Density functional theory study of crown ether-magnesium complexes: from a solvated ion to an ion trap

Metal ion detection rests on host-guest recognition. We propose a theoretical protocol for designing an optimal trap for a desired metal cation. A host for magnesium ions was sought for among derivatives of crown ethers 12-crown-4, 15-crown-5, and 18-crown-6. Mg-crown complexes and their hydrated counterparts with water molecules bound to the cation were optimized using density functional theory. Based on specific geometric criteria, Interacting quantum atoms analysis and density functional theory-based molecular dynamics of Mg-crown complexes immersed in water, crown ethers for optimal accommodation of Mg2+ in aqueous solution were identified. Selectivity of the chosen crowns towards Na+, K+, and Ca2+ ions is addressed.

On the propensity of formation of cyclobutane dimers in face-to-face and face-to-back uracil stacks in solution

UV irradiation of RNA leads to the formation of intra- and inter-strand crosslinks of cyclobutane type. Despite the importance of this reaction, relatively little is known about how the mutual orientation of the two bases affects the outcome of the reaction. Here we report a comparative nonadiabatic molecular dynamics study of face-to-back (F2B) and face-to-face (F2F) stacked uracil-water clusters. The computations were performed using the second-order algebraic-diagrammatic-construction (ADC(2)) method. We found that F2B stacked uracil-water clusters either relax non-reactively to the ground state by an ethylenic twist around the CC bond or remain in the lowest nπ* state in which the two bases gradually move away from each other. This finding is consistent with the low propensity for the formation of intra-strand cyclobutane dimers between adjacent RNA bases. On the contrary, in F2F stacked uracil-water clusters, in addition to non-reactive deactivation, we found a pro-reactive deactivation pathway, which may lead to the formation of cyclobutane uracil dimers in the electronic ground state. On a qualitative level, the observed photodynamics of F2F stacked uracil-water clusters explains the greater propensity of RNA to form inter-strand cyclobutane-type crosslinks.

Alkaline earth cations binding mode tailors excited-state charge transfer properties of guanine quadruplex: A TDDFT study

Quadruplexes formed by nucleic acids and their derivates tend to chelate different monovalent and bivalent cations, which simultaneously affect their excited electronic states properties. Cation binding to every and every other cavity of the central ion channel could be exploited for tuning exited-state charge transfer properties. In this work we utilize set of descriptors constructed on the basis of the one-electron transition density matrix obtained using linear-response TDDFT to study excited states properties of four crystallized tetramolecular quadruplexes that chelate alkaline earth cations (Ca²⁺, Sr²⁺ and Ba²⁺). Here, we show that alkaline earth cations situated at adjacent vacancies promote existence of the nucleobase-metal charge separation (CS) states, contrary to the structures with cations that occupy every second available vacancy. We argued that stabilization of these CS states is due to the strong electric field that stabilizes d orbitals of the cations which accept an excited-electron. Moreover, CS content is increased and redshifted below the first bright transition when number of the chelated cations is increased. Hydration effects stabilized CS states and increased their relative content. We also identified electron detachment states in the broad energy range for the Ca²⁺ containing system. These findings are valuable for understanding and development of the novel nanostructures based on the quadruplex scaffold with adjustable optical properties.

Proton leap: shuttling of protons onto benzonitrile

The detailed description of chemical transformations in the interstellar medium allows deciphering the origin of a number of small and medium - sized organic molecules. We present density functional theory analysis of proton transfer from the trihydrogen cation and the ethenium cation to benzonitrile, a recently discovered species in the Taurus Molecular Cloud 1. Detailed energy transformations along the reaction paths were analyzed using the interacting quantum atoms methodology, which elucidated how the proton carrier influences the lightness to deliver the proton to benzonitrile's nitrogen atom. The proton carriers' deformation energy represents the largest destabilizing effect, whereas a proton's promotion energy, the benzonitrile-proton Coulomb attraction, as well as non-classical benzonitrile-proton and carrier-proton interaction are the dominant stabilizing energy components. As two ion-molecule reactions proceed without energy barriers, rate constants were estimated using the classical capture theory and were found to be an order of magnitude larger for the reaction with the trihydrogen cation compared to that with the ethenium cation (∼10^-8 and 10^-9 cm³ s^-1, respectively). These results were obtained both with quantum chemical and ab initio molecular dynamics simulations (the latter performed at 10 K and 100 K), confirming that up to 100 K both systems choose energetically undemanding routes by tracking the corresponding minimum energy paths. A concept of a turning point is introduced, which is an equivalent to the transition state in barrierless reactions.

