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T Kraska

Publications and source records attributed to T Kraska.

At least 19 recordsLinked to original sources
PubMed2006

Molecular-dynamics simulation of argon nucleation from supersaturated vapor in the NVE ensemble.

The possibility to conduct simulations of homogeneous nucleation of argon from a supersaturated vapor phase using a microcanonical or NVE ensemble is evaluated (NVE: number of particles N, volume V, and energy E are constant). In order to initiate a phase separation kinetic energy is removed from the system in one step which transfers the system into a supersaturated state. After this temperature jump the simulation is continued in a NVE ensemble. The simulations are performed for different initial-state points and different temperature jumps. The cluster formation and growth over the course of the adiabatic simulations are analyzed. The progression of the temperature being related to the cluster size in NVE systems is traced. Also the influence of the size of the simulation system is investigated. For a certain range of low supersaturation a dynamic coexistence between two states has been found. Furthermore, the obtained nucleation rates are correlated with two simple functions. By applying the nucleation theorems to these functions the size and excess energy of the critical cluster are estimated. The results are consistent with other theoretical data and experimental data available in the literature.

Journal Article↗
PubMed1997

Amiodarone in restoration and maintenance of sinus rhythm in patients with chronic atrial fibrillation after unsuccessful direct-current cardioversion.

BACKGROUND: When direct-current (DC) cardioversion is used, sinus rhythm can be restored, at least temporarily, in 80-90% of patients with atrial fibrillation. However, there is a small but significant group of patients with chronic atrial fibrillation in whom DC cardioversion has failed to restore sinus rhythm. The value of antiarrhythmic drug pretreatment before DC cardioversion is still controversial. HYPOTHESIS: The aim of our study was to assess (1) the effectiveness of repeat DC cardioversion in patients with chronic atrial fibrillation after pretreatment with amiodarone, and (2) the efficacy of amiodarone in maintaining sinus rhythm after repeat cardioversion. METHODS: Forty-nine patients with chronic atrial fibrillation after ineffective DC cardioversion were included in the study. Repeat DC cardioversion was performed after loading with oral amiodarone, 10-15 mg/kg body weight/day for a period necessary to achieve the cumulative dose of over 6.0 g. RESULTS: Spontaneous conversion to sinus rhythm during amiodarone pretreatment was achieved in 9 of 49 patients (18%). Direct-current cardioversion was performed in 39 patients and sinus rhythm was achieved in 23 of these patients (59%). Mean heart rate decreased from 95 beats/min before to 68 beats/min after DC cardioversion (p < 0.001). Systolic blood pressure significantly (p < 0.05) decreased from 126 +/- 23 to 108 +/- 25 mmHg. Complications occurring in four patients just after electroconversion were well tolerated and of short duration. After 12 months, 52% of patients maintained sinus rhythm on low dose (200 mg/day) amiodarone therapy. CONCLUSION: Pretreatment with amiodarone and repeat DC cardioversion allows for restoration of sinus rhythm in about 65% of patients with chronic atrial fibrillation after first ineffective DC cardioversion. Direct-current cardioversion can be performed safely with the use of standard precautions in patients who are receiving amiodarone. At 12 months' follow-up, more than 50% of patients maintain sinus rhythm on low-dose amiodarone after successful repeat cardioversion.

Amiodarone↗
PubMed1995

[P-wave ekg averaging technique--a new method of selecting patients with paroxysmal atrial fibrillation].

The aim of study was to assess the value of signal averaged ecg for detection of patients (pts) at risk for paroxysmal atrial fibrillation (paf). We examined three groups of pts: group I-41 pts with nonvalvular paf, group II-20 pts with hypertension and/or ischemic heart disease without paf and group 3-26 health persons, without organic heart disease. In all pts the signal-averaged electrocardiogram triggered by P waves was recorded. Seven parameters of the spatial magnitude of filtered P wave were measured. Significant difference between group I and group II or III was found in most parameters. Using the method of multidimensional variance analysis we constructed "the diagnostic vector" in multidimensional parameters space, which was used to determine patients belonging to group. Total percent of right decision was 85%. These findings suggest that pts at risk for paf could be detected while in sinus rhythm by using the P wave-triggered signal-averaged ecg.

Adult↗
PubMed1993

[Influence of diabetes on the clinical course and hospital mortality of patients with recent myocardial infarction].

In group of 1026 patients with recent myocardial infarction (from program "Streptokinase in acute myocardial infarction"--patients below 70 years old, up to 12 hours from the onset of the symptoms) we analyzed the influence of diabetes on clinical course and hospital mortality. In this group were 77 patients with noninsulin-dependent diabetes (NIDDM), and 21 patients were insulin-dependent diabetes (IDDM). The risk factors of coronary heart disease and myocardial infarction in the past were significantly more often in patients with diabetes than in subjects without diabetes. In hospital mortality was significantly higher (p < 0.05) in group of patients with diabetes (17.3%) than in group without diabetes (9.5%). Reinfarction in the hospital period occurred significantly more often in diabetes group (p < 0.01). Congestive heart failure was observed in 50% patients with diabetes and in 32.3% cases without diabetes (p < 0.01), the left ventricle aneurysm occurred accordingly 9.8% i 5.2% (N.S.). Early ventricular fibrillation and atrio-ventricular blocks occurred with the same frequency in the both groups. We analyzed also the influence of thrombolytic therapy on clinical course in patients with diabetes proving the benefit of this treatment.

