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Biomedical subjects

A Baumbach

Publications and source records attributed to A Baumbach.

At least 73 records · Page 4Linked to original sources
PubMed1993

Acute vessel closure following excimer laser coronary angioplasty: can we predict it?

Of 124 consecutive patients undergoing elective excimer laser coronary angioplasty, 33 (26%) had periprocedural occlusion following excimer laser irradiation. Successful management (reopened vessel, no death, no myocardial infarction, no emergency bypass surgery) including repeat lasing, subsequent percutaneous transluminal coronary angioplasty, use of intracoronary nitroglycerin or streptokinase was achieved in 32 of the patients with acute occlusion following excimer laser coronary angioplasty. In one patient a nonfatal anterior myocardial infarction occurred. A late event occurred in two patients despite patency at the control angiography 24 h later. Multiple logistic regression modeling was used to examine the relationship between various characteristics and the risk of acute vessel closure. The preprocedural and procedural variables analyzed included progressive spasm prior to occlusion and lesion morphology after intervention (angiographic complications after percutaneous transluminal coronary angioplasty were prospectively divided into class 0, no complication, and classes 1-3, according to purely descriptive morphological characteristics). These showed a multivariate correlation with acute occlusion during excimer laser coronary angioplasty. These results suggest that acute vessel closure during stand-alone excimer laser coronary angioplasty is a benign but unpredictable event.

Acute Disease↗
PubMed1993

Effect of exercise on valvular resistance in patients with mitral stenosis.

OBJECTIVES: This exercise study assessed the relation between valvular resistance and flow in patients with mitral stenosis. BACKGROUND: Valvular resistance has been proposed as an alternative measure of stenotic valvular lesions, which is speculated to remain stable under changing hemodynamic conditions. METHODS: In 35 of 40 patients with pure or predominant mitral stenosis, continuous wave Doppler measurements of the mitral stenotic jet were possible at rest and during supine bicycle ergometry. Simultaneously, transvalvular flow was assessed by thermodilution technique. For calculation of valvular resistance, the mean mitral valve pressure gradient was determined according to the simplified Bernoulli equation and divided by transvalvular flow. Additionally, effective mitral valve area was calculated according to the continuity equation method, dividing flow by the mean diastolic flow velocity. RESULTS: Valvular resistance was 65 +/- 32 dynes.s.cm-5 at rest and increased to 82 +/- 43 dynes.s.cm-5 at 25 W (p < 0.001). The most prominent increase in valvular resistance (rest to 25 W 63 +/- 28 to 95 +/- 48 dynes.s.cm-5, p < 0.001) was found in those patients who had no or only a moderate (< 20%) change in effective mitral valve area. In contrast, valvular resistance remained constant (67 +/- 36 vs. 70 +/- 32 dynes.s.cm-5) in patients with a significant (> or = 20%) increase in mitral valve area with exercise. CONCLUSIONS: In patients with mitral stenosis, the exercise-induced changes in valvular resistance are heterogeneous. This is the result of the variable response of mitral valve area to an increase in flow. In the individual patient, mitral valve area can significantly increase, a factor that has to be taken into account when interpreting the hemodynamic relevance of the obstruction. Calculated valvular resistance is flow dependent and has no advantage over valve area calculations for quantifying mitral stenosis.

Adult↗
PubMed1993

Acute closure during coronary excimer laser angioplasty and conventional balloon dilatation: a comparison of management outcome and prediction.

