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Biomedical subjects

A Buchwald

Publications and source records attributed to A Buchwald.

At least 37 records · Page 2Linked to original sources
PubMed1991

Intravascular ultrasound imaging of human coronary arteries after percutaneous transluminal angioplasty: morphologic and quantitative assessment.

An intravascular ultrasound catheter system was used in patients to assess the effect of percutaneous transluminal coronary angioplasty. In 14 out of 16 patients, the intravascular ultrasound catheter could be successfully advanced to the site of a previous dilatation. Qualitative assessment of the cross-sectional images revealed intimal thickening and an increase of ultrasound reflectance and calcification at atherosclerotic coronary arteries. A disruption of the obstructing plaque and evidence for local dissections (11 of 14 cases) were observed after angioplasty. The quantitative comparison between angiography and the ultrasound measurement showed a close correlation for vessel sites distant to the dilatation (r = 0.91 for vessel diameter; r = 0.86 for luminal area; p less than 0.001). After angioplasty, the quantitative evaluation of the dilated area was possible in 11 cases. The correlation of angiographic and sonographic measurements of these segments was good for the assessment of the vessel diameter (r = 0.82, p less than 0.001), but poor for the determination of the luminal area (r = 0.48, p = 0.10). This difference reflected the complex morphology of the vessel lumen after angioplasty, which would be better assessed by the cross-sectional sonographic technique than by contrast angiography. The intravascular imaging of coronary arteries provides a new and unique method to obtain information on the plaque morphology and composition, and to assess the local effects of interventional procedures and their complications.

Aged↗
PubMed1991

Excimer laser angioplasty in coronary artery disease.

The results of coronary excimer laser angioplasty were evaluated in 70 patients. Forty-five patients had laser angioplasty of coronary stenoses. Twenty-five patients in a total of 35 attempts had wire-guided laser recanalization of chronic coronary occlusions, resulting in a success rate of 71%. Immediate results in both groups demonstrated the efficacy of this technique without serious side-effects. Stenoses were reduced from 90 +/- 5% to 48 +/- 18% diameter reduction (mean +/- standard deviation) by excimer laser angioplasty. Residual stenosis in recanalized vessels after laser angioplasty was 52 +/- 19%. In slightly more than half of the patients with a residual stenosis greater than 50% after excimer laser angioplasty, subsequent balloon angioplasty was performed for further stenosis reduction. While satisfactory immediate results were achieved by excimer laser angioplasty intermediate follow-up revealed a restenosis rate in the same range as with balloon angioplasty.

Aged↗
PubMed1990

Recanalization of chronic total coronary arterial occlusions by percutaneous excimer-laser and laser-assisted angioplasty.

A low primary success and high restenosis rate after recanalization of chronic total occlusions by conventional coronary angioplasty have encouraged the application of new interventional techniques like excimer-laser angioplasty. In 39 patients with a coronary occlusion for 1 to 12 months, recanalization was attempted by laser angioplasty through a multifiber-catheter coupled to a pulsed XeCl excimer laser. After successful passage of the occlusion by a standard guidewire in 27 patients (69%), the laser catheter was advanced over the central guidewire and crossed the occlusion in 25 patients (64%). In 2 patients with unsuccessful passage of the laser catheter, the subsequent attempt with a low profile balloon catheter also failed. In 19 of the 25 patients with successful laser recanalization, the residual stenosis exceeded 50% and was therefore followed by additional balloon angioplasty. The average residual stenosis after laser was 61 +/- 17% of the vessel diameter, and after balloon angioplasty 28 +/- 9% (n = 19), whereas after laser angioplasty alone it was 38 +/- 5% (n = 6). No complications associated with the laser application were observed. Angiographic control after 24 hours showed a reocclusion of 2 (8%) recanalized vessels. In this pilot study, laser angioplasty proved to be a safe and feasible method for the treatment of chronic total coronary occlusions. Because it was necessary to guide the catheter by a central wire, the primary success was limited by a successful passage of the wire of the occlusion. The rate of stand-alone laser angioplasty has to be increased by future improvements of the technique to enable a comparative evaluation of this method with conventional angioplasty.

Angioplasty, Laser↗
PubMed1990

[Intravascular ultrasonic diagnosis. In vivo findings before and after angioplasty in peripheral arterial occlusive disease].

In 15 patients (13 men, two women, mean age 63 [47-75] years) with peripheral arterial occlusive disease in stages IIB-IV (Fontaine) intravascular ultrasound findings were compared with the angiographic results before and after treatment. In 12 patients stenosis (n = 10) or occlusion (n = 2) of the iliac artery (n = 2) or the superficial femoral artery (n = 10) were treated by conventional balloon angioplasty; in three patients with occlusion of the superficial femoral artery excimer laser angioplasty was performed. There was good correlation between measurements of vessel diameter by the two techniques (r = 0.93, P less than 0.001). Ultrasound scanning provided additional informations regarding the thickness of the plaque, the density or firmness of the stenosis and the degree of calcification. The therapeutic outcome was quantified by measuring the gain in lumen diameter. The authors also assessed the morphological changes following angioplasty in the vicinity of the obstructing plaque. In the light of the ultrasound findings it was considered necessary to undertake further dilatation in four out of the 12 patients treated by balloon dilatation. The results indicate that intravascular ultrasound imaging is a valuable complement to angiography for monitoring of therapeutic results after vascular interventions.

Aged↗
PubMed1990

[Acute effects of the angiotensin converting enzyme inhibitor ramipril in patients with coronary heart disease].

We investigated the acute effect of the new long-acting ACE-inhibitor ramipril on angina-limited exercise tolerance and exercise-induced ST-depression in 18 normotensive patients with angiographically confirmed coronary artery disease in a double-blind, placebo-controlled study. Patients underwent a repeat exercise ECG 24 hours following either 5 mg ramipril p.o. or placebo. Plasma-ACE activity (nmol/min x ml) in the ramipril-group (n = 8) was significantly reduced 24 hours after 5 mg ramipril compared to placebo (n = 10): 14.0 +/- 2.0 vs 87.2 +/- 13.5, p less than 0.001. Exercise-induced ST-segment depression was not different before and after ramipril or placebo. Heart rate at rest and during angina-limited exercise was not different between the first exercise-ECG and that after ramipril or placebo, nor between the groups. Systolic arterial pressure (mmHg) was slightly, but insignificantly, lower after than before ramipril at rest (113.8 +/- 5 vs 125 +/- 6.8) and at maximal exercise, 1.5 watt/kg (150 +/- 9.4 vs 158.3 +/- 13.3). In the placebo group, blood pressure at rest and during exercise was not different before and after placebo: 126 +/- 4.7 vs 125.5 +/- 7.5 and 157.5 +/- 3.8 vs 158 +/- 3.6. Rate-pressure-product (mmHg/min x 1000) at rest prior to (8.42 +/- 0.83 and 8.95 +/- 0.51) and after ramipril or placebo (8.00 +/- 0.94 and 8.93 +/- 0.71) showed no significant difference. Similarly, rate-pressure-product at maximal exercise was equal among the groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1990

Malignant restenosis after primary successful excimer laser coronary angioplasty.

In a series of 20 coronary excimer laser angioplasties, two patients presented with a peculiar type of malignant restenosis 6 and 8 weeks after a successful laser angioplasty procedure. One patient had a successful recanalization of an occluded left anterior descending (LAD) coronary artery and the second patient had a successful angioplasty of a subtotal proximal stenosis of the left anterior descending coronary artery. After the procedure, no ischemia could be demonstrated by exercise ECG and thallium scintigraphy. Both patients were free of angina until the sudden development of nocturnal angina several hours before reangiography, which showed subtotal restenosis in both cases. One patient had a mammaria graft on the LAD and the second patient underwent a successful balloon angioplasty. This uncommon sudden and malignant development of restenosis seems to be related to the excimer laser angioplasty procedure and warrants some caution with the indiscriminative use of this new angioplasty procedure.

Aged↗
PubMed1990

Alterations of the mitochondrial respiratory chain in human dilated cardiomyopathy.

The defects underlying the impairment of systolic pump function in human dilated cardiomyopathy (DCM) are not known. We isolated mitochondrial particles from 10 hearts of transplant recipients with DCM and from nine normal hearts not used for transplantation. Yield was similar in both groups (2.77 vs 2.81 mg mitochondrial protein per gram heart). Cytochrome content (difference spectrophotometry) was found reduced in DCM mitochondria, e.g. cytochrome c was 0.295 +/- 0.06 in the DCM group and 0.371 +/- 0.04 mumol g-1 in the control group (P less than 0.05). Enzymatic activity of the cytochrome-containing complexes III (3.77 +/- 0.82 vs 4.95 +/- 1.15 mumol min-1.mg-1) and IV (2.63 +/- 0.96 vs 3.65 +/- 0.6 mumol min-1.mg-1) of the respiratory chain was reduced in the DCM group (P less than 0.05). Complex IV, the cytochrome c oxidase, in the DCM group showed impaired activity also in whole heart homogenates (0.173 +/- 0.04 vs 0.258 +/- 0.8 mumol min-1.mg-1). Subunit composition of the cytochrome c oxidase on sodium dodecyl sulphate-gel electrophoresis did not differ between DCM and normal hearts. Activity of complexes II and V of the respiratory chain, not containing cytochromes, was unchanged in DCM mitochondria compared with the control group. The present data show a decrease in cytochrome content and in cytochrome-dependent enzyme activity in human dilated cardiomyopathy. Further studies are necessary to clarify whether these findings are specific for dilated cardiomyopathy or whether they are epiphenomena of failing hearts.

Apyrase↗
PubMed1990

[Acute hemodynamic effects of the vasodilator beta blocker carvedilol in heart failure].

The beta-blocker carvedilol has been shown to induce vasodilation in patients with coronary artery disease. In a double-blind, randomized, placebo-controlled cross-over study, we looked for the acute vasodilating effect after i.v. administration in patients with heart failure. In 10 patients with coronary artery disease and six patients with dilated cardiomyopathy, all with an ejection fraction lower than 40%, the rate-pressure-product during supine ergometry and Swan-Ganz-catheterization rose to a significantly smaller extent after 5 mg carvedilol i.v. compared to placebo. This was mainly due to a lower heart rate at rest and during exercise, while blood pressure was not changed compared to placebo. Calculated total peripheral resistance during exercise after carvedilol was higher--significantly so in the CAD-group--than after placebo. These results show that in patients with heart failure, an acute vasodilating effect of i.v. carvedilol is not detectable.

Adrenergic beta-Antagonists↗
PubMed1990

[Short- and long-term results following implantation of the new Wiktor stent in acute coronary occlusion following PTCA].

Ten patients, two women and eight men, were treated with the new balloon-expandable Wiktor Stent for acute coronary occlusion after PTCA. Two patients presented with an acute myocardial infarction. Stents with a diameter of 3.0 or 3.5 mm were implanted into the right coronary artery (n = 7), the left anterior descending (n = 2) artery, and the left circumflex coronary artery (n = 1). Stent implantation in the target segment was successful in all cases. Afterwards, patients received coumadine for 3 months and 100 mg acetylsalicyclic acid per day. We observed one acute occlusion after 8 h. Late occlusion occurred in two patients after cessation of anticoagulation within 3 weeks. Control angiography after 6 months in seven patients revealed stenosis within the stent in two cases.

Aged↗
PubMed1989

[Excimer laser angioplasty in arterial obstructive disease. Clinical experience with guidewire-controlled catheter systems].

Percutaneous transluminal laser angioplasties (PTLA) were performed in nine patients (7 males, 2 females, aged 52-81 years) with peripheral vascular disease, stages IIB-IV (Fontaine's classification), with 75% stenosis (5 patients) or occlusion (4 patients) in the area of the superficial femoral artery. Two catheter systems were used. One was a monofiber catheter (600 microns) with eccentric guidewire, the other a multifiber catheter with 12 concentrically arranged fibres (200 microns each) and a central guidewire. An XeCl-excimer laser (308 nm), with a pulse duration of 50 ns and pulse frequency of 15-30 Hz, served as the laser source. It was possible in all patients to reduce the stenosis of 75-100% to 35-70% or reopen the occlusion without laser-associated complications. To remove the residual stenosis PTLA was followed by balloon dilatation in seven patients and by application of a Simpson atherectomy catheter in one patient: these measures reduced the degree of stenosis to 20-40%.

Aged↗
PubMed1989

A three-cycle in vivo evaluation of reconditioned direct-bonding brackets.

To evaluate the potential for reducing costs without impairing the quality of orthodontic treatment, the practicality of the reuse of direct bonding brackets has been evaluated for three 1 1/2-year cycles. Although the percentage of appliances damaged during removal and those of enlarged slots slightly increases with each reuse, the average arch wire adjustments needed to accommodate the variety of cases and the percentages of bond failures remain almost the same. The reuse of "dissolution"-reprocessed appliances thus becomes an effective way by which the clinician can keep overhead costs lower while the cost of new appliances are steadily climbing.

Adolescent↗
PubMed1989

Cyanide toxicity.

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Cyanides↗
PubMed1989

Effect of intracoronary superoxide dismutase on regional function in stunned myocardium.

