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Biomedical subjects

B Meier

Publications and source records attributed to B Meier.

At least 343 records · Page 19Linked to original sources
PubMed1991

Stenting of superior vena cava and inferior vena cava for symptomatic narrowing after repeated atrial surgery for D-transposition of the great vessels.

Double venous stenting of the superior vena cava and inferior vena cava was successfully performed after failed balloon angioplasty in a young woman who had venoatrial narrowing and kinking after repeated Mustard procedure for D-transposition of great vessels. Self-expanding metallic stents were used. Angiography showed that the first stent was fully patient after six months when a second stent was implanted. This operation was followed by sustained clinical improvement. The present report shows the feasibility and success of stenting of the great veins when postoperative narrowing or kinking is unresponsive to balloon angioplasty alone.

Adolescent↗
PubMed1991

Long-term results of coronary balloon angioplasty.

Long-term results after coronary balloon angioplasty are characterized by an eventful early period up to six months, with about a 30% recurrence rate per lesion, and by a stable situation thereafter. Myocardial infarction due to the dilated site is extremely rare during follow-up because the smooth, elastic, inner lining of a restenosis is much less prone to thrombosis than the initial plaque. A positive effect of coronary angioplasty on survival has not been documented, but there is clear functional improvement over the natural course of the untreated disorder. The improvement is comparable to that attained by bypass surgery if repeat angioplasty during the first months is considered as part of the procedure rather than as proof of failure.

Angioplasty, Balloon, Coronary↗
PubMed1991

Relative risk analysis of angiographic predictors of restenosis within the coronary Wallstent.

BACKGROUND: Late angiographic narrowing has been observed following coronary implantation of the Wallstent. To identify the angiographic variables that predict restenosis within the stented segment, a retrospective study of data from the European Wallstent core laboratory was performed. METHODS AND RESULTS: Follow-up angiograms (excluding patients with in-hospital occlusions) were analyzed for 214 lesions in 176 patients (78% restudy rate). The incidence of restenosis within the stented segment was 35% by lesion and 35% by patient for criterion 1 (greater than or equal to 0.72 mm loss in minimal luminal diameter) and 24% by lesion and 24% by patient for criterion 2 (diameter stenosis greater than or equal to 50% at follow-up). The association between 16 variables and restenosis was determined by a relative risk ratio assessment. Variables with significant risk ratios for restenosis with criterion 1 were use of multiple stents/lesion (relative risk, 1.56; 95% confidence interval [CI], 1.08-2.25) and oversized (unconstrained stent diameter exceeding reference diameter greater than 0.7 mm) stents (relative risk, 1.64; 95% CI, 1.10-2.45), and for criterion 2, oversizing by more than 0.70 mm (relative risk, 1.93; 95% CI, 1.13-3.31), bypass grafts (relative risk, 1.62; 95% CI, 0.98-2.66), use of multiple stents/lesion (relative risk, 1.61; 95% CI, 0.97-2.67) and residual diameter stenosis more than 20% post stenting (relative risk, 1.51; 95% CI, 0.91-2.50). CONCLUSIONS: It is concluded that several angiographic variables are significantly associated with late angiographic narrowing after stenting in the coronary arteries. We suggest that stent operators avoid excessive oversizing in the selection of stent diameter and the use of multiple stents per lesion to lessen the risk of late restenosis.

Blood Vessel Prosthesis↗
PubMed1991

Comparative studies on a superoxide dismutase exhibiting enzymatic activity with iron and manganese as active cofactor.

The SOD of Propionibacterium freudenreichii, ssp. shermanii belongs to a new group of SOD's capable of retaining activity with either Fe or Mn as active metal cofactor. Both enzymes exhibit identical secondary structure and immunological determinants. Hydrogen peroxide irreversibly inhibits both enzymes. The protein moiety of the Fe- and Mn-SOD could be digested with trypsin to a single active fragment.