Of 523 consecutive patients undergoing elective percutaneous transluminal coronary angioplasty (PTCA) and 83 patients treated with coronary excimer laser angioplasty (ELCA), 17 (3.3%) had in-laboratory occlusion following PTCA and 25 (30%) following ELCA; they were enrolled into a prospective study. Successful management (reopened vessel, patency at repeat angiography within 24 h, no death, no myocardial infarction (MI), no emergency bypass surgery) including repeat lasing, subsequent PTCA, use of intracoronary nitroglycerin or streptokinase was achieved in 24 (96%) of the 25 patients with acute occlusion during ELCA. An anterior MI occurred in one patient of the laser group. Repeat balloon dilatation was successfully performed in seven of the 17 patients (41%) with acute closure during PTCA. Among the 10 patients with persistent occlusion after PTCA, five developed a limited myocardial infarction (35%). One patient required emergency CABG, and died peri-operatively. Severe spasm prior to occlusion defined by a new coronary flow depression without evidence of dissection or thrombus showed a significant positive association with acute occlusion during ELCA (P = 0.0008). Thus, in contrast to occlusion during PTCA, subsequent balloon dilatation was successfully performed in the majority of patients with acute occlusion during ELCA, implying that different underlying mechanisms are responsible for this complication. In this limited patient group, occlusion after excimer laser angioplasty was much more frequent than closure during PTCA, but was infrequently associated with major events such as myocardial infarction or death.

Acute Disease↗
PubMed1993

[In vitro studies of shock wave effects during ablation of normal and atherosclerotic vascular wall by excimer laser].

Ablation of atherosclerotic plaque and normal arterial wall was performed using a xenon-chloride-excimer laser with a wavelength of 308 nm and a pulse duration of 115 ns. The light was transmitted via a 600 micron fiber and adjusted to an energy density of 3.5 J/cm2. The acoustic signals generated by the laser pulse were measured with hydrophones consisting of polyvinylidenefluoride with active diameters of 0.3 mm and recorded on a dual-channel digital storage oscilloscope using either a 0.5 m coaxial cable or a broadband transmission system. From 19 cadavers human aortic tissue segments were excised and macroscopically classified as either normal or calcified atherosclerotic plaque. Approximately 500 measurements were performed in saline and blood each. Histological analysis was carried out after the experiments to verify the macroscopic diagnosis and to correlate the acoustic responses with the tissue characteristics. For "normal" arterial segments, maximum peak pressure was 1.25 MPa +/- 0.85 MPa, rise time 163 ns +/- 43 ns, and pressure increase 8.2 kPa +/- 5.4 kPa/ns in saline. For calcified, atheromatous segments a significantly higher maximum pressure (2.20 MPa +/- 1.16 MPa), a significantly shorter rise time (69.9 ns +/- 25.8 ns), and a significantly higher pressure increase (32.3 kPa +/- 21.3 kPa/ns) was found in saline (p < or = 0.0001). In blood, maximum peak pressure was 1.29 MPa +/- 0.43 MPa, rise time 93.3 ns +/- 27.7 ns, and pressure increase 14.6 kPa +/- 5.2 kPa/ns for "normal" arterial segments. Maximum peak pressure (2.28 MPa +/- 0.63 MPa) and pressure increase (32.8 kPa +/- Pa/ns) were significantly higher for calcified tissue segments.(ABSTRACT TRUNCATED AT 250 WORDS)

Angioplasty, Balloon, Laser-Assisted↗
PubMed1992

Success rate and incidence of restenosis following coronary excimer laser angioplasty: results of a single center experience.

The initial single center experience of percutaneous coronary excimer laser angioplasty is described for the first three series of 147 patients. Sixty patients were treated with a prototype 1.4-mm laser catheter, 40 patients with improved transmission devices, and the third series of 47 patients with an increased pulse width of the laser system allowing improved energy transmission. In 17 patients (12%) laser angioplasty could not be initiated due to inability to cross the lesion with the guidewire or to place the catheter coaxially within the vessel. In 32 patients (58%) of series 1, 11 patients (31%) of series 2, and 17 patients (43%) of series 3, additional balloon dilatation following laser treatment was necessary due to vessel closure (24%) or due to an insufficient angiographic result (35%). There was one death in series 1 (2%) and 2 (3%) each, one perforation in series 2 (3%), two transmural myocardial infarctions in series 1 (4%), and one myocardial infarction in series 2 (3%). During the 6-month follow-up period one patient in series 2 (2%), and one patient in series 3 (3%) died. Angiographic restenosis was found in 22, 12, and 11 patients of series 1 (40%), 2 (34%), and 3 (27%), respectively. No patient developed a transmural myocardial infarction. Thus, percutaneous coronary excimer laser angioplasty can be performed as a safe and feasible procedure in patients with coronary artery disease.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1992

Spontaneous splenic rupture complicating acute Q fever.

