Biomedical subjects

H-H Sievers

Publications and source records attributed to H-H Sievers.

10 recordsLinked to original sources

PubMed2006

Autonomously contracting human cardiomyocytes generated from adult pancreatic stem cells and enhanced in co-cultures with myocardial biopsies.

Myocardial regeneration with artificially applied cardiomyocytes is emerging as a promising issue of significant scientific and clinical impact. Nevertheless the source of cells for human cardiomyocyte differentiation especially from adult tissue is still unclear. We hypothesized that human pancreatic stem cells may differentiate into cardiomyocyte-like cells and may increase in number when co-cultured with myocardial tissue. Adult stem cells were harvested from pancreatic tissue of patients undergoing operative procedures including the pancreas. The cells were selected, cultured and passaged. To promote self-differentiation into cardiomyocytes, human pancreatic stem cells were co-cultered with biopsies of human myocardium. After co-culture and breeding, cells were phenotyped as well with respect to RNA, protein and cardiomyocyte specificity at the electron-microscopic level.Pancreatic stem cells have already differentiated spontaneously into cardiomyocyte-like cells performing netlike cell clusters with rare but distinct multilocular cellular autonomous contractions with a frequency of about 20 beats per minute. The number of contracting areas however could be enhanced by co-culture with human myocardial biopsies. On RNA and protein levels as well as in electron-microscopy, evidence for cardiomyocyte specificity is shown. To the best of our knowledge this is the first report demonstrating the feasibility of generating autonomously contracting cardiomyocyte-like cells from adult human pancreatic stem cells and their enhancement by myocardial co-culture. This procedure might prove to be an alternative source and method for myocardial regenerative medicine.

Adult↗

PubMed2005

[Aortic valve operation in young adults].

Young adults who have to undergo aortic valve surgery will frequently have (relative) contraindications to oral anticoagulation therapy because either pregnancy is planned or their life-style is very active. This review focuses on the surgical options available and assesses the literature focusing on the experience with each option obtained in young adults. There are no randomized studies in this age group which compare mechanical aortic valve replacement with any alternative option with regard to survival, need for reoperation, or quality of life. Among the alternative techniques, the Ross-procedure (pulmonary autograft) and aortic valve repair are of special interest. With the Ross-procedure, there is a rather large experience in young adults, and the results up to 10 years postoperatively are excellent. Unfortunately, there is only limited experience with this technique beyond that time.

Abnormalities, Drug-Induced↗

PubMed2005

The extent of akinesis is predictive of the in-hospital mortality from endoaneurysmorrhaphy.

Endoaneurysmorrhaphy (EAR) has become an important therapeutic option in the treatment of patients with left ventricular (LV) aneurysm and congestive heart failure. Today, more and more patients are referred for EAR with a dilated akinetic LV rather than a classic dyskinetic LV aneurysm. Little is known about the contribution of the extent of akinesis to perioperative mortality. We reviewed the data of 147 patients with anterior left ventricular aneurysms undergoing EAR. Seventy percent of the patients were male; mean age was 62+/-9 years. Demographic, hemodynamic, angiographic and surgical variables were analyzed using univariate statistic tests in order to determine risk factors for in-hospital mortality.Eighty-two percent of the LV aneurysms had at least some dyskinesia, but 70% were mainly akinetic. 133 patients had additional bypass surgery, one had additional mitral valve replacement. In-hospital mortality was 4.1% (n=6). Risk factors for in-hospital mortality were the total extent of akinetic myocardium (p=0.027) in the 30 degrees RAO view and the duration of cardiopulmonary bypass (CPB, p=0.0068) which was itself dependent on the LV ejection fraction (p=0.001), the number of stenosed coronary arteries (p=0.004), and the extent of akinesis (p=0.023). The extent of dyskinesia was not associated with either perioperative mortality (p=0.36) or CPB duration. EAR can be performed with acceptable perioperative results. Because akinesis increases in many patients with time, and because the duration of ECC was dependent on variables reflecting the severity of the underlying heart disease, our findings underscore the importance of optimal timing for the surgical intervention.