Water-Mediated Interactions Enhance Alkaline Earth Cation Chelation in Neighboring Cavities of a Cytosine Quartet in the DNA Quadruplex

Larger Coulombic repulsion between divalent cations compared to the monovalent counterparts dictates the cation-cation distance in the central ion channel of quadruplexes. In this work, density functional theory and a continuum solvation model were employed to study bond energies of alkaline earth cations in adjacent cavities of the central ion channel. Four crystallized tetramolecular quadruplexes with various geometric constraints and structural motifs available in the Protein Data Bank were examined in order to understand how the cation binding affinities could be increased in aqueous solution. A cytosine quartet sandwiched between guanine quartets has a larger bond energy of the second alkaline earth cation in comparison with guanine and uracil quartets. Four highly conserved hydrogen-bonded water molecules in the center of the cytosine quartet are responsible for a higher electrostatic interaction with the cations in comparison with guanines' carbonyl groups. The reported findings are valuable for the design of synthetic quadruplexes templated with divalent cations for optoelectronic applications.

Self-assembly of rylene-decorated guanine ribbons on graphene surface for optoelectronic applications: a theoretical study

We are witnessing a change of paradigm from the conventional top-down to the bottom-up fabrication of nanodevices and particularly optoelectronic devices. A promising example of the bottom-up approach is self-assembling of molecules into layers with predictable and reproducible structural, electronic and optical properties. Nucleobases possess extraordinary ability to self-assembly into one-, two-, and three-dimensional structures. Optical properties of nucleotides are not suitable for wider application to optoelectronics and photovoltaics due to their large optical band gap, which is in contrast to rylene-based dyes that have been intensively investigated in organic optoelectronics. However, these lack the self-assembly capability of nucleobases. Combinations of covalently decorated guanine molecules with rylene type chromophores present 'the best of the both worlds'. Due to the large size of such compounds and its flexible nature their self-assemblies have not been fully understood yet. Here, we use a theoretical approach to study the structural, energetic and optical properties of rylene-based dye decorated guanine (GPDI), as self-assembled on a graphene sheet. Particularly we utilize the density-functional based tight-binding method to study atomic structure of these systems including the potential energy surface of GPDI and stability and organization of single- and multilayered GPDIs on graphene sheet. Using density-functional theory (DFT) we employ the energy decomposition analysis to gain a deeper insight into the contributions of different moieties to stability of GPDI films. Using time dependent DFT we analyze optical properties of these systems. We find that atomically thin films consisting of only a few molecular layers with large surface areas are more favorable than isolated thick islands. Our study of excited states indicates existence of charge separated states similar to ones found in the well-studied hydrogen bonded organic frameworks. The self-assembly characterized with a large homogeneous coverage and long-living charge-separated states provide the great potential for optoelectronic applications.

Simulation of UV absorption spectra and relaxation dynamics of uracil and uracil-water clusters

Despite many studies, the mechanisms of nonradiative relaxation of uracil in the gas phase and in aqueous solution are still not fully resolved. Here we combine theoretical UV absorption spectroscopy with nonadiabatic dynamics simulations to identify the photophysical mechanisms that can give rise to experimentally observed decay time constants. We first compute and theoretically assign the electronic spectra of uracil using the second-order algebraic-diagrammatic-construction (ADC(2)) method. The obtained electronic states, their energy differences and state-specific solvation effects are the prerequisites for understanding the photodynamics. We then use nonadiabatic trajectory-surface-hopping dynamics simulations to investigate the photoinduced dynamics of uracil and uracil-water clusters. In contrast to previous studies, we found that a single mechanism - the ethylenic twist around the C[double bond, length as m-dash]C bond - is responsible for the ultrafast component of the nonradiative decay, both in the gas phase and in solution. Very good agreement with the experimentally determined ultrashort decay time constants is obtained.

Entropy Analysis of COVID-19 Cardiovascular Signals

The world has faced a coronavirus outbreak, which, in addition to lung complications, has caused other serious problems, including cardiovascular. There is still no explanation for the mechanisms of coronavirus that trigger dysfunction of the cardiac autonomic nervous system (ANS). We believe that the complex mechanisms that change the status of ANS could only be solved by advanced multidimensional analysis of many variables, obtained both from the original cardiovascular signals and from laboratory analysis and detailed patient history. The aim of this paper is to analyze different measures of entropy as potential dimensions of the multidimensional space of cardiovascular data. The measures were applied to heart rate and systolic blood pressure signals collected from 116 patients with COVID-19 and 77 healthy controls. Methods that indicate a statistically significant difference between patients with different levels of infection and healthy controls will be used for further multivariate research. As a result, it was shown that a statistically significant difference between healthy controls and patients with COVID-19 was shown by sample entropy applied to integrated transformed probability signals, common symbolic dynamics entropy, and copula parameters. Statistical significance between serious and mild patients with COVID-19 can only be achieved by cross-entropies of heart rate signals and systolic pressure. This result contributes to the hypothesis that the severity of COVID-19 disease is associated with ANS disorder and encourages further research.

