A multilayered electrospun graft as vascular access for hemodialysis.

Despite medical achievements, the number of patients with end-stage kidney disease keeps steadily raising, thereby entailing a high number of surgical and interventional procedures to establish and maintain arteriovenous vascular access for hemodialysis. Due to vascular disease, aneurysms or infection, the preferred access-an autogenous arteriovenous fistula-is not always available and appropriate. Moreover, when replacing small diameter blood vessels, synthetic vascular grafts possess well-known disadvantages. A continuous multilayered gradient electrospinning was used to produce vascular grafts made of collagen type I nanofibers on luminal and adventitial graft side, and poly-ɛ-caprolactone as medial layer. Therefore, a custom-made electrospinner with robust environmental control was developed. The morphology of electrospun grafts was characterized by scanning electron microscopy and measurement of mechanical properties. Human microvascular endothelial cells were cultured in the graft under static culture conditions and compared to cultures obtained from dynamic continuous flow bioreactors. Immunofluorescent analysis showed that endothelial cells form a continuous luminal layer and functional characteristics were confirmed by uptake of acetylated low-density-lipoprotein. Incorporation of vancomycin and gentamicin to the medial graft layer allowed antimicrobial inhibition without exhibiting an adverse impact on cell viability. Most striking a physiological hemocompatibility was achieved for the multilayered grafts.

Acute aortic dissection versus aortic root aneurysm: comparison of indications for valve sparing aortic root reconstruction.

OBJECTIVES: To prove whether different indications for valve sparing aortic root reconstruction may have an impact on the outcome and longevity of the repair. METHODS: From July 1993 to March 2003, the reimplantation technique for valve sparing aortic root reconstruction was applied to 232 patients. In 44 patients, indication for operation was acute aortic dissection type A (AADA). These patients were compared with 44 randomised patients operated for aortic root aneurysm (root) by matched pair analysis with respect to age, gender, time point of operation and presence of Marfan's syndrome. Peri- and post-operative courses with focus on survival and valvular stability were analysed. RESULTS: Pre-operative grade of aortic insufficiency was 2.4+/-1 in root vs. 1.5+/-1.7 in AADA (P = 0.004) Mean CPB-time (214+/-60 vs. 171+/-42 min;P < 0.001), aortic cross clamp time (158+/-40 vs. 129+/-39 min; P = 0.001) and stay on ICU (5.2+/-9 vs. 1.7+/-1 days; P = 0.034) were longer for AADA, while hospitalisation was comparable (14+/-10 vs. 14+/-7 days; P = 0.88). Five patients (11.4%) from AADA died peri-operatively compared to no patient from root (P = 0.055). None of the early deaths were valve-related. Re-thoracotomy rate was 6.8% for both groups. Mean follow-up was 19+/-21 months for AADA vs. 28+/-21 months for root (P = 0.038) Survival at 3 years was 88+/-5% for AADA and 100% for root (P = 0.028). Freedom from valvular reoperation was 97+/-2.7% for root and 97+/-3% for AADA at 3 years (P = 0.44). At last investigation, mean grade of aortic insufficiency for AADA was 0.2+/-0.3 compared to 0.3+/-0.3 for root (P = 0.34) CONCLUSIONS: Regardless of the underlying indication, the aortic valve preserving reimplantation technique can be performed with favourable functional results.

Acellularized porcine heart valve scaffolds for heart valve tissue engineering and the risk of cross-species transmission of porcine endogenous retrovirus.

OBJECTIVE: Acellularized porcine heart valve scaffolds have been successfully used for heart valve tissue engineering, creating living functioning heart valve tissue. However, there is concern about the possibility of porcine endogenous retrovirus transmission. In this study we investigated whether acellularized porcine heart valve scaffold causes cross-species transmission of porcine endogenous retrovirus in a sheep model. METHODS: Acellularized porcine pulmonary valve conduits (n = 3) and in vitro autologous repopulated porcine pulmonary valve conduits (n = 5) were implanted into sheep in the pulmonary valve position. Surgery was carried out with cardiopulmonary bypass support. The animals were killed 6 months after the operation. Blood samples were collected regularly up to 6 months after the operation and tested for porcine endogenous retrovirus by means of polymerase chain reaction and reverse transcriptase-polymerase chain reaction. In addition, explanted tissue-engineered heart valves were tested for porcine endogenous retrovirus after 6 month in vivo. RESULTS: Porcine endogenous retrovirus DNA was detectable in acellularized porcine heart valve tissue. However, 6 months after implantation of in vitro and in vivo repopulated acellularized porcine heart valve scaffolds, no porcine endogenous retrovirus sequences were detectable in heart valve tissue and peripheral blood. CONCLUSION: Acellularized porcine matrix scaffolds used for creation of tissue-engineered heart valves do not transmit porcine endogenous retrovirus.