Aged↗

PubMed2005

Echocardiographic and hemodynamic characteristics of reconstructed bicuspid aortic valves at rest and exercise.

Repair of diseased bicuspid aortic valves has gained increasing interest as an alternative to conventional valve replacement. Hemodynamic data at exercise have not been reported before. The aim of this study was to investigate the clinical and echocardiographic status of patients after bicuspid aortic valve repair at rest and exercise. Between 03/94 and 09/02 a reconstruction of an incompetent bicuspid aortic valve was performed in 25 patients (mean age 35+/-12.1 years, group A, mean insufficiency 2.8 preoperatively). Patients were investigated clinically and echocardiographically after 2.1+/-2.4 (0.1-8.9) years at rest and exercise and compared to 20 controls (group B). Clinical followup was complete. There were no deaths, reoperations, thromboembolic or bleeding complications. At last examination 21 patients were in NYHA class I, n=4 in NYHA class II and mean aortic valve insufficiency (AI) was 1.0 with one patient having an AI>II degrees. Maximum and mean pressure gradient (dPmax/mean) across the aortic valve at rest were 14+/-5.5/7+/-2.6 mmHg for patients of group A and 7+/-2.5/3.6+/-1.1 mmHg in group B. Mean AVA at rest was 2.6+/-0.8 (group A) vs 2.9+/-0.6 cm(2) (group B, p=0.025), valvular resistance 13.4+/-4.8 (group A) vs 13.6+/-2.9 dyn x s x cm(-5) (group B, p>0.05). All individuals were stressed up to 100 W (dPmax/mean 21+/-6.8/11+/-3.6, group A vs 11+/-2.9/6+/-1.3 mmHg, group B). 56% of group A and 85% of group B could be stressed up to 175 W with dPmax/mean 24.5+/-8.3/12+/-4.2 and 16+/-3.6/8+/-1.4 mmHg, respectively (p<0. 01). Heart rate and blood pressure behavior were comparable. Left ventricular mass regression (preoperatively 369.3+/-76.4 vs 277.3+/-80.7 g at last examination, p<0.01) was significant in group A but did not reach normal values (group B, 227.8+/-71.1; p<0.01). Bicuspid aortic valve reconstruction reduces left ventricular volume load significantly. Although residual mild subclinical obstruction and incompetence were observed, the behavior of hemodynamics at exercise was comparable to controls. The clinical relevance of these findings in long term follow-up has to be evaluated.

Adolescent↗

PubMed2003

[The Ross procedure (pulmonary autograft) as an alternative for aortic valve replacement].

BACKGROUND AND OBJECTIVE: The Ross procedure (pulmonary autograft) has since the 1980s attracted growing interest as an alternative to the widely practised insertion of a prosthetic aortic valve. The 12-year experience of a consecutive series from one centre are reported here. PATIENTS AND METHODS: Between February 1990 and January 2002 a Ross procedure, predominantly with the subcoronary technique, was performed in 244 consecutive patients with aortic valve disease (244 men, 54 women, mean age 46 +/- 13.5 years). Annual follow-up clinical examinations (mean postoperative period 32.9 +/- 29.5 months in 99 % of the cohort) were performed. RESULTS: Perioperative mortality was 0.8 % (n=2), and there were two late deaths unrelated to the aortic valve disease. Seven patients had to be re-operated for failure of the homograft (n=4) or autograft (n=4). According to clinical criteria, 99 % of the followed-up patients were in New York Heart Association (NYHA) functional class I or II, only two patients, with pulmonary comorbidity, were in class III. Echocardiography demonstrated autografts with nearly normal transvalvular gradient (mean maximal pressure gradient 6.5 +/- 3.3 mmHg), while nine patients had second-degree aortic regurgitation. The mean maximal gradient across the homograft valve in the pulmonary position was 12.0 +/- 6.9 mmHg, while ten patients had second-degree and one had third-degree pulmonary regurgitation. CONCLUSION: The technically demanding Ross procedure produced excellent clinical and hemodynamic mid-term results. It is thus an appealing alternative to the widely used replacement by a prosthetic valve. Definitive assessment awaits further long-term follow-up.

