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Hans-H Sievers

Publications and source records attributed to Hans-H Sievers.

At least 19 recordsLinked to original sources
PubMed2007

Subcoronary Ross procedure in patients with active endocarditis.

BACKGROUND: The Ross procedure has gained increasing interest as an attractive alternative to a prosthetic aortic valve substitute within the last decade. Because of a probably better resistance to infection as one of its advantages, the pulmonary autograft is theoretically preferable for active endocarditis. METHODS: Between June 1994 and July 2003, the Ross procedure was performed using the subcoronary and inclusion technique in 296 patients (231 male, 65 female). Twenty patients had an active endocarditis of the aortic valve at the time of operation. A bicuspid valve was present in 10 patients. One patient had previous aortic valve surgery. Clinical and echocardiographic follow-up was complete. RESULTS: Early mortality was 1, late mortality was 0. There were no recurrence of endocarditis and no neurologic events during the mean follow-up of 47.3 +/- 28.6 months. All patients were in New York Heart Association class I. Mean and maximum pressure gradient across the autograft was 3.5 +/- 2.0 and 6.5 +/- 3.4, respectively, with no autograft insufficiency in 15, 1+ in 4. Comparing postoperative with the last investigations, there were no significant changes of pressure gradients or grade of regurgitation. Mean and maximum homograft pressure gradients were 7.9 +/- 3.7 and 16.2 +/- 8.1 mm Hg, respectively, at last investigation; most patients had no or mild homograft regurgitation (0+, n = 13; 1+, n = 5; 2+, n = 1). CONCLUSIONS: Native valve endocarditis can be treated with excellent results using the Ross procedure with the subcoronary and inclusion technique, with low mortality and morbidity rates and a very low recurrence rate of endocarditis.

Adult↗
PubMed2007

Pulmonary homograft muscle reduction to reduce the risk of homograft stenosis in the Ross procedure.

OBJECTIVE: The Ross procedure has gained increasing interest as an attractive alternative for aortic valve replacement. Despite its advantages, there is a certain risk of structural valve deterioration, especially of the pulmonary homograft as a result of shrinkage and subsequent stenosis predominantly at the muscular annulus. Theoretically, reduction of homograft muscle tissue could reduce this risk. METHODS: From February 1996 through December 2002, a total of 238 patients (mean age 44 +/- 13.2 years) underwent the Ross procedure with the subcoronary technique with follow-up investigations before discharge and after 12 and 24 months. To estimate the importance of homograft muscle reduction within our institution-specific risk factor scale for change of transhomograft pressure gradient with time, we performed a generalized estimating equation approach, which identified homograft muscle reduction, higher body surface area in male patients, younger patient age, smaller homograft diameter, blood transfusions, and follow-up time as independent risk factors demonstrating a high beta value (-2.8638) for muscle reduction. To find out whether muscle reduction influences transhomograft pressure gradient, we compared patients with (group A, n = 39) and without (group B, n = 199) muscle reduction. The other mentioned independent risk factors were not different between groups, except for blood transfusions (group A greater than B, P < .01), indicating a negative bias for group A. RESULTS: The maximum pressure gradient across the homograft was lower in patients with muscle reduction before discharge (4.5 +/- 2.8 mm Hg group A vs 6.2 +/- 3.8 mm Hg group B, P = .004) and after 1 (9.3 +/- 5.8 vs 13.1 +/- 8.4 mm Hg, P = .028) and 2 years (10.8 +/- 7.6 vs 13.7 +/- 7.5 mm Hg, P = .013). No significant differences were found concerning homograft insufficiency. CONCLUSIONS: We provide some evidence that transhomograft pressure gradient can be reduced significantly within the first 2 years after operation by homograft muscle reduction. Longer term follow-up is necessary to evaluate this promising operative technique further.

Adolescent↗
PubMed2006

[Reconstructive surgery of the aortic valve: the Ross, David, and Yacoub procedures].

