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Biomedical subjects

R Siebenmann

Publications and source records attributed to R Siebenmann.

At least 19 recordsLinked to original sources
PubMed1995

[Acquired heart diseases and pregnancy].

Understanding of the mechanisms of cardiovascular and hemodynamic adaptation during pregnancy helps to prevent or manage complications in cardiac patients during gestation. Manifestations of coronary heart disease are exceptional during pregnancy and delivery. The same is true of disorders of the pericardium. Peripartal cardiomyopathy is a myocardial disorder of undetermined cause occurring shortly before, during or after delivery, which may take a fatal course. Hypertrophic obstructive or non-obstructive cardiomyopathy is compatible with gestation and delivery without serious complications in most cases. Rheumatic mitral stenosis was the most common cardiac disorder until the 1950s. Nowadays it is rarely seen in this country. Surgical and other interventional therapies have greatly changed the outlook in pregnant women with valvular heart disease. A highly controversial issue is heart valve replacement in young women and management of anticoagulation during pregnancy. Like any other drug therapy, anticoagulation during gestation requires careful weighing of the benefit for the mother against toxic and teratogenic effects for the fetus. In women with heart disease the management of pregnancy should start, if possible, before conception. Thorough counseling and proper planning of pregnancy and of therapeutic measures is essential in order to avoid or manage complications.

Abnormalities, Drug-Induced↗
PubMed1994

Both ETA and ETB receptors mediate contraction to endothelin-1 in human blood vessels.

BACKGROUND: Endothelin (ET)-1 has potent vascular effects. Two endothelin receptors have been cloned, namely, the ETA receptor, which preferentially binds ET-1, and the ETB receptor, which equally binds ET-1 and ET-3 and preferentially sarafotoxin S6c. We characterized endothelin receptor subtypes on vascular smooth muscle and endothelium of isolated human internal mammary artery (IMA) and vein (IMV) and porcine coronary artery (PCA) using the ETA antagonists FR139317 and BQ-123, the ETB ligand sarafotoxin S6c, and the ETA/ETB antagonist Ro 47-0203 (bosentan). METHODS AND RESULTS: In endothelium-denuded IMA and PCA and less so in IMV, FR139317 and BQ-123 (in PCA only) shifted the concentration-contraction curves to ET-1 parallel to the right. However, even at 10(-5) mol/L, FR139317 did not inhibit a high-sensitivity portion of the concentration-contraction curve. Moreover, the ETB receptor agonist sarafotoxin S6c induced contraction in vessels preincubated with FR139317. IMV was significantly more sensitive to the contractile effect of ET-1 and sarafotoxin S6c than was IMA (P < .05). Prolonged incubation with sarafotoxin S6c (to downregulate ETB receptors) and FR139317 eliminated the contraction resistant to FR139317. The ETA/ETB receptor antagonist bosentan caused a parallel shift of the concentration-contraction curve to the right at all concentrations of endothelin. ETB receptor mRNA was detected by Northern blot analysis in IMA and aortic smooth muscle cells. In precontracted IMA and PCA with endothelium, sarafotoxin S6c did not cause endothelium-dependent relaxations, whereas transient responses occurred in IMV. CONCLUSIONS: Vascular smooth muscle cells of human IMA, IMV, and PCA contain both ETA and ETB receptors, whereas the endothelium of IMA and PCA does not express functional ETB receptors linked to nitric oxide and/or prostacyclin production. Hence, inhibition of endothelin-induced contraction in patients requires the use of combined ETA/ETB antagonists.

Animals↗
PubMed1993

Different effects of angiotensin-converting enzyme inhibition in human arteries and veins.

The renin-angiotensin system (RAS) participates in the regulation of vascular tone; its effects were studied in human internal mammary artery (IMA) and saphenous vein (SV) suspended in organ chambers for isometric tension recording. The angiotensin-converting enzyme (ACE) inhibitor enalaprilat (10(-7) M) markedly augmented endothelium-dependent relaxations to bradykinin in SV (concentration shift: 10-fold; n = 6; p < 0.005), but not in IMA; in both blood vessels, it had no effect on endothelium-dependent relaxations to acetylcholine. The contractions to angiotensin I (Ang I; 10(-7) M) were markedly inhibited by enalaprilat (10(-7) M) in SV (control: 34 +/- 6% of 100 mM KCl; treatment: 18 +/- 6%; n = 7; p < 0.05) but not in IMA (control: 33 +/- 4%; treatment: 30 +/- 6%; n = 7; NS) and abolished by the Ang II receptor antagonist DuP 753 (10(-7) M) in both blood vessels. Ang II (10(-7) M) induced more pronounced contractions than Ang I in IMA (63 +/- 4%) and SV (63 +/- 5%; n = 5-6; p < 0.05 vs. Ang I), which was markedly inhibited by DuP 753 (10(-7) M; IMA: 21 +/- 5%; SV: 32 +/- 5%; p < 0.05). Thus, in SV but not IMA, ACE inactivates bradykinin and thereby blunts endothelium-dependent relaxations to the peptide and converts Ang I to Ang II.

Acetylcholine↗
PubMed1992

Similar endothelium-dependent relaxation, but enhanced contractility, of the right gastroepiploic artery as compared with the internal mammary artery.

The right gastroepiploic artery is an alternative coronary bypass graft. The excellent graft function of the internal mammary artery has been related to its physiologic properties, particularly to endothelial function. Isolated artery rings were suspended in organ chambers for recording of isometric tension. Norepinephrine and potassium chloride evoked threefold greater contractions in the gastroepiploic artery than in the mammary artery (p less than 0.01 to 0.05), whereas the sensitivity to the catecholamine was comparable. Acetylcholine induced endothelium-dependent relaxations, but the sensitivity (pD2: 6.7 +/- 0.3) and maximal relaxation (81% +/- 9%) were slightly less in the gastroepiploic artery than in the mammary artery (pD2: 7.6 +/- 0.2; 100% +/- 0%; p less than 0.05). Histamine induced endothelium-dependent relaxations with a similar sensitivity (pD2: 7.5 +/- 0.3 and 7.2 +/- 0.1), whereas the maximal relaxation was slightly enhanced in the gastroepiploic artery. The relaxation to the nitric oxide donor SIN-1 was identical in the two arteries. Thus the right gastroepiploic artery exhibits better contractility than the internal mammary artery but comparable endothelium-dependent and endothelium-independent relaxations. The good endothelial function of the gastroepiploic artery might be important for graft function and patency, whereas the enhanced contractility may facilitate vasospasm, especially in the presence of high circulating levels of catecholamines.

Acetylcholine↗
PubMed1991

[Developments in mitral valve surgery].

Between 1987 and 1990 we operated on 104 patients for mitral valve disease. If possible the valve was reconstructed according to CARPENTIER's technique: 8 of 28 stenotic, 43 of 57 regurgitant and 2 of 7 mixed lesions were repaired. Twelve patients underwent re-replacement of a previously inserted mitral prosthesis. Six patients died early (7.8% after replacement, 8% after isolated replacement, 3.7% after repair and 2% after isolated repair). Five of these six patients were in NYHA class IV preoperatively. Seven patients died late after a mean observation period of 18 months (5 after replacement, 1 after double valve replacement and 1 after repair and multiple coronary bypass surgery). Prognosis is best for patients whose valve can be repaired and who are not already in NYHA class IV. The postoperative NYHA class for surviving patients is excellent (1.3 in the replacement group and 1.2 after repair).

Adult↗
PubMed1991

[Use of the right gastroepiploic artery as a coronary bypass graft. Indications, technique and early results].

435 isolated coronary artery procedures have been performed between January and December 1989 at the HerzZentrum Hirslanden. In 93% of the cases, one or two internal mammary arteries (IMA) and in 7%, saphenous vein grafts only were used as a bypass conduit. In 12 patients, the right gastroepiploic artery (RGE) was used as a free (3) or pedicled (9) graft to the posterior surface of the heart. This group of 12 patients was analyzed in a retrospective study. Postoperative complications in this group included one myocardial infarction and reexploration for intraabdominal bleeding in the same patient. All patients were discharged from hospital after an average of 9.7 days. After a mean follow-up time of 5 months, all patients are in NYHA-functional class I without antiischemic drugs. Postoperative angiography in 7 patients (mean postoperative interval 4 months) showed all 13 IMA-grafts and 5 RGE-grafts patent, 1 RGE-conduit is occluded, 1 RGE-graft could not been assessed for technical reasons. The RGE is an viable additional arterial bypass conduit and an alternative to other grafts. Indications for use of the RGE are lack of sufficient other conduits, calcified ascending aorta, coronary reoperation after vein graft failure and probably young patients with severe hyperlipidemia.

Arteries↗
PubMed1991

[Emergency surgery for PTCA complications: tactics and results].

Incidence, risk and results of emergency coronary bypass surgery after failed percutaneous transluminal coronary angioplasty (PTCA) have been analyzed in a retrospective study. Failed PTCA has been defined as visible pathology (dissection, occlusion) of the dilated vessel associated with acute chest pain and ECG changes. From 3-1-1987 to 11-30-1990, 23 patients of 433 (5%) underwent emergency surgery for failed PTCA (19 male, 4 female, mean age 55 +/- 8 years). PTCA was performed in 16 cases of one-vessel-disease, 3 cases of two-vessel-disease and 4 cases of three-vessel-disease. All had an ejection fraction beyond 40%. 19 patients remained in stable hemodynamic condition. In average 2.1 vessels have been bypassed; in 13 cases the internal mammary artery (IMA) has been used, in 10 cases the saphenous vein (VSM) only. No early nor late death occurred. The perioperative infarction rate is 30%. Comparing the group with IMA and the group with VSM only, no difference could be found regarding the number of unstable hemodynamics, the use of catecholamines nor the perioperative infarction rate. After a mean follow-up period of 14.3 months, 21 patients are in NYHA class I, 2 in NYHA class II. Emergency coronary bypass surgery can be performed with low risk and favorable results, if the operation is timed without delay after the onset of acute chest pain and ECG changes in failed PTCA. The infarction rate is remarkably higher than in elective coronary surgery. The use of the IMA seems to be no additional risk factor.

Angioplasty, Balloon, Coronary↗
PubMed1990

Interaction between endothelin-1 and endothelium-derived relaxing factor in human arteries and veins.

Endothelin-1 is a 21-amino acid endothelial vasoconstrictor peptide that may be the physiological antagonist of endothelium-derived relaxing factor (EDRF). Endothelin-1 (10(-11)-3 x 10(-7) M) evoked potent contractions of isolated internal mammary arteries, internal mammary veins, and saphenous veins, which were enhanced in internal mammary veins as compared with internal mammary arteries (concentration shift, 6.3-fold; p less than 0.05) but not in the saphenous veins. Endothelial removal augmented the response to the peptide (at 3 x 10(-7) M) in internal mammary arteries (p less than 0.05) but not in veins. In the artery, EDRF released by acetylcholine or bradykinin reversed endothelin-1-induced contractions; in saphenous veins, both agonists were much less effective compared with the artery and veins contracted with norepinephrine (p less than 0.005-0.01). This inhibition of endothelium-dependent relaxations in veins occurred at half-maximal contractions but was most prominent at maximal contractions to the peptide. Nitric oxide similarly inhibited contractions to endothelin-1 and norepinephrine in internal mammary arteries, whereas in veins that were contracted with endothelin-1 but not with norepinephrine, the relaxations were blunted (p less than 0.005). The nitric oxide donor SIN-1 and sodium nitroprusside induced complete relaxations of internal mammary arteries but were less effective in veins contracted with endothelin-1 (p less than 0.005). Thus, in normal human arteries, EDRF inhibits endothelin-1-induced contractions, whereas the peptide specifically attenuates the effects of EDRF and nitrovasodilators in veins. This may be important in pathological conditions associated with increased levels of endothelin-1 and in veins used as coronary bypass grafts.

Acetylcholine↗
PubMed1989

[Results of the initial 50 heart transplantations in Zurich].

During the first 40 months of the new Heart Transplantation Program (September 1985 until December 1988) a total of a 160 patients were evaluated for transplantation at the University Hospital in Zurich. 50 patients eventually came to heart transplantation, while one patient underwent a heart-lung transplant. In the same period 9 patients accepted for transplantation died on the waiting list before transplantation. All 50 hearts were transplanted orthotopically. Follow-up treatment, immunosuppression and diagnostics for rejection are described. There was no operative mortality in this group. Two patients died early and three died late. For the first consecutive 50 heart transplant patients, showing a total of 732 patient months, actuarial survival was calculated at 90.1% at one and two years, and at 79.5% at three years. "Enlarged Heart Transplantation Program" describes some of the secondary activities spurred by the new Heart Transplantation Program.

Actuarial Analysis↗
PubMed1989

Late failure of systemic ventricle after atrial correction for transposition of great arteries.

The incidence of late systemic ventricular failure (SVF) was determined in 220 early survivors of atrial correction for transposition of great arteries (TGA), operated upon between 1964 and 1985. SVF was defined as either severe heart failure (NYHA class III or IV) or death due to the same cause, in the absence of other haemodynamic disturbances. The actuarial survival rate was 96% after 1, 94% after 5 and 87% after 10 years. SVF occurred in 16/220 patients (7.2%). SVF was more common in complex TGA (TGA + VSD or PS or both) with 11/99 patients (11%) than in simple TGA with 5/121 patients (4.1%), P less than 0.01. Actuarial freedom from SVF was 97% at 5, and 92.5% at 10 years. SVF caused 10/25 (40%) late deaths. SVF occurred from the 1st postoperative year up to 20 years after correction (average interval 6.3 years). In 1 of 2 patients a systemic atrioventricular (AV) valve annuloplasty did not improve SVF. Heart transplantation was performed in 2 patients and 1 is on the waiting list. SVF is a rare late complication of atrial correction for TGA with a constant incidence in the late course. SVF is more common in complex TGA.

Actuarial Analysis↗
PubMed1989

Postinfarction ventricular septal defect--surgical strategies and results.

Twenty consecutive patients with postinfarction ventricular septal defect (VSD) were subjected to surgery: there were 8 females and 12 males with a mean age of 67 +/- 9 years. Nine acute patients developed cardiogenic shock, and intra-aortic balloon pump was started before surgery (with IABP). Eight acute patients showed preoperatively relatively stable hemodynamics, and surgery was feasible without previous use of the intra-aortic balloon pump (without IABP). The interval between myocardial infarction and surgery was 13 days for 17 acute cases. In the group with IABP the interval was 8 +/- 5 days versus 19 +/- 11 days in the group without IABP (p less than 0.025). VSD patch closure was performed in 20/20, resection of infarct in 10/20, transventricular approach without resection of infarct in 3/20, patch enlargement of the left ventricle in 2/20, plicature of an aneurysm in 3/20, aorto-coronary bypass in 10/20 (number of bypasses: 2.1 +/- 1.3) and mitral annuloplasty in 1/20. The perioperative 30 days mortality was 5/20 (25%) for the whole series. In the group with IABP mortality was 4/9 (44%) versus 1/8 (13%) in the group of acute patients without IABP (p less than 0.05). Mean follow-up for the 15 surviving patients was 1.7 +/- 1.0 years. Two patients died during the first year, one of them due to carcinoma. After 1 year, mean NYHA functional class was assessed 1.5 +/- 0.6. One patient showed a residual VSD which was closed surgically. Immediate closure of a postinfarction ventricular septal defect is the therapy of choice of this complication of acute myocardial infarct with a natural history showing an extremely high mortality.

Aged↗
PubMed1989

Internal-mammary coronary artery grafts: is their superiority also due to a basically intact endothelium?

The internal mammary artery (IMA) is a superior conduit for coronary artery revascularization and many factors have been suggested for explanation of this superiority. IMA and saphenous vein grafts have been systematically analysed with scanning electron microscopy (SEM) in a series of 11 patients undergoing coronary artery revascularization. At the time of implantation endothelial damage is almost absent in internal-mammary-artery (IMA) grafts; small areas of exposed subendothelial matrix may be present but are essentially non-thrombogenic as reflected by the lack of clots in these areas. In contrast the endothelium of harvested human saphenous veins (SV) shows large thrombogenic defects with exposed collagenous fibrils. The extent and deepness of the defects deteriorated in the period between removal of the vein and its attachment to the aorta. We conclude that long-term superiority of IMA grafts may also be due to the lack of primary intimal defects.

Adult↗
PubMed1989

Endothelium-derived relaxing factor and protection against contractions induced by histamine and serotonin in the human internal mammary artery and in the saphenous vein.

We investigated the release of endothelium-derived relaxing factor (EDRF) in response to serotonin and histamine in the human internal mammary artery and saphenous vein. The arteries and veins were obtained intraoperatively and were suspended in organ chambers to record isometric tension. In mammary arteries, histamine (10(-8) to 3 X 10(-6) M) induced relaxations in rings with (70 +/- 5%, IC50, 6.5 +/- 0.2) but not without endothelium (p less than 0.005 for rings with compared with those without endothelium, n = 7-10). The response was inhibited by methylene blue or hemoglobin, but not meclofenamate, and, therefore, EDRF was delineated as the mediator. Because chlorpheniramine but not cimetidine inhibited the response, EDRF was released by the H1-histaminergic receptor (n = 5-8). In contrast, in saphenous veins, histamine caused only weak or absent endothelium-dependent relaxations, but contractions were enhanced in rings with endothelium (p less than 0.05, n = 6). Serotonin did not induce endothelium-dependent relaxations, but contractions were markedly greater in veins compared with arteries (p less than 0.005, n = 6). The endothelium inhibited the maximal contraction to serotonin in arteries (p less than 0.034) but not in veins. Thus, EDRF protects against contractions induced by histamine and serotonin in the mammary artery but not in the saphenous vein. This may be important for improved graft function and patency of the artery compared with that of the vein.

Endothelium, Vascular↗
PubMed1989

Lethal air embolism during arthroscopy. A case report.

We report a case of lethal air embolism during diagnostic arthroscopy using air to distend an acutely injured knee. Air had escaped from the joint through an intra-articular fracture and entered the venous system. During arthroscopy, pressure within the joint may be 5 to 10 times higher than venous pressure, so any medium may escape. We advise that the use of air, especially in freshly injured joints, should be abandoned in favour of saline or carbon dioxide.

Adult↗
PubMed1989

Late functional deterioration after atrial correction for transposition of the great arteries.

Late anatomic and functional results were evaluated in 220 consecutive survivors who underwent surgery in 1964-1984 for atrial correction of transposition of the great arteries (TGA). Actuarial survival was 87% at 10 years and 83% at 20 years and was higher in patients with simple than in those with complex TGA (92% vs. 84% at 10 years). Although 83% of simple TGA and 78% of complex TGA survivors belong to the oligosymptomatic or asymptomatic group, failure of the systemic ventricle occurred in 17 (7.7%) patients. This failure was more common in patients with complex than in those with simple TGA (12.1% vs. 4.1%, p less than 0.05); actuarial incidence of such failure was 3% at 5 years and 11% at 15 years, and it caused 10 of 25 (40%) of late deaths. Late dysrhythmias necessitating pacemaker implantation had an incidence of 9.8% at 10 years. Reoperations were performed in 20 (9.1%) patients, with 12 of 23 (52%) reoperations occurring in the first 2 years after correction. Stenosis of caval inflow (eight patients), or residual atrial or ventricular septal defects (eight patients) were the most common causes of reoperation. Systemic atrioventricular valve incompetence necessitating surgery occurred in only three patients. Atrial correction gives good late results, but late functional deterioration occurs in some patients.

Child↗
PubMed1989

[Clozapine-induced cholestatic jaundice: a case report].

We report on a patient who became jaundiced during treatment with clozapine (Leponex). Histologically, cholestatic hepatitis with single-cell necroses of hepatocytes and infiltration of the portal zones with eosinophilic granulocytes were found. The patient recovered after discontinuation of clozapine, and liver function tests returned to normal within 4 weeks. This adverse effect of clozapine suggests that this "atypical" tricyclic neuroleptic resembles the phenothiazines both with regard to therapeutic spectrum and side effects.

Aged↗
PubMed1989

[Surgery of traumatic aortic rupture].

This report describes the clinical presentation, diagnosis, surgery and results of patients with acute traumatic rupture of the aorta in a series of 21 consecutive patients. Direct cross-clamping without additional methods of spinal cord protection was used in 18/21 patients (86%). Direct suture was possible in 12/21 patients (60%). In the remaining patients, the repair was carried out by interposition of a Dacron graft. Overall mortality was 7/21 patients (33%). However, in 3 patients with severe polytrauma irreversible brain damage was the cause of death whereas 2 patients died from septicemia and myocardial infarction, respectively. No paraplegia nor paraparesis occurred in the surviving patients which were operated by direct cross-clamping of the aorta and rapid reanastomosis without additional methods of spinal cord protection.

Adolescent↗