The significance of the metal cation in guanine-quartet – metalloporphyrin complexes

The distinct positions of the divalent metal ions with respect to the porphyrin ring are responsible for different interaction energies between metalloporphyrins and the guanine quartet.

A new theoretical model for hexagonal ice, Ih(d), from first principles investigations

Due to their great importance in science, technology, and the life sciences, water and ice have been extensively investigated over many years. In particular, hexagonal ice Ih has been of great interest since it is the most common form of ice, and several modifications, Ih(a), Ih(b) and Ih(c) are known, whose structural details are still under discussion. In this study, we present an alternative theoretical model, called Ih(d), for the hexagonal ice modification in space group P63/mmc (no. 194), based on first-principles calculations that have been performed using DFT-LDA, GGA-PBE, and hybrid B3LYP and PBE0 functionals.

Elucidating Solvent Effects on Strong Intramolecular Hydrogen Bond: DFT-MD Study of Dibenzoylmethane in Methanol Solution

The dynamic aspect of solvation plays a crucial role in determining properties of strong intramolecular hydrogen bonds since solvent fluctuations modify instantaneous hydrogen-bonded proton transfer barriers. Previous studies pointed out that solvent-solute interactions in the first solvation shell govern the position of the proton but the ability of the electric field due to other solvent molecules to localize the proton remains an important issue. In this work, we examine the structure of the O-H⋅⋅⋅O intramolecular hydrogen bond of dibenzoylmethane in methanol solution by employing density functional theory-based molecular dynamics and quantum chemical calculations. Our computations showed that homogeneous electric fields with intensities corresponding to those found in polar solvents are able to considerably alter the proton transfer barrier height in the gas phase. In methanol solution, the proton position is correlated with the difference in electrostatic potentials on the oxygen atoms of dibenzoylmethane even when dibenzoylmethane-methanol hydrogen bonding is lacking. On a timescale of our simulation, the hydrogen bonding and solvent electrostatics tend to localize the proton on different oxygen atoms. These findings provide an insight into the importance of the solvent electric field on the structure of a strong intramolecular hydrogen bond.

A Mobile Crowd Sensing Application for Hypertensive Patients

Mobile crowd sensing (MCS) is an application that collects data from a network of conscientious volunteers and implements it for the common or personal benefit. This contribution proposes an implementation that collects the data from hypertensive patients, thus creating an experimental database using the cloud service Platform as a Service (PaaS). The challenge is to perform the analysis without the main diagnostic feature for hypertension—the blood pressure. The other problems consider the data reliability in an environment full of artifacts and with limited bandwidth and battery resources. In order to motivate the MCS volunteers, a feedback about the patient’s current status is created, provided by the means of machine-learning (ML) techniques. Two techniques are investigated and the Random Forest algorithm yielded the best results. The proposed platform, with slight modifications, can be adapted to the patients with other cardiovascular problems.

The UVA response of enolic dibenzoylmethane: beyond the static approach

The nπ* and ππ* states of dibenzoylmethane are vibronically coupled and their crossing occurs during the excited-state intramolecular proton transfer.

Beneficial Effects of Polyphenol-Rich Chokeberry Juice Consumption on Blood Pressure Level and Lipid Status in Hypertensive Subjects

Epidemiological studies have shown a positive association between intake of foods rich in antioxidants and lower incidence of cardiovascular disease development. Polyphenols are considered the most abundant and important dietary antioxidants. The aim of this study was to evaluate effects of polyphenol-rich chokeberry juice consumption on 24-h ambulatory monitored blood pressure (BP) level in subjects with no pharmacologically treated high normal BP or grade I hypertension. Twenty-three subjects (12 men and 11 women) aged 33-67 were enrolled and instructed to consume 200 mL of juice daily for 4 weeks. Participants were divided in two groups, based on prevalence of sympathetic or parasympathetic activity. Measurements of biochemical parameters and heart rate variability analysis were also applied. At the end of the intervention period, average 24-h and awake systolic and diastolic BP were significantly decreased (P<.05). This was more pronounced in the group with prevalence of sympathetic activity. Significant reduction in triglyceride level (P<.05) and a reducing effect on total and low-density lipoprotein cholesterol were also found. Obtained results indicate a positive impact of regular chokeberry juice consumption on BP and lipid status in pharmacologically untreated hypertensive subjects.

