The electrocardiographic (ECG) assessment of the T peak-T end (Tpe) intervals has been used in many clinical studies, but several related physiological aspects have not been reported. Specifically, the sources of the Tpe differences between different ECG leads have not been systematically researched, the relationship of Tpe duration to underlying heart rate has not been firmly established, and little is known about the mutual correspondence of Tpe intervals measured in different ECG leads. This study evaluated 796,620 10-s 12-lead ECGs obtained from long-term Holters recorded in 639 healthy subjects (311 female) aged 33.8 ± 9.4 years. For each ECG, transformation to orthogonal XYZ lead was used to measure Tpe in the orthogonal vector magnitude (used as a reference for lead-to-lead comparisons) and to construct a three-dimensional T wave loop. The loop roundness was expressed by a ratio between its circumference and length. These ratios were significantly related to the standard deviation of Tpe durations in different ECG leads. At the underlying heart rate of 60 beats per minute, Tpe intervals were shorter in female than in male individuals (82.5 ± 5.6 vs 90.0 ± 6.5 ms, p < 0.0001). When studying linear slopes between Tpe intervals measured in different leads and the underlying heart rate, we found only minimal heart rate dependency, which was not systematic across the ECG leads and/or across the population. For any ECG lead, positive Tpe/RR slope was found in some subjects (e.g., 79 and 25% of subjects for V2 and V4 measurements, respectively) and a negative Tpe/RR slope in other subjects (e.g., 40 and 65% for V6 and V5, respectively). The steepest positive and negative Tpe/RR slopes were found for measurements in lead V2 and V4, respectively. In all leads, the Tpe/RR slope values were close to zero, indicating, on average, Tpe changes well below 2 ms for RR interval changes of 100 ms. On average, longest Tpe intervals were measured in lead V2, the shortest in lead III. The study concludes that the Tpe intervals measured in different leads cannot be combined. Irrespective of the measured ECG lead, the Tpe interval is not systematically heart rate dependent, and no heart rate correction should be used in clinical Tpe investigations.

• Klíčová slova
• ECG lead comparison, T wave peak, T wave spatial loop, heart rate dependency, sex differences,
• Publikační typ
• časopisecké články MeSH

Three-dimensional angle between the QRS complex and T wave vectors is a known powerful cardiovascular risk predictor. Nevertheless, several physiological properties of the angle are unknown or poorly understood. These include, among others, intra-subject profiles and stability of the angle relationship to heart rate, characteristics of angle/heart-rate hysteresis, and the changes of these characteristics with different modes of QRS-T angle calculation. These characteristics were investigated in long-term 12-lead Holter recordings of 523 healthy volunteers (259 females). Three different algorithmic methods for the angle computation were based on maximal vector magnitude of QRS and T wave loops, areas under the QRS complex and T wave curvatures in orthogonal leads, and weighted integration of all QRS and T wave vectors moving around the respective 3-dimensional loops. These methods were applied to orthogonal leads derived either by a uniform conversion matrix or by singular value decomposition (SVD) of the original 12-lead ECG, giving 6 possible ways of expressing the angle. Heart rate hysteresis was assessed using the exponential decay models. All these methods were used to measure the angle in 659,313 representative waveforms of individual 10-s ECG samples and in 7,350,733 individual beats contained in the same 10-s samples. With all measurement methods, the measured angles fitted second-degree polynomial regressions to the underlying heart rate. Independent of the measurement method, the angles were found significantly narrower in females (p < 0.00001) with the differences to males between 10o and 20o, suggesting that in future risk-assessment studies, different angle dichotomies are needed for both sexes. The integrative method combined with SVD leads showed the highest intra-subject reproducibility (p < 0.00001). No reproducible delay between heart rate changes and QRS-T angle changes was found. This was interpreted as a suggestion that the measurement of QRS-T angle might offer direct assessment of cardiac autonomic responsiveness at the ventricular level.