The aortic valve consists of three cusps attached to the wall of the aortic root. During the cardiac cycle, the aortic root undergoes complex movements that precede and aid opening and closing of the aortic valve. The aortic valve cusps themselves form thin-walled pocket-like structures, made from specialized tissue with fibrous, elastic, nervous, and muscular properties. The complex interactions of this tissue with the aortic root and within the cardiac cycle are only incompletely understood yet. In summary, the aortic valve is a complex structure which shows a perfect function in systole and diastole and under a wide range of hemodynamic conditions. No valve prosthesis (so far) can keep up with the function of the native aortic valve. Therefore, surgical techniques have been invented that aim at sparing the aortic valve or replacing it with very similar autologous tissue. Besides the resulting (near) normal valve function, one appealing advantage of these techniques is that oral anticoagulation can be abandoned completely. If the valve cusps themselves are normal, but the aortic root is aneurysmatic or dissected (with or without resulting secondary aortic insufficiency), the aortic valve can be spared by resecting the aortic root tissue and replacing it by a vascular graft. The aortic valve can then be implanted into the vascular graft in a way described by David, or can be remodeled into it (Yacoub technique) - in this case, the graft first needs to be incised at its base so that the three commissures of the valve can be sewn into the three incisions. This way pseudosinuses within the vascular graft are created. The sinuses within the aortic root are considered important for aortic valve function and coronary perfusion. On the other hand, incisions at the base of the vascular graft harbor the potential for redilatation of the aortic root because of a missing circular fixation. Such a fixation is achieved by the David technique. Therefore, there is a great debate in the surgical community which valve-sparing technique is the best and numerous modifications of the original techniques exist. A clear clinical advantage of one technique over the other could not be demonstrated so far, but many authorities advise that the David technique is to be used preferentially in patients with Marfan's syndrome (or other connective tissue disorders) and those with a very wide basal aortic root. If the aortic valve cusps themselves are diseased and cannot be reconstructed, the autologous pulmonary valve is the most physiological substitute. Replacing the aortic valve with the autologous pulmonary valve is named Ross procedure. The defect in the right ventricular outflow tract that is created while harvesting the autograft must be reconstructed during the same procedure; usually, a pulmonary valve allograft is used for this purpose. With all reconstructive surgical techniques and with all autologous replacements there is a risk of reoperation, mainly (besides technical issues) because it is feared that leaving autologous tissue in place leads to recurrence of the original illness. The published results, however, with aortic valve-sparing surgery and with the Ross procedure show that the risk of reoperation appears to be very acceptable. This statement is especially true for the Ross procedure for which more and longer experience exists worldwide. Echocardiographic studies show that the aortic valve function after valve-sparing techniques and - especially - after the Ross procedure is indeed excellent. Therefore, patients with aortic root pathologies or aortic valve diseases should be informed about valve-sparing aortic root reconstructive techniques or the Ross procedure. The choice of technique should be made in close contact between patient, cardiologist, and cardiac surgeon. However, the described techniques require extensive experience within the surgical team.

Aortic Aneurysm↗
PubMed2005

Ross procedure and left ventricular mass regression.

BACKGROUND: Return of left ventricular mass to normal is considered to be a favorable result of aortic valve replacement. The Ross procedure provides near normal hemodynamics and thus allows studies of left ventricular (LV) reverse remodeling. LV mass regression may be influenced by surgical technique (subcoronary [SC] versus root replacement [RR]). METHODS AND RESULTS: Data from the German Ross Registry were analyzed. A total of 646 patients (mean age: 43.6+/-12.7 years, range: 16 to 71 years; SC technique n=295, RR technique n=351) underwent a Ross procedure in 7 participating centers from 1990 to 2004. The patients underwent preoperative and postoperative echocardiographic evaluations. Mean follow-up time was 3.5+/-2.5 years (range 0.12 to 13.7 years). Follow-up completeness was 97%. The LV mass index (LVMI) decreased significantly during follow-up in both groups (SC: 209+/-53 preoperatively to 154+/-48 at 1-year follow-up, [P<0.01 versus preoperative values] to 149+/-51 g/m2 at 2-year follow-up, [P=NS 1-year versus 2-year follow-up] versus RR: from 195+/-56 preoperatively to 144+/-51 at 1-year follow-up [P<0.01 versus preoperative values] to 140+/-49 g/m2 [P=NS 1-year versus 2-year follow-up]). LVMI regression remained stagnant 1 year after the Ross procedure in most patients in both groups. On the basis of multivariate analysis, predictors for incomplete LVMI regression after the autograft procedure were high preoperative LVMI, smoking, and uncontrolled diastolic hypertension. CONCLUSIONS: At mid-term echocardiographic follow-up, patients of both groups had favorable autograft hemodynamics. Risk factors for incomplete postoperative LVMI regression in our study were smoking and persistent diastolic hypertension. This emphasizes the importance of cessation of smoking and treatment of arterial hypertension, even in younger patients, after corrected aortic valve disease.