When do the symptoms of autonomic nervous system malfunction appear in patients with Parkinson's disease?

BACKGROUND/AIM

Dysautonomia appears in almost all patients with Parkinson's disease (PD) in a certain stage of their condition. The aim of our study was to detect the development and type of autonomic disorders, find out the factors affecting their manifestation by analyzing the potential association with demographic variables related to clinical presentation, as well as the symptoms of the disease in a PD patient cohort.

METHODS

The patients with PD treated at the Clinic of Neurology in Belgrade during a 2-year period, divided into 3 groups were studied: 25 de novo patients, 25 patients already treated and had no long-term levodopa therapy-related complications and 22 patients treated with levodopa who manifested levodopa-induced motor complications. Simultaneously, 35 healthy control subjects, matched by age and sex, were also analyzed.

RESULTS

Autonomic nervous system malfunction was defined by Ewing diagnostic criteria. The tests, indicators of sympathetic and parasympathetic nervous systems, were significantly different in the PD patients as compared with the controls, suggesting the failure of both systems. However, it was shown, in the selected groups of patients, that the malfunction of both systems was present in two treated groups of PD patients, while de novo group manifested only sympathetic dysfunction. For this reason, the complete autonomic neuropathy was diagnosed only in the treated PD patients, while de novo patients were defined as those with the isolated sympathetic dysfunction. The patients with the complete autonomic neuropathy differed from the subjects without such neuropathy in higher cumulative and motor unified Parkinson's disease rating score (UPDRS) (p < 0.01), activities of daily living scores (p < 0.05), Schwab-England scale (p < 0.001) and Hoehn-Yahr scale. There was no difference between the patients in other clinical-demographic characteristics (sex, age at the time of diagnosis, actual age, duration of disease, involved side of the body, pain and freezing), but mini mental status (MMS) score and Hamilton depression and anxiety rating scale were significantly lower (p < 0.05).

CONCLUSION

Our results confirm a high prevalence of autonomic nervous system disturbances among PD patients from the near onset of disease, with a predominant sympathetic nervous system involvement. The patients who developed complete autonomic neuropathy (both sympathetic and parasympathetic) were individuals with considerable level of functional failure, more severe clinical presentation and the existing anxiety and depression.

Bradbury-Eggleston syndrome - an unusual cause of gastroesophageal reflux disease (GERD)

The report presents a case of a 46-year-old male patient, previously treated because of dysphagia, pyrosis, vertigo while standing up and impotency. Manometric and pH-metric analysis showed presence of gastroesophageal reflux disease (GERD) caused by transient relaxation of lower esophageal sphincter (TRLES). Heart-rate variability showed decreased sympathetic function. Electromyoneurography showed a neurological lesion in muscles of upper extremities. The patient received midodrine and clonazepam which resolved this condition. These findings suggest that a neurological disorder can be a cause of GERD.

Anxiety, personality traits and quality of life in functional dyspepsia-suffering patients

BACKGROUND

Psychosocial stressors either acute or more sustained frequently precede the onset and exacerbation of the symptoms of the functional dyspepsia (FD). Depressive mood and quality of life have been already reported for interference in functional dyspepsia suffering patients.

METHODS

The examination were performed on 60 FD patients (30 females and 30 males), aged 20-79 years, 60 peptic ulcer subjects and 60 healthy volunteers in which we have investigate levels of anxiety and depression, personality traits and quality of life.

RESULT

According to the Hamilton Depression and Anxiety Rating Scales, the population with FD had the average score which classified them into the group of patients with the moderate depression (20.57 ± 4.45). Personality traits estimation based on data obtained by the Eysenck personality questionnaire revealed higher neuroticism scores in the group with functional dyspepsia. Both parameters, level of the neuroticism and anxiety level, expressed highly significant level of mutual concordance. Patients with functional dyspepsia reported a greater adverse impact of symptoms of emotional distress and food and drink problems.

CONCLUSION

Results are indicating that the depression and anxiety level is the highest in patients with functional dyspepsia and that anxiety level corroborates with the neuroticism level from the Eysenck scale. Psychological disturbances are influencing the quality of life mostly in patients with dyspepsia in the form of emotional distress and the problem with the food and beverage intake.

Comparative effect of bisoprolol and losartan in the treatment of essential hypertension

OBJECTIVE

We investigated the effects of bisoprolol and losartan on subjects with essential hypertension, by conducting heart rate variability (HRV) analysis of ECG signals. Our intention was to establish the set of linear and nonlinear heart rate variability parameters, which could be used as a noninvasive markers in the treatment of hypertension.