Q fever is usually a self-limited febrile illness that involves the lungs and the liver. Acute complications are rare. We present the case of a 30-yr-old patient with spontaneous splenic rupture during the course of acute Q fever infection. He was admitted to the hospital with high temperature and the radiological signs of an atypical pneumonia. Forty-eight hours after admission, he developed shock. Because of free intraabdominal liquid, a laparatomy was performed that revealed a tear in the enlarged spleen. A splenectomy was performed. The diagnosis of Q fever was established by a significant titer increase in complement fixation test and IgM-ELISA. Serological investigations into the patient's surroundings revealed evidence of Q fever infection in 10 additional persons. Q fever should be taken into account as a possible differential diagnosis in patients with unexplained febrile illness and symptoms of pneumonia. The acute course of Q fever infection can be complicated by splenic rupture. The diagnosis of an acute infection with Coxiella burnetii often requires serologic testing of a second serum sample obtained at least 10 days after the onset of symptoms. Q fever should be ruled out in cases of unexplained splenic rupture particularly in Q fever endemic areas.

Adult↗
PubMed1992

[Acute and long-term results of coronary Excimer laser angioplasty].

Laser and catheter technology have been considerably improved within the first 2 years of the clinical use of coronary excimer laser angioplasty. Furthermore, patient selection has changed due to increasing operator experience. We report on the acute- and long-term results achieved in 163 patients in three subgroups with different system parameters and catheter technology. In the initial series 1 (N:60) a prototype catheter with a diameter of 1.4 mm was used. In series 2 and 3, we employed improved transmission devices with 1.3, 1.5 or 1.8 mm. In series 3 the pulsewidth was increased from 60 ns to 115 ns. The target vessel was the LAD in 68%, the LCX in 10%, and the RCA in 21%. According to the AHA/ACC Lesion classification there were 13% type A, 26% type B1, 55% type B2, and 5% type C lesions. Stand-alone laser angioplasty was performed in 23/60 (38%), 24/40 (60%), and 34/64 (53%) in series 1, 2, and 3, respectively. Additional balloon angioplasty was necessary in 32, 11, and 21 interventions. Failure of laser angioplasty occurred in five patients of series 1 and 2, and nine patients of series 3. Frequently observed complications included coronary spasm in 18 to 32%, dissections in 16% to 33%, and vessel closure in 18 to 27%. Myocardial infarction occurred in three patients in the first and one patient of the second and third series. There was one in-hospital death in series 1 and 2.(ABSTRACT TRUNCATED AT 250 WORDS)

Angioplasty, Laser↗
PubMed1991

Usefulness of morphologic parameters in predicting the outcome of coronary excimer laser angioplasty.

The treatment of complex coronary lesions with conventional balloon angioplasty is associated with a reduced success rate and an increased incidence of complications. To evaluate the influence of lesion morphology on the outcome of coronary excimer laser angioplasty, morphologic parameters of 148 target lesions in 147 consecutive patients were determined. Morphologic analysis included target vessel, involved vessel segment, vessel diameter, minimal lumen diameter, length of the lesion, single discrete (concentric/eccentric) or complex lesions (occlusions, bifurcational, tandem or long segmental lesions), American College of Cardiology/American Heart Association Task Force classification, lesion location in curved or straight vessel segments, prestenotic vessel tortuosity and the direction of the laser approach in curved vessels with eccentric lesions. Failure of laser angioplasty occurred in 17 patients because of failed guidewire placement (n = 8), catheter placement (n = 6), or inability to pass the lesion with the laser catheter (n = 3). Successful stand-alone laser angioplasty was achieved in 68 procedures. In 63 interventions additional balloon angioplasty was necessary (n = 60) or stand-alone laser angioplasty was not successful (n = 3). The frequency of complex lesions, particularly total occlusions (p less than 0.001) and prestenotic vessel tortuosity (p = 0.002) was significantly increased in the group with failed laser attempts. Statistical analysis of the morphologic parameters in successful stand-alone laser interventions compared with combined or unsuccessful interventions revealed no significant difference. These data suggest that failure of laser angioplasty occurs because of low catheter flexibility and the need for guidewire support in treating totally occluded vessels.(ABSTRACT TRUNCATED AT 250 WORDS)

Angioplasty, Laser↗
PubMed1991

[Laser angioplasty of coronary stenoses].

Percutaneous transluminal coronary laser angioplasty is still undergoing clinical trials. The laser systems employed are of the pulsed type - for the most part the excimer laser - which are more effective for removing calcified plaque and have a lower complication rate than continuous wave lasers. While the long-term results are comparable with those achieved with balloon dilatation, the primary success rate of laser angioplasty alone is not yet up to the standards of balloon angioplasty. Improvements may be expected through the further development of catheter systems and the introduction of new techniques with more accurate and specific ablation of arteriosclerotic plaques.

Angioplasty, Laser↗
PubMed1991

Potential use of holmium lasers for angioplasty: evaluation of a new solid-state laser for ablation of atherosclerotic plaque.

Tissue effects of the mid-IR Holmium laser (emitting at a wave-length of 2130 nm) were evaluated. This wavelength is attractive because it combines high water absorption and easy transmission through standard optical fibres. The laser was pulsed with pulse durations in the range of 100 microseconds and repetition rates between 2 and 6 Hertz. For all experiments a repetition rate of 2 Hertz was used. The laser beam was coupled into waterfree quartz fibers with core diameters of 200 and 800 microns with an efficiency of 70 and 80%, respectively. Ablation of atherosclerotic plaque has been performed at an ablation threshold of 10J/cm2 for the 800 microns and 40J/cm2 for the 200 microns fibre. Removal of calcified plaque was possible. Ablation efficiency increased in a non-linear fashion with increasing pulse energies. The ablation rate per pulse was approximately 2 mm at energy fluences of 1000J/cm2 for the 200 microns fibre and 1.25 mm at energy fluences of 70J/cm2 for the 800 microns fibre; a further increase in energy densities did not result in higher ablation rates. On macroscopic examination only very limited thermal injury was found in crater adjacent tissue structures. Crater edges were even and did not reveal signs of crater charring or debris in the crater lumen. However, the histologic specimens revealed zones of thermal damage extending 100 up to 1000 microns lateral into adjacent tissue. Thermal damage increased with increasing radiant exposures and depended on the medium used.

Angioplasty, Laser↗
PubMed1991

Effects of intracoronary nitroglycerin on lumen diameter during early follow-up angiography after coronary excimer laser atherectomy.

The incidence of coronary vasospasm during and following excimer laser atherectomy is considerable. The aim of this study was to investigate vasoconstriction of the target vessel during early follow-up angiography. In 50 patients an angiogram was performed 24 hours after intervention. Nineteen patients were treated with stand-alone laser atherectomy (group I), another 19 with laser and additional balloon angioplasty (group II) and 12 with balloon angioplasty alone (group III). Lumen diameter and percent stenosis before and after intracoronary application of 0.1 mg nitroglycerin were determined. The differences were compared between groups I, II and III, and for patients with (N = 14) and without (N = 24) vasospasm during laser atherectomy. There was a significant increase in lumen diameter, of 0.17 +/- 0.28 mm, after nitroglycerin in group I, of 0.18 +/- 0.29 mm in group II (P = 0.02) and of 0.03 +/- 0.21 mm in group III (ns). In patients with vasospasm during laser atherectomy the average increase in lumen diameter was 0.28 +/- 0.24 mm (P less than 0.01), and in patients without vasospasm 0.12 +/- 0.29 mm (P = 0.09). We conclude that one day after coronary excimer laser atherectomy intracoronary nitroglycerin significantly affects lumen diameter at the site of previous stenosis, an effect undetectable after balloon angioplasty. Thus, vasoconstriction after excimer laser ablation seems to be a common phenomenon and is prolonged in patients with vasospasm during the previous intervention.

Adult↗
PubMed1991

[Perforation of the vascular wall after coronary excimer laser angioplasty].

A 56-year-old patient with recurrent episodes of angina pectoris at rest was admitted for left-heart catheterization. The coronary angiogram revealed two-vessel disease with a subtotal stenosis in the circumflex artery and a long 90% stenosis in the proximal part of the left anterior descending artery. On the basis of symptoms and coronary morphology laser angioplasty was performed. After a total of 99 s of energy delivery extravasation of dye occurred at the site of ablation. Due to acute vessel occlusion subsequent PTCA was performed, resulting in a satisfactory angiographic result. Extravasation of dye was terminated after PTCA and was absent at short-term follow-up angiography. No signs of pericardial effusion were detectable by two-dimensional and M-mode echocardiography. A control angiogram disclosed the identical result the day after the acute intervention, and the patient could be discharged with a normal exercise test 1 week later.

Angina Pectoris↗
PubMed1990

Percutaneous coronary excimer laser angioplasty in patients with stable and unstable angina pectoris. Acute results and incidence of restenosis during 6-month follow-up.

A clinical study was conducted to evaluate the efficacy and safety of percutaneous coronary excimer laser angioplasty in 60 patients with coronary artery disease. Forty-nine patients had stable exertional angina, and 11 patients had unstable angina despite medical therapy. A novel 1.4-mm diameter catheter with 20 quartz fibers of 100-microns diameter each arranged concentrically around a central lumen suitable for a 0.014-in. flexible guide wire was coupled to an excimer laser. A commercial excimer laser emitting energy at a wavelength of 308 nm with a pulse duration of 60 nsec was used. The laser was operated at 20 Hz. Mean energy transmission was 30 +/- 5 mJ/mm2. In five of the 60 patients, laser angioplasty was not attempted. In 23 patients with laser ablation alone, percent stenosis decreased from 76 +/- 14% before to 27 +/- 17% after ablation and was 34 +/- 15% at the early follow-up angiogram. In 32 patients, additional balloon angioplasty was performed because of vessel closure after laser ablation in 11 and an insufficient qualitative result in 21 patients. Of the 11 patients with unstable angina, one patient died due to vessel closure 3 hours after intervention, and two patients developed a myocardial infarction. In 22 of 47 patients with late follow-up angiography, restenosis within the 6-month follow-up period occurred. Rate of restenosis was higher in patients treated with laser ablation and balloon angioplasty (16 of 28) than in patients treated with laser ablation alone (six of 19). These results suggest that coronary excimer laser angioplasty for ablation of obstructive lesions is feasible and safe in patients with stable angina. However, development of new catheter systems is necessary for an improved success rate.

Adult↗
PubMed1990

[Percutaneous coronary excimer laser angioplasty].

Available preliminary clinical studies have shown that ablation of atherosclerotic plaques can be achieved by means of pulsed excimer laser coronary angioplasty via flexible energy transmission systems. The goal of current studies using improved catheter technology is to enhance the acute success rate since, based on initial studies, it can be assumed that only about 40 to 45% of the patients can be successfully treated. The on-going investigations were carried out primarily with three different excimer laser systems which employ a wavelength of 308 nm but differing pulse widths and transmission systems. In the first American multicenter study by Litvack and Margolis a catheter system was used with a pulse width of 180 to 220 ns. The fibers have a shaft diameter of 100 microns with a conically-thickened distal end measuring 200 microns, the ablative area encompasses 35 to 45% of the total catheter tip surface. The excimer laser used in the second American multicenter study by Sanborn and Isner has a pulse width of 120 ns. This catheter is relatively unflexible due to the 200 microns fiber diameter. The ablative catheter tip area is 25 to 30%. In Tübingen a system was used with a pulse width of 60 ns. The energy is transmitted through fibers with a diameter of 100 microns. The effective ablative area in the first series of patients was about 15%, in the second series about 25 to 30%. At present, the energy density of all three systems is comparable with at least 25 to 35 mJ/mm2. Since there is currently no means for accurate assessment, the question of whether a shorter pulse width of comparable energy density is more effective than the longer pulse width, remains an open issue. The flexibility of the systems used by Margolis and in Tübingen enable ablation not only of proximal, but also arteriosclerotic plaques located in the middle-third of vessels. The flexibility and steerability, however, are inferior to balloon catheter systems. In the study carried out by Litvack and Margolis, in which more than 600 patients have been treated, and the results from 514 patients reported, there was no patient selection in the first series. The study by Sanborn and Isner included 88 patients. Due to the relatively unflexible catheter system, only those patients were treated who had proximal stenosis of the left anterior descending or right coronary artery or marginal branches of the circumflex artery without marked tortuosity.(ABSTRACT TRUNCATED AT 400 WORDS)

Angioplasty, Balloon, Coronary↗
PubMed1990

[Percutaneous coronary Excimer laser angioplasty in patients with coronary heart disease].

To verify the efficacy and safety of percutaneous coronary excimer laser angioplasty in patients with coronary artery disease a prospective study was conducted in 60 patients. The application of laser light was possible in 55 of the 60 patients. A novel 1.4-mm diameter catheter with 20 quartz fibers of 100-microns diameter, each arranged concentrically around a central lumen suitable for an 0.014-inch flexible guide wire was used. The light source was a commercial excimer laser emitting energy at a wavelength of 308 nm, with a pulse duration of 60 ns. The laser was operated at 20 Hz; mean energy transmission was 30 +/- 5 mJ/mm2. In 23 of the 55 patients treated with excimer laser energy the qualitative angiographic results were sufficient. In 32 patients additional balloon angioplasty was necessary, either because of an insufficient result or due to vessel closure after laser ablation. In 47 of the 55 patients control angiography was performed within the 6-month follow-up period. Rate of restenosis was higher in patients treated with laser ablation and subsequent balloon angioplasty (16 of 28) than in patients treated with laser ablation alone (6 of 19). Results of the 6-month observation period suggest that 1) coronary excimer laser angioplasty in combination with subsequent balloon angioplasty results in a considerable increase of the restenosis rate; 2) the exclusive use of laser ablation also results in a restenosis rate comparable to balloon angioplasty alone; and 3) the impact of this new method using improved application systems and higher energy transmission has to be determined in further studies.

Angina Pectoris↗
PubMedDate not supplied

Inhibition of smooth muscle cell proliferation after local drug delivery of the antimitotic drug paclitaxel using a porous balloon catheter.

Percutaneous transluminal coronary angioplasty is an accepted treatment for coronary artery disease. The major limitation, however, is the high incidence of restenosis which limits the long-term benefit of this intervention. Paclitaxel is a new antiproliferative agent that has generated considerable scientific interest since it was introduced in clinical trials in the early 1980s. Recent in vitro studies have shown that paclitaxel has considerable antiproliferative activity in human coculture systems. In the present study the efficacy of paclitaxel was investigated after development of an intimal plaque by electrical stimulation and additional cholesterol diet and subsequent balloon angioplasty in 63 New Zealand White rabbits. Local drug delivery of paclitaxel was accomplished in 30 rabbits with a porous balloon catheter (35 holes, hole diameter 75 microm, 2.5 mm catheter diameter). Paclitaxel was administered locally with 4 ml (solution 10(-5) mol/L) using an injection pressure of 2 atm. To study the extent of restenosis and morphological changes, the animals were sacrificed 7, 28 or 56 days after intervention. After staining procedures quantification of SMC proliferation, intimal macrophages and morphological analyses were performed. Paclitaxel plasma concentrations were measured using HPLC technique. One week after balloon angioplasty the arteries treated with local paclitaxel delivery showed an insignificant trend towards a reduction in intimal smooth muscle cell proliferation (untreated 8.4 +/- 4.9 % vs paclitaxel treated 2.4 +/- 2.4 %, p = NS). However, this resulted in a significant reduction of stenosis degree of 66 % 8 weeks after intervention compared to the untreated group (untreated 41 +/- 18 % vs paclitaxel treated 14 +/- 11 %, p = 0.005). In conclusion, locally delivered paclitaxel prevented neointimal thickening in the rabbit carotid artery after balloon angioplasty. Local paclitaxel treatment may therefore be a clinical option for the prevention of restenosis after coronary interventions. However, further preclinical studies have to prove long-term efficacy and safety.

Angioplasty, Balloon, Coronary↗