Impact of preoperative aortic root diameter on long-term aortic valve function after valve sparing aortic root reimplantation.

BACKGROUND: Valve sparing aortic root reimplantation technique in patients with aortic root aneurysm have shown excellent mid-term results. In conjunction with the diameter of the aortic root the mechanical leaflet stress increase, which might have an impact on long-term aortic valve function after valve sparing aortic root reimplantation. METHODS AND RESULTS: From July 1993 to October 2001, 168 patients with aortic root aneurysm underwent valve sparing aortic root reimplantation. Patients with type A aortic dissection were excluded. Thus, 123 patients were analyzed. We identified 47 patients with an preoperative aortic root diameter exceeding 60 mm (group A), 58 patients with an diameter between 50 and 60 mm (group B), and 18 patients with a diameter less than 50 mm (group C). The groups were compared regarding mortality, long-term survival, freedom from reoperation, freedom from severe and moderate aortic valve insufficiency (AI), and postoperative morbidity. Mean follow-up (group A 43+/-26 months, group B 40+/-25 months, group C 23+/-19 months; group C versus group A, P=0.005; group C versus group B, P=0.011) was shorter in group C. Perioperative mortality (group A 2.2%, group B 1.9%, group C 5.2%; P=ns) was comparable between the groups with each one patient. The 3-year survival for group A was 98+/-2%, for group B 96+/-3%, and for group C 100+/-0% (P=ns). Freedom from reoperation for group A was 98+/-2%, for group B 96+/-3%, and for group C 88+/-8% (P=ns). Four patients developed severe or moderate AI, thus freedom from severe and moderate AI for group A was 100+/-0%, for group B 88+/-8%, and for group C 94+/-5% (P=ns). During follow-up no thromboembolic or bleeding events were noticed. CONCLUSIONS: Our data show that the preoperative diameter of the aortic root has no impact on the longevity of the repair. Thus, the reimplantation technique can be recommended for all patients presenting with an aortic root aneurysm and normal leaflets regardless of the aortic root diameter.

[Ross procedure with combined replacement of the ascending aorta: impact on autograft root function and distensibility]. / Aorta ascendens-Ersatz und Ross-Operation: Einfluss auf die Distensibilität der Neo-Aortenwurzel.

BACKGROUND: The safety and effectiveness of combined aortic root autograft replacement in combination with ascending aorta replacement has been demonstrated recently. Replacement of the ascending aorta with a vascular prosthesis results in an increase in aortic root distension, and aortic root wall stress. In this study we aimed to assess the autograft root dimensions, distensibility, and autograft valve function in patients after Ross operation combined with replacement of the ascending aorta compared to patients who underwent Ross operation only. PATIENTS AND METHODS: Echocardiographic follow-up was performed on 28 patients after Ross operation with complete root replacement only (group R) and 12 patients who received an additional replacement of the ascending aorta (group R/A). The mean follow-up time was 24.9 +/- 17.2 months. Autograft root dimensions, root distensibility and valve function were assessed by echo-cardiography. The aortic root was measured at the level of the annulus, sinus of valsalva, and sinotubular junction. The distensibility was calculated as percent change of radius. RESULTS: The mean distensibility at the annulus level was higher in group R/A (18.4 +/- 6.8% vs 13.4 +/- 8.1%; p = 0.047); at the level of the sinus of valsalva and sinotubular junction no differences were observed. The autograft pressure gradient was within physiological limits in all patients. The majority of patients showed a competent autograft valve (group R: AI 0 degree; 83%, AI I degree; 14%, AI II degree; 3%; group R/A: AI 0 degree; 75%, AI I degree; 25%). CONCLUSIONS: Replacement of the ascending aorta with a non-compliant prosthesis does not effect root dimension, distensibility, and valve function.

Acute dissection of the ascending aorta: first results of emergency valve sparing aortic root reconstruction.