This study investigates the ischemic-time dependency of dysfunction in reversibly ischemic myocardium and the effect of postischemic oxygen free radical scavenging thereupon. In open chest pigs, occlusion of the distal left anterior descending coronary artery (LAD) for 4 (n = 5), 8 (n = 5), or 12 min (n = 5) resulted in paradoxical systolic and diastolic regional function, measured by ultrasonic crystals. With onset of reperfusion, systolic shortening (SS) and diastolic lengthening (DL) normalized completely in the 4- and 8-min groups, followed by a significant decrease to 50% control in the 8-min group. In the 12-min group, recovery of SS and DL was only partial. In two further groups, animals received an intracoronary infusion of either recombinant human superoxide dismutase (SOD, n = 6) or placebo (n = 6), starting with reperfusion after an 8-min LAD occlusion. SOD improved recovery of SS compared with placebo (p less than 0.05), but DL and the depression of SS during later reperfusion were not influenced. Mitochondrial function after 90 min of reperfusion was not impaired in ischemic-reperfused compared to control myocardium. We conclude that the degree of postischemic dysfunction increases with the duration of ischemia. Oxygen free radical scavenging by SOD, starting not before reperfusion, fails to prevent myocardial stunning. Mitochondrial function is intact in such myocardium.

Adenosine Diphosphate↗
PubMed1989

Effect of alpha-tocopherol (vitamin E) in a porcine model of stunned myocardium.

Oxygen free radicals have been suggested to cause the myocardial damage resulting in the prolonged contractile depression following brief periods of regional ischemia. In pigs, we infused the natural antioxidant alpha-tocopherol as its water-soluble acetate [0.3 g/kg intravenously (i.v.), n = 6] three times during 1 week, prior to thoracotomy, 8-min distal left anterior coronary artery (LAD) occlusion and 90-min reperfusion. Plasma levels of alpha-tocopherol [high-performance liquid chromatography (HPLC)] on the experimental day were 148.91 +/- 21.47 micrograms/ml as compared to preinfusion control of 0.51 +/- 0.14 micrograms/ml. Myocardial levels of alpha-tocopherol were elevated to 93.15 +/- 14.78 micrograms/g as compared to 4.08 +/- 0.60 microgram/g in the control group (n = 6). Malondialdehyde levels in ischemic-reperfused myocardium of the treatment group were insignificantly lower (441.96 +/- 59.55 nmol/g) as compared to the control group (500.9 +/- 72.72 nmol/g). Heart rate was significantly higher in the treatment group by the end of the experiments (135 +/- 10 vs. 105 +/- 4 beats/min, p less than 0.01). Regional segment shortening (SS, sonomicrometry) became normal within 1 min of reperfusion in both the treatment and the control group. During the following 10 min, SS decreased to 52 +/- 6% of preischemic control in the alpha-tocopherol group and to 54 +/- 7% in the control group (NS). SS remained at these depressed values throughout the reperfusion period. Pretreatment with the antioxidant alpha-tocopherol resulted in a tendency to lower lipid peroxidation products but did not prevent development of contractile depression in reversibly ischemic reperfused myocardium.

Animals↗
PubMed1989

[Excimer laser coronary angioplasty in high-grade stenoses and chronic occlusion].

Excimer-laser-angioplasty offers the advantage of minimal thermal injury to adjacent tissue compared to other laser ablation techniques. Highly flexible glass-fiber-catheter systems are now available, and are capable of transmitting sufficient energy densities to ablate even calcified atherosclerotic coronary plaques. We report initial results of excimer-laser-ablation of severe coronary stenoses and occlusions in 17 patients. An excimer-laser (308 nm) with a pulse duration of 50 ns and a repetition rate of 10 to 40 Hz served as laser source. Eight patients had a chronic total occlusion (RCA, n = 4, RCx, n = 3, LAD, n = 1), nine patients had 90% to 95% stenoses (LAD, n = 7, RCA, n = 2). In all cases a laser-catheter consisting of 17 circumferentially orientated 100 microns glass-fibers and a central 15/1000-inch lumen could be advanced to the stenoses/occlusion over a guidewire that had been passed across the stenoses/occlusion. Stenoses diameter could be reduced by 41.5 +/- 10.1% in all patients and vessel lumen was further increased by subsequent balloon dilatation in 10 cases. After 24 h, 16 vessels were patent and showed no restenoses; one recanalized RCA was found reoccluded. We observed no complications, such as perforation, spasm, or thrombi.

Aged↗