Biomedical subjects

M Höher

Publications and source records attributed to M Höher.

64 records · Page 4Linked to original sources

PubMed1988

The clinical significance of coronary angioscopy in patients with coronary heart disease.

The feasibility and safety of coronary endoscopy was evaluated in three sets of investigations: in 7 cadaver hearts, in 11 patients undergoing coronary bypass surgery, and in 30 patients during routine cardiac catheterization prior to coronary balloon angioplasty (PTCA). In three of the seven cadaver hearts the lumen of the arteries appeared normal. In three diffuse atherosclerotic lesions, and in one, a high-grade, tight stenosis were observed. In nine of eleven patients in the operation room, the lesions of interest could be visualized, and high-grade stenoses were found in all. In addition, in three patients with unstable angina pectoris, fresh thrombi were seen at the site of stenosis. In six of the nine patients, the periphery of the native coronary vessel was found to have no further stenotic regions. During cardiac catheterization in 17/30 patients, the lesion of interest could be examined angioscopically, and in 13 instances the stenosis appeared excentric and irregularly shaped. In three instances, multiple ulcerations were seen in the stenotic area. In two of the five patients, intimal ruptures were found following PTCA, which could not be documented angiographically. Coronary endoscopy provides valuable additional information on the nature and appearance of atherosclerotic lesions. It can be performed clinically without great harm to the patients. Despite some limitations, it will probably become a routine diagnostic tool in patients undergoing routine coronary angiography, balloon angioplasty or high-frequency angioplasty, and coronary bypass grafting.

Angioplasty, Balloon↗

PubMed1988

Coronary angioscopy during cardiac catheterization and cardiac surgery.

Coronary angioscopy (CA) was performed in 30 patients (pts) during cardiac catheterization (Group 1) and in 11 pts during coronary bypass surgery (Group 2) using ultrathin fiberoptic angioscopes (phi 1.2-1.8 mm). For percutaneous CA (Group 1) the angioscope was introduced through a 9F guiding catheter from the femoral artery. The viewing field was cleared by flushing Ringer's solution and short-time occlusion of the coronary ostium by the guiding catheter. In Group 2 CA was performed retrogradely from the distal arteriotomy and through the bypass vein during flushing with cardioplegic solution. In Group 1 in 17/30 pts the coronary artery could be successfully examined by CA. In 13 pts the obstruction was eccentric and irregular shaped. In 2/5 pts, in whom CA was performed successfully pre and post balloon dilatation, CA after PTCA revealed an intimal rupture without clinical or angiographical signs of the intimal dissection. In Group 2 in 9/11 pts good visualization of stenoses could be achieved. At the obstruction site CA revealed thrombi in 3 pts and ulcer in 1 pts. In contrast to angiography, which estimates the lumen diameter of a segmental lesion, CA gives information about the luminal shape and the underlying substance of the obstruction (e.g. atheroma, thrombus, ulceration). The main problems in percutaneous CA are the insufficient intraluminal guidance, the insufficient depth of view of the angioscopes, and the limited examination time.

Cardiac Catheterization↗

PubMed1988

Pathophysiology of unstable angina pectoris--correlations with coronary angioscopic imaging.

Different patho-anatomical and functional factors are considered to be involved in patients with unstable angina pectoris. Among these are a pre-existing plaque based on coronary atherosclerosis, the development of fissures or dissections of the plaque (often combined with thrombus formation at the site of the plaque) coronary vascular tone, and theoretically primary aggregation of platelets at a site of apparently normal vascular endothelium. Several comprehensive studies on patients who died from acute myocardial infarction or unstable angina, have convincingly shown that complications of an atherosclerotic plaque like fissures, dissections and thrombus formation may be present in 60 to 90% of cases. In addition, two groups of investigators, who have applied coronary angioscopy for direct visualization of offending coronary arteries, have confirmed these results, since in about 60-80% of patients with unstable angina complicated atheromata, i.e. rupture, ulceration, thrombus formation, could be documented, whereas in all patients with stable angina an uncomplicated atheroma was seen angioscopically. On the basis of these results a hypothetical sequence of events in patients with stable angina, unstable angina and acute myocardial infarction has been proposed. Stable angina pectoris may be seen in patients with uncomplicated atheroma in one of the major coronary artery branches. When dissections, ulcerations and thrombus formation occur as a complication of a formerly smooth plaque, patients show the clinical syndrome of unstable angina. If an occlusive thrombus develops, the patient will run into a fresh myocardial infarction.(ABSTRACT TRUNCATED AT 250 WORDS)

Angina Pectoris↗

PubMed1988

ST segment changes in healthy volunteers during Holter monitoring and exercise stress test.

