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L Koch

Publications and source records attributed to L Koch.

At least 37 records · Page 2Linked to original sources
PubMed1996

Differences in the morphology of unstable and stable coronary lesions and their impact on the mechanisms of angioplasty. An in vivo study with intravascular ultrasound.

The aim of this study was to compare the morphology of stable and unstable coronary lesions using intravascular ultrasound in patients undergoing coronary balloon angioplasty and to determine whether lesion morphology had any influence on the mechanism of balloon angioplasty. Thirty three (15 stable and 18 unstable) patients undergoing single lesion percutaneous transluminal coronary angioplasty were studied with intravascular ultrasound before and after intervention. All examinations, recorded on S-VHS video tape, were studied off-line and matched sites from the point of minimum lumen area after the procedure and the corresponding site prior to intervention were compared. The morphology of lesions before intervention was noted and the mechanisms of angioplasty (vessel stretch, lesion remodelling and lesion tears) were determined by comparing pre- and post-interventional morphology and dimensions. The only significant morphological difference between stable and unstable lesions was the presence of a demarcated inner layer in unstable lesions, delimited by a fine circumferential line. This pattern was noted in 77% (14/18) of unstable lesions and in 7% (1/15) of stable lesions (P < 0.01). Unstable lesions tended to have more echolucent zones than stable lesions (72% (13/18) vs 46% (7/15), P = 0.13). The mechanisms of angioplasty were also found to differ. Whereas lesion remodelling (or 'compression') was seen in 77% (14/18) of unstable lesions, it occurred in only 13% (2/15) of stable lesions and mean lesion cross-sectional area reduction was greater in unstable lesions, - 14.8 +/- 8.3% (2.1 +/- 1.3 mm2) compared to stable lesions, - 4.1 +/- 8.4% (0.42 +/- 0.9 mm2), P < 0.01. In contrast, vessel stretch was seen more frequently in stable lesions (73%, 11/15) compared to unstable lesions (22%, 4/18) P < 0.01 and the mean increase in vessel cross-sectional area was + 13.5 +/- 6.8 (1.6 +/- 0.9 mm2) in stable lesions compared to + 5.5 +/- 5.6% (0.8 +/- 0.9 mm2) in unstable lesions, P < 0.01. Lesion tear was present to a similar degree in both groups of patients. In this observational study we found a set of echographic markers that distinguished unstable lesions. The mechanisms of angioplasty differed between stable and unstable angina, with greater lesion remodelling seen in unstable lesions and vessel stretch in stable lesions. Taken together, these findings suggest that the markers we describe may be echographic indicators of mural thrombus.

Angina Pectoris↗
PubMed1995

[Reconstruction methods for 3D imaging and quantification of intracoronary ultrasound cross-sectional images using biplanar fluoroscopy. Initial experiences in vitro and in vivo].

In this investigation, we studied the feasibility of 3D-reconstruction from 2D cross-sectional intracoronary ultrasound images. A computer-aided, automated 3D-reconstruction was used to generate cylindrical and sagittal format of vessels in vitro (n = 9) and in vivo (n = 48). Ultrasound 2D-images were acquired with a 20 MHz mechanical intracoronary ultrasound catheter (Boston Scientific). A slow pullback (about 1 mm/s) of the catheter was performed during continuous recording of the ultrasound images. The recorded 2D-images were then fed to an image processing computer. Correction and scaling of the axial vessel dimensions was performed by the assessment of the catheter position in the simultaneously recorded biplane fluoroscopy. Digitized data were then processed to 3D-images with use of voxel space modeling. The 3D-views from any plane can be reconstructed. The in-vitro study demonstrated that the reconstructed images were able to correctly portray the pathological changes of the vessel wall in all specimen as proved by pathologic examination. In the in-vivo study, 3D-reconstruction provided not only a spatial visualization of the coronary arterial disorders (such as coronary aneurysm, coronary dissection, spontaneous plaque rupture etc.) but also provides the potential to quantify the mass of lesions. By combining sagittal and cylindrical views, 3D-reconstruction enables longitudinal and orthogonal imaging of the both the vessel lumen and vessel wall, therefore, it has the advantage of cross-sectional viewing as obtained from intracoronary ultrasound and the longitudinal viewing as derived from coronary angiography. These preliminary results of the study indicate that 3D-reconstruction of coronary segments is a promising technique for studying coronary artery disease. Analysis can be based not only on single or multiple cross-sectional images but also on vessel segments facilitating serial studies as for instance studies assessing the progression and regression of atherosclerosis.

Aortic Dissection↗
PubMed1995

Cardiac baroreflex sensitivity and sodium excretion are reduced both by a deficit and an excess of dietary salt in the conscious dog.

In 10 conscious, chronically instrumented beagle dogs we studied the effects of four different dietary sodium intakes (mmol Na/kg body wt/day: 14.5 [excess], 7.5 [high], 2.5 [normal], and 0.5 [low] [plus an additional standardized sodium depletion produced by peritoneal dialysis several days before the experiments]) on cardiac baroreflex sensitivity and renal response to an acute saline load. Full sigmoid barocurves were produced by intravenous injection of phenylephrine (2.5 to 20 micrograms/kg) and nitroglycerine (2.5 to 30 micrograms/kg). The gain of this relationship was significantly decreased by both an excess and low sodium intake (8.0 +/- 1.0 and 8.3 +/- 0.8 beats/min/mm Hg, respectively) when compared with the 2.5 and 7.5 (12.1 +/- 1.4 and 16.0 +/- 1.7 beats/min/mm Hg, respectively) mmol Na/kg/day sodium intake. Water and sodium excretion in response to saline infusion were lower in the 0.5 and 14.5 mmol/kg/day sodium intake groups in spite of the higher atrial natriuretic peptide and lower plasma renin activity and plasma aldosterone levels in the latter. Mean arterial blood pressure, heart rate, and central venous pressure increased during saline loading in all groups; hematocrit and plasma protein concentration decreased similarly in all groups. The results suggest that the rapid renal homeostatic response to an acute salt load in animals kept chronically on normal or moderately increased dietary sodium intake is regulated by baroreflex control of the renal homeostatic response. Excess dietary sodium intake attenuates baroreflex sensitivity and delays sodium and water excretion after acute loading.

Animals↗
PubMed1994

Assessment of spontaneous coronary artery dissection by intravascular ultrasound in a patient with unstable angina.

We describe a case of spontaneous coronary artery dissection that gave rise to post infarction unstable angina. An ambiguous angiographic appearance was shown by intracoronary ultrasound to arise from an extensive coronary dissection. The dissection membrane separating true and false lumina and features to suggest sluggish flow and early thrombosis in the false lumen were observed. No increase in lumen calibre was evident on ultrasound after PTCA (probably a consequence of the relatively large ultrasound catheter blank), but coronary flow reserve measured with intracoronary Doppler did improve and the patient remained stable and free of angina following the procedure.

Angina, Unstable↗
PubMed1994

The sociology of entrenchment: a cystic fibrosis test for everyone?

In this article we introduce the notion of entrenchment to conceptualize the processes in which new technological options, through the interactions between a variety of actors, become viable and established practices in society, both satisfying and modifying needs and interests. The notion of entrenchment we use as a framework for an analysis of developments and debates in the field of cystic fibrosis testing and screening in Denmark. On the one hand, it appears that the development and introduction of cystic fibrosis (CF) screening to some extent is predetermined both by existing networks of human genome researchers, clinical geneticists, patients (organizations), funding organizations, and regulatory agencies, and by existing practices like that of prenatal diagnosis. On the other hand, in Denmark, the content and future of CF screening is shaped in ongoing processes or articulation of demand for screening and of its cultural and political acceptability, processes which also involve political decision-making and which (may) result in new networks and regimes. Yet, what appears to be an inherent and undecided part of the process of entrenchment of CF screening in Denmark, is how to allocate responsibilities and authority to decide what is acceptable and what not.

Cystic Fibrosis↗
PubMed1994

Spontaneous plaque rupture visualized by intravascular ultrasound.