Bacterial Proteins↗
PubMed1991

Evidence for superoxide dismutase and catalase in mollicutes and release of reactive oxygen species.

The presence of superoxide dismutase was demonstrated in 21 strains of mollicutes, including achuloplasmas, mycoplasmas and ureaplasmas. Additionally, catalase activities were demonstrated in nearly 50% of the cell lysates, whereas no peroxide activities were detectable. The production of O2- and H2O2 with glucose as substrate was demonstrated for 8 strains of 10 strains tested. Anaerobic mycoplasmas showed the highest amount of radical production, whereas superoxide dismutase and catalase activities were in the range of activities estimated for aerobic mollicutes. Some pathogenic strains additionally released compounds into the culture medium, which stimulated O2- production by PMNs.

Aerobiosis↗
PubMed1991

Is Plasmodium falciparum aldolase useful for rational drug design?

P. falciparum lacks a functional citric acid cycle. Unlike most tissues of the mammalian host, it is totally dependent on glycolysis for energy generation. A compound which selectively inhibits the parasite's ATP-generating machinery is therefore a potential antimalarial agent. Such a drug may interact in two ways: a) by inhibiting the activity of an enzyme or b) by disturbing the micro-organization of consecutive enzymes in a metabolic pathway. In mammalian tissues the glycolytic pathway involves the cytoskeleton as a matrix to keep phosphofructokinase, aldolase and glyceraldehyde-3-phosphate dehydrogenase in an optimal sterical position for rapid substrate conversion. For instance, these three enzymes bind to the band 3 protein in erythrocytes or to actin in muscle cells. P. falciparum aldolase binds with very high affinity to the band 3 protein of human erythrocyte ghosts. However, the true in vivo site of association is believed to be actin II of P. falciparum. This actin has a sequence element which is almost identical to that of the band 3 aldolase binding site. We therefore suppose that plasmodia exploit a similar matrix organization. If true, the association of these enzymes with the cytoskeleton is a target for novel antimalarials. In contrast to all vertebrate aldolases, P. falciparum and P. berghei aldolases have two neighbouring lysine residues near the carboxy-terminus. We show here that mutagenesis of these basic residues has an effect on the catalytic constants Vmax and KM and moreover, the ability to bind to band 3 is reduced.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1990

[Intermediate results of balloon valvuloplasty in children with congenital aortic valve stenosis].

Eleven children with aortic valve stenosis requiring treatment underwent percutaneous balloon valvuloplasty instead of surgery. Three were newborns or infants and 8 were aged 2-18 years. Aortic valve gradient was 45-160 mm Hg (mean 83 mm Hg) before valvuloplasty; after the procedure the gradients ranged from 7-43 mm Hg (mean 25). One newborn with critical stenosis and associated left ventricular fibroelastosis died 48 hours after valvuloplasty. All others showed marked clinical improvement after the procedure. Main complications included permanent loss of peripheral pulses in the catheterized leg (2 cases, age 2 months and 20 months) and aortic valve regurgitation. This was estimated as moderate (++) in 2 and moderately severe (3+) in one; it was minimal or absent in the others. All patients were followed up for 3 months to 4 years. There was one recurrence of aortic stenosis, 2 years after valvuloplasty, requiring surgery. Two infants also underwent late surgery after successful valvuloplasty, one for mitral valve replacement and one for severe subvalvular aortic stenosis. In the remaining seven children the good initial result was maintained. Aortic valve gradient was estimated with Doppler at regular intervals and did not increase significantly over the follow-up period. In conclusion, balloon valvuloplasty is an alternative to open heart surgery in aortic valve stenosis in the young; both procedures are palliative.

Adolescent↗
PubMed1990

[Coronary angiography, percutaneous transluminal coronary angioplasty and coronary surgery, valvular interventions and anti-arrhythmia agents and fibrinolysis for acute myocardial infarction in Switzerland].