MATERIALS AND METHODS

Sixty subjects with essential hypertension included in this study were divided in two groups. During the four weeks medical treatment, the first group was administered with daily oral dose of 5 mg of bisoprolol and the second with daily oral dose of 50 mg of losartan. We recorded ECG signals, and performed HRV analysis of consecutive RR time intervals, before and after a month of pharmacological therapy.

RESULTS

IN THE CASE OF BISOPROLOL, STATISTICALLY THE MOST SIGNIFICANT CHANGES OF HRV PARAMETERS WERE: TP (1814.1 ± 1731.3 ms(2) vs. 761.3 ± 725.0 ms(2), P < 0.0001), RR (870.2 ± 105.7 ms vs. 1027.2 ± 150.0 ms, P < 0.0001), HR (70.81 ± 8.42 bp/min vs. 60.10 ± 9.52 bp/min, P < 0.0001). In the case of losartan, the most significant changes were: SDNN (43.16 ± 17.27 ms vs. 237.98 ± 118.54 ms, P = 0.002), rmSDD (27.09 ± 18.27 ms vs. 46.82 ± 37.71 ms, P = 0.003), SD2 (55.18 ± 20.6 vs. 70.67 ± 26.12, P < 0.019) and DF2 (0.69 ± 0.21 vs. 0.86 ± 0.25, P < 0.014).

CONCLUSION

Effects of bisoprolol and losartan were especially manifested among the set of linear HRV parameters. As a consequence of effect of losartan, we singled out the nonlinear parameters SD2 and DF2.

Comparison of two nutritional assessment methods in gastroenterology patients

AIM: To investigate and compare efficacy and differences in the nutritional status evaluation of gastroenterology patients by application of two methods: subjective global assessment (SGA) and nutritional risk index (NRI).

METHODS: The investigation was performed on 299 hospitalized patients, aged 18-84 years (average life span 55.57 ± 12.84), with different gastrointestinal pathology, admitted to the Department of Gastroenterohepatology, Clinical and Hospital Center “Bezanijska Kosa” during a period of 180 d. All the patients, after being informed in detail about the study and signing a written consent, underwent nutritional status analysis, which included two different nutritional indices: SGA and NRI, anthropometric parameters, bioelectrical impedance analysis, and biochemical markers, within 24 h of admission.

RESULTS: In our sample of 299 hospitalized patients, global malnutrition prevalence upon admission varied from 45.7% as assessed by the SGA to 63.9% by NRI. Two applied methods required different parameters for an adequate approach: glucose level (5.68 ± 1.06 mmol/L vs 4.83 ± 1.14 mmol/L, F = 10.63, P = 0.001); body mass index (26.03 ± 4.53 kg/m²vs 18.17 ± 1.52 kg/m², F = 58.36, P < 0.001); total body water (42.62 ± 7.98 kg vs 36.22 ± 9.32 kg, F = 7.95, P = 0.005); basal metabolic rate (1625.14 ± 304.91 kcal vs 1344.62 ± 219.08 kcal, F = 9.06, P = 0.003) were very important for SGA, and lymphocyte count was relevant for NRI: 25.56% ± 8.94% vs 21.77% ± 10.08%, F = 11.55, P = 0.001. The number of malnourished patients rose with the length of hospital stay according to both nutritional indices. The discriminative function analysis (DFA) delineated the following parameters as important for prediction of nutritional status according to SGA assessment: concentration of albumins, level of proteins, SGA score and body weight. The DFA extracted MAMC, glucose level and NRI scores were variables of importance for the prediction of whether admitted patients would be classified as well or malnourished.

CONCLUSION: SGA showed higher sensitivity to predictor factors. Assessment of nutritional status requires a multidimensional approach, which includes different clinical indices and various nutritional parameters.

Cardiac autonomic nervous system in patients with myotonic dystrophy type 1

The purpose of the present study was to evaluate cardiac autonomic nervous system (ANS) in patients with myotonic dystrophy type 1 (DM1). The function of ANS was studied in 20 patients with DM1 and 15 healthy controls. All subjects were investigated by a battery of six cardiovascular autonomic tests and power spectral analysis of heart rate variability (HRV). Only one patient had normal autonomic function. Two (10%) patients had mild, 10 (50%) moderate and 7 (35%) severe autonomic dysfunction. Thirteen (65%) patients had vagal and 4 (20%) sympathetic hyperactivity. Seven (35%) patients had vagal and 15 (75%) sympathetic dysfunction. Eighteen (90%) patients had orthostatic hypotension. The 24-hour time domain parameters of SDNN (SD of the NