Biomedical subjects

P Osypka

Publications and source records attributed to P Osypka.

At least 19 recordsLinked to original sources

PubMed1997

Preliminary results achieved by a computer-assisted system for controlled balloon dilatation of coronary and peripheral arteries.

In percutaneous balloon angioplasty the extent of trauma to the vessel as determined by slope of balloon inflation, peak pressure, and inflation time is crucial to the success of the intervention. These parameters are still not standardized and hence open to the operator. To elucidate this problem, a computer-assisted PTCA system (CAPS) was developed. CAPS is composed of a motor driven unit, a central processing and power unit, and a notebook. A syringe is clamped onto the motor unit and connected to a pressure gauge. CAPS may be linked to all types of balloon catheters. The notebook allows for preselection of peak pressure, slope of pressure increase, and inflation time. During balloon inflation, adjustments are made in a closed-loop system. On a screen, the inflation process is supervised in digital numbers and analogous curves. After the procedure, patient data and inflation curves may be recalled for analysis. In conclusion, CAPS by controlled inflation theoretically may reduce the mechanical trauma to the arteries. Further refinements should aim at gaining information on the lesions' characteristics and on the dilatation process itself.

Angioplasty, Balloon, Coronary↗

PubMed1997

Interventional atrioseptostomy by application of monopolar high-frequency alternating current. In vitro evaluation of a new device.

RATIONALE AND OBJECTIVES: The authors evaluate the use of a new device for interventional creation of atrial septal defects (ASD) working with high-frequency alternating current in an in vitro study with porcine atria. METHODS: The device consists of a symmetrical cage of six superelastic monofile wires, including a microthermistor that is placed via a catheter into a punctured hole in the porcine foramen ovale. The device is used as a differential electrode for monopolar, temperature-controlled application of high-frequency alternating current for thermal modelling of ASD. RESULTS: Application of current for 60 seconds caused temperature-dependent, sized ASDs. CONCLUSION: In vivo animal studies to evaluate possible side effects and long term patency of the ASDs are justified and warranted.

Animals↗

PubMed1996

-Occlusion of atrial septal defect with a new occlusive device-.

An atrial septum defect was closed with an ASDOS (Babic) occluder in 13 patients aged from 22 to 67 years. The diameters of the ASD ranged from 12 to 36 mm, the left to right shunt from 35% to 70%. With one exception, the occluder could be implanted in all patients. Two patients with an oversized ASD (diameter 31 and 36 mm respectively) had to be operated after 8 h and 2 weeks, respectively. In one patient, a small asymptomatic hemopericardium was detected after 24 h by routine echocardiogram and in another patient a single umbrella arm fracture was noticed by routine x-ray 4 months after the implantation. No further complications occurred. Follow-up is now 3 months to 1 year. With one exception, there was no residual shunt as measured by oximetry.

Adult↗

PubMed1989

Radiofrequency ablation of ventricular myocardium using active fixation and passive contact catheter delivery systems.

This study examined the qualitative and quantitative effects of radiofrequency energy using active fixation and passive contact catheter delivery systems on normal bovine atrium and ventricle and diseased human ventricle in vitro. Two active fixation (custom screw-in or suction electrode) catheters and two passive contact (custom ring or standard electrode) catheters were used with a 500 kHz radiofrequency current generator. Linear regression analysis between lesion dimensions and power output showed excellent correlation coefficients for all catheter delivery systems except the suction catheter. Lesion sizes also increased with duration of radiofrequency energy delivery at low power using the USCI quadripolar catheter. Lesion size in diseased human ventricle was considerably smaller than in the normal ventricle. Comparison of induced lesion dimensions using pulsed and continuous delivery modes showed only minor differences. Tissue impedance was relatively constant during energy delivery. Arcing was associated with a sudden increase in voltage and impedance and a sudden decline in current. This was most frequently observed at high power and with the suction electrode catheter. The use of high (50 W) power output and prolonged application (up to 180 seconds) in atrium and ventricle did not induce perforation. We conclude that a variety of catheter delivery systems can be used for effective radiofrequency energy delivery and ablation in atrial and ventricular myocardium in the pulsed or continuous mode. Impedance changes during radiofrequency ablation cannot be used to guide the extent of ablation but do detect arcing during the procedure.

Animals↗

PubMed1988

[High-frequency angioplasty in coronary disease. Initial clinical experiences].

After extensive animal experiments a new method of high-frequency current coronary angioplasty (HFCA) via a specially developed catheter system was used in ten patients with haemodynamically significant coronary artery stenoses. In eight patients the stenoses affected the anterior interventricular branch (AIVB), in one patient each the circumflex branch and the right coronary artery, respectively. In nine patients the stenosis cross-section was reduced by at least 20% (from a mean of 91.9% +/- 5.8% to 52.6 +/- 17.5%). In three patients HFCA was followed by balloon angioplasty. The total number of applications per patient ranged from 3 to 12 (mean total duration of current flow: 3.9 +/- 1.0 s). There was only one severe complication, in a patient with subtotal AIVB occlusion after initially successful HFCA: balloon angioplasty successfully restored the lumen to the post-HFCA state. The new technique of HFCA is worthy of further development. It promises to be a valuable addition or alternative to balloon coronary angioplasty.

Adult↗

PubMed1975

[Safety problems during the use of electromedical apparatus in man].

The stimulating action of an electric current on the human body is determined by the strength of the current, the direction, frequence and duration of action of the current. Measurements of sensation have shown that even with strengths of currents of about 15 to 20 mA (50 Hz), a complete cramp of the arm musculature occurs, whereby a voluntary relaxation of the part under tension is no longer possible. The inner resistance of the human body (without skin resistance) is between 650 and 1300 Ohm, according to the direction of the current. Electric field strengths on the heart have shown that disturbances of heart action always occur when the electric field produced by an outer circle of current round the heart is in the order of 80 mV/cm. This means that currents passed through the heart of even 80 muA can produce lethal ventricular fibrillation. On the basis of practical examples from clinical cases, the danger of micro shocks is shown. The question of a security check list is discussed.

Animals↗

PubMed1974