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T Novotný

Publications and source records attributed to T Novotný.

10 recordsLinked to original sources
PubMed2006

Electron transport in single-wall carbon nanotube weak links in the Fabry-Perot regime.

We fabricated reproducible high transparency superconducting contacts consisting of superconducting Ti/Al/Ti trilayers to gated single-wall carbon nanotubes. The reported semiconducting single-wall carbon nanotubes have normal state differential conductance up to 3e2/h and exhibit clear Fabry-Perot interference patterns in the bias spectroscopy plot. We observed subharmonic gap structure in the differential conductance and a distinct peak in the conductance at zero bias, which is interpreted as a manifestation of the supercurrent. The gate dependence of this supercurrent as well as the excess current are examined and compared to the coherent theory of superconducting quantum point contacts with good agreement.

Journal Article↗
PubMed2006

[Mutational analysis of LQT genes in individuals with drug induced QT interval prolongation].

BACKGROUND: In a long list of non-cardiovascular drugs a risk of QT interval prolongation and thus an increased risk of malignant arrhythmias has been described. The precise mechanism remains unclear. Many of these drugs are potent blockers of cardiac ion channels. Thus, prolongation of repolarization could be caused by latent ion channel genes mutations which are revealed under stress conditions. GROUP OF PATIENTS AND METHODS: Patients were recruited in screening of antipsychotic drugs with proarrhythmic potential, another sporadic cases were reffered from regional hospitals. In 13 individuals pathologic values of corrected QT interval (> 0.44 s in males, > 0.46 s in females) were observed. Eleven patients gave their consent to mutational analysis of KCNQ1, KCNH2, SCN5A, KCNE1, KCNE2 and KCNJ2 genes (associated with congenital long QT syndrome). RESULTS: At present complete results of mutational analysis are available in 8 patients. In 5 individuals changes in DNA sequence were found which are considered normal variants according to the literature (nucleotide and aminoacid polymorphisms, intronic variants). In 1 male a KCNQ1 gene mutation A590T was identified (yet not reported in literature). CONCLUSION: Mechanisms of drug-induced QT interval prolongation is complex and it cannot be explained simply by ion channel disorders.

DNA Mutational Analysis↗
PubMed2005

[Retromuscular mesh repair of a hernia in a scar according to Rives--our first experience].

The authors present a group of 24 patients with hernias in scars operated from February 2004 to January 2005 (12 months) using a retromuscular reconstruction procedure according to Rives. 20 procedure following central laparotomies and 4 procedures following lateral laparotomies were conducted. The defect sizes ranged from 5 to 16 cm. A polypropylene mesh was used which was placed between the rectus abdominis muscle and the posterior leaf of the rectus abdominis sheath. The mesh was covered by the fascia with a minimum overlap of 5 cm in all directions. The mean follow- up period was six months (1-12 months) and no early relapses were recorderd. The complications rate was acceptable--1x secondary wound healing, 2x seroma, 1x non-transmural MI in a patient with a cardiac ischemic disorder. The retromuscular reconstruction procedure according to Rives appears to be an appropriate method for management of large ventral hernias with excellent results and minimum complications.

Abdominal Muscles↗
PubMed2003

[Molecular genetic aspects of arrhythmias].