Aged↗
PubMed1992

[Prognostic value of an early peak CK-MB in plasma of patients treated with streptokinase for acute myocardial infarction].

111 patients below 70 years old, with the first acute myocardial infarctions, 6 hours since the pain occurred--have been treated with streptokinase i.v. In 102 patients we obtained full curve of CK-MB activity. Early peak of CK-MB activity < 15 hours after onset of symptoms we have observed in 59 patients, and late peak of CK-MB activity > 15 hours in 43 patients. There was not any significant statistics differences between early and late groups in frequency of: early ventricular fibrillation (< 48 hours), complex ventricular arrhythmia (in 21 day), heart failure and in-hospital mortality. 1 patient died in hospital in early group and in late group also died 1 patient. The follow-up period was from 10 to 48 months (av. 26 +/- 13). 100 patients left the hospital and the full informations we have obtained in 97 cases. No one died in that time. In the group with early peak CK-MB activity we observed more often the unstable angina and the new myocardial infarction (21%) than in the group with late peak of CK-MB activity (15%), but these differences were nonsignificant. In conclusion our results don't confirm that the early peak of CK-MB activity is the positive risk factor of unstable angina and the new myocardial infarction.

Adult↗
PubMed1992

[Effect of coronary artery patency after myocardial infarction on ventricular late potentials].

This study evaluated the relation between patency of the infarct related artery and the presence of ventricular late potentials (VLP) on the signal-averaged electrocardiogram (ECG). 44 patients (pts) after myocardial infarction (MI) (35 men, 9 women; mean age 50 years) were studied by coronary angiography. measurement of ejection fraction and signal-averaged ECG. The infarct-related artery was closed in 15 pts and open in 29 pts. There was no difference in age, previous MI and location of infarct between the two study groups. Thrombolytic therapy in acute stage of MI was significantly often (p less than 0.05) in pts with open (59%) than closed (13%). The incidence of VLP was significantly higher (p less than 0.05) in group of pts with closed (40%) than open artery (7%). These data indicate that patency of the infarct-related artery has a beneficial effect on the electrophysiologic substrate for serious ventricular arrhythmias.

Action Potentials↗
PubMed1992

[A method of averaged ECG signal does not identify patients with ventricular tachycardia in disorders of intraventricular conduction].

Conduction defect are known to delay and fragment the ecg signal and may be expected to cause changes on the signal-averaged ecg that mimic ventricular late potentials. The aim of our study was to asses whether signal-averaged ECG (SAE) identify patients (pts) with sustained ventricular tachycardia (VT) after myocardial infarction (MI) who display right or left bundle branch block (RBBB or LBBB). We studied 23 pts with RBBB and 25 pts with LBBB. SEA was recorded with bidirectional filters at 25-250 HZ and 40-250 Hz using Simson method. The total filtered QRS duration (QRSd), root mean square voltage in the terminal 40ms of the QRS (RMS40) and low amplitude signal duration less than 40uV (LAS40)) were measured. Signal-averaged parameters with a filter at 25-250 Hz were: [table: see text] Signal-averaged parameters with a filter at 40-259 Hz were: [table: see text] In conclusion SAE parameters do not allow separation of pts with sustained VT from pts with RBBB or LBBB after MI. These data indicate that conduction defects have effects on signal-averaged ecg parameters and may result in masking of ventricular late potentials.

Action Potentials↗
PubMed1991

Value of the atrial signal-averaged electrocardiogram in identifying patients with paroxysmal atrial fibrillation.

Atrial signal-averaged electrocardiogram was compared between 25 patients with paroxysmal atrial fibrillation and 20 healthy persons without atrial arrhythmias (control). The duration time of the high frequency (50-250 Hz) P wave was significantly (P less than 0.01) prolonged in the groups of patients with paroxysmal atrial fibrillation compared with the control group (116 +/- 16.4 versus 92 +/- 8.1 msec). The diagnostic value of the duration of the high frequency P wave for identifying patients with paroxysmal atrial fibrillation was 104 msec. Using this criterion, a sensitivity of 76% and a specificity of 90% were achieved. Our observation has shown that the atrial signal-averaged electrocardiogram is a useful technique for identifying patients with paroxysmal atrial fibrillation.

Adult↗
PubMed1990

[Clinical significance of mitral valve insufficiency detected by Doppler echocardiography in acute myocardial infarction].

