SOLO or PM without concomitant procedures
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3.2. Comparison of patients with only AVR after exclusion of additional factors
To get more comparable subgroups in the following all patients with any concomitant procedures (inclusive radiofrequency ablation), preoperative treatment with Acetylsalicylic acid, preoperative platelet levels below 100 Gpt/l, reoperations, endocarditis, early postoperative bleeding with the need of reoperation or platelet substitution and postoperative diagnosis of HIT were excluded to eliminate effects potentially influencing the postoperative platelet course. In none of these patients postoperative echocardiography detected a paravalvular leakage.
The data of these subgroups were analyzed using Wilcoxon–Mann–Whitney rank sum test. There are significant differences in the recovery of the platelet counts between these SOLO- and the PM-subgroups beginning on the third postoperative day (Table 3).
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Table 3 Mean platelet counts for SOLO and PM, patients without concomitant procedures treated between February 2005 and August 2006. Furthermore, the platelet levels before discharge (d) are to be seen
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3.3. Influence of patient's age on the SOLO platelet course
To investigate the influence of patient's age on the SOLO platelet course, these patients were divided into two subgroups; one group of the patients younger than the over all mean age (73.9 years; subgroup mean age 68.3 years) and another group of the older patients (subgroup mean age 78.1 years). No significant differences were detectable (Table 4).
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Table 4 Platelet counts for SOLO patients treated between February 2005 and August 2006, depending on patient's age
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3.4. Influence of extracorporeal circulation (ECC) time on the SOLO platelet course
To investigate the influence of ECC time on the SOLO platelet course two subgroups were created; one group of patients with ECC time >114 min (mean 140.7 min) and another group of patients with ECC time <115 min (mean 89.7 min). The overall mean ECC time was 114.6±35 min. No significant differences between these groups were observed after day one (Table 5).
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4. Discussion
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The data analyzed in this study reveal undefined differences in postoperative platelet count recovery, depending on the used aortic valve prosthesis. Furthermore, they refer to differences of platelet counts in the follow-up. The causes for this phenomenon are unclear.
A slower recovery of platelet counts in the SOLO-group was seen for all used valve sizes and not related to the duration of bypass time nor with patient's age.
Postoperatively, all patients received the similar anticoagulation protocol, including the use of intravenous heparin, which may similarly affect platelets.
Microhemodynamic effects of the prosthesis structure or depending on the implantation technique and/or specific chemical preparations of biological prosthesis tissue could act as a trigger for the described phenomenon. It seems to be possible that transient unspecific activation of platelets result in diffuse consumption and lower platelet levels.
In 2006 the group of Le Guyader in Limoges observed platelet activation after aortic valve replacement with two kinds of mechanical valves (Omnicarbon, St Jude Medical Regent) and three kinds of bioprostheses (St Jude Medical Epic, Sorin Mitroflow, Carpentier Edwards Perimount) in 33 patients assessing platelet P-selectin expression, platelet-leukocyte conjugate formation and platelet micro particles. At the eighth day after implantation they found platelet activation of bioprostheses and bileaflet mechanical valves. Two months after surgery in these cases platelet activation had returned to the basic level observed prior to surgery in the bileaflet valve group, whereas it was still increased in the bioprosthesis group [2].
In 1997, Lehner et al. investigated the biocompatibility of commercially available bioprostheses either pre-treated or not with autologous endothelial cells in a model of adult baboons. After 40 days no endothelial cells were detectable on the leaflets' surface of the non-endothelialized prostheses. Fibrin deposits and platelet aggregates were observed on the bioprostheses' surface, but not on the pre-treated valves [3].
In conclusion, slower postoperative recovery of platelet levels in some kinds of aortic valve prostheses could be a sign of higher platelet activation.
Platelet activation has been correlated with thromboembolic complications in previous reports [4–6].
In 2005, Grubitzsch et al. reported one case of reoperation for suspected valve thrombosis after AVR with SOLO [7]. In our clientele one patient of the SOLO-group underwent reoperation for suspected valve thrombosis. In this case we found a blockaded non-coronary cusp due to thrombus formation partly occluding the valve. Beholz et al. described this phenomenon in patients after AVR with implantation of another kind of stentless aortic valve prosthesis (Pericarbon Freedom) as a result from immobilization and subsequent partial valve thrombosis of the non-coronary cusp in case of implantation technique with non-symmetric sinuses of Valsalva [8].
However, in all patients treated in our clinic with biological AVR there were no obvious bleeding- or thromboembolia related differences influencing the clinical outcome between the prostheses groups. Nevertheless, we investigate patients in a follow-up to observe the occurrence of such possible complications.
In conclusion, the present paper describes a phenomenon of significant differences in the recovery of patient's platelet counts after biological aortic valve replacement with different kinds of prostheses.
The causes for and the clinical implications of this phenomenon are not yet assessed. To investigate platelet activation, platelet levels and clinical outcome after AVR with different biological prostheses a prospective study should be arranged.
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References
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- Beholz S, Liu J, Dushe S, Konertz WF. The Freedom Solo Valve: superior hemodynamic results with a new stentless pericardial valve in aortic valve replacement. J Heart Valve Dis 2007 Jan;16:49–55.[Medline]
- Le Guyader A, Watanabe R, Berbe J, Boumediene A, Cogne M, Laskar M. Platelet activation after aortic prosthetic valve surgery. Interact CardioVasc Surg 2006;5:60–64.
- Lehner G, Fischlein T, Baretton G, Murphy JG, Reichart B. Endothelialized biological heart valve prostheses in the non-human primate model. Eur J Cardiothorac Surg 1997;11:498–504.[Abstract]
- Geiser T, Sturzenegger M, Genewein U, Haberli A, Beer JH. Mechanisms of cerebrovascular events as assessed by procoagulant activity, cerebral micro emboli, and platelet micro particles in patients with prosthetic heart valves. Stroke 1998;29:1770–1777.[Abstract/Free Full Text]
- Nieuwland R, Berckmans RJ, Rotteveel-Eijkan RC, Maquelin KN, Roozendaal KJ, Jansen PG, Ten Have K, Eijsman L, Hack CE, Sturk A. Cell-derived micro particles generated in patients during cardiopulmonary bypass are highly procoagulant. Circulation 1997;96:3534–3541.[Abstract/Free Full Text]
- Cohen Z, Gonzales RF, Davis-Gorman GF, Copeland JG, McDonagh PF. Thrombin activity and platelet micro particle formation are increased in type 2 diabetic platelets: a potential correlation with caspase activation. Thromb Res 2002;107:217–221.[CrossRef][Medline]
- Grubitzsch H, Linneweber J, Kossagk C, Sanli E, Beholz S, Konertz WF. Aortic valve replacement with new-generation stentless pericardial valves: short-term clinical and hemodynamic results. J Heart Valve Dis 2005 Sep;14:623–629.[Medline]
- Beholz S, Konertz WF. Avoiding early partial valve thrombosis of the Pericarbon Freedom stentless valve. J Heart Valve Dis 2007 Jan;16:91–92.[Medline]
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Abstract
1. Introduction