The sequencing of human genome was completed in 2001. The position of particular DNA base is established-i.e. we know all "letters" in the "book" but we understand only limited number of "words" i. e. only limited number of genes was identified. And the human genome consists of about 30,000 genes from which through the mechanism of alternative RNA splicing more than 100,000 genes can be derived. All the genes of one individual form the genotype. The expression of genotype in particular environment forms the phenotype. What is not present in genotype can neither be present in phenotype. In the last decade a substantial progress was achieved in understanding of membrane processes mostly due to research of relatively rare inherited monogenous arrhythmic syndromes--first of all the long QT syndrome. It is caused by mutations in ion channel genes and it provides a model of arrhythmogenesis on molecular level. Ventricular arrhythmias are important cause of mortality in patients with cardiovascular diseases. New studies have provided strong evidence for familial sudden cardiac death (SCD) aggregation and therefore also genetic influence. Parental history of SCD increases the relative risk of SCD for offspring to 1.8. In the case of both maternal and paternal SCD events the risk for offspring is a remarkable 9.4. There are 3 pathways by which genetic variation may contribute to risk for SCD: 1. alterations in electrogenesis and conduction, 2. formation and stability of atherosclerotic plaque, thrombogenesis and ischemia within the coronary circulation, 3. control of myocardial excitability and vascular motorics. The main objective of both today and future research is identification of inheritable "molecular" risk factors of arrhythmias. Understanding of this level of pathophysiological processes will subsequently lead to new generation of both diagnostic and therapeutic methods.

Arrhythmias, Cardiac↗
PubMed2002

[Arterial diseases in women using combined hormonal contraceptives].

OBJECTIVE: To determine the association between myocardial infarction and cerebral stroke and use of combined oral contraceptives. DESIGN: Review of literature. SETTING: Department of Obstetrics and Gynaecology, Hospital of Merciful Brothers, Brno, Czech Republic. METHODS: Identification of methodologically sound studies able to address the topic. Studies were identified by Medline database search. RESULTS: Five the most recent and important studies were the main source of information (Oxford Family Planning Association Contraception Study 1984, Royal College of General Practitioners' Study 1994, WHO Collaborative Study of Cardiovascular Disease and Steroid Hormone Contraception 1996, 1997, Transnational Study on Oral Contraceptives and the Health of Young Women 1997, Myocardial Infarction and Oral Contraceptives Study, 1997). Generally there was no evidence of a significantly increased risk of arterial wall disease in healthy non smoked users younger than 35 years. No difference between second and third generation oral contraceptives on risk of arterial wall disease were found. In the most of cases of myocardial infarction or stroke one or more risk factor were identified. Two of the most relevant risk factors are smoking and the absence of blood pressure control. CONCLUSION: The risk of arterial cardiovascular system diseases seems not to be increased at no-risk users (healthy non-smoker younger than 35 years).

Contraceptives, Oral, Combined↗
PubMed2000

[Pacemaker dysfunction during use of a mobile telephone].

Ubiquitious electronic equipment increases the number of potential sources of electromagnetic interference with sufficient energy to influence a pacemaker function. Besides others the mobile phone play important role. A 76 year-old female patient with pacemaker was hospitalized because of bilateral congestive heart failure. During ECG telemetry a short episode of pacemaker dysfunction was recorded. In a period of 15 seconds at first a pulse output inhibition occurred, then an undersensing was present. In all the 24-hour recording no other similar episode was observed. Such an utterly atypical picture lead to a direct question on mobile telephone calling. The patient confirmed that during a visit of her relatives she was really using a mobile phone. The GSM (Global System for Mobile Communication) phones operate on a carrier frequency of 900 MHz which is modulated generally in pulses about 8 Hz and 2 Hz. These signals can be falsely detected as an intrinsic heart activity by a pacemaker or they are analysed to be an electromagnetic interference. As a result a pacemaker inhibition, an asynchronous pacing and in dual chamber systems also a ventricular triggering can be present. These reactions usually do not occur if the distance between phone and pacemaker is higher than 10 cm. With some measures patients with pacemakers can safely use mobile phones. In pacemaker dependent patients a careful approach is necessary.

Aged↗
PubMed2000

[The role of ergometric testing in diagnosis of latent long QT syndrome].