An intravascular ultrasound examination was performed in order to evaluate an angiographically complicated lesion. Intravascular ultrasound was able to demonstrate spontaneous plaque rupture in a patient with recent acute subendocardial infarction. The inconclusive angiographic appearance was clarified by the intravascular examination and led us to conclude that the myocardial infarction was due to plaque rupture with subsequent thrombotic occlusion, which had spontaneously resolved by the time of the study.

Aged↗
PubMed1994

Intravascular ultrasound imaging of angiographically normal coronary arteries: a prospective study in vivo.

Intravascular ultrasound imaging (IVUS) was performed to elucidate the discrepancy between clinical history and angiographic findings and to measure the diameter and area of the lumen of the normal left coronary artery in 55 patients who presented with chest pain but had normal coronary angiograms. The left coronary artery (LCA) was scanned with a 4.8F, 20 MHz mechanically rotated ultrasound catheter at 413 sites. Atherosclerotic lesions were identified at 72 (17%) sites in 25 patients. The mean (SD) (range) plaque area was 5.55 (3.56) mm2 (2-26 mm2) and it occupied 28.8 (9.6)% (13-70%) of the coronary cross sectional area. Calcification was detected at 24 (33%) atherosclerotic sites in nine patients. The correlation coefficients for the lumen dimensions measured at normal sites by IVUS and by angiography were r = 0.93 (SEE = 0.43) mm for lumen diameter and r = 0.89 (SEE = 4.27) mm2 for lumen area (both p < 0.001). 16 of the 30 patients in whom no atherosclerotic plaques were detected in the LCA lumen by IVUS had no risk factors of coronary artery disease. The cross sectional area of 90 consecutive images of left main coronary artery (LMCA), proximal left anterior descending coronary artery (proximal LAD), and mid LAD was measured in these 16 subjects. The mean (SEM) areas at end diastole were LMCA 17.33 (7.98) mm2; proximal LAD 13.56 (5.85) mm2; mid LAD 9.75 (4.67) mm2. During the cardiac cycle the cross sectional area changed by 10.2 (4.0)% in the LMCA, by 8.3 (4.7)% in the proximal LAD, and by 9.8 (4.0)% in the mid LAD. In 11 patients with plagues the change in cross sectional area in plague segments (5.8(3.1)%) was significantly lower than in the segments from patients without plagues (p < 0.001). Lumen area reached a maximum in early diastole rather than in late diastole. IVUS can imagine atherosclerotic lesions that are angiographically silent; it also provides detailed information about plague characteristics. The variation in coronary cross sectional area during the cardiac cycle should not be ignored during quantitative analysis. Maximum dimensions in normal segments are reached in early diastole. Further studies are needed to clarify the clinical significance of atherosclerosis detected by IVUS in patients presenting with chest pain but normal coronary angiography.

Adult↗
PubMed1994

Comparison of intravascular ultrasound and angiography in the assessment of myocardial bridging.

BACKGROUND: In autopsy, myocardial bridging is a common finding. With coronary angiography, a systolic compression, mainly of the left anterior descending coronary artery, is observed in 1% to 3% of the patients. Controversy exists concerning the functional importance of this finding. To obtain a functional insight into the myocardial bridging, intravascular ultrasound and intracoronary Doppler were performed. METHODS AND RESULTS: Intracoronary ultrasound and Doppler were performed in 14 patients with angiographic evidence of systolic vessel compression ("milking effect") in the left anterior descending coronary artery. The 4.8F, 20-MHz ultrasound catheter could not be advanced through the entire myocardial bridge segment in 6 of the 14 patients studied because the lumen was < 1.6 mm. In these patients, only the proximal parts of the bridge segment were scanned. The changes in cross-sectional shape during the cardiac cycle were determined for both the normal proximal segment and the bridge segment by use of a semiautomatic computer program. Intracoronary Doppler (20 MHz) was performed in 7 patients with a 3F catheter. A highly characteristic systolic eccentric or concentric compression with delayed relaxation in diastole of the myocardial bridging segment was clearly visualized in all patients. The cross-sectional lumen area variation was 40 +/- 25% in the bridging segments and 9 +/- 7% in the normal segments (P < .01). No atherosclerotic lesions were detected in the bridge or the distal segment in the 8 patients in whom the IVUS catheter was successfully advanced through the entire myocardial bridge. However, atherosclerotic plaques were found in the segments proximal to the bridge in 12 of 14 patients (86%). The resting mean flow velocity was 6.4 +/- 1.2 cm/s; the maximal mean flow velocity after intracoronary administration of 10 mg papaverine was 14.1 +/- 3.4 cm/s. The coronary flow velocity reserve was 2.2 +/- 0.7. A highly characteristic pattern showing a prominent peak in coronary velocity in early diastole was observed in 86% of patients, and this pattern was enhanced after injection of intracoronary papaverine. CONCLUSION: Intravascular ultrasound demonstrated a characteristic systolic compression of the bridge segments. The delayed compression release may explain the characteristic sharp early diastolic peak in coronary flow velocity found with intracoronary Doppler in vessels with myocardial bridging. Reduced coronary flow reserve may be related to this phenomenon, possibly explaining signs of ischemia detected in some of the patients, but may alternatively be a result of the presence of atherosclerosis in the segment proximal to the bridge in these patients.