Doppler echocardiography revealed in the third week of the recent myocardial infarction a pattern of mitral insufficiency in 27 (36%) of the 75 patients studied. Mitral insufficiency was usually associated with the more severe clinical course of myocardial infarction, with more frequent supraventricular and ventricular arrhythmias, heart failure, and with more extensive infarction area, as compared with the patients without mitral failure. A decreased contractibility of the left ventricle wall (especially in patients with anterior myocardial infarction accompanied by mitral insufficiency and enlargement ventricular dimension) may suggest its role in the development of mitral insufficiency in myocardial infarction. The results show the need of Doppler echocardiography in recent myocardial infarction to detect patients with an increased risk.

Adult↗
PubMed1989

[Value of recording late ventricular potentials in patients with a history of myocardial infarction].

The aim of the work was to determine the values of the registration of late ventricular potentials (PPK) in order to identify patients with paroxysmal ventricular tachycardia following myocardial infarction. PPK was found in 26 out of 30 patients (87%) with episodes of ventricular tachycardia and only in 6 out of 50 (12%) patients without such rhythm disorders following myocardial infarction (p less than 0.001). No PPK were found in any of 25 healthy persons of the control group. No significant difference was found in the frequency of complex ventricular extrasystolic beats (III-V cl. according to Lown) in 24-hour ambulatory electrocardiogram between patients with paroxysmal ventricular tachycardia (47%) and patients without such episodes in anamnesis (30%). The recording of PPK in chest surface leads makes it possible to identify patients with paroxysmal ventricular tachycardia following cardiac infarct.

Action Potentials↗
PubMed1988

Prognostic significance of late potentials after myocardial infarction.

Signal-averaged electrocardiograms (ECGs) were registered before hospital discharge in 120 consecutive patients (pts) with first acute myocardial infarction (MI). 26 pts (22%) had abnormal signal-averaged ECGs - late potentials (LP). Pts with LP had a more serious clinical course than pts without LP: sustained ventricular tachycardia (VT) (27% vs. 2%; p less than 0.01), left ventricular aneurysm (35% vs. 11%; p much less than 0.05) and greater infarct size (62 +/- 35 vs. 43 +/- 22 CK-MB gEq; p less than 0.01). Complex ventricular ectopic activity was more often in pts with LP than in those without LP (54% vs. 28%; p less than 0.05). During an up to 18-month follow-up (mean 13) 6 pts presented sustained VT and 2 died suddenly. 5 pts with sustained VT and 2 pts who died suddenly had LP. The sensitivity of the signal-averaged ECG as a predictor of arrhythmic events was 86%, with a specificity of 82%. Signal-averaged ECGs provide prognostic information in identifying arrhythmic events after MI.

Aged↗
PubMed1986

The effect of infarct size on atrioventricular and intraventricular conduction disturbances in acute myocardial infarction.

The effect of infarct size estimated from serial CK-MB isoenzyme determinations on the incidence of atrioventricular and intraventricular conduction disturbances was examined in 250 patients suffering their first myocardial infarction. The size of the infarct was significantly greater (P less than 0.001) in 72 patients with conduction disturbances than in 178 without conduction defects (54 +/- 29 vs. 35 +/- 22 CK-MB gEq). The largest size was observed in 10 patients with bifascicular block (71 +/- 38 CK-MB gEq). Within the group of patients with intraventricular conduction disturbances, the size of the infarct was significantly greater (P less than 0.01) when localized inferiorly rather than anteriorly (91 +/- 10 vs. 58 +/- 27 CK-MB gEq). The size in those patients with complete atrioventricular block and anterior infarction was larger than in those with an inferior lesion (76 +/- 21 vs. 52 +/- 33 CK-MB gEq). The size in those patients with inferior infarction and complete block was significantly greater (P less than 0.05) than in patients with similarly positioned infarction without conduction disturbances (52 +/- 33 vs. 35 +/- 22 CK-MB gEq). There was no significant difference in the size of infarct when inferior infarction was complicated by first- and second-degree block in comparison to those without conduction defects (38 +/- 23 vs. 35 +/- 22 CK-MB gEq). A correlation was observed between the size of infarction and the incidence of conduction disturbances (P less than 0.001); the greater the size the higher the incidence of conduction disturbances.

Adult↗
PubMed1985

Haemodynamic effects of nitroglycerin infusion in patients with postinfarction heart failure.

On the basis of their own 5-year experience, the authors discuss the indications for, and limitations of, intravenous infusion of nitroglycerin (NTG). In 42 patients with postinfarction heart failure, NTG produced a significant reduction of left ventricular filling pressure, regardless of its initial value. In patients with normal or only slightly elevated left ventricular filling pressure, NTG caused a decrease in cardiac index and mean arterial pressure as well as, in the earliest phase of infusion, an increase in peripheral resistance. Similar trends were observed also in patients with markedly elevated left ventricular filling pressure if mean arterial blood pressure fell by more than 20%. Taking into consideration that the range of the effective doses was very wide (15-150 micrograms/min), the authors believe that intravenous NTG infusion is indicated mainly in cases of manifest heart failure and should be administered under strict control of the dosage and with careful monitoring of the therapeutic effects.

Adult↗