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Biomedical subjects

T Katila

Publications and source records attributed to T Katila.

At least 19 recordsLinked to original sources
PubMed1992

Localization of accessory pathways in Wolff-Parkinson-White syndrome by high-resolution magnetocardiographic mapping.

Fifteen patients with Wolff-Parkinson-White syndrome were studied with standard 12-lead electrocardiogram, invasive electrophysiologic study, and high-resolution magnetocardiographic (MCG) mapping. In addition, intraoperative epicardial mapping was performed in seven surgically treated patients. The MCG characteristics of ventricular preexcitation for different locations of the atrioventricular accessory pathways were described in terms of morphology and field patterns. Three mathematical source models in semi-infinite conducting space were used for localization computations: the current dipole model, the truncated current multipole model and the magnetic dipole model. Finally, the localization results of MCG and invasive mappings and electrocardiograms were compared. The mean three-dimensional distance between the localization results obtained from MCG maps and electrophysiologic study was 3.9 cm for the magnetic dipole model, 4.8 cm for the truncated current multipole model, and 7.3 cm for the current dipole model. The corresponding distances in the seven intraoperatively mapped cases were 2.3 cm for the magnetic dipole model, 5.2 cm for the truncated current multipole model, and 6.3 cm for the current dipole model. In conclusion, noninvasive MCG mapping may significantly contribute to the invasive catheter mapping for optimal preoperative localization of preexcitation site and atrioventricular accessory pathways in Wolff-Parkinson-White syndrome.

Adult↗
PubMed1992

The effects of thrombolytic therapy on the high-resolution electrocardiogram after myocardial infarction.

The effects of thrombolytic treatment was studied in 109 consecutive patients 9-11 days after their first acute myocardial infarction by high-resolution electrocardiography (ECG), 24 h Holter monitoring, exercise test and radionuclide ventriculography. Thirty-seven patients were treated with intravenous thrombolytic agents. Thrombolytic treatment was assessed by clinical criteria to be successful in 22 patients and probably successful in 12 patients. Thrombolysis failed in three patients and 72 patients did not receive thrombolytic treatment (control group). Measurements made on the high-resolution and filtered (60 Hz high-pass) vectormagnitude complex included the total duration, the duration of the potential less than 40 microV, the root mean square (RMS) voltage in 10 ms intervals over the first 50 ms and RMS voltage of the last 40, 50 and 60 ms. The filtered QRS duration was significantly shorter in reperfused patients compared with the control group (83 +/- 10 vs 89 +/- 12 ms; P = 0.017). In inferior infarcts (n = 57) the filtered QRS duration was 83 +/- 11 ms in reperfused and 89 +/- 10 ms in non-reperfused patients (P = 0.044), but in anterior infarcts (n = 52) there was no difference. The RMS voltage of the initial 50 ms of the QRS was higher in the reperfused than in non-reperfused anteroseptal infarcts (38 +/- 14 v 23 +/- 10 microV; P = 0.022). Patients successfully treated with thrombolytic agents within the first 2 h had higher RMS voltage of the terminal 40 ms of the QRS than patients treated within 2-4 h (38 +/- 17 vs 27 +/- 17 microV; P = 0.03).(ABSTRACT TRUNCATED AT 250 WORDS)

Electrocardiography, Ambulatory↗
PubMed1991

Mathematical modelling for biomagnetic localization.

Non-invasive biomagnetic measurements are feasible for obtaining functional information concerning the electrical activity of the human heart and brain. These methods have turned out to be promising in localizing various bioelectric sources in the body. For example, in magnetocardiographic studies of localizing arrhythmogenic tissue and both normal and abnormal conduction pathways between the atrial and the ventricles, the best accuracies reported are comparable to the results obtained by the invasive methods. We consider here basic principles of biomagnetic source localization methods, focusing on the magnetocardiographic mapping.

Action Potentials↗
PubMed1991

Magnetocardiographic localisation and modelling.

In our magnetocardiographic (MCG) localisation studies, two modelling approaches have been applied: (a) modelling the sources with dipole and quadrupole moments in a general multipole expansion and using a homogeneous, semi-infinite volume conductor, and (b) using a single current dipole source in a homogeneous, realistically shaped torso. Both approaches have been successfully applied in localising the premature ventricular excitation site in patients suffering from the Wolff-Parkinson-White syndrome. In addition, we have participated in developing a model of propagation of electrical activation in the ventricles. Anisotropic conductivity properties and spiral arrangement of myocardial fibres are included in the model.

Heart Function Tests↗
PubMed1991

Magnetocardiographic functional localization using current multipole models.

High-resolution magnetocardiographic mapping was applied to localize the ventricular preexcitation site in ten patients suffering form Wolff-Parkinson-White syndrome. Three different source models were tested, consisting of the dipole and quadrupole moments in a general multipole expansion. Noninvasive localizations were performed by computations based on measured magnetic maps without a priori assumptions of the source location and without imposing any constraints. In all cases, the computed results were compared with invasive localization results obtained by catheter mapping technique. Preoperative catheterization localizes the atrial end of the accessory pathway, while our method localizes the ventricular preexcitation site. Of the models used, the average three-dimensional difference between the invasive localization results and the HR-MCG results was smallest 2.9 cm for the source model consisting of the magnetic dipole. The preexcitation site was very deep in all cases. The current dipole alone was inaccurate in estimating the source depth, but inclusion of the quadrupole moments improved the results. Two of the patients underwent surgery to interrupt the accessory pathway, which provided further validation for the noninvasive localizations.

Adult↗
PubMed1991

Magnetocardiographic functional localization using a current dipole in a realistic torso.

We describe a fast and numerically effective biomagnetic inverse solution using a moving dipole in a realistic homogeneous torso. We applied the localization model and high-resolution magnetocardiographic mapping to localize noninvasively the ventricular preexcitation site in ten patients suffering from Wolff-Parkinson-White syndrome. In all cases, the computed localization results were compared to the results obtained by invasive catheter technique. Using a standard-size torso model in all cases, the average 3-D distance between the computed noninvasive locations and the invasively obtained results was 2.8 +/- 1.4 cm. When the torso was rescaled to better match the true shape of the subject in five cases, the 3-D average was improved to 2.2 +/- 1.0 cm. This accuracy is very satisfactory, suggesting that the method would be clinically useful.

Adult↗
PubMed1991

Original waveform of lung sound crackles: a case study of the effect of high-pass filtration.

In lung sound research, low-frequency noise usually disturbs the sound signal being recorded. Some researchers therefore use high-pass filtration before the final analysis. In this study, the effect of digital and analog high-pass filtration on the morphology of the lung sound crackles is evaluated. The original nonprefiltered crackle waveform is presented, and the effect of the high-pass filtration on the crackle waveform characteristics is elucidated in one patient with silicoasbestosis.

Acoustics↗
PubMed1991

Crackles in patients with fibrosing alveolitis, bronchiectasis, COPD, and heart failure.

We have studied the crackling lung sounds of ten patients with cryptogenic fibrosing alveolitis, ten with bronchiectasis, ten with chronic obstructive pulmonary disease, and ten with heart failure by analyzing frequency, waveform, and timing of crackles. The upper frequency limit of inspiratory sounds was higher in CFA than in COPD or in HF. The period of crackling was shorter in COPD than in CFA or BE. Inspiratory crackling terminated significantly earlier in COPD than in CFA, BE, or HF. The initial deflection width and the two-cycle duration of the expanded waveforms of crackles were smaller in CFA than in BE, COPD, or HF. The largest deflection width was smaller in CFA than in BE, HF, or COPD and smaller in BE than in HF. The results indicate that crackling lung sounds in different diseases have distinctive features and that their analysis can be of diagnostic value.

Bronchiectasis↗
PubMed1991

Sensitivity limits in biomagnetic measurements.

It is important to understand the character and the contribution of thermal magnetic noise in designing the measurement site and the instrumentation for biomagnetic measurements. The ultimate limit of the sensitivity is the thermal noise due to the object under study. In the case of the human body, it has been estimated to be about 0.1/square root of Hz. Magnetically shielded rooms are necessary for ultrasensitive biomagnetic measurements of human subject, but they also generate external noise which in some cases may become detectable. This noise problem can be avoided if the innermost walls are constructed of magnetically soft ferromagnetic material. Close to the conducting walls the thermal noise is higher than at the centre. Thus, the shielded room should be relatively large in size. The gantry and other things inside the room may contain metal parts, which can cause excess noise. The intensity depends on the conductivity, geometry, location and movement of these parts. In comparison to bioelectric studies, this inductive noise coupling demands extra attention. In most biomagnetic measurements performed inside a magnetically shielded room, the limiting factor of the sensitivity is the thermal noise caused by electrically conducting thermal shielding used inside the cryogenic measurement dewar. Fortunately, it is possible to reduce the noise contribution arising from the superinsulation in the dewar by careful design. The properties and dynamics of the SQUIDs are well understood nowadays. Studies of the nonlinear character in the coupling between the SQUID and external detection coil have made it possible to reduce the noise contribution of the sensor itself.(ABSTRACT TRUNCATED AT 250 WORDS)

Bioelectric Energy Sources↗
PubMed1991

Onset of luteal activity in foaling and seasonally anoestrous mares treated with artificial light.

Sixty-four mares (27 foaling, 37 barren or maiden), mainly Finnhorses, were subjected to treatment with 14.5 h of light and 9.5 h of darkness, starting at the beginning of December. The onset of cycling in non-foaling mares was estimated by weekly serum progesterone determinations. All of the non-foaling mares cycled in the middle of March. They started to cycle on average in the middle of February, 11.1 weeks after the beginning of the trial. There were statistically significant differences in relation to breed (Finnhorses started to cycle 2 weeks later than warm blooded, p less than 0.02) and in relation to age (brood mares with mean age 10 years, started to cycle 10 days later than those 3 years old, p less than 0.03). However, there was no statistical significant relation to previous lactation, although lactating mares lactating up to the previous autumn started to cycle 7 days later than dry mares (p less than 0.15). Artificial insemination of 14 mares in the 2nd oestrus of the year, in March, resulted in 12 foalings in the subsequent year (86%). The following winter, all pregnant mares (N = 27) were exposed to the same kind of light treatment, starting on 1st December. The 1st mare foaled at the end of January. The time from foaling to 1st post partum ovulation was significantly longer (17.0 days) in foalings taking place within 10 weeks from the beginning of the light treatment period, than in foalings occurring after more than 10 weeks of lighting (12.1 days) (p less than 0.01).

Anestrus↗
PubMed1991

Onset of luteal activity in non-foaling mares during the early breeding season in Finland.

The luteal activity in mares was studied in the Equine Research Station (ERS) and in trotting stables (TS) in South-Finland. The mares were Standardbreeds in the TS and mainly Finnhorses in the ERS. Between January and June blood was collected once a week for serum progesterone determinations. The mares in the ERS were distributed in 1 of 3 groups: three-years old not yet in training (N = 38), brood mares (N = 21) and mares in training (N = 47). A 4th group was the mares in training in the trotting stables (N = 73). Every 5th mare in the ERS and every 4th mare in the trotting stables were cycling already at the beginning of the year. Onset of luteal activity in anoestrous mares was most common in the middle of May. Over 95% of the mares were cycling at the beginning of June. In the ERS 40% of the Finnhorse mares in training were cycling through the winter. The three-years old and the brood mares were all anoestrous during winter. They started to cycle on average before the middle of May. Anoestrous training mares started before the middle of April. Anoestrous Finnhorse mares began to cycle later than warm blooded mares in all of the groups studied. Mares which had foaled the previous year were more often anoestrous during the winter than dry mares. The time of year when cycling began in a particular mare tended to be the same from year to year (p less than 0.01).

