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Biomedical subjects

K R Karsch

Publications and source records attributed to K R Karsch.

At least 19 recordsLinked to original sources
PubMed1992

Case report: formation of vessel aneurysm after stand alone coronary excimer laser angioplasty.

Formation of aneurysms in coronary arteries can be observed following percutaneous transluminal balloon angioplasty but has not been reported previously after coronary excimer laser angioplasty in humans. Stand alone coronary excimer laser angioplasty was performed in a 49-year-old man with a 75% left anterior descending artery stenotic lesion and exertional angina, documenting a good angiographic result postintervention. Control angiography 6 months after the procedure revealed an aneurysm distal to a 90% restenosis in the area of ablation.

Angioplasty, Laser↗
PubMed1992

Ultrafast imaging of tissue ablation by a XeCl excimer laser in saline.

To determine the temporal evolution of laser induced tissue ablation, arterial wall specimens with either hard calcified or fatty plaques and normal tissue were irradiated in a 0.9% saline solution using a XeCl excimer laser (wavelength 308 nm, energy fluence 7 J/cm2, pulse width 30 ns) through a 600 microns fused silica fiber pointing perpendicular either at a 0.5 mm distance or in direct contact to the vascular surface. Radiation of a pulsed dye laser (wavelength 580 nm) was used to illuminate the tissue surface. The ablation process and the arising bubble above the tissue surface were recorded with a CCD camera attached to a computer based image-processing system. Spherical cavitation bubbles and small tissue particles emerging from the irradiated area have been recorded. The volume of this bubble increased faster for calcified plaques than for normal tissue.

Angioplasty, Laser↗
PubMed1992

Pressure recovery in aortic stenosis: an in vitro study in a pulsatile flow model.

OBJECTIVES: This study was designed to study pressure recovery in various models of aortic valve stenosis by performing hemodynamic measurements under physiologic conditions in a pulsatile aortic flow circuit. The results were used to validate calculations of pressure recovery based on theoretic considerations derived from fluid dynamics. BACKGROUND: Pressure recovery in aortic stenosis has not been systematically analyzed. METHODS: Stenoses varying in size, shape (circular, Y-shaped, slitlike) and inlet configuration (sharp-edged, nozzle-shaped inlet, artificially stenosed bioprostheses) were used. Aortic pressures were measured at multiple sites distal to the stenotic orifice to determine pressure gradients and recovery. RESULTS: With decreasing orifice area (2, 1.5, 1 and 0.5 cm2) pressure recovery increased (5, 7, 10 and 16 mm Hg, respectively) and the index pressure recovery to maximal peak to peak gradient decreased (56%, 37%, 24% and 14%, respectively). For a given orifice size of 0.5 cm2, this index ranged between 12% for a Y-shaped orifice and 15% for a circular orifice with a nozzle (cardiac output 4 liters/min). Increasing the cardiac output increased pressure recovery, whereas the ratio of pressure recovery to maximal pressure gradient remained constant. CONCLUSIONS: The index pressure recovery to transvalvular pressure gradient, which expresses the hemodynamic relevance of pressure recovery, decreases with increasing severity of aortic stenosis but is independent of transvalvular flow. Thus, pressure recovery is of minor importance in severe aortic stenosis but may account for discrepancies between Doppler and manometric gradients observed in patients with mild to moderate aortic stenosis or a prosthetic valve in the aortic position.

Aortic Valve Stenosis↗
PubMed1992

Effect of heart rate on transmitral flow velocity profile and Doppler measurements of mitral valve area in patients with mitral stenosis.