OBJECTIVE: Acute dissection of the ascending aorta requires immediate surgical intervention. In this study, we report our first results with valve sparing aortic root reconstruction removing all the diseased tissues. METHODS: From August 1995 to December 2000, 22 patients with acute aortic dissection of the ascending aorta (Stanford type A) underwent valve sparing aortic root reconstruction. Their ages ranged from 20 to 76 years (52+/-15, 68% males). Dissection was found in the ascending aorta (3 patients) or both in the ascending aorta and aortic arch (19 patients; 86%). Course and length of hospitalization, echocardiographic and clinical follow-up, complications and mortality were analysed. RESULTS: Mean cardiopulmonary bypass time was 212+/-56 min (134-352 min), mean aortic cross clamp time was 157+/-24 min (114-205 min). In patients undergoing additional arch replacement (n=19), circulatory arrest was 35+/-18 min (11-75 min). After reconstruction, intraoperative echocardiography showed aortic insufficiency (AI) grade 0 in 16 patients (84%) and grade 1 in three patients (16%). Stay in intensive care unit was 2.1+/-0.7 days, and postoperative hospitalization was 21+/-14.4 days. There were three perioperative deaths (14%). Mean post-operative follow-up was 18.4+/-18 months (0.4-65.4 month). One patient died 10 months postoperatively. At follow-up, no patient suffered AI grade 2 or higher, and no reoperation for aortic valve failure was necessary. All patients presented with a favorable exercise tolerance being in New York Heart Association functional class I or II. CONCLUSION: Valve sparing aortic root reconstruction in patients with type A dissection can be performed with acceptable intraoperative mortality and morbidity and excellent results during follow-up. The complete resection of the diseased aorta is particularly appealing.

[Anticoagulation in pregnant women after artificial heart valve replacement: is low-molecular-weight heparin an alternative?]. / Antikoagulation bei schwangeren Frauen nach künstlichem Herzklappenersatz: Ist niedermolekulares Heparin eine Alternative?

We report on the case of a 24-year-old pregnant woman with acute mechanical mitral valve thrombosis due to a treatment failure of low molecular weight heparin (LMWH) for permanent anticoagulation following mechanical valve replacement. Initially, our patient was put on oral warfarin for anticoagulation, but when her pregnancy was perceived the anticoagulation regimen was switched to daily subcutaneous administration of LMWH in order to minimize the risk of warfarin-induced embryopathy. During her 24th week of gestation she developed acute life-threatening pulmonary edema and hemodynamic instability, which was caused by an acute thrombosis of her artificial mitral valve. In an emergency operation the thrombozed valve was replaced by a porcine biological heart valve. The patient recovered uneventfully and gave birth to a healthy child in her 35th gestational week by cesarean section. In addition we discuss the rationale of different anticoagulation regimens with regard to maternal and fetal outcome with special consideration of LMWH as an alternative strategy to oral anticoagulation during pregnancy in women with mechanical heart valves.

Influence of modified ultrafiltration on coagulation, fibrinolysis and blood loss in adult cardiac surgery.

OBJECTIVES: Modified ultrafiltration (MUF) significantly reduce blood loss and transfusion requirements in pediatric cardiac surgery presumably by a reduction in inflammatory mediators which decrease the inflammatory axes and decrease the cross-activation of fibrinolysis and thrombosis. The influence of MUF on blood loss and homologous blood transfusion in adult cardiac surgery has not yet been determined. Furthermore, data about the influence on routine coagulation tests, platelet activation as well as the coagulation and fibrinolytic systems are limited. METHODS: In a prospective randomized study 48 patients scheduled for elective myocardial revascularization were randomized into a control group (n=16), a conventional ultrafiltration (CUF) group (n=16) and a MUF group (n=16). Perioperatively, serial blood samples were drawn at specific intervals to evaluate coagulation, fibrinolysis, and platelet function. RESULTS: Neither the coagulation nor the fibrinolytic system was positively influenced by MUF or CUF. The routine clotting tests were comparable except for a significantly higher antithrombin III activity after MUF compared to the CUF control group persisting 24 h postoperatively. Platelet factor 4 activity and platelet counts showed no differences among the groups. MUF considerably reduced the postoperative blood loss (MUF, 6.4+/-1.7 ml/kg bw per 24 h vs. CUF, 9.2+/-2.5 ml/kg bw per 24 h (P=0.003) vs. control, 8.9+/-2.2 ml/kg bw per 24 h (P=0.008)) and allogeneic blood transfusion (MUF, 2.0+/-3.4 ml/kg bw per 24 h vs. CUF, 6.9+/-5.1 ml/kg bw per 24 h (P=0.034) vs. control, 7.0+/-6.3 ml/kg bw per 24 h (P=0.029)). CONCLUSIONS: MUF in adult cardiac surgery significantly reduces postoperative blood loss and transfusion requirements. The mechanism for reduced blood loss could not be elucidated in this study.

Valve-sparing aortic root replacement (remodeling/reimplantation) in acute type A dissection.

BACKGROUND: High reoperation rates after supracommissural tube graft replacement for acute type A dissection due to sinus of Valsalva dilation have been reported. Valve-sparing operations focusing on the replacement of the sinus of Valsalva are an appealing alternative. The applicability of these techniques in acute type A dissection remains debatable and results are limited. METHODS: From 1992 to 1998, 20 patients with acute type A dissection received a valve-sparing aortic root replacement. Two different types of aortic valve-sparing operations were performed: the remodeling technique in 11 patients and the reimplantation technique in 9 patients. Patients were followed for 26 +/- 18 months. Echocardiographic studies were performed every 6 months. RESULTS: There were 2 early postoperative deaths and no late death, no reoperation, and no thromboembolic events. The latest echocardiographic studies of the 18 survivors showed a competent valve in 12 and a trivial aortic valve insufficiency in 6 patients. The mean aortic valve pressure gradient was 4.3 +/- 1.3 mm Hg. CONCLUSIONS: These midterm results support the surgical strategy of valve-sparing aortic root replacement in patients with acute type A dissection.

Adjuvant treatment of deep sternal wound infection with collagenous gentamycin.

BACKGROUND: The treatment of deep sternal wound infections remains controversial. Currently advocated procedures carry the risk of reinfections. The significance of local antibiotic-releasing systems as an adjuvant therapy to avoid reinfections is the subject of the presented study. METHODS: Forty-two patients with deep sternal wound complication were treated with radical wound debridement, sternal refixation, retrosternal suction drainage, bilateral pectoralis major muscle flaps, and placement of collagenous drug carrier loaded with gentamycin (Sulmycin Implant) underneath, above, and between the sternal edges. RESULTS: No treatment failure and death were observed in our patients. Side effects after adjuvant treatment with collagenous gentamycin were not detected. CONCLUSIONS: The preliminary results of adjuvant therapy with collagenous gentamycin in combination with surgical debridement leads to excellent results in the treatment of early deep sternal wound infections with no death and no primary treatment failures. This technique is easy to perform, reliable, and safe. For final judgment controlled randomized trials are mandatory.

Opening and closing characteristics of the aortic valve after different types of valve-preserving surgery.

BACKGROUND: The surgical approach to aortic root aneurysm and/or dissection remains controversial. The use of valve-sparing operations, which are thought to have many advantages, is increasing. We hypothesized that the particular technique and type of surgery could influence valve motion characteristics and function. Therefore, we studied the instantaneous opening and closing characteristics of the aortic valve after the main 2 types of valve-sparing surgery. METHODS AND RESULTS: In 20 patients (10 with tube replacement of the aortic root, group A; and 10 with separate replacement of the sinuses of Valsalva, group B) and 10 controls (group C), transthoracic and transesophageal studies on aortic valve dynamics were performed. Three distinct phases of aortic valve motion were identified. They were as follows: (1) a rapid opening, with a velocity of 20.9+/-4.2 cm/s in group C, 27.1+/-10.9 cm/s in group B (P=NS), and 58.3+/-18.4 cm/s in group A (group A versus group C, P<0. 001; group A versus group B, P=0.001); (2) a slow systolic closure, with 12.5+/-6.6% and 10.8+/-2.2% of maximal opening in groups C and B, respectively (P=NS), and 3.8+/-1.6% in group A (group A versus group C, P=0.001; group A versus group B, P<0.001); and (3) a rapid closing movement, with a velocity of 26.3+/-5.6 cm/s in group C, 32. 4+/-11.4 cm/s in group B (P=NS), and 21.8+/-3.5 cm/s in group A (group A versus group C, P=NS; group A versus group B, P=0.008). The pressure strain of the elastic modulus was different in groups C and B only at the commissures (682+/-145 g/cm(2) versus 1896+/-726 g/cm(2), respectively; P<0.001). At all root levels, the distensibility was reduced in group A (P<0.001). Systolic contact of aortic cusps and wall occurred only in group A. CONCLUSIONS: Near-normal opening and closing characteristics can be achieved by a technique that preserves the shape and independent mobility of the sinuses of Valsalva.

Management of porcelain aorta during coronary artery bypass grafting.

