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Biomedical subjects

M Kochs

Publications and source records attributed to M Kochs.

At least 73 records · Page 4Linked to original sources
PubMed1992

Magnetocardiographic non-invasive localization of accessory pathways in the Wolff-Parkinson-White syndrome by a multichannel system.

Electrical activity can be localized by magnetocardiography (MCG) non-invasively. In this study a 37-SQUID (Super Conducting Quantum Interference Device) sensor multi-channel system (KRENIKON) was used to assess the potential of magnetocardiography to localize accessory pathways with a multichannel system. Seven WPW patients were studied by means of magnetocardiography. Prior to the MCG recordings, the site of the accessory pathway had been determined in all patients by invasive catheter mapping. MR images of the heart were used for anatomical correlation. The magnetocardiographic localization of the accessory pathway corresponded with catheter mapping within 2.1 cm on average (total range: 0-5 cm). This is thus, a promising new method for non-invasive localization of accessory pathways in WPW patients.

Adult↗
PubMed1992

Direct current application: easy induction of ventricular fibrillation for the determination of the defibrillation threshold in patients with implantable cardioverter defibrillators.

For the determination of the defibrillation threshold, the induction of ventricular fibrillation is mandatory. However, in severely damaged hearts it is sometimes difficult to induce ventricular fibrillation by rapid stimulation or alternating current. Only rapid nonclinical ventricular tachycardias may result, and their cardioversion threshold may be different from the defibrillation threshold. Therefore, it was the purpose of this study to test the potential of direct current (DC) application to rapidly induce ventricular fibrillation in patients with an implanted cardioverter defibrillator. The defibrillation threshold had to be determined in 13 patients (9 with coronary heart disease, 4 with dilative cardiomyopathy, ejection fraction 35%) during and 2 weeks after the implantation of a cardioverter defibrillator. DC was applied 37 times by a commercially available 9-V DC battery via a bipolar catheter for about 3 seconds. Ventricular fibrillation was induced 23 times (62%) and rapid nonclinical ventricular tachycardias were induced six times (16%). In one patient clinical ventricular tachycardia was observed. In seven instances (19%) sinus rhythm remained. In 12 of the 13 patients, ventricular fibrillation could be induced by DC. Thus, the induction of ventricular fibrillation by DC application may serve as an additional tool to induce ventricular fibrillation, determining the defibrillation threshold in implantable cardioverter defibrillator patients.

Cardiac Catheterization↗
PubMed1992

[Determination of normal values of the aortic blood flow profile using continuous Doppler echocardiography from apical and suprasternal echo position].

The present study was undertaken to measure normal aortic blood velocity profiles by means of continuous wave Doppler echocardiography from apical and suprasternal positions in 40 healthy adults. The profiles in the ascending aorta were measured from both positions, whereas the profiles in the descending aorta were measured only from the suprasternal position. The highest values for the maximal flow velocities were found in the ascending aorta from the suprasternal position (1.28 +/- 0.18 m/s), the lowest values for the maximal flow velocities were found in the descending aorta (1.17 +/- 0.22 m/s). This trend was also found for the mean velocity values. As to the time parameters, a longer acceleration time for the descending aorta was remarkable (106 +/- 24 ms), whereby the mean values for the ejection time for the descending aorta (308 +/- 25 ms, suprasternal: 320 +/- 30 ms). The highest values for the acceleration were found in the ascending aorta (suprasternal: 1526 +/- 531 cm/s2, apical: 1422 +/- 330 cm/s2) and the lowest values in the descending aorta (1208 +/- 378 cm/s2). Regarding the maximal velocity index there was no significant difference for the maximal values between the different transducer positions. The results of the regression analysis showed only a weak correlation of the maximal velocity values in the different transducer positions. This means that for follow-up examinations only those values should be used that were obtained from the same transducer position.

Adult↗
PubMed1992

Short-term reproducibility of gas exchange measurements during bicycle exercise in patients with mild to moderate congestive heart failure.

A series of 45 patients with congestive heart failure due to coronary disease had semisupine bicycle exercise tests (ramp protocol, 10 W/min) on two occasions separated by 3 to 7 days in order to determine the short-term reproducibility of gas exchange measurements during symptom-limited exercise. The percentage difference (PD) between each pair of measurements (m1, m2; PD = 100%.(m2-m1): m1) were calculated. The mean PD values (+/- 1 sigma) and the single determination standard deviations (SDSD) for exercise tolerance (ET, W), peak heart rate (pHR, 1/min), peak oxygen uptake (pVO2, ml/min/kg), peak carbon dioxide output (pVCO2, ml/min/kg), and peak minute ventilation (pVE, l/min) were as follows: [table: see text] No patient reached a plateau of oxygen uptake during the last portion of the ramp exercise test. Thus, pVO2 is not an objective endpoint. The single determination standard deviations show that exercise tolerance and peak oxygen uptake do not differ as to their reproducibility. The absolute values of PD were not a function of exercise tolerance for any of the parameters studied. The PD values for ET and pVO2 were normally distributed. The data suggest that a change in ET and pVO2 must exceed 27% and 28% between two sequential studies in an individual patient in order to be significant at the 5% level, respectively. For the one-tailed test situation, the changes in ET or pVO2 must be greater than 23% in order to be significant.