Adolescent↗
PubMed2005

Histopathologic findings in a novel decellularized pulmonary homograft: an autopsy study.

Innovative valved conduits for reconstruction of the right ventricular outflow tract are desirable to overcome the risk of valve deterioration of conventional homografts. This study describes the histopathology of a novel decellularized pulmonary homograft (SynerGraft) implanted in the right ventricular outflow tract of a 60-year-old man 5 weeks before death. The histomorphology of this decellularized homograft showed integrity of its extracellular matrix and a gradual cellular infiltrate consisting predominantly of macrophages, resembling an early nonspecific inflammatory phase of recellularization without any signs of a specific immunologic interference 5 weeks after implantation. Whether this morphologic appearance precedes the desired repopulation with autologous fibroblasts remains to be established.

Autopsy↗
PubMed2005

Ross procedure in a quadricuspid aortic valve.

A quadricuspid aortic valve is a rare congenital cardiovascular abnormality, and when present, it is associated with aortic valve regurgitation. If aortic valve replacement is required, mechanical or biological prostheses are used. We report the case of a patient with a severely regurgitant quadricuspid aortic valve in whom a Ross procedure was performed.

Aortic Valve↗
PubMed2005

In vitro hydrodynamics, cusp-bending deformation, and root distensibility for different types of aortic valve-sparing operations: remodeling, sinus prosthesis, and reimplantation.

OBJECTIVE: Preserving aortic valve cusps during operations for aortic root pathology theoretically offers several advantages over alternative prosthetic valve-bearing conduits. Functional properties of different valve-sparing techniques under defined conditions are not well studied. METHODS: Fresh porcine aortic roots were investigated in a pulsatile flow simulator, either native root or after different types of valve-sparing procedures (remodeling, sinus prosthesis, and reimplantation). Functional parameters, such as transvalvular pressure gradient, closing volume, cusp-bending deformation, and distensibility at different levels of the root were analyzed. RESULTS: The mean pressure gradient was highest in reimplantation techniques (8.4 +/- 1.8 mm Hg) compared with sinus prostheses (7.2 +/- 0.9 mm Hg, P = .01) and remodeling techniques (6.8 +/- 1.0 mm Hg, P = .002), mirror imaging the closing volume (reimplantation, 1.5 +/- 0.4 mL; sinus prostheses, 2.3 +/- 0.7 mL [P < .001]; remodeling, 3.4 +/- 1.1 mL [P < .001]). Bending deformation indices increased significantly from remodeling (0.45 +/- 0.05) and sinus prostheses (0.58 +/- 0.06) to reimplantation techniques (0.73 +/- 0.09). Dynamic changes in area of all techniques were decreased at the sinotubular junction and the commissural and sinus levels when compared with those seen in native roots but increased at the annular level for techniques with unfixed annulus (remodeling and modified sinus prosthesis). CONCLUSIONS: In vitro the various aortic valve-sparing operations differed characteristically in their ability to spare valve function, none of them completely meeting native valve behavior. The remodeling techniques exhibited valve dynamics closest to those of the native aortic root. The more the aortic valve is fixed with noncompliant prosthetic material, the more the native root dynamics are impaired.

Animals↗
PubMed2004

A novel, form-stable, anatomically curved vascular prosthesis for replacement of the thoracic aorta.

