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H H Sievers

Publications and source records attributed to H H Sievers.

At least 37 records · Page 2Linked to original sources
PubMed2001

Influence of 5-hydroxytryptamine on aortic valve competence in vitro.

BACKGROUND AND AIM OF THE STUDY: The contraction of cusp tissue has been implicated to play a role in aortic valve function. The effect of the contractile agent 5-hydroxytryptamine (5-HT) on the competence of isolated aortic roots has been assessed, and the vasomotor properties of 5-HT on aortic root tissue examined. METHODS: Isolated porcine aortic roots were pressurized with Kreb's solution through the aortic arch. 5-HT was added in increasing concentrations (10(-7) to 10(-5) M) and the degree of leakage measured over time. In additional experiments, portions of sinotubular junction, sinus, annular and cusp tissue were set up in organ baths, placed under tension, and challenged with 5-HT (10(-9) to 10(-5) M). Viability of each valve structure was assessed by addition of KCl (90 mM). RESULTS: The rate of leakage from intact aortic roots increased when 10(-6) and 10(-5) M 5-HT was added. The maximum effect, observed at 10(-5) M 5-HT, was equal to an increase of 61.8+/-23.0% above control (p <0.05). The perfusion pressure at each concentration of 5-HT was unchanged. This response was inhibited by the 5-HT2A receptor antagonist ketanserin. Addition of KCl to isolated valve structures gave a mean contractile response of 0.8+/-0.1mN for cusp, 19+/-11.0 mN for annular, 29+/-8.0 mN for sinus, and 23+/-8.0 mN for sinotubular junction tissue (each n = 4). Only cusp tissue contracted when treated with 5-HT, with a maximum 105.5+/-17.2% (n = 4) of the response to KCl. The response to 5-HT was blocked by the 5-HT2A-receptor antagonist ketanserin at 10(-6) M (n = 4). None of the other aortic root structures responded to 5-HT. CONCLUSION: These results show that 5-HT influences the competence of isolated porcine aortic valves. This effect is contributed by contraction of the cusp tissue, and is mediated by 5-HT2A receptors. These effects may contribute to the association between valve dysfunction, 5-HT and certain appetite suppressants.

Animals↗
PubMed2000

Clenbuterol-supported dynamic training of skeletal muscle ventricles against systemic load: a key for powerful circulatory assist?

BACKGROUND: The profound loss of power that occurs in skeletal muscle after electrical conditioning has been the major limiting factor in its clinical application. This study investigates a 3-fold approach for chronic conditioning of skeletal muscle ventricles (SMVs) combining electrical transformation, dynamic training against systemic load, and pharmacological support with clenbuterol. METHODS AND RESULTS: In 10 adult male goats, SMVs were constructed from latissimus dorsi muscle wrapped around an intrathoracic training device with windkessel characteristics. SMVs were stimulated electrically and trained dynamically by shifting volume against systemic load. Group 1 goats were controls (n=5), and group 2 goats (n=5) were supported with clenbuterol (150 microg 3 times a week). SMV dynamics were recorded weekly over 5 to 8 months: peak pressure (P(max)), stroke volume (SV), volume displacement per minute (VD), stroke work per day (SW/d), and maximum rates of pressure generation, +dP/dt(max), and decay, -dP/dt(max). In group 1, after 149.5+/-2.7 days (n=4), data were P(max)=70.8+/-4.7 mm Hg, SV=3.2+/-1.2 mL, VD=62.3+/-21.1 mL/min, SW/d=0.8+/-0.4 kJ, +dP/dt(max)=64+/-13 mm Hg/s, and -dP/dt(max)=156+/-32 mm Hg/s. These parameters were significantly improved (P<0.007) in the clenbuterol-treated group 2 after 151+/-2.7 days: P(max)=176.2+/-43.8 mm Hg, SV=23.3+/-6.1 mL, VD=568.2+/-186.1 mL/min, SW/d=9.1+/-2.2 kJ, +dP/dt(max)=1134+/-267 mm Hg/s, and -dP/dt(max)=1028+/-92 mm Hg/s. In 2 SMVs of group 2, VD increased to 1090 and 1235 mL/min after 202 and 246 days of training, respectively. At termination, myosin heavy chains were totally transformed into myosin heavy chain-1 in all SMVs. CONCLUSIONS: This clenbuterol-supported dynamic training provides powerful SMVs that may have important clinical implications for the treatment of end-stage heart failure by muscular blood pumps.