Age Factors↗
PubMed1990

Fertility of mares after postovulatory insemination.

In a first experiment, 11 Finnhorse mares were examined every six hours during late oestrus by rectal palpation and ultrasonography to determine the time of ovulation. The mares were inseminated over one to three subsequent cycles, 6-12 (n = 5), 12-18 (n = 5), 18-24 (n = 5) and 24-30 (n = 5) hours after ovulation. Pregnancies were terminated by prostaglandin injection 21 days after insemination. All mares inseminated within 18 hours of ovulation conceived but no mare inseminated 24 hours or more after ovulation conceived. In a second experiment, 14 mares were examined every day at about the same time and inseminated after ovulation had been detected, within 0-27 hours of ovulation. Pregnancies were terminated by prostaglandin injection 25 days after insemination and the animals inseminated again. Forty-six per cent of the mares (13 out of 28) were pregnant 16 days after insemination but there was early embryonic death in five mares, i.e. only 29% of the mares became and remained pregnant. The equine ovum seems to be capable of being fertilized for at least 18 hours after ovulation. However, the high incidence of early embryonic death in the second experiment suggests that the viability of the embryo may have decreased.

Animals↗
PubMed1990

Milk and serum progesterone levels in mares after ovulation.

Twenty-four Finnhorse mares were examined by rectal palpation and ultrasonography every 6 h during late oestrus to determine the time of ovulation. Milk and serum samples were collected every 6 h after the detected ovulation for progesterone analysis. The progesterone rises took place within 0-54 h and 0-60 h after ovulation, in milk and serum, respectively. Statistically significant differences (p less than 0.05) in progesterone levels were observed for the first time 12-18 h and 18-24 h after ovulation, in serum and milk, respectively, as compared to progesterone levels 0-6 h after ovulation.

Animals↗
PubMed1989

A preliminary study on the use of betaine as a cryoprotective agent in deep freezing of stallion semen.

In a preliminary experiment, betaine was added in concentrations ranging from 0 to 3.0 percent to stallion semen diluted with 4% glycerol extender. Motility of frozen-thawed semen was better in the extenders with high betaine concentration than in those of low concentration or the control. In a subsequent experiment, betaine was added to extended semen from five stallions to make a 2.5% betaine concentration. Two different cooling rates were used. The effect of betaine on spermatozoal motility was positive at both cooling rates studied. Motility of frozen-thawed 2.5% betaine semen samples was significantly (p less than 0.001) higher than that of the control samples.

Animals↗
PubMed1989

Predicting ovulation in the mare on the basis of follicular growth and serum oestrone sulphate and progesterone levels.

Follicular growth and hormone determinations were used to predict ovulation in the mare. Thirty Finnhorse mares were used for the investigation and 38 oestrous cycles were studied. The mares were examined by rectal palpation and ultrasonography every 6 hours during late oestrus. Daily blood samples were obtained for progesterone and oestrone sulphate determination. The preovulatory follicle grew 3 mm a day up to 2 days before ovulation. The size then remained constant, before diminishing by 2-3 mm during the last 12 hours. The maximal diameter of the follicle was 43 +/- 4 mm. In 89% of the follicles the round shape became more irregular before ovulation. During the last 24 hours before ovulation 37 of 38 follicles were regarded as mature on rectal palpation. The oestrone sulphate level was highest 24-48 hours before ovulation, the first decrease being observed most commonly around ovulation (+/- 1 day). The size of the follicle was the most reliable criterion in the prediction of ovulation.

Animals↗
PubMed1989

Embryo transfer in subfertile mares.

Four subfertile mares (at least 2 barren years) were used as donors in an embryo transfer program. The embryo recovery rate was 50%, varying between 0-100. The transfer of 9 embryos resulted in the pregnancy rate of 44%. The efficiency of embryo transfer using subfertile mares is low. In this material 20% of flushings resulted in a pregnancy.

Animals↗