Blood Flow Velocity↗
PubMed1993

Coronary artery remodeling in atherosclerotic disease: an intravascular ultrasonic study in vivo.

BACKGROUND: Pathologic studies have revealed that coronary arteries undergo compensatory enlargement in the presence of atherosclerosis. METHODS: In order to assess coronary artery remodeling in vivo, we used intravascular ultrasound to examine 46 patients (36 men and 10 women; aged 58.2 +/- 6.8 years) with non-calcified plaques. The vessel, lumen, and plaque areas of the atherosclerotic and of normal proximal and distal segments were determined. RESULTS: A total of 92 atherosclerotic segments were analyzed. The degree of stenosis ranged from 9.2 to 92.8% (mean 34.1 +/- 16.9%) and the plaque area from 2 to 19.6 mm2 (mean 6.3 +/- 3.6 mm2). The vessel area of the atherosclerotic segment (mean 20.4 +/- 7.3 mm2) was larger than that of the proximal segment (mean 18.7 +/- 7.3 mm2, P = 0.018). The vessel area increased in proportion to plaque area. This relationship can be described using the equation y = 23.5(1-e-0.35x). The difference between the vessel area in the atherosclerotic segment and that in the proximal normal segment correlated with the percentage of stenosis (r = 0.53, P < 0.005) until the degree of stenosis exceeded 45%. CONCLUSION: This study indicates that coronary artery remodeling, previously observed in pathologic studies, can be evaluated using intravascular ultrasound in vivo. As a result of the compensatory enlargement of the vessel, coronary angiography cannot be used to detect or exclude the early signs of coronary atherosclerosis.

Adult↗
PubMed1989

The prevalence of unsuspected thyroid pathology in 300 sequential autopsies, with special reference to the incidental carcinoma.

Three-hundred whole thyroid glands were collected at autopsy from patients who had no known clinical history of thyroid disease, and who varied from 13 to 82 years of age; 200 were male and 100 female. Thyroid glands were weighed, measured, and examined after previous formalin fixation. Histologic examination was done in 16 areas from both lobes and isthmus, and divided into three levels, anterior, medial, and posterior. All areas suspected of neoplasia macroscopically were identified and studied microscopically; other areas were collected randomly for microscopic examination in the proportion of one fragment per 5 grams of tissue. In all cases both benign and malignant neoplasias were an incidental finding, seen in 6.6% of the cases and with no relation to the patient's main disease. Overall, there were malignant neoplasias in 2.33% but occult carcinoma comprised 1% of the cases. The incidence of other thyroid pathologies, all of them unrelated to the main disease of the patient, are also reported.

Adolescent↗
PubMed1989

[Distribution of manganese and its modification by magnesium and cobalt in the guinea pig].

Five groups of 8 guinea-pigs each had been treated by manganese, magnesium, cobalt or their combination over a period of 26 days. The concentration of the metals administered had been determined in the liver, pancreas, kidney, adrenal gland, spleen and brain and been compared with the adequate rates of a sample group of 8 animals. Mutual influences could be stated. Statements on the interaction mechanisms could not be derived.

Animals↗