PubMed Health⌕ Search

Biomedical subjects

B Fiser

Publications and source records attributed to B Fiser.

At least 37 records · Page 2Linked to original sources
PubMed1992

Noninvasive determination of baroreflex sensitivity in man by means of spectral analysis.

The spectral analysis technique was applied for noninvasive assessment of heart-rate baroreflex sensitivity (BRS). The coherence between fluctuation of blood pressure and heart rate at 0.1 Hz and at respiratory frequency is high. This fact enables the assessment of BRS by means of calculating the modulus (or gain) of the transfer function between variations in blood pressure and heart rate. The noninvasive continuous blood pressure registration according to Penáz was used. During voluntarily controlled breathing intervals, the amplitude of 0.1 Hz and respiratory peaks in the spectra of heart rate and blood pressure changed markedly. Nevertheless, the average sensitivity of the baroreflex (modulus) changed insignificantly. This result indicated that the stability of BRS can be advantageous for the use of BRS in clinical practice. The difference between the modulus at 0.1 Hz and at the breathing rate indicates that baroreflex is only one of the factors causing respiratory arrhythmia. We also compared the determination of BRS by spectral analysis with the following alternative method: both lower extremities were occluded for 5 minutes. The release of pressure in the occluding cuffs decreased blood pressure which was followed by a baroreceptor-mediated increase of heart rate. Both methods correlated, but more detailed analysis revealed the role of the low pressure receptors in BRS determined by spectral analysis.

Blood Pressure↗
PubMed1990

Individual features of circulatory power spectra in man.

Rhythms of resting fluctuations of circulatory parameters in man reveal a considerable interindividual variability. We posed the question whether these rhythms are long-term individual characteristics. In nine healthy subjects aged 19-23 years the blood pressure and the finger blood flow were recorded by indirect continuous methods, together with cardiac intervals and respiratory movements. These recordings were repeated in each subject after 1 year. The power spectra of all the parameters recorded were calculated for 5-min periods. The shape of spectra and the division of power into four ranges of frequencies were compared to the spectra recorded after 1 year in each subject and the degree of similarity was evaluated by means of correlation analysis. The average measures of similarity (correlation coefficients) were high, cardiac intervals 0.527, systolic pressure 0.782, pulse pressure 0.755, diastolic pressure 0.709, mean blood pressure 0.673, blood flow 0.818 and respiration 0.627. All these values were higher than values obtained by comparison of spectra of two individuals chosen randomly. The differences were statistically significant for cardiac intervals (Wilcoxon test: P less than 0.05), pulse pressure (P less than 0.05) and respiration (P less than 0.01). These results have shown that interindividual variability of circulatory and respiratory spectra was greater than the intraindividual one. The resting circulatory rhythms are very stable individual features.

Adult↗
PubMed1989

[Echocardiographic diagnosis of total anomalous pulmonary venous return].

Based on experience with the examination of 33 children with total anomalous pulmonary venous return (TAPVD), the authors submit on account of basic echocardiographic (ECHO) findings and the examination procedure in TAPVD. The findings of two-dimensional ECHO reveal a typical enlargement of the right atrium and ventricle; in the four-chamber projection the pulmonary veins do not enter the left atrium but they join behind the left atrium. The site of the orifice of TAPVD in supracardial TAPVDS is found from a suprasternal approach, in intracardial TAPVD in the four-chamber projection, in infradiaphragmatic TAPVD from a subcostal approach. Doppler echocardiography reveals an impaired venous flow in the confluent on the pulmonary veins and in structures into which the pulmonary veins lead. ECHO makes it possible to assess the diagnosis of TAPVD by a non-invasive approach, to find the site of the orifice and indicate operation without the use of invasive examination methods.

Echocardiography↗
PubMed1985

Effect of a low sodium medium, ouabain and noradrenaline on relaxation of the myocardium of the perfused rabbit heart.

Random stimulation of the perfused heart allows relationships between the rate of contractions (dP/dtmax), the size of contraction (Pmax) and the rate of relaxation (dP/dtmin) of contractions of varying intensity to be studied. The present study concerns these relationships during perfusion with ouabain, a low sodium medium and noradrenaline. Isolated rabbit hearts were perfused with Tyrode solution (O2 95%, CO2 5%, 36.4 degrees C), the isovolumic contractions of the left ventricle were recorded and the right ventricle was stimulated at random for 30 s (pulse width 10 ms, voltage double the threshold value). Perfusion was then switched over to perfusion with ouabain solution (10(-6) mol.l-1), with noradrenaline solution (10(-6) mol.l-1) or with low sodium solution (with 31% of the normal Na concentration). When spontaneous contraction size had attained a stable level, random stimulation was repeated. During random stimulation, dP/dtmin was directly proportional to Pmax (dP/dtmin = k1.P max) and to dP/dtmax (dP/dtmin = k2.dP/dtmax). Ouabain and low sodium did not change k1 or k2 and noradrenaline did not change k2. The increase in k1 during noradrenaline perfusion corresponds to shorter duration of contraction. It was found that dP/dtmax, which corresponds to the sarcoplasmic calcium concentration at the outset of activation, was the main factor determining the relaxation rate during ouabain, noradrenaline and low sodium perfusion.

Animals↗
PubMed1985

Results of total repair of tetralogy of Fallot after previous subclaviopulmonary or aortopulmonary anastomosis.

Total repair of tetralogy of Fallot was performed in 69 patients after the primary construction of a Blalock (28 patients) or a Waterston (41 patients) anastomosis. A total of 7 patients (10.1%) died. One to 5 yrs after correction, 62 patients (89.9%) survive: 52 (75.4%) are in a very good condition, 7 (10.1%) are in a good condition and the condition of 3 (4.4%) is unsatisfactory. 8 (11.6%) patients have serious late complications. The result of correction is not much influenced by the previous Blalock anastomosis (mortality rate 6.9%). After the Waterston anastomosis, however, there are frequent serious complications (pulmonary hypertension in 25.0% of patients), which adversely affect the result and increase mortality (12.5%) of the subsequent correction. The authors prefer two-stage repair of tetralogy of Fallot in the first two years of life. By administration of beta-blockers and prostaglandins they endeavour to postpone the construction of a Blalock anastomosis or an anastomosis performed by means of a polytetrafluoroethylene vascular prosthesis up to the age when the pulmonary artery branches are at least 4 mm in diameter. They plan the subsequent correction to be performed between the 2nd and the 5th year of age.

Aorta, Thoracic↗
PubMed1984

Results of radical surgical correction of ventricular septal defect.

This study evaluates results of radical correction of simple and complex ventricular septal defect in 85 children. 35 children were under 3 years of age. Two babies operated at the age of 6 and 8 months in a critical condition died after surgery. Total operation mortality was 2.3%. In 51 patients examined one year and more after surgery, the long-term results are in 90% of the cases excellent and in 10% favourable. In none of the patients did the authors find an unfavourable result of the operation. The authors regard radical surgical correction of ventricular septal defect as a method of choice regardless of the patient's age and weight.

Adolescent↗