Besides the description of the activities of the Working Group PTCA and Fibrinolysis of the Swiss Society of Cardiology, number and distribution of coronary angiograms and angioplasties (PTCA) and aortocoronary bypass operations performed in 13 Swiss centers during 1989 are presented and commented. It is of note that the number of PTCA procedures has increased further during the last year, whereas the number of bypass operations stayed fairly constant over the last three years. PTCA is done today almost as frequently as coronary artery bypass surgery in Switzerland. There are, however, marked differences between individual centers: the number of PTCA procedures in relation to coronary angiograms varies between 5% and over 40%. A large part of these interventions is performed at private hospitals. More than 85% of the PTCA procedures were single vessel procedures. Catheter interventions on heart valves and on the conductive system were done almost exclusively at University Hospitals. The 1989 survey of the treatment of acute myocardial infarction with fibrinolysis covers only hospitals with catheterization laboratories and is therefore not entirely representative for the total activity in Switzerland. Almost 20% (0-80%) of all patients admitted for acute myocardial infarction received fibrinolysis with important differences between individual centers.

Angiocardiography↗
PubMed1990

Long-term results of successful and failed angioplasty for chronic total coronary arterial occlusion.

The results over a mean period of 2 years of successful percutaneous transluminal coronary angioplasty (PTCA) in 100 consecutive patients with chronic total coronary occlusion were compared with those in 100 consecutive patients whose PTCA was unsuccessful. The groups were comparable in terms of gender, age and arteries attempted. A control angiography in the group with successful PTCA was performed in 62 patients and showed a restenosis in 28 (45%). Repeat PTCA was performed in 21 versus 1 patient with failed PTCA (p less than 0.0001). At follow-up, in the group with successful PTCA, there were 57 symptom-free patients versus 26 patients in the group with failed PTCA (p less than 0.0001). Coronary artery bypass surgery was performed in 7 versus 37 patients (p less than 0.0001), and there were 5 versus 3 deaths (difference not significant), respectively. In the group with successful PTCA, 27 of 82 patients (33%) had positive stress test results, compared with 49 of 85 patients (58%) in the group with unsuccessful PTCA (p less than 0.001). The double product (beats/min x mm Hg/100) in patients with successful PTCA improved from 247 +/- 57 before PTCA to 277 +/- 61 (p less than 0.001) at follow-up, whereas it did not significantly change in patients with failed PTCA. The work load (W) in patients with successful PTCA improved from 95 +/- 34 before PTCA to 124 +/- 40 at follow-up (p less than 0.001). In patients with failed PTCA, work load improved less significantly, from 98 +/- 37 before PTCA to 108 +/- 34 at follow-up (p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Angioplasty, Balloon, Coronary↗
PubMed1990

[Interventional catheterization in the treatment of congenital and acquired heart defects].

The treatment of heart defects by interventional catheterization started in 1982, when the first report on balloon dilatation of pulmonary valve stenosis was published. Similar techniques have since been extended to many other lesions. Presently, two types of catheter intervention have come into use. The first is dilatation of stenotic lesions by inflatable balloons: the main defects treated include pulmonary valve stenoses, aortic valve stenoses, coarctation of the aorta and peripheral pulmonary artery stenoses. Second, it is now possible to close defects and unwanted vessels, such as a persistent ductus arteriosus, with umbrella-like devices introduced through catheters. While balloon dilatation has clearly become the treatment of choice for pulmonary valve stenosis, other applications remain either controversial (e.g. balloon dilatation of coarctation) or experimental (e.g. closure of atrial or ventricular septal defects). Time will tell what is the exact role of interventional cardiology, keeping in mind that surgery provides excellent results with minimal morbidity and mortality in these lesions.

Cardiac Catheterization↗
PubMed1990

Evidence for superoxide dismutase and catalase in mollicutes and release of reactive oxygen species.