To study the effect of heart rate changes on Doppler measurements of mitral valve area atrial pacing was performed in 14 patients with mitral stenosis and sinus rhythm. Continuous wave Doppler and haemodynamic measurements were performed simultaneously at rest and during pacing-induced tachycardia. (1) Mitral valve area was determined using the conventional pressure half time method. (2) Additionally, mitral valve area was calculated with a combined Doppler and thermodilution technique according to the continuity equation. (3) Simultaneous invasive measurements were used for calculation of the mitral valve area according to the Gorlin formula. With increasing heart rate (69 +/- 13-97 +/- 15-114 +/- 13 beats min-1) mitral valve area either determined by the continuity equation (1.0 +/- 0.2-1.0 +/- 0.3-1.1 +/- 0.4 cm2) or the Gorlin formula (1.2 +/- 0.3-1.2 +/- 0.4-1.3 +/- 0.4 cm2) remained constant. Both methods correlated closely not only at rest (r = 0.88, SEE = 0.11 cm2, P less than 0.001), but also during atrial pacing (first level: r = 0.95, SEE = 0.10 cm2, P less than 0.001, second level: r = 0.95, SEE = 0.13 cm2, P less than 0.001). In contrast, mitral valve area calculated according to the pressure half time method increased significantly during atrial pacing (1.0 +/- 0.3-1.8 +/- 0.5-2.0 +/- 0.5 cm2).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

Comparison of pulsed laser-assisted angioplasty and balloon angioplasty in femoropopliteal artery occlusions.

The authors performed a prospective, comparative study of 96 patients (age, 41-87 years) with femoropopliteal artery occlusions. Laser-assisted angioplasty was performed in 64 patients with 9- and 7-F over-the-wire multifiber catheters. Supplemental balloon dilation was performed after laser angioplasty. Thirty-two patients underwent excimer laser angioplasty (ELA), and 32 underwent pulsed dye laser angioplasty (DLA). The remaining 32 patients underwent conventional balloon angioplasty (BA). The length of occlusions was 3-10 cm (mean, 6.3 cm). Lesion characteristics in the three patient groups were similar. Technical success rates were 84% for ELA, 78% for pulsed DLA, and 81% for conventional BA. The 1-year clinical success rate was 69% (22 of 32 patients) in the ELA group, 63% (20 of 32 patients) in the pulsed DLA group, and 66% (21 of 32 patients) in the BA group (differences were not significant). Laser-assisted angioplasty with multifiber catheters in femoropopliteal artery occlusions did not help improve the technical success rate and 1-year clinical success rate when compared with those of conventional BA.

Adult↗
PubMed1992

Inhibition of cellular proliferation after experimental balloon angioplasty by low-molecular-weight heparin.

BACKGROUND: The proliferative response induced by balloon angioplasty is known to be an important factor in the development of restenosis after successful coronary angioplasty. METHODS AND RESULTS: To study the effects of low-molecular-weight heparin (LMWH) on cellular proliferation after experimental balloon angioplasty, LMWH (3.9 kd, 400 anti-Xa units/kg/day) was given to 20 male New Zealand White rabbits. After an intimal fibromuscular plaque was induced by electrical stimulation in the right carotid artery, LMWH was applied during the 7 days after balloon dilatation. As the control group, 20 other rabbits underwent balloon angioplasty without application of LMWH. The vessels were excised 3, 7, 14, and 28 days after balloon treatment. During the final 18 hours before the rabbits were killed, bromodeoxyuridine was applied. Intimal wall thickness increased from 13 +/- 5 cell layers (preangioplasty control group) to 20 +/- 6 cell layers in the LMWH-treated group at 28 days (p less than 0.05). In contrast, histological examination of control animals 28 days after angioplasty revealed a significant increase to 35 +/- 15 cell layers (p less than 0.01). Immunohistological quantification showed a significant increase (p less than 0.001) of cells undergoing DNA synthesis at 3 (10.2 +/- 4.2%) and 7 (7.7 +/- 4.8%) days after balloon dilatation in control animals. In contrast, at 3 and 7 days after balloon treatment, the percentage of cells undergoing DNA synthesis in LMWH-treated rabbits was lower (3 days, 2.7 +/- 1.8%; 7 days, 1.9 +/- 0.3%) than the corresponding untreated controls but showed a significant increase (p less than 0.01) compared with the preangioplasty controls. The differences between the two groups were statistically significant, however (3 days, p less than 0.01; 7 days, p less than 0.05). As early as 14 days after angioplasty, the extent of cellular proliferation was normalized and was comparable to the preintervention levels in both groups. CONCLUSIONS: Our data indicate that the proliferative response after balloon angioplasty can be reduced in vivo by early treatment with LMWH and thus encourage further clinical investigations.

Angioplasty, Balloon↗
PubMed1992

Vascular injury and time course of smooth muscle cell proliferation after experimental holmium laser angioplasty.