• Klíčová slova
• ECG measurements, healthy volunteers, heart rate, heart rate hysteresis, long-term ECG, polynomial regression, sex differences, spatial QRS-T angle,
• Publikační typ
• časopisecké články MeSH

OBJECTIVE: To test the hypothesis that in recipients of primary prophylactic implantable cardioverter-defibrillators (ICDs), the non-planarity of ECG vector loops predicts (a) deaths despite ICD protection and (b) appropriate ICD shocks. METHODS: Digital pre-implant ECGs were collected in 1948 ICD recipients: 21.4% females, median age 65 years, 61.5% ischaemic heart disease (IHD). QRS and T wave three-dimensional loops were constructed using singular value decomposition that allowed to measure the vector loop planarity. The non-planarity, that is, the twist of the three-dimensional loops out of a single plane, was related to all-cause mortality (n=294; 15.3% females; 68.7% IHD) and appropriate ICD shocks (n=162; 10.5% females; 87.7% IHD) during 5-year follow-up after device implantation. Using multivariable Cox regression, the predictive power of QRS and T wave non-planarity was compared with that of age, heart rate, left ventricular ejection fraction, QRS duration, spatial QRS-T angle, QTc interval and T-peak to T-end interval. RESULTS: QRS non-planarity was significantly (p<0.001) associated with follow-up deaths despite ICD protection with HR of 1.339 (95% CI 1.165 to 1.540) but was only univariably associated with appropriate ICD shocks. Non-planarity of the T wave loop was the only ECG-derived index significantly (p<0.001) associated with appropriate ICD shocks with multivariable Cox regression HR of 1.364 (1.180 to 1.576) but was not associated with follow-up mortality. CONCLUSIONS: The analysed data suggest that QRS and T wave non-planarity might offer distinction between patients who are at greater risk of death despite ICD protection and those who are likely to use the defibrillator protection.

• Klíčová slova
• Biomarkers, Defibrillators, Implantable, Electrocardiography,
• MeSH
• defibrilátory implantabilní * škodlivé účinky   MeSH
• elektrokardiografie metody   MeSH
• funkce levé komory srdeční MeSH
• ischemická choroba srdeční * komplikace   MeSH
• lidé MeSH
• náhlá srdeční smrt etiologie   prevence a kontrola   MeSH
• nemoci koronárních tepen * komplikace   MeSH
• rizikové faktory MeSH
• senioři MeSH
• srdeční arytmie diagnóza   terapie   etiologie   MeSH
• tepový objem MeSH
• Check Tag
• lidé MeSH
• mužské pohlaví MeSH
• senioři MeSH
• ženské pohlaví MeSH
• Publikační typ
• časopisecké články MeSH

AIMS: Increased spatial angle between QRS complex and T wave loop orientations has repeatedly been shown to predict cardiac risk. However, there is no consensus on the methods for the calculation of the angle. This study compared the reproducibility and predictive power of three most common ways of QRS-T angle assessment. METHODS AND RESULTS: Electrocardiograms of 352 healthy subjects, 941 survivors of acute myocardial infarction (MI), and 605 patients recorded prior to the implantation of automatic defibrillator [implantable cardioverter defibrillator (ICD)] were used to obtain QRS-T angle measurements by the maximum R to T (MRT), area R to T (ART), and total cosine R to T (TCRT) methods. The results were compared in terms of physiologic reproducibility and power to predict mortality in the cardiac patients during 5-year follow-up. Maximum R to T results were significantly less reproducible compared to the other two methods. Among both survivors of acute MI and ICD recipients, TCRT method was statistically significantly more powerful in predicting mortality during follow-up. Among the acute MI survivors, increased spatial QRS-T angle (TCRT assessment) was particularly powerful in predicting sudden cardiac death with the area under the receiver operator characteristic of 78% (90% confidence interval 63-90%). Among the ICD recipients, TCRT also predicted mortality significantly among patients with prolonged QRS complex duration when the spatial orientation of the QRS complex is poorly defined. CONCLUSION: The TCRT method for the assessment of spatial QRS-T angle appears to offer important advantages in comparison to other methods of measurement. This approach should be included in future clinical studies of the QRS-T angle. The TCRT method might also be a reasonable candidate for the standardization of the QRS-T angle assessment.