The analysis of ST segment changes during Holter monitoring is one important diagnostic method for detection and diagnosis of silent myocardial ischaemia. To assess the specificity and sensitivity of ST segment alterations as a diagnostic tool, 106 healthy medical students (43 females, 57 males, aged 18-36 years, mean age 26 +/- 4 years) and 26 children (14 females, 12 males, aged 12-17 years, mean 14 +/- 3 years) with no history of heart disease and normal findings during physical examination were studied by exercise stress test and Holter monitoring. Criteria for exclusion were a history of hypertension, diabetes mellitus and ST segment alterations during conventional 12-lead ECG. Due to these criteria, eight volunteers had to be excluded from the study. The exercise stress test (maximum work load protocol) revealed no pathological ST segment depressions. During Holter monitoring seven episodes of ST segment depressions (greater than or equal to 1.0 mm planar or downsloping, duration greater than or equal to 1.0 min) were found. Typical ST segment depressions detected by Holter monitoring may be found in healthy subjects. Therefore this finding has to be considered cautiously as a diagnostic tool for evaluation of patients with suspected coronary heart disease.

Adolescent↗

PubMed1988

[Methods for the detection of ventricular late potentials. High amplification ECG, signal averaging technic, frequency analysis and intracardiac mapping].

Circumscribed areas of injured myocardium which lead to late ventricular depolarization represent the pathologic-anatomic substrate for reentry mechanisms potentially capable of propagating ventricular tachycardia at the ventricular level. If the myocardial area from which delayed ventricular depolarization and, consequently, late potentials eminate, exceeds a critical minimal size, documentation of such signals can not only be achieved with direct endocardial mapping or catheter mapping but also by means of special high-resolution ECG techniques from the body surface. Since high amplification of the conventional ECG results in registration of noise signals in amplitude of up to 50 microV, late potentials with their amplitudes at the body surface ranging from 5 to a maximum of 20 microV, can only be discriminated after substantial enhancement of the signal-to-noise ratio. The noise arises from no less than three sources: physiologic noise, for example, from muscle activity; electronic noise from amplifiers and background noise of 50 or 60 Hz, respectively. To improve the signal-to-noise ratio, currently three methods are employed: sequential or temporal signal averaging, spatial signal averaging and fast Fourier transformation analysis of the frequency spectrum of the highly-amplified ECG. Temporal signal averaging has the purpose of smoothing randomly-occurring background noise and, at a specified point in time of the ECG cycle, to sum the signal incurred. The effectivity of this technique, however, is subject to certain conditions: the signal to be registered and the background noise must be independent from each other, the noise must be stationary and show normal random distribution, the signal of interest must be periodic and/or coupled with a fixed interval to a point in the ECG cycle which can be used as a trigger. The quality of the averaged signal is dependent on trigger stability. There are three approaches to trigger processing: voltage threshold determination, slope detection and the pattern matching technique, the accuracy, reliability and time-consumption of which increases in the order listed. A trigger stability of +/- 0.5 ms is necessary to detect ventricular late potentials with sufficient sensitivity and without meaningful deformation or attenuation of their form and temporal extent. Intercurrently, a number of commercially-acquirable signal averaging computers have been made available which differ with respect to registration and analysis.(ABSTRACT TRUNCATED AT 400 WORDS)

Atrioventricular Node↗

PubMed1988

[Diagnostic significance of angioscopy in patients with coronary heart disease].

Coronary angioscopy (CA) using ultrathin fiberscopes was performed in 30 patients with coronary heart disease during cardiac catheterization and in 11 patients during bypass surgery. For percutaneous CA the angioscope was introduced from the femoral artery through a 9F guiding catheter. During short-time occlusion of the coronary ostium by the tip of the guiding catheter the viewing field was flushed with Ringer's solution. Intraoperative CA was performed both by the retrograde and antegrade way during flushing with cardioplegic solution. Percutaneous CA was successful in 57% of patients. 13 patients showed eccentrically and irregularly shaped stenoses and 3 of these patients had an additional plaque rupture. In 2/5 patients CA after PTCA revealed intimal dissections not visualized by angiography. Intraoperative CA was successful in 9/11 patients. In 3 patients nonocclusive thrombi were found at the site of the coronary lesion. Additionally we studied the efficacy of angioscopic guidance during intravascular radiofrequency application. In 11/11 thrombotically occluded peripheral vessels this new method allowed a nearly complete recanalization. There was only one perforation of the vessel. We conclude, that CA is a powerful diagnostic tool providing prognostically relevant information in the diagnosis of coronary heart disease.

Animals↗

PubMed1987

Sequential or single pulse defibrillation? Investigations towards energy reduction in experimental animals.