Adult↗

PubMed2003

Decellularized pulmonary homograft (SynerGraft) for reconstruction of the right ventricular outflow tract: first clinical experience.

INTRODUCTION: Cryopreserved homograft valve conduits have been used to reconstruct the right and left ventricular outflow tract. Long-term studies have shown homograft degeneration and calcification, and it has been postulated that immunological mediated phenomena in a manner similar to that seen in chronic rejection may contribute to the degeneration process. The development of a decellularized, non-glutaraldehyde-fixed valve conduit creates a non-immunogenic connective tissue matrix for autologous recellularization by host cells. The aim of the study was to characterize the clinical and hemodynamic pattern in human implants of the novel decellularized pulmonary homografts (SynerGraft). METHODS: Reconstruction of the right ventricular outflow tract was performed in 17 patients: 15 patients with aortic valve disease and the Ross procedure, and two patients with redo procedures following Fallot tetralogy and severe pulmonary regurgitation. Patients with the Ross procedure with standard cryopreserved homografts as neopulmonic conduits served as controls. Within the follow-up over six months morphological and hemodynamic parameters were characterized by echocardiography: maximal and mean pressure gradient across the right and left ventricular outflow tract, their effective orifice areas, determination of neopulmonic and neoaortic regurgitation. RESULTS: One patient died six weeks following surgical treatment due to non-valve related end-stage cardiopulmonary failure; all patients were free of valve-related complications during the follow-up period. The matched Ross patients showed a gradual but significant increase of both the maximal and mean pressure gradient across the right ventricular outflow tract (Delta P max 5.5+/-2.5 to 11.4+/-6.4 mmHg, p=0.002; Delta P mean 3.0+/-1.3 to 6.2+/-3.9 mmHg, p=0.003), whereas in the SynerGraft group increase of pressure gradients were measurable but did not reach statistical significance (Delta P max 7.1+/-3.7 to 10.1+/-3.9 mmHg, p=0.11; Delta P mean 3.6+/-1.6 to 5.5+/-2.3 mmHg, p=0.12). The pulmonary effective orifice areas decreased in the control group from 1.74+/-0.33 to 1.18+/-0.36 cm(2)/m(2) (p=0.001). Within the SynerGraft group time dependent reduction of the orifice area was significantly less (1.51+/-0.37 to 1.25+/-0.26 cm(2)/m(2); p=0.08). CONCLUSION: Up to six months after implantation reconstruction of the right ventricular outflow tract with decellularized homografts was safe, stable, and the morphological and hemodynamic features are promising.

Adult↗

PubMed2002

Operative procedure and volumetry in experimental biomechanical hearts.

BACKGROUND: To date, skeletal muscle ventricles (SMVs) have been integrated into the circulation by a second operation following construction, vascular delay and several weeks of electrical conditioning. Recently, intra-thoracic SMVs around a mock system contracted against a pressure of 70 mmHg for several months immediately after construction in the presence of clenbuterol. This indicates that the two-step procedure may be exchanged for a clinically favorable one-step operation. The stroke volume is tested intra-operatively. METHODS: In twelve Boer goats, the latissimus dorsi muscle was folded in a double layer around a polyurethane chamber, which was integrated into descending thoracic aorta. This muscular flow-through chamber containing a stabilizing inner layer denoted "Biomechanical Heart" (BMH) showed immediate activity against systemic pressure. The conductance catheter method was applied for analysis of intra-operative stroke volume. RESULTS: The one-step operative procedure employed was practicable in all 12 goats. Operative complications were eliminated without difficulty. Intraoperative application of the conductance catheter resulted in BMH with a stroke volume of 55 +/- 14 ml. In the best BMH on postoperative day 132, a continuous pumping capacity of 1.4 l/min was measured. This BMH functioned up to day 414 postoperatively, and failed due to a rupture of the pumping chamber. CONCLUSION: This operative procedure and dynamic volumetry of experimental Biomechanical Hearts might be relevant for clinical use.