• MeSH
• akční potenciály * MeSH
• defibrilátory implantabilní MeSH
• dospělí MeSH
• elektrická defibrilace přístrojové vybavení   MeSH
• elektrokardiografie * normy   MeSH
• hodnocení rizik MeSH
• infarkt myokardu diagnóza   mortalita   patofyziologie   MeSH
• lidé středního věku MeSH
• lidé MeSH
• mladý dospělý MeSH
• náhlá srdeční smrt epidemiologie   MeSH
• prediktivní hodnota testů MeSH
• prognóza MeSH
• reprodukovatelnost výsledků MeSH
• rizikové faktory MeSH
• senioři MeSH
• srdeční arytmie diagnóza   mortalita   patofyziologie   chirurgie   MeSH
• srdeční frekvence * MeSH
• studie případů a kontrol MeSH
• Check Tag
• dospělí MeSH
• lidé středního věku MeSH
• lidé MeSH
• mladý dospělý MeSH
• mužské pohlaví MeSH
• senioři MeSH
• ženské pohlaví MeSH
• Publikační typ
• časopisecké články MeSH
• srovnávací studie MeSH

Human-secreted Ly-6/uPAR-related protein-2 (SLURP-2) regulates the growth and differentiation of epithelial cells. Previously, the auto/paracrine activity of SLURP-2 was considered to be mediated via its interaction with the α3β2 subtype of the nicotinic acetylcholine receptors (nAChRs). Here, we describe the structure and pharmacology of a recombinant analogue of SLURP-2. Nuclear magnetic resonance spectroscopy revealed a 'three-finger' fold of SLURP-2 with a conserved β-structural core and three protruding loops. Affinity purification using cortical extracts revealed that SLURP-2 could interact with the α3, α4, α5, α7, β2, and β4 nAChR subunits, revealing its broader pharmacological profile. SLURP-2 inhibits acetylcholine-evoked currents at α4β2 and α3β2-nAChRs (IC50 ~0.17 and >3 μM, respectively) expressed in Xenopus oocytes. In contrast, at α7-nAChRs, SLURP-2 significantly enhances acetylcholine-evoked currents at concentrations <1 μM but induces inhibition at higher concentrations. SLURP-2 allosterically interacts with human M1 and M3 muscarinic acetylcholine receptors (mAChRs) that are overexpressed in CHO cells. SLURP-2 was found to promote the proliferation of human oral keratinocytes via interactions with α3β2-nAChRs, while it inhibited cell growth via α7-nAChRs. SLURP-2/mAChRs interactions are also probably involved in the control of keratinocyte growth. Computer modeling revealed possible SLURP-2 binding to the 'classical' orthosteric agonist/antagonist binding sites at α7 and α3β2-nAChRs.

• MeSH
• adaptorové proteiny signální transdukční MeSH
• alfa7 nikotinové acetylcholinové receptory metabolismus   MeSH
• buněčné linie MeSH
• buňky PC12 MeSH
• CHO buňky MeSH
• Cricetulus MeSH
• dospělí MeSH
• epilepsie temporálního laloku patologie   MeSH
• evokované potenciály fyziologie   MeSH
• GPI-vázané proteiny metabolismus   MeSH
• keratinocyty metabolismus   MeSH
• krysa rodu Rattus MeSH
• lidé středního věku MeSH
• lidé MeSH
• nikotinové receptory metabolismus   MeSH
• nukleární magnetická rezonance biomolekulární MeSH
• oocyty metabolismus   MeSH
• počítačová simulace MeSH
• proliferace buněk fyziologie   MeSH
• receptory muskarinové metabolismus   MeSH
• vazba proteinů fyziologie   MeSH
• vazebná místa fyziologie   MeSH
• Xenopus MeSH
• zvířata MeSH
• Check Tag
• dospělí MeSH
• krysa rodu Rattus MeSH
• lidé středního věku MeSH
• lidé MeSH
• ženské pohlaví MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• adaptorové proteiny signální transdukční MeSH
• alfa7 nikotinové acetylcholinové receptory MeSH
• GPI-vázané proteiny MeSH
• LYNX1 protein, human MeSH Prohlížeč
• nicotinic receptor alpha3beta2 MeSH Prohlížeč
• nikotinové receptory MeSH
• receptory muskarinové MeSH

BACKGROUND: Abnormal heterogeneity of myocardial electrophysiologic processes increases the risk of malignant arrhythmias. The aim of the studywas to assess changes ofrepolarization homogeneity in patients after acute myocardial infarction (MI) using morphological parameters obtained from long-term 12-lead electrocardiographic recordings. METHODS: In the group of 200 patients (45 females, 155 males) a long-term (10 minutes supine) 12-lead electrocardiographic recording (SEER MC, GE Medical) was performed 48-72 hours after acute myocardial infarction. The following parameters were calculated using experimental software: total cosine R to T (TCRT) and Twave residuum (TWR). The results were correlated with Q wave evolution and left ventricular ejection fraction (LVEF). RESULTS: Distinguishing the MI type (Q vs nonQ) the following values were obtained: TCRT: 0.17 +/- 0.61 vs 0.16 +/- 0.49, p = 0.52, absolute TWR: 21,200 +/- 21,700 vs 25,700 +/- 29,300, p = 0.3, relative TWR: 0.0012 +/- 0.0017 vs 0.0017 +/- 0.0026, p = 0.28. Stratification according to LVEF (< or = 40% vs > 40%) led to: TCRT: -0.03 +/- 0.66 vs 0.25 +/- 0.54, p = 0.01, absolute TWR: 29,700 +/- 32,400 vs 21,300 +/- 21,500, p = 0.14, relative TWR: 0.0021 +/- 0.0047 vs 0.0013 +/- 0.0021, p = 0.48. CONCLUSION: TCRT is a robust measurement of the spatial angle between the QRS complex and T wave loops which is related to LVEF. The results concerning TWR might indicate that this parameter is independent of LVEF, which needs to be confirmed in further analyses in a larger population.

• MeSH
• elektrofyziologické techniky kardiologické MeSH
• elektrokardiografie ambulantní * MeSH
• funkce levé komory srdeční MeSH
• infarkt myokardu patofyziologie   MeSH
• lidé středního věku MeSH
• lidé MeSH
• senioři MeSH
• tepový objem MeSH
• Check Tag
• lidé středního věku MeSH
• lidé MeSH
• mužské pohlaví MeSH
• senioři MeSH
• ženské pohlaví MeSH
• Publikační typ
• anglický abstrakt MeSH
• časopisecké články MeSH

BACKGROUND: In concurrence of our recent findings of the elevation of QT dispersion (QTd) in the group of pregnant women, mathematical approaches were developed aimed to give possible geometrical explanation whether the observed changes result from the rotation or from the changed position of the heart. METHODS AND RESULTS: Mathematical model of the cardiac electrical field approximated as a time variable dipole in a homogenous spatial conductor was developed. From the experimental vectocardiographic records, representing time course of the cardiac dipole, body surface potential maps were calculated on the basis of the model. To validate the adequacy of the model, the reconstructed electrocardiograms were compared with the empiric data. To determine the effects of rotation, original empiric VCG data of the control group were transformed accordingly the hypothetic pregnancy related changes. Calculated surface electrocardiograms were then compared with empiric cardiograms of the pregnant women. CONCLUSIONS: Based on the results, several conclusions can be drawn: 1) QT dispersion is associated also with the geometrical relations between the direction of cardiac vector during the terminal phase of repolarization and the direction of axes in the given system of leads. The dispersion then has its typical occurrence at the thoracic surface--minimums of the QT duration are found in the plane perpendicular to the axis of the terminal vector lead. 2) When the duration of repolarization is estimated from the classic thoracic leads within the phisiological variations of terminal-depolarization vector orientations, can exist that in some cases the minimum of QT interval is and in others it is not recorded by the lead system. Value of QT dispersion between these two extremes will be significantly different. 3) In case of the horizontal declination of the heart, the ECG signal in most of the leads of the body surface mapping has a higher voltage than in case of vertical declination due to a smaller angle between axes of the terminal vector and most of the leads. Such fact will contribute to more accurate reading of the T wave end and to the estimation of QT interval, usually with smaller value of QTd. 4) The change of the cardiac electrical field corresponding to the changed position of the heart (rotation) does not result by itself in QTd changes, if it is evaluated from the records from the whole thorax. Obversely, horizontalization of the heart contributes more to the evaluation of lower QTd values, as it is given above. 5) More then the result of geometrical changes, QT dispersion found in the group women in high level of pregnancy is an effect of changes in the T loop morphology, which was observed in this group. Another possible explanation of the observed dispersion is the non-dipolar character of the electrical field changes during pregnancy.

• MeSH
• dospělí MeSH
• elektrokardiografie * MeSH
• lidé MeSH
• mapování potenciálů tělesného povrchu MeSH
• modely kardiovaskulární * MeSH
• srdce fyziologie   MeSH
• srdeční arytmie patofyziologie   MeSH
• těhotenství MeSH
• vektorkardiografie MeSH
• Check Tag
• dospělí MeSH
• lidé MeSH
• těhotenství MeSH
• ženské pohlaví MeSH
• Publikační typ
• anglický abstrakt MeSH
• časopisecké články MeSH