BACKGROUND: In vitro experiments have shown that holmium laser energy can effectively ablate even calcified plaque in human arterial vessels. Because high-energy densities from holmium lasers can easily be transmitted through quartz fibers, this solid-state laser has been suggested as an alternative intraluminal treatment of atherosclerotic plaque. METHODS AND RESULTS: To develop an intimal plaque, 35 New Zealand White rabbits underwent electrical stimulation of their right carotid artery for 28 days. Subsequently, in 25 rabbits, holmium laser angioplasty (wavelength, 2.12 microns; pulse duration, 150 microseconds; energy density, 350 mJ/mm2) was performed. To study the morphological results, the vessels were excised after 7, 14, 28, and 42 days. Cross sections were analyzed in regard to laser-specific injury. Staining of alpha-actin was used to identify smooth muscle cells (SMCs). After bromodeoxyuridine labeling, the extent of proliferation (number of cells undergoing DNA synthesis) was determined by using a monoclonal antibody. Holmium laser ablation resulted in an initial decrease of the numbers of intimal cell layers in the early group (7 days after treatment: 5 +/- 1 cell layers with 76 +/- 39 microns; control: 13 +/- 3 cell layers with 144 +/- 44 microns). Quantification of SMCs undergoing DNA synthesis in the intima (control: 51 +/- 19 cells/mm2) showed a significant increase of labeled cells after 7 (216 +/- 74 cells/mm2, p = 0.003) and 14 days (281 +/- 139 cells/mm2, p = 0.011). Integrity of the internal elastic lamina was disrupted in all animals after intervention. Seven and 14 days after treatment, a considerable reduction of medial cell nuclei was found in 10 of 12 animals. SMC proliferation in the medial layer was increased within the first 2 weeks after laser ablation (168 +/- 113 cells/mm2; control: 8 +/- 4 cells/mm2; p = 0.023). Six weeks after holmium laser angioplasty, SMC proliferation had returned to control levels in the intima and remained increased in the medial layer. This proliferative response resulted in a significant increase of intimal thickening within 6 weeks after laser ablation (30 +/- 6 cell layers, 375 +/- 97 microns resp.; p = 0.001 each). CONCLUSIONS: Holmium laser treatment leads to considerable vessel wall injury and results in SMC proliferation in the intimal and medial layer with a maximum of proliferative activity within the first 2 weeks. Subsequently, this results in considerable intimal and medial hyperplasia within 6 weeks after treatment.

Angioplasty, Laser↗
PubMed1992

Holmium:YAG laser angioplasty. Experimental ablation of vascular tissue via flexible ring catheters.

This experimental study was designed to define the potential value of a mid-infrared holmium laser in the free running mode for angioplasty. Immediately after removal, fresh normal and diseased human cadaveric arteries were irradiated under saline with a Ho:YAG laser (wavelength 2.13 microns). The laser was pulsed at 3 Hz, 250 microseconds pulse width and fluences of 10 to 40 J/cm2. The laser beam was coupled to ring catheters with multiple low-OH quartz fibers. The tip of the delivery device was held in direct contact with the vessel surface with the laser beam oriented perpendicularly. Ablation of atherosclerotic plaque was accomplished at an ablation threshold of 10 J/cm2. The ablation rate was 2.1 to 8.3 microns/pulse. Removal of calcified plaque was only partially effective. There were marked thermal effects with vacuolizations extending up to 1505 +/- 178 microns into the adjacent tissue. Laser light at the mid-infrared wavelength of 2.13 microns is supposed to be attractive as it is readily absorbed in water and can easily be transmitted through optical fibers. However, Q-switching seems to be essential to minimize thermal side effects and to make effective ablation of calcium possible.

Angioplasty, Laser↗
PubMed1992

[Role of smooth muscle cell proliferation after balloon angioplasty].