The presence of superoxide dismutase was demonstrated in 21 strains of mollicutes, including achuloplasmas, mycoplasmas, and ureaplasmas. No superoxide dismutase activities or only traces were detectable in fresh prepared cell lysates, whereas activities were evident after dialysis of the cell lysates. A further increase in superoxide dismutase activities was observed after the cell lysates were heated to 65 degrees C for 30 s. This might be due to the destruction of enzymatic reactions interfering with the activity tests. Additionally, catalase activities were demonstrated in nearly 50% of the cell lysates, whereas no peroxidase activities were detectable. The production of O2- and H2O2 with glucose as substrate was demonstrated for 8 of 10 strains tested. No correlation to the pathogenicities of the strains was indicated. Anaerobic mycoplasmas showed the highest amount of radical production, whereas superoxide dismutase and catalase activities were in the range of activities estimated for aerobic mollicutes.

Acholeplasma↗
PubMed1990

Nonselective preoperative digital subtraction angiography of internal mammary arteries.

In preparation for coronary bypass surgery, digital subtraction angiography (DSA) was used to assess the caliber of the left and right internal mammary arteries and to exclude stenoses of their feeding arteries. In 100 patients (86 males, mean age 56 +/- 9 years) DSA was performed with a Siemens Digitron 2 device. A frontal projection was used in 18 patients, and a 10-20 degree right anterior oblique projection was used in 82 patients. The flow was 10 to 25 ml/sec; 20 ml was injected in 45 patients, 30 ml in 41, 40 ml in 5, 50 ml in 8, and 60 ml in 1 patient. Judged on the proximal third, visualization of the left and the right internal mammary artery was good in 80 and 72, fair in 17 and 20, and bad in 3 and 8 arteries, respectively. The diameter (mm) was 2.7 +/- 0.4 (range 1.8-3.4) and 2.7 +/- 0.3 (range 2.0-3.5), and visible length (cm) was 8 +/- 5 (range 1-24) and 9 +/- 4 (range 2-22) for the two arteries, respectively. The 10-20 degree right anterior oblique view separated the left internal mammary artery better from the descending aorta than the frontal view. In more pronounced right anterior oblique views the ascending aorta interfered with the right internal mammary artery. The quality was not different with 20 ml or 30 ml injections. The feeding arteries could not be assessed in 4 patients. One left subclavian artery was found occluded at the orifice. Incidentally, 2 distal right subclavian stenoses and 2 carotid stenoses were detected.(ABSTRACT TRUNCATED AT 250 WORDS)

Angiography, Digital Subtraction↗
PubMed1990

Assessment of the "long sheath" technique for percutaneous aortic balloon valvuloplasty.

A 100 cm-long 16.5 F valvuloplasty catheter introducer was assessed as an adjunct for percutaneous transluminal aortic valvuloplasty (PTAV) via the femoral artery in 31 patients with severe aortic stenosis. Observed improvements in peak systolic gradient (81.6 +/- 29.9 mm Hg vs. 35.5 +/- 16.0 mm Hg, P less than 0.000001) and aortic valve area (0.6 +/- 0.4 cm2 vs. 1.0 +/- 0.6 cm2, P less than 0.00001) were similar to those achieved in a control group (C) of 17 patients in which no femoral sheath was used. However, a shorter procedure duration (211 +/- 81 min vs. 117 +/- 30 min, P less than 0.001) and a reduced rate of vascular complications at the femoral puncture site (41% vs. 6.5%) were observed in patients in whom the long sheath (LS) technique was used. The frequency of other PTAV-related complications was comparable (C = 35%, LS = 29%, P = n.s.). Other technical advantages of this device are: 1) prevention of looping and bending of the balloon catheter in tortuous vessels and easy positioning of the balloon across the aortic orifice provided by the LS trackability, 2) stabilisation of the balloon during inflation, 3) monitoring of supravalvular aortic pressure provided by the side-arm of the LS and reliable measurement of systolic gradient, and 4) the ability to perform aortograms without the need of another catheter in the ascending aorta. Thus, in our experience, the long sheath technique is a valuable adjunct for PTAV.

Aged↗