Animals↗
PubMed2000

Association of serology with the endovascular presence of Chlamydia pneumoniae and cytomegalovirus in coronary artery and vein graft disease.

BACKGROUND: Chemotherapeutic treatment for patients with symptomatic coronary artery disease to reduce cardiovascular events may be initiated in response to elevated antibody titers against Chlamydia pneumoniae or cytomegalovirus. How antibody titers are associated with the endovascular presence of these microorganisms is still unclear. METHODS AND RESULTS: Antibody titers against C pneumoniae (microimmunofluorescence) and cytomegalovirus (ELISA) in patients undergoing primary (coronary desobliterates, n=80) or repeated CABG (occluded vein grafts, n=45) were correlated with the endovascular presence of the 2 microorganisms. C pneumoniae was detected by means of a nested polymerase chain reaction (PCR) and by culturing. Both conventional PCR and quantitative PCR were applied for detection of cytomegalovirus. C pneumoniae (PCR/culture) was detected in 19/9% (15/80 and 7/80) of coronary desobliterates and in 18/11% (8/45 and 5/45) of occluded vein grafts. There was no statistical evidence that IgG values differed between patients with or without C pneumoniae detection who were undergoing primary CABG. In contrast, repeated-CABG patients with a positive PCR (P=0.0027) or C pneumoniae culture (P=0.0018) had distinctly elevated IgG titers compared with patients in whom C pneumoniae was not detected. Cytomegalovirus could not be detected in the examined specimens. CONCLUSIONS: Cytomegalovirus infection does not seem to be associated with advanced coronary artery lesions. C pneumoniae antibody titers are not associated with the endovascular presence of C pneumoniae in patients with coronary artery disease. The observed strong association between elevated IgG titers and the detection of C pneumoniae in occluded vein grafts warrants further investigation.

Aged↗
PubMed2000

[Intermediate term clinical results after endoaneurysmorrhaphy in left ventricular aneurysm].

Endoaneurysmorrhaphy (EAR) in postinfarct ventricular aneurysms leads to excellent short-term results. However, the temporal response of EAR is widely unknown. Thus, the indication for surgical treatment of patients with ventricular aneurysms is not well defined. EAR was performed in 157 patients (6/1993-6/1999) with symptomatic ventricular aneurysms (median NYHA III). Factors influencing cardiac mortality and morbidity during follow-up were determined by univariate and multivariate analysis. Perioperative mortality was low: 5%. Mortality during follow-up was 3.3% per year, resulting in a 5-year survival rate of 78%. NYHA classification ameliorated significantly from the preoperative status compared to the follow-up period (median NYHA II; p < 0.001). Multivariate analysis identified preexisting arterial occlusive disease and advanced age (> 70 years) as significant factors influencing medium-term mortality. Implantation of the left internal mammary artery was associated with a better survival rate. Endoaneurysmorrhaphy can be performed with low perioperative mortality, will result in a significant amelioration of the cardiac clinical status and offers low medium-term mortality. Our data indicate that EAR seems to be the procedure of choice for patients with symptomatic ventricular aneurysms.

Aged↗
PubMed2000

[Ross operation in aortic valve diseases].