With introduction of the automatic implantable cardioverter-defibrillator for treatment of medically refractory ventricular arrhythmias, many investigations are focussing on possibilities of reducing the energy necessary for defibrillating the heart to obtain a more adequate size and a longer durability of the generator. Several studies favour the sequential pulse delivery, using three electrodes, either endocardial, epicardial or subcutaneous plates, to improve defibrillation performance of low energy shocks. However, the validity of this conclusion remains equivocal since two different electrode configurations were used for single and sequential defibrillation. In the present study the influence of sequential pulse delivery, pulse sequence and resultant current pathways on defibrillation energy requirements were examined in comparison with single-shocks between the same epicardial electrode configuration as well as four orthogonally positioned patches. The energy requirement for 100% efficiency could be reduced by sequential pulsing with a time interval of 1 msec thus yielding significant superiority compared to single pulse defibrillation using three electrodes. The same reliable defibrillation and reduced threshold has been obtained by using four electrodes and one single shock. The addition of a third electrode alone had no influence on the energy requirements. Therefore, we have to discuss a different electrophysiological mechanism for sequential defibrillation than for single shocks with an extended current distribution over the heart using four electrodes. Possibly the action potential of the single cell of the fibrillating heart is of interest in reflecting the efficiency of sequential pulse defibrillation. By influencing the action potential pharmacologically in some animals, the optimal time interval for double shocks could be extended up to 7 msec.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1986

[First clinical experience with coronary endoscopy].

In four different groups coronary endoscopy and endoscopy of peripheral vessels was carried out, using two ultrathin fibre endoscopes with a working length of 120 cm and a diameter of 1.4 or 1.8 mm. In a first series of seven cadaver hearts, normal vessels were found in three, one had high-grade stenosis and in the remaining three there were flat whitish atheromatous changes, rather scar-like in appearance. In a second series of 16 patients, the vascular wall in the iliac region was easily visualised in ten, while six showed diffuse atherosclerotic changes of the wall. In a third group of eight patients, coronary endoscopy was carried out at the time of balloon-catheter dilatation; endoscopy was successful in five patients. In two of them, the stenosis or occlusion to be dilated by balloon was visualised. In a fourth series, good visualisation of the vessels was obtained intraoperatively in seven out of nine patients, and in addition the course of the vessel distal to the stenosis as well as the site of anastomosis with the venous bypass graft could be seen. No serious side-effects of the procedure have yet been observed. Coronary endoscopy opens up a new dimension in the morphological assessment of coronary vascular changes. The method must, however, still be regarded as experimental.

Angioplasty, Balloon↗

PubMed1983

[Colloid osmotic pressure--a parameter of postoperative protein therapy. A pilot study].

120 intensive-care patients were examined postoperatively in a pilot study. The patients were divided into two groups. In group 1 human albumin was given when the serum protein concentration decreased below 5 g%, in group 2 when the colloid osmotic pressure (COP) decreased below 27 cmH2O. Patients of group 2 received less human albumin, but despite the lower human albumin supply these patients did not worse postoperatively as compared to group 1. On the contrary, the trend could be observed that the periods of ventilation were shorter (possibly due to the lower volume load of the patients) and the serum creatinine concentrations were lower (possibly due to the increased supply of crystalloid solutions) if smaller amounts of albumin were given. It may be concluded that the postoperative human albumin supply is unnecessary if the COP ranges 27 cmH2O or more.

Adult↗

PubMedDate not supplied

High-dose diltiazem prevents migration and proliferation of vascular smooth muscle cells in various in-vitro models of human coronary restenosis.

BACKGROUND: Restenosis after coronary angioplasty is considered to be caused mainly by increased migration and proliferation of smooth muscle cells (SMC). The concept of local, site-specific delivery of pharmacologic therapies has opened the door for new, high-dose drug regimes. METHODS AND RESULTS: SMC were isolated by enzymatic disaggregation with collagenase/elastase from human coronary plaque tissue of 29 patients (pSMC) and post mortem from the coronary media of 33 corpses (mSMC). Endothelial cells were isolated from human umbilical veins by enzymatic disaggregation with collagenase/dispase. By positive reaction with antibodies against smooth muscle alpha-actin and von Willebrand factor cells were identified as SMC or endothelial cells. In proliferation studies 5-150 micrograms/ml diltiazem was added to the culture media of pSMC, mSMC and endothelial cells. After 5 days there was a significant dose-dependent inhibition of cell proliferation (for pSMC with > 50 micrograms/ml, for mSMC with > 25 micrograms/ml, and for endothelial cells with > 5 micrograms/ml). In migration studies the effect of 5-150 micrograms/ml diltiazem on the velocity of migration of pSMC was investigated over a period of 48 h. Administration of diltiazem at concentrations of 100 and 150 micrograms/ml caused a significant inhibition of the migration of pSMC. The cytoskeletal components smooth muscle alpha-actin, vimentin, and alpha-tubulin of pSMC and the expression of von Willebrand factor of endothelial cells were investigated after an incubation period of 5 days with 50 and 150 micrograms/ml diltiazem. In the transfilter coculture model the effect of 50 micrograms/ml diltiazem on mSMC was investigated after mechanical injury of cocultured endothelial cells. Administration of diltiazem at a concentration of 50 micrograms/ml inhibited the development of a neointimal proliferate in the transfilter coculture model significantly (P < 0.001). CONCLUSIONS: A high dose of diltiazem inhibited the migratory and proliferative activities of coronary SMC significantly. In further experimental studies the effect of locally applied high doses of diltiazem on postangioplasty restenosis should be elucidated.

Actins↗