Adult↗
PubMed1991

Effects of atenolol, slow-release nifedipine, and their combination on respiratory gas exchange and exercise tolerance in stable effort angina.

The effects of atenolol, nifedipine, and their combination on gas exchange and exercise tolerance were studied in 27 patients with effort angina and normal global ventricular function in an open-label and randomized cross-over trial. Symptom-limited semi-supine exercise tests using a ramp protocol (20 W/min) with simultaneous breath-by-breath analysis of gas exchange were carried out after a 4-day wash-out period and after consecutive 2-week treatment periods with atenolol (50 mg b.i.d.), slow-release nifedipine (20 mg b.i.d.), and their combination (b.i.d.). Exercise tolerance was not significantly higher with atenolol than with nifedipine [118(24) vs 113(23) W]. Combination therapy [120(23) W] was more effective than monotherapy with nifedipine (p less than 0.05) but produced no further increase in exercise tolerance over atenolol monotherapy. Maximum oxygen uptake was not significantly different among the treatments. In the range of light to moderate exercise, the slope of the VO2-workload regression line expressed as ml.min-1.W-1 was lower with atenolol than with nifedipine [8.64(1.59) vs 10.28(1.74), p less than 0.005] and intermediate with combination therapy [9.99(1.83)]. The intercept on the VO2 axis was higher with atenolol than with nifedipine [366(111) vs 299(113) ml.min-1, p less than 0.05]. A similar pattern of results was seen when the drug effects on the slope of the VCO2-workload relation were analyzed. VE was higher with nifedipine than with atenolol at all points of the regression analysis [greater than 30 W].(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

Localization of ectopic ventricular depolarization by ISPECT-radionuclide ventriculography and by magnetocardiography. ISPECT and MCG for ectopic mapping.

Since catheter or surgical techniques for ablating the arrhythmogenic substrate in patients with SVT due to accessory pathways or those with VT are now available, exact localization of the substrate is mandatory. We report preliminary results of two new non-invasive techniques for localizing either the site of earliest ventricular contraction using ISPECT, or the site of initial ventricular depolarization by magnetocardiography (MCG) in WPW syndrome and in VT patients. Thirteen patients with WPW syndrome and 8 patients with sustained VTs were studied with ISPECT. In 9/13, comparative catheter mapping data were available. Two patients had two Kent bundles. 13/15 Kent bundles could be localized by ISPECT. In 5/9 patients the area of Kent bundle insertion was identical with ISPECT and catheter mapping, in 3 correlation was fair, and in 2 patients with 2 Kent bundles ISPECT failed to localize their insertion. In 3/8 patients with VT catheter mapping could not be performed for hemodynamic reasons. In 2/5 patients the area of VT focus was identical with both methods, in one patient it was adjacent to each other, and in 2/5 patients a larger anatomic distance of the focus was found with both methods. In 3/7 patients with WPW the MCG showed the site of Kent bundle insertion, which was identical to that seen by catheter mapping. In one patient the area was adjacent, and in 3 more distant from the site determined by catheter mapping. In 1/2 patients with 2 Kent bundles, one of these could be detected by MCG. In 1/3 patients with VT, the site of VT focus was identical with both methods, but in the remaining two a distance of 3-4 cm was observed between the area seen with MCG and that with catheter mapping. In 4 further VT patients with stable and uniform ventricular late potentials, ventricular late magnetic activity was found with different QRS lengths within the single MCG channels. From our results we conclude that both ISPECT and MCG seem to become very promising non-invasive techniques for localizing ectopic ventricular depolarization in WPW syndrome and VT patients. However, these methods have to be refined, improved and validated by further systematical studies.

Action Potentials↗
PubMed1991

Chemical ablation by subendocardial injection of ethanol via catheter--preliminary results in the pig heart.

This study was set up to discover how a subendocardial application of ethanol administered via a catheter would affect an animal model. A 7 F bipolar catheter with a lumen, through which a 2 mm needle was inserted, was placed in the left ventricle of 11 pigs. Altogether, 33 subendocardial injections into the left ventricular myocardium were performed under fluoroscopic control using a mixture of 0.5-1.5 ml ethanol and 0.5-1 ml iopamidol as contrast medium. The mixtures were injected into the apical, lateral and septal walls of the left ventricle. After 25 days, the hearts were removed and the lesions examined pathologically. The calculated volume of the lesions was about 60 mm3, the area in projection to the endocardium about 35 mm2, the depth relative to the endocardium about 1.5 mm and the maximum diameter about 8 mm. Perforation of the myocardial wall by pericardial injection occurred twice without further complications. Subendocardial application of concentrated ethanol by catheter caused a controlled local necrosis. This technique may become a new approach with which to treat ventricular tachycardia by chemical ablation.

Animals↗
PubMed1991

Biomagnetic noninvasive localization of accessory pathways in Wolff-Parkinson-White syndrome.

It was our purpose to assess the clinical relevance of noninvasive magnetocardiographic localization of accessory pathways. Nine patients with Wolff-Parkinson-White (WPW) syndrome were studied. For all of them the site of the accessory pathway was known from invasive catheter mapping. A 37-SQUID (superconducting quantum interference device) sensor multichannel system (KRENIKON) was used, allowing synchronous registration with all channels. The site of the electrophysiological activity at the beginning of the delta wave was determined. Magnetic resonance images of the heart were obtained to correlate the biomagnetically localized activity with the anatomy. Magnetocardiographic localization of the bypass tract corresponded with catheter mapping with a spatial difference of 0-5 cm, 1.8 cm on the average, compared to the results obtained by catheter mapping. Thus, magnetocardiography is a promising new method for noninvasive localization of accessory pathways in WPW patients. This may streamline further invasive procedures.

Adult↗
PubMed1991

[In vitro balloon treatment of coronary plaque material of the human: effect of dilation time on proliferation of smooth muscle cells].

The proliferation of smooth muscle cells (SMC) seems to be an important factor in the development of restenosing events after angioplasty. Primary stenosing plaque material was obtained from human coronary arteries by thrombendarterectomy. Specimens were cut in small pieces and dilated in a flexible tube with a balloon-catheter (Medtronic 18K2030E) for 1 min., 5 min. and 10 min. at 3 atm. For the isolation of plaque cells the expant technique was used. The majority of plaque cells was identified as smooth muscle cells by positive reaction with monoclonal antibodies against smooth muscle alpha-actin. For the cultivation of SMC a mixture of Waymouth's MB 752/1 and Ham F-12 (1:1) was used. After 8 weeks cell number was analysed by a cell counter (Casy I, Schärfe System). There was a clear increase of SMC-proliferation in dependence to the duration of angioplasty (1 min. = 100%, 5 min. = 112%, 10 min. = 153%). If these data are confirmed by clinical and experimental studies, the duration of angioplasty has to be considered as a risc factor for the development of restenosis.

Angioplasty, Balloon, Coronary↗
PubMed1991

[Cell culture as a prescreening system for drug prevention of restenosis?].

Migration and proliferation of smooth muscle cells (SMC) from the media into the subendothelial space are important steps in the development of restenosing events after angioplasty; therefore a medical inhibition of this activity seems to be of clinical interest. Primary stenosing plaque material of 20 patients and restenosing plaque material of 6 patients was removed by atherectomy (Prof. Höfling, Dr. Bauriedel, Munich). For the isolation of plaque cells a mixture of Collagenase/Elastase was used. The vast majority of plaque cells was identified as smooth muscle cells by positive reaction with monoclonal antibodies against smooth muscle alpha-Actin. Propranolol (10(-4) mol/l to 10(-9) mol/l), Prednisolone (10(-3) mol/l to 10(-8) mol/l) and Etoposide (10(-4) mol/l to 10(-9) mol/l) were added to the cultures one day after seeding. After 3 days cell number and cell size distribution were analysed in a cell counter (Casy I, Schärfe System, Reutlingen). While Propranolol didn't change proliferative activity of SMC, Prednisolone caused a slight, but dose dependent inhibition of SMC-proliferation. Etoposid inhibited SMC-proliferation even below clinical concentrations to 50%. The local application of steroid or cytostatic agents might improve long term results after angioplasty. The clinical relevance of this 'Prescreening System' has to be evaluated by experimental and clinical studies.

Angioplasty, Balloon↗
PubMed1990

Hemodynamic profile of carvedilol.

Several so-called multiple-action compounds have been developed, such as medroxalol (alpha and beta blockade, and beta-2 stimulation), celiprolol (alpha-2 and beta-1 blockade, and beta-2 stimulation) and carvedilol (beta blockade and vasodilatation) for the treatment of patients with arterial hypertension and with coronary heart disease. Carvedilol exerts relatively uniform peripheral effects, i.e. a reduction of both systolic and diastolic blood pressure at rest and during exercise, and a decrease in the resting and exercise heart rate. Blood pressure fall due to carvedilol may be induced by its vasodilating effect, as documented by measurements of forearm blood flow and peripheral vascular resistance. Moreover, renal hemodynamics does not seem to be significantly altered by carvedilol. Carvedilol may also produce an improvement of the LV contractile status in patients with CHD and impaired LV function, mainly due to afterload reduction, in addition to its antianginal effect, which is due mainly to the beta-blocking properties of this substance. From the studies mentioned it may be concluded that carvedilol is a useful and promising drug for treating patients with both arterial hypertension and with coronary artery disease.

Adrenergic beta-Antagonists↗