UNLABELLED: Currently used standard mechanical and bioprosthetic heart valves all have limitations that produce less than optimal results. The pulmonary autograft offers a promising alternative with theoretical advantages that have to be proven for final judgement of this innovative surgical technique. METHODS AND RESULTS: A survey including the international registry with 2523 patients enrolled since 1987 is provided along with the author's 10 years experience of 157 patients. The age of the patients ranges between one and 79 years. The indication is expanding integrating concomitant procedures like repair or replacement of aneurysms of the aortic root and ascending aorta, mitral valve reconstruction, coronary bypass grafting, etc. The operative mortality ranges between 0.6 and 2.5%. No anticoagulation is necessary. The function of the autograft is excellent. Late incidence of significant aortic insufficiency (> 2+) remains less than 5%. Even at exercise there is no pressure gradient across the autograft. Autograft failure with autograft revision or replacement stands at 1-4%. Homograft function is also found to be excellent. Right ventricular outflow tract revision rate ranges between 1-1.3%. In a few patients (7%), maximal pressure gradients between 20 and 35 mmHg developed across the homograft without major impairment of right ventricular function. CONCLUSIONS: The multicenter data confirm the superior performance of the autograft not matched by any other biological or mechanical valve replacement. Scientific efforts are required to further improve long-term function especially of the neopulmonary valve.

Adolescent↗
PubMed2000

Hydrodynamics of aortic arch vessels during perfusion through the right subclavian artery.

BACKGROUND: Performing subclavian artery cannulation in patients with an atherosclerotic ascending aorta or acute aortic dissection is of growing interest. To increase knowledge about pressure and flow distribution in the arch vessels, we investigated the in vitro perfusion characteristics in right subclavian artery cannulation. METHODS: Pressures and flow rates in the arch vessels of an aortic arch model were measured during perfusion through the right subclavian artery with different geometries and varying flow rates. Flow visualization was performed by laser light. RESULTS: In normal subclavian artery geometries, pressure and flow showed a significant increase in only the right common carotid artery (8 mm Hg and 25.5 mL/min, respectively, at 5.5 L/min pump flow). In cases of 50% stenosis at the right subclavian artery origin, a reduction of pressure and flow (6 mm Hg and 22.5 mL/min, respectively, at 5.5 L/min pump flow) in the right carotid artery caused by a suction effect was observed. CONCLUSIONS: Right subclavian artery cannulation provides a valuable alternative for ascending aortic cannulation, enabling nearly balanced arch vessel perfusion. Stenosis at the right subclavian artery origin carries the potential risk of slightly reduced perfusion of the right common carotid artery with questionable clinical relevance.

Adult↗
PubMed2000

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.

Aortic Dissection↗
PubMed2000

Size and distensibility of the aortic root and aortic valve function after different techniques of the ross procedure.

OBJECTIVES: In the Ross procedure, 3 different techniques are used for aortic valve replacement with the pulmonary autograft: freestanding root, inclusion, and subcoronary implantation. The objective of this study was to evaluate echocardiographically the influence of the particular operative technique on dimension, distensibility, and valve function. METHODS: Between February 1990 and August 1998, the Ross procedure was performed in 111 patients (mean age, 48.6 +/- 14.1 years; range, 15.2-70.6 years), with 1 early and 1 late death, 1 autograft replacement, and 1 patient lost to follow-up. The remaining patients underwent the freestanding root (n = 9 patients), inclusion (n = 14 patients), and subcoronary techniques (n = 84 patients). Echocardiography was performed at a mean follow-up of 26 +/- 21.3 months after operation and was compared with the echocardiographic findings of the control subjects (n = 10 subjects). Root sizes were measured at the level of the anulus, sinus, and supra-aortic ridge; the distensibility was calculated as pressure strain elastic modulus and percent change of radius. RESULTS: Size and distensibility of the aortic root were normal, except for a larger diameter at the sinus level in the root technique in comparison to the subcoronary technique (P <.05; maximum diameter, 41.3 +/- 8.6 mm vs 32.6 +/- 4.0 mm). Aortic valve function was comparable among groups with low pressure gradients and most patients with no or trace aortic insufficiency. CONCLUSIONS: The freestanding root, inclusion, and subcoronary techniques in the Ross procedure provide comparable excellent hemodynamics, normal root size, and distensibility, except for the enlarged sinus diameter in the freestanding root. These results may have some impact on the operative procedure and follow-up investigations.

Adult↗
PubMed2000

Up to seven years of experience with the Ross procedure in patients >60 years of age.

OBJECTIVES: The objective of this study was to compare the outcome of patients >60 years of age with younger patients after the Ross procedure. BACKGROUND: Currently, the Ross procedure is performed predominantly in young patients. Main arguments against the Ross procedure in the elderly are the complexity of the operation and related risks. Experience with the Ross procedure in patients >60 years of age is scarce. METHODS: Between February 1990 and August 1998, the Ross procedure was performed in 27 patients (15 men and 12 women) >60 years of age (mean 64.2 +/- 3.1 years, range 60.5 to 70.6; group A) and in 84 patients (68 men, 12 women) <60 years of age (mean 43.8 +/- 12.4 years, range 15.2 to 59.4; group B). Echocardiography was applied at a mean follow-up of 28.4 +/- 21.0 and 25.2 +/- 21.4 months, respectively, to determine hemodynamic variables (ejection fraction, fractional shortening, stroke volume, cardiac output), cardiac dimensions and autograft and homograft valve function. RESULTS: There was one early and one late (esophageal bleeding) death in group B; the mortality rate was 0% in group A. One autograft was replaced because of a subvalvular aneurysm, and one patient was lost to follow-up (group B). There were no significant differences in cardiac dimensions, grade of insufficiencies across homografts and autografts and hemodynamic variables, except for a higher pressure gradient across the homograft in group B (maximal pressure gradient 11.3 +/- 5.6 vs. 7.7 +/- 4.6 mm Hg in group A). The median New York Heart Association functional class was I in both groups. CONCLUSIONS: Our seven years of experiences (mean follow-up 28 months) indicate that the Ross procedure may be performed in selected patients >60 years of age without increased risk for mortality or complications in experienced centers.

Adolescent↗
PubMed2000

An in vitro evaluation of a new cannula tip design compared with two clinically established cannula-tip designs regarding aortic arch vessel perfusion characteristics.

We investigated in vitro aortic arch vessel perfusion characteristics of single and multiple jet-stream cannulae and a new dispersion stream tip aortic cannula. Pressures and flows of all arch vessels were measured while directing cannulae jets at the different arch vessels using 6 l/min pump flow. The highest increase in pressure above the set systemic level of 80 mmHg and increase in flow above the set normal flow distribution in the arch vessels occurred in the jet-streamed arch vessels with the single stream cannula. The values were as follows: 29 mmHg and 118 ml/min for the innominate artery, 28 mmHg and 42 ml/min for the left common carotid artery, and 25 mmHg and 54 ml/min for the left subclavian artery. The dispersion stream cannula showed increases in pressure and flow, followed by the multiple stream cannula. Aortic cannula tips and the orientation of jets are potential sources of imbalances of arch vessel perfusion with possible clinical implications regarding perfusion of arch vessels during extracorporeal circulation.

Aorta↗
PubMed1999

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.

Adult↗
PubMed1999

Detection of Chlamydia pneumoniae but not cytomegalovirus in occluded saphenous vein coronary artery bypass grafts.

BACKGROUND: A causal relation between atherosclerosis and chronic infection with Chlamydia pneumoniae and/or cytomegalovirus (CMV) has been suggested. Whether the unresolved problem of venous coronary artery bypass graft occlusion is related to infection with C pneumoniae and/or CMV has not been addressed. METHODS AND RESULTS: Thirty-eight occluded coronary artery vein grafts and 20 native saphenous veins were examined. Detection of C pneumoniae DNA was performed by use of nested polymerase chain reaction (PCR). Homogenisates from the specimen were cultured for identification of viable C pneumoniae. Both conventional PCR and quantitative PCR for detection of CMV DNA were applied. Differential pathological changes (degree of inflammation, smooth muscle cell proliferation [MIB-1]) were determined and correlated to the detection of both microorganisms. C pneumoniae DNA could be detected in 25% of occluded vein grafts. Viable C pneumoniae was recovered from 16% of occluded vein grafts. Except for 1 native saphenous vein, all control vessels were negative for both C pneumoniae detection and culture. All pathological and control specimens were negative for CMV DNA detection. Pathological changes did not correlate with C pneumoniae detection. CONCLUSIONS: Occluded aorto-coronary venous grafts harbor C pneumoniae but not CMV. The detection of C pneumoniae in occluded vein grafts warrants further investigation.