BACKGROUND: Patients with porcelain aorta carry a high risk of systemic embolism during coronary artery bypass grafting. No currently proposed surgical approach avoids manipulation of the heavily calcified ascending aorta. A novel surgical approach avoiding manipulation of the porcelain aorta was evaluated with regard to its efficacy in prevention of atheroemboli. METHODS: The following surgical protocol was performed in 23 patients with porcelain aorta: (1) arterial cannulation of the axillary artery, (2) hypothermic fibrillatory arrest for performance of the distal anastomosis, and (3) construction of the proximal anastomosis to the inominate artery or to a disease-free area of the ascending aorta during hypothermic circulatory arrest. RESULTS: The postoperative course was uneventful in all patients. No patient experienced a cerebrovascular accident or visceral organ injury as a result of atheroemboli. CONCLUSIONS: The proposed surgical approach is safe and reliable in patients with porcelain aorta and has the potential to reduce the prevalence of stroke and systemic embolization associated with coronary artery bypass grafting in patients with porcelain aorta.

Discrepancies between sizer and valve dimensions: implications for small aortic root.

BACKGROUND: Precise labeling of sizer and valve diameters is crucial for optimal valve selection especially in the small aortic root. This study examines the accuracy of manufacturers' markings on small aortic prostheses and sizers. METHODS: Sizer and valve dimensions of 22 different mechanical aortic prostheses (19 to 23 mm) were evaluated by caliper micrometer measurements. RESULTS: Nearly all sizers exceeded their marked dimensions by up to 1.0 mm. Measured tissue annulus diameters for 19-mm-labeled valves varied between 18.3 and 19.6 mm, for 21-mm valves from 20.5 to 21.6 mm, and for 23-mm valves from 22.4 to 23.5 mm, respectively. The orifice areas ranged from 1.5 to 2.06 cm2 for 19-mm valves, from 2.0 to 2.55 cm2 for 21-mm valves, and from 2.4 to 3.09 cm2 for 23-mm valves, respectively. CONCLUSIONS: Actual sizer dimensions and tissue annulus diameters of various small mechanical aortic prostheses varied considerably from their marked diameters. These differences should be considered to ensure the optimal prosthesis selection for each patient.

Continuous venovenous haemofiltration in neonates with renal insufficiency resulting from low cardiac output syndrome after cardiac surgery.

Acute renal insufficiency is a common complication after surgery for congenital cardiovascular defects in neonates and is associated with a high incidence of morbidity and mortality. The authors reviewed their experience with continuous venovenous haemofiltration in neonates and infants with acute renal insufficiency resulting from low cardiac output following cardiovascular surgery. Twelve critically ill patients with pharmacologically intractable fluid overload were treated with continuous venovenous haemofiltration over a period of 42 months. All patients were mechanically ventilated and dependent on high doses of catecholamines. Continuous venovenous haemofiltration was started 64.2(28.2) h postoperatively and maintained for a period of 8 to 195 h. A negative fluid balance was achieved in all patients (2.1(0.5) ml/kg per h). No complications relating to continuous venovenous haemofiltration were evident during the treatment. The survival rate was 59% (seven of 12). Continuous venovenous haemofiltration is a valid and simple method for controlling fluid overload in neonates and infants with low cardiac output.

Cardiovascular dynamics and dimensions after bicaval and standard cardiac transplantation.

Bicaval orthotopic cardiac transplantation leaving the right atrium intact has been introduced recently into clinical practice as an alternative to the standard method. To determine the effect of the surgical technique, 27 patients were studied at rest and supine exercise 19 +/- 5 months after bicaval orthotopic cardiac transplantation (group A, n = 15) and 22 +/- 7 months after standard orthotopic cardiac transplantation (group B, n = 12). Resting hemodynamics showed no difference between groups. With exercise, a significantly higher right atrial pressure was noted in group B. Echocardiographic analysis showed asynchronous right atrial contraction in 83% of group B patients versus none in group A. Resting right ventricular dimensions were significantly greater in group B (right ventricular end-diastolic diameter, 3.27 +/- 0.44 cm versus 2.88 +/- 0.35 cm [p < 0.05]; right ventricular end-diastolic area, 21.3 +/- 2.85 cm2 versus 17.1 +/- 2.01 cm2 [p < 0.005]). A higher incidence and significantly higher grade of tricuspid regurgitation were found throughout exercise in group B. The exercise duration (17.34 +/- 3.53 minutes versus 14.04 +/- 4.11 minutes [p < 0.05]) and the exercise capacity (1.17 +/- 0.25 W/kg versus 0.93 +/- 0.34 W/kg [p < 0.05]) were increased in group A. These data provide some evidence that the bicaval technique of cardiac transplantation improves cardiovascular dynamics and dimensions as well as exercise capacity.