PURPOSE: Current replacement of the thoracic aorta performed with straight vascular prostheses may cause kinking, potentially affecting hemodynamics and promoting vortices and thrombus formation. A novel vascular prosthesis, resistant to pressure-related shape deformation, was designed to imitate the curved anatomy of the thoracic aorta. DESCRIPTION: A woven velour prosthesis was trimmed with cross-sutures along a marked line, resulting in a curved-shaped anatomic form, and was compared with conventional straight and thermally fixed curved grafts. The vascular prostheses were fixed at both ends at various base distances (8, 10, 12, 14, and 16 cm) and pressurized. To imitate the neck vessels an abutment was fixed at the upper convexity of the grafts. Radius of curvature or depth of kinking was measured at different pressures (100, 125, and 150 mm Hg). Pressure gradients and flow profiles were further analyzed in an aortic arch glass model. EVALUATION: When pressurized the straight and the thermally fixed protheses showed double kinking before and behind the abutment at all pressures and distances. Kinking depth increased with increasing pressure and less base distance. Transkinking pressure gradients increased with the degree of kinking. In a glass model flow profiles showed postkinking turbulences and vortex formation. The newly designed vascular prosthesis showed no kinking and remained form stable at all test conditions. CONCLUSIONS: This novel curved vascular prosthesis for replacement of the thoracic aorta demonstrates form stability compared with conventional straight and thermally fixed vascular prostheses in an aortic arch model, with smaller pressure gradients and flow disturbances.

Aorta, Thoracic↗
PubMed2004

Improved hydrodynamics of a new aortic cannula with a novel tip design.

BACKGROUND: Reduction of atheroembolic complications during cardiopulmonary bypass remains a major challenge in cardiac surgery. New cannula tip designs may help to attenuate this problem by improved hydrodynamics. METHODS: Pressure gradients and back pressures of a new aortic cannula tip design were measured and compared with the Medos X-Flow, Sarns Soft-Flow and Argyle THI cannulae at various flow rates in a mock circulation followed by flow visualization. RESULTS: Pressure gradients were the lowest for the new cannula. Back pressures of the new cannula were up to 84% lower than for the Argyle cannula. The back pressure profile and flow visualization of the new cannula showed broad centric flow dispersion with a transcannula increase of flow area from 38 mm2 to 139 mm2. CONCLUSIONS: The new design of an aortic cannula tip provides improved hydrodynamics, with low pressure gradients, low back pressures and a uniform central dispersion of flow, reducing the sandblasting effect.

Aorta↗
PubMed2003

Prophylactic gamma radiation of unaffected vein grafts failed to prevent vein graft disease in a chronic hypercholesterolemic porcine model.

OBJECTIVE: The value of prophylactic brachytherapy on vein graft disease is unknown. METHODS AND RESULTS: Vein bypass grafts in 23 hypercholesterolemic pigs after ex vivo gamma irradiation of the vein grafts (10, 20, and 40Gy) and 16 control veins were analyzed regarding: (1) expression of platelet-derived growth factor (PDGF-AA and -BB, ELISA); (2) smooth muscle cell (SMC) proliferation/cell death (double-immunohistochemistry Mib-1/TUNEL/SMC alpha-actin); and (3) vessel wall dimensions. Planimetric data on vessel wall dimensions revealed no positive effect of gamma radiation on neointima formation and inner lumen diameter. On the contrary, vein grafts subjected to 40Gy were significantly more likely to be occluded and to have reduced inner lumen and increased neointima formation. Radiation therapy had no effect on PDGF expression and SMC proliferation/cell death. The mean inner lumen diameter decreased as PDGF-AA expression increased. CONCLUSIONS: Prophylactic gamma radiation of unaffected vein grafts failed to prevent vein graft disease in a hypercholesterolemic porcine model. High-dose radiation (40Gy) resulted in more frequent graft occlusion and vein sclerosis.

Anastomosis, Surgical↗
PubMed2002

Lung protection during total cardiopulmonary bypass by isolated lung perfusion: preliminary results of a novel perfusion strategy.