Animals↗

PubMed2002

Circulating microemboli after composite replacement or valve-sparing aortic root surgery.

BACKGROUND: The purpose of this study was to determine whether microembolic signals (MES) occur after valve-sparing operations on the aortic root. One of the advantages of these procedures relates to the freedom of macroemboli without anticoagulation. Whether this holds true for circulating microemboli has not yet been verified. METHODS: For comparison, 8 male patients (mean age: 51.8 +/- 12.8 years) were investigated 20.5 +/- 8.4 months after implantation of a mechanical composite graft (group I) and 9 female and 7 male patients (mean age 55.0 +/- 13.4 years) 23.5 +/- 20.0 months after valve-sparing replacement of the aortic root (group II). The middle cerebral artery was insonated for 2 periods of 30 min, breathing room air or O 2 at 9 l/min. RESULT: Breathing room air, the amount of MES was considerably smaller in group II (0.94 +/- 1.95 vs. 56.1 +/- 58.9 per 30 min, p = 0.006). The difference was less pronounced (0.5 +/- 1.3 vs. 28.9 +/- 42.6 per 30 min, p = 0.009) breathing oxygen. Breathing oxygen reduced MES significantly in group I (p < 0.05) but not in group II (p > 0.05). CONCLUSIONS: Aortic valve-sparing operations induce MES at a significantly lower rate than composite aortic valve replacement using a mechanical valve.

Aorta↗

PubMed2002

Influence of arteriotomy shape on power losses across in vitro cavopulmonary connections.

BACKGROUND: In the Fontan circulation power supply for maintaining adequate lung perfusion via a total cavopulmonary connection is limited. This study, aiming at the detection of energy consuming variables, compares the influence of two different pulmonary arteriotomy shapes on power losses across cavopulmonary connections. METHODS: Two types of surgical junctions of cavopulmonary connections were studied in a mock circulation. Firstly a slot-shaped incision and secondly an oval-shaped excision within the pulmonary artery was performed. The cross sections of native caval veins were sutured end-to-side with the edges of the incised and excised pulmonary arteries, respectively. Pressures and flows were measured at total flow rates varying from 1200 ml/min to 6000 ml/min and power losses calculated. RESULTS: Power losses were, in dependence of total flow, 10.66-32.64% lower across the oval-shaped junctions if compared to the corresponding slot-shaped junctions (p<0.05). CONCLUSIONS: Surgical junctions including an oval excision within the pulmonary artery may reduce power losses across cavopulmonary connections if compared to simple slot-shaped incisions. These findings may have some influence on surgical techniques to improve hemodynamics of cavopulmonary connections.

Anastomosis, Surgical↗

PubMedDate not supplied

Does caval aplanarity influence power losses across in vitro cavopulmonary connections?

Optimally designed cavopulmonary connections are desirable to reduce transanastomotic power loss. Since aplanarity of the total cavopulmonary connections results from the natural anterior-posterior position of the superior vena cava and the right pulmonary artery, the aim of this study was to investigate the influence of aplanarity of caval offset on transanastomotic power losses. Two types of cavopulmonary connections, a planar cross-like connection and a nonplanar V-shaped anastomosis, were studied in a mock circulation, comparing for each type native porcine vessels and Perspex glass models. Total flow varied between 1200 and 6000 ml/min at superior to inferior caval flow ratios of SVC/IVC = 50/50% and 33/67%, respectively. Pressures and flows were measured and power losses calculated. No significant differences in power losses were found between the planar and aplanar connections for native vessels or for Perspex glass models. Power losses across the native preparations in each configuration were significantly higher than those in the corresponding Perspex glass model. The simulation of the natural aplanar V-shaped caval offset in total cavopulmonary connections used to bypass the right ventricle seems to have no relevant additional effect on in vitro power losses compared to planar connections.

Adolescent↗