Adult↗
PubMed1999

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.

Aged↗
PubMed1999

Addition of a small curvature reduces power losses across total cavopulmonary connections.

BACKGROUND: In the Fontan circulation the vis a tergo for lung perfusion is limited. The hypothesis of this in vitro study was that energy dissipation at the common cavopulmonary connection can be reduced by the addition of caval curvature. METHODS: Two Perspex models were analyzed, the commonly used crosslike cavopulmonary connection (model 1) and a modified curved configuration (model 2). Pressures and flows across the connections were measured simultaneously at various caval and pulmonary artery flow splits and resistances. Mixing of inferior and superior caval fluid was evaluated. RESULTS: Caval pressure oscillations occurred in model 1 only. Curvature reduced power losses in all settings significantly (alpha = 0.05), most successfully at adult caval flow ratios and at high flow rates. At equal pulmonary resistances pulmonary flow was balanced in both models. The inferior caval fluid is preferably directed to the right lung in model 2 predominantly for caval flow conditions in younger patients. CONCLUSIONS: Our data show that the modified curved cavopulmonary connection is hydrodynamically advantageous but might impair caval fluid mixing in younger children.

Age Factors↗
PubMed1999

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.

Aged↗
PubMed1999

An in-vitro evaluation of aortic arch vessel perfusion characteristics comparing single versus multiple stream aortic cannulae.

OBJECTIVE: During extracorporeal circulation design and orientation of aortic cannulae tips mainly determine flow pattern in the aortic arch and arch vessels which is the objective of this in vitro study, comparing single versus multiple stream cannulae. METHODS: In an aortic arch glass model, jet streams of 21-24 French aortic cannulae which were inserted in the ascending aorta were directed alternatively at the different arch vessels. Flows and pressures in the arch vessels were measured at pump flows of 3-6 l/min. RESULTS: With optimal orientation of the jet stream in the aortic arch, no preferential flow in the arch vessels was seen. In the single jet stream aortic cannulae group a significant parallel increase in flow and pressure in the jet streamed arch vessels compared to the non-jet streamed arch vessels occurred (P < 0.05). With the jet stream directed on vessel 2 (left carotid vessel) there was a significant pressure and flow difference comparing the two non-jet streamed vessels with each other (P < 0.03). In the single stream 24 French cannulae the highest vessel pressure of 168 mmHg and an increase in flow of 186 ml/min was measured in the jet streamed left carotid artery at 6 l/min pump flow. The multiple stream cannulae provoked the highest vessel pressure of 106 mmHg in the corresponding jet streamed vessel and an increase in flow of 20 ml/min. CONCLUSION: Tip design of aortic cannulae and the orientation of its jet stream are potential sources of remarkable imbalance of arch vessel perfusion especially with single jet stream cannulae. These effects are more pronounced with single jet stream cannulae. These results may have important clinical implications regarding perfusion of arch vessels during extracorporeal circulation.

Aorta, Thoracic↗
PubMed1999

Successful dilatation of the small aortic root for implantation of a larger valve prosthesis.

Optimal hemodynamic performance is of paramount importance when implanting a prosthesis in a patient with a small aortic annulus. In order to avoid prosthesis size/patient body surface area mismatch, current techniques advocate aortic annulus patch enlargement or the use of a supra-annular prosthesis to ensure the implantation of an appropriately sized aortic valve. We present the first description of mechanical dilatation of a small aortic annulus as a simple alternative method.

Aged↗