BACKGROUND: The long QT syndrome is a genetically determined disease based on mutations of ion membrane channel genes. The resulting prolongation of repolarization increases a risk of malignant ventricular arrhythmias and sudden death. The diagnosis is problematic in individuals with borderline or even normal corrected QT interval value. Ventricular arrhythmias in this syndrome are often provoked by exercise, therefore exercise testing is considered as a useful differential diagnostic method. METHODS: In a 24-member family an occurrence of the long QT syndrome was established clinically in 7 patients. In other 3 members borderline corrected QT interval values were found (0.44-0.46 s). In these individuals a stress testing by bicycle ergometry was performed. RESULTS: During exercise in a 28-year old man (patient III/6) the corrected QT interval prolonged to 0.53 s, in a 27-year old man (patient III/2) and in a 20-year old woman (patient III/9) physiological QT interval shortenings were observed (0.4 s during peak exercise). The diagnosis was confirmed by molecular genetic investigation. In patient III/6 (along with other symptomatic family members) a mutation in exon 7 of KCNQ1 (previously called KVLQT1) gene was found. In patients III/2 and III/9 no signs of KCNQ1 gene pathology were present. CONCLUSIONS: In families with clinically established diagnosis of long QT syndrome occurrence the exercise testing reveals previously asymptomatic individuals, at least in LQT1 type (which is the most common). In general stress testing and measurement of QT interval dynamics is a necessary part of arrhythmological investigation especially in young individuals with history of syncope.

Adult↗
PubMed1999

[Electric programmed ventricular stimulation using a permanent cardiac pacing system--a noninvasive method in arrhythmia].

BACKGROUND: Complex forms of ventricular arrhythmias often occur in patients with an implanted permanent cardiac pacing system. Some of the pacemakers are provided with software which allows electrophysiological testing of the cardiac conduction system by coupling with an external diagnostic pacemaker via their programmer. This method is non-invasive. METHODS AND RESULTS: In a group of 26 patients (19 males, 7 females) with an implanted pacemaker (Paragon III, Synchrony III, Sensorithm--all Pacesetter) complex ventricular arrhythmias were observed (class Lown IVa and higher). In these patients the electrical stability of the myocardium was tested by the described method (protocol: incremental pacing 90-220 bpm, pacing drives 110 bpm and 140 bpm with 1-3 extrastimuli). Complex ventricular arrhythmias were induced in 42% patients (n = 11), in this subgroup 55% (n = 6) was non-sustained ventricular tachycardia, 36% (n = 4) sustained ventricular flutter, 9% (n = 1) sustained ventricular tachycardia. Patients with non-sustained ventricular tachycardia were treated with beta-blockers, in the others the effective therapy was selected according to electrophysiological testing (amiodarone in 4 patients, ICD in 1 patient). During a 24-month follow-up the overall mortality was 7.7% (n = 2), sudden death mortality was 3.8% (n = 1). CONCLUSIONS: Programmed ventricular stimulation performed by a permanent cardiac pacing system is a simple and above all non-invasive method with no need for fluoroscopy. It can be repeated several times. It is not possible to pace from the right ventricle outflow tract. This is the main disadvantage. Nevertheless, by using non-invasive risk stratification methods (echocardiography, signal averaged ECG, heart rate variability, baroreflex sensitivity, dispersion of QT interval) the patients in need of an invasive study can be identified. This method can be considered an alternative screening method and a standard part of the investigation of the algorithm in patients with a previously implanted pacemaker.

Arrhythmias, Cardiac↗
PubMed1998

[Optimalization of rate adaptation using Holter functions in DDD/R pacemakers].

Introduction of the pacing rate adaptation according to the momentary metabolic needs added other programmable parametres which demand physician's attention during the initial postimplantation programmation and also in follow-up of pacemaker patients. The parametres setting is strictly individual with a need of feedback control. In some devices it is enabled by Holter functions as a part of pacemaker software. These methods were used to set the rate adaptive parametres in the group of 23 patients with implanted DDD/R pacemaker. The walking stress test was used. Model follow-up situations are presented in 3 case reports. Using Holter functions enables the physician to put patient's subjective complains in relation with actual heart rate--this is used to optimize the parametres of rate adaptation. The authors consider the Holter functions a necessary part of rate adaptive pacemaker software.

Aged↗