BACKGROUND: The present pilot study was conducted to evaluate the effect of isolated short-term lung perfusion during cardiopulmonary bypass (CPB) on inflammatory response and oxygenation. METHODS: A total of 24 patients undergoing elective cardiac surgery with routine CPB were prospectively assigned to three groups. Group I (n = 7), control subjects receiving neither lung perfusion nor ultrafiltration; group II (n = 9), patients undergoing lung perfusion; and group III (n = 8), patients undergoing lung perfusion plus ultrafiltration. Lung perfusion consisted of single-shot hypothermic pulmonary artery perfusion with oxygenated blood. Proteins indicative of leukocyte activation and lung injury were measured in plasma and bronchoalveolar lavage fluid (BALF). The alveolar-arterial oxygen gradient (A-aDO2) and the oxygenation index (PO2/FiO2) were also determined. RESULTS: Oxygenation values were best preserved in group III, followed by group II. After CPB, elastase-alpha1-proteinase inhibitor complex had increased in plasma in all groups; in BALF it increased in groups I and II, but not in group III. Alpha2-macroglobulin increased significantly in BALF in group I but not in groups II and III. CONCLUSIONS: These preliminary results provide some evidence that single-shot hypothermic lung perfusion with oxygenated blood at the beginning of CPB may have a protective effect on the lungs, especially when combined with ultrafiltration.

Adult↗
PubMed2002

Development of muscular blood pumps performed in a one-step operation.

Up to now, the employment of skeletal muscle ventricles (SMVs) has required a two-step operation, that is, first, the construction followed by a vascular delay and electrical conditioning, and second, the integration into circulation by a second operation. As shown previously, clenbuterol increased the power of electrically conditioned SMVs wrapped around a mock system. These clenbuterol-supported SMVs pumped successfully from construction to several months against a pressure of 60-70 mm Hg. Due to these successful former experiments, a muscular blood pump has been employed via a one-step procedure, trained within the circulation under the support of clenbuterol. It appeared to be hemodynamically relevant and is expected to become clinically practicable for the treatment of end-stage heart failure.

Animals↗
PubMed2002

In vitro hydrodynamics of the Embol-X cannula.

BACKGROUND: Prevention of intraoperative plaque dislodgement in patients with atherosclerotic ascending aorta by development of innovative aortic cannula designs gains growing interest in cardiac surgery. To increase knowledge about the hydrodynamics of the innovative Embol-X cannula, which includes an intra-aortic filter device targeting at atheromatous emboli capture, was the aim of the present study. METHODS: Pressure gradients and back pressures of the Embol-X cannula were measured at varying flow rates in a mock circulation and compared with two commonly used single-stream cannulae. RESULTS: At a flow rate of 5.5 l/min, pressure gradients across the Argyle and the RMI cannulae were 48% and 62% and back pressures 25% and 47% lower than the corresponding values across the Embol-X cannula. CONCLUSIONS: The novel concept of integrating a filter device may provide clinical advantages concerning neurologic outcome. Further in vivo studies seem to be desirable to obtain more information concerning the clinical effects of the Embol-X cannula hydrodynamics.

Cardiac Surgical Procedures↗
PubMed2002

Hydrodynamics of the new Medos aortic cannula.

BACKGROUND: Postoperative neurologic complications in cardiac surgery patients are considered to be associated with the design of an aortic cannula and its hydrodynamic profile. To gain knowledge about the hydrodynamics of a new cannula type, based on the integration of a helical stator in its tip, was the aim of the present study. METHODS: Pressure gradients and back pressures of the new Medos aortic cannula were measured and compared with a commonly used single-stream cannula at varying flow rates in a mock circulation. Additionally, flow visualization was performed by ink injection. RESULTS: Pressure gradients across the Medos cannula were 25.5-31.8% lower at all flow rates measured when compared to the reference cannula. Back pressures of the Medos cannula were 64.1-67.9% lower than reference back pressures. CONCLUSIONS: The Medos cannula provides improved hydrodynamic characteristics, probably reducing the risk of atherosclerotic embolism and cerebral malperfusion by avoidance of high back pressures and sandblasting effect.

Aorta↗
PubMed2002

Valve-sparing aortic root remodeling for pulmonary autograft aneurysm.

The case is reported of a 42-year-old patient who underwent a Ross procedure for aortic valve insufficiency due to endocarditis in 1991, using the free-standing root technique. Autograft valve function was stable for up to 10 years postoperatively, though dilation of the autograft root occurred. With an increasing size of the root diameter (50 mm), however, progressive aortic regurgitation developed which necessitated reoperation. A valve-sparing autograft root remodeling procedure, according to Yacoub, was performed with excellent resultant valve function.

Adult↗