The long-term success of percutaneous transluminal coronary angioplasty (PTCA) is severely limited by the high incidence of restenosis, which occurs in up to 30 to 40% of primary successfully treated patients. Several postmortem and experimental studies have demonstrated that restenosis after balloon angioplasty is caused by intimal proliferation of smooth muscle cells (SMCs). As a result of the vessel wall injury due to the mechanical intervention, endothelial injury and platelet aggregation at the site of dilatation can be observed. SMCs are activated for migration and proliferation in the early phase after angioplasty by subsequent expression of several growth factors, activation of macrophages, and expression of a variety of mitogens (Figure 1). Since several other alternative interventional devices like atherectomy, excimer laser angioplasty and stenting are also limited by the occurrence of SMC proliferation following treatment, there is an obvious need for a pharmacological approach to inhibit SMC proliferation after PTCA. It has been shown in experimental studies that the proliferative response of the vessel wall in the intima occurs within the first seven days after dilatation. A significant increased mitosis rate of SMCs in the media, however, can be observed within three weeks after intervention (Figure 2). As suggested by several authors, macrophages are thought to play an important role in the restenosis process after balloon angioplasty. However, our experimental results demonstrate that no significant accumulation of macrophages occurred prior to seven days following balloon angioplasty (Figure 3).(ABSTRACT TRUNCATED AT 250 WORDS)

Angioplasty, Balloon, Coronary↗
PubMed1992

Atherosclerosis--where are we heading?

Aim of this review is, to analyse the current knowledge of the pathogenesis of atherosclerosis from the viewpoint of a clinical cardiologists. All the current ideas about the pathogenesis of atherosclerosis have been derived from the theories of three pathologists. The first was Rokitanski 1852, his theory was somewhat modified by Virchow 1856 and revitalised and modified again by Ross in 1986. All current theories however are based on the term response to injury leading to accelerated atherosclerosis. Following the classification of Stary et al. and the suggestions of the report of the Committee on Vascular Lesions of the Council of Arteriosclerosis the early lesions (Stary class I and II) should be renamed as normal vascular adaptation to physical or chemical causes. These causes include not only shears stress or turbulences due to increased blood pressure but also hypercholesterolemia and certain changes of plasma protein content. The classification of Fuster et al. is mainly dependent on a mechanical injury to the arterial wall induced by the interventional cardiologist. Thus far, it seems questionable, if such a response to injury is indeed the leading mechanism ultimately resulting in advanced arteriosclerosis. In view of the multifactorial processes involved in the pathogenesis of either adaptation or then accelerated arteriosclerosis we have to admit, that our insight is still limited. Thus far, the only lesson to be learned for practising clinicians is that we have to accept that the process of normal adaptation of the vascular arterial wall to the abnormal development of a clinical significant lesion is dynamic and is not well characterized by the response-to-injury theory. We do know that even in the stage of acute coronary syndromes lesion changes are unpredictable. This coincides with the finding from the experimental laboratory that lesion growth is episodic and a result of different stages of activity of the involved cell types and growth factors. Thus, we should avoid looking only for certain stages but rather accept that this is 1. a normal adaptative alteration of the arterial wall which might 2. result in accelerated atherosclerosis due to genetic determination of smooth muscle cells and accumulation of a variety of growth factors.

Animals↗
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

Value of a modified continuity equation method to quantify mitral valve area in patients with mitral stenosis and sinus rhythm.

To quantify valve area in mitral stenosis, a modified continuity equation method using continuous wave Doppler and thermodilution measurements was applied. In 14 patients with mitral stenosis and sinus rhythm (age: 49 +/- 11 years), transmitral flow velocity was recorded by continuous wave Doppler during right and left heart catheterization. Mitral valve area was calculated by three different methods: 1. According to the continuity equation, stroke volume (thermodilution technique) was divided by the registered time velocity integral of the mitral stenotic jet (continuous wave Doppler). 2. Mitral valve area was calculated by the pressure half-time method. 3. Simultaneous pulmonary capillary wedge and left ventricular pressure measurements were used for determination of mitral valve area according to the Gorlin formula. The mitral valve area determined by application of the continuity equation (y) showed a close correlation to the valve area calculated by the Gorlin equation (x): y = 0.73x + 0.12, SEE = 0.11 cm2, r = 0.88, P less than 0.001. In contrast, the correlation between mitral valve area determined by pressure half-time (y) and the Gorlin formula (x) was not as good: y = 0.77x + 0.11, SEE = 0.26 cm2, r = 0.65, P less than 0.05. Thus, the continuity equation method using combined continuous wave Doppler and thermodilution technique allows a valid determination of mitral valve area. In patients with mitral stenosis and sinus rhythm, this technique is superior to the noninvasive determination of mitral valve area by the conventional pressure half-time method.

Adult↗
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

Smooth muscle cell proliferation and restenosis after stand alone coronary excimer laser angioplasty.

It has been shown that coronary excimer laser angioplasty can remove atherosclerotic intracoronary tissue. Stand alone coronary excimer laser angioplasty was successfully performed in a 53 year old white man with 90% stenosis of the left anterior descending coronary artery and exertional angina (Canadian Cardiovascular Society class III). The lesion was reduced to a 30% residual stenosis with use of a 1.2 mm and subsequently a 1.8 mm diameter laser catheter. Early follow-up angiography 24 h later revealed persistent patency and unchanged lesion diameter of the target vessel. The patient was free of symptoms during the 2 month follow-up period, but died suddenly while playing in a tennis tournament 63 days after the procedure. Postmortem histologic examination revealed 80% restenosis at the lesion site without plaque disruption or thrombosis. Specific staining of the histologic specimen for smooth muscle cells using alpha-actin revealed significant smooth muscle cell proliferation at the site of coronary excimer laser angioplasty. However, most of the vessel narrowing appeared to be due to underlying fibrotic plaque as a result of insufficient tissue ablation. This was probably related to the size of the currently available catheters, which are too small to create a large channel.

Angioplasty, Laser↗
PubMed1991

[Peripheral excimer laser angioplasty. The indications, methods and clinical results].

Between March 1989 and January 1990, percutaneous transluminal excimer laser angioplasty was performed in 61 patients (40 men and 21 females; mean age 66 [41-86] years) with 65 peripheral arterial occlusions (iliac: 11, femoropopliteal: 48, tibial: 5, left subclavian artery: 1). The average ankle-arm index before treatment was 0.45 (0.2-0.8) for iliac, 0.52 (0-0.7) for femoropopliteal and 0.3 (0.1-0.4) for tibial occlusion. Recanalization was successful in 58 occlusions, but additional balloon dilatation was necessary in 54. The mean residual stenosis degree after laser application was 54%, after balloon dilatation 22%. Postangioplasty thromboembolism occurred in five patients. Intravascular stents were implanted in 11 patients because of extensive dissection or high-grade restenosis. After four weeks the clinical findings were improved in 54 of the 58 patients, in 47 even after six months. At that point the average ankle-arm index was 0.88 (0.5-1.1) after iliac, 0.79 (0.6-1.15) after femoropopliteal and 0.6 (0.4-0.7) after tibial recanalization.

Adult↗
PubMed1991

Long-term clinical course of patients with angina and angiographically normal coronary arteries.

In 88 of 103 consecutive patients with angina and normal coronary arteries, follow-up data could be achieved 6-11 years (9.2 +/- 1.2 years) after diagnostic left heart catheterization. Three of these patients died during follow-up (two noncardiac deaths and one death with no identifiable etiology). One patient suffered a documented myocardial infarction. In 40 patients (47%) chest pain diminished, while symptoms were unchanged in 20 (24%) or even worse in 25 (29%). Resolution or persistence of chest pain could not be predicted either by the character of pain (typical vs. atypical), the presence of hypertension, a left bundle-branch block, a positive exercise electrocardiogram or pathological pulmonary artery pressures during exercise, documentation of myocardial bridges, local wall motion abnormalities, or a left ventricular end-diastolic pressure greater than or equal to 13 mmHg. However, continuing chest pain was significantly more common in patients who revealed a 'slow-flow phenomenon' at initial coronary arteriogram. Thus, in patients with angina and normal coronary arteries the long-term course regarding frequency of morbid cardiac events is benign. However, more than half of the patients reported chest pain to be similar or even worse than at catheterization. Most clinical and invasive results at initial evaluation had no predictive value for the persistence of symptoms. The impact of 'slow-flow' in coronary arteriography, which was a phenomenon almost exclusive to patients with constant or even worse chest pain at follow-up, should be evaluated in larger patient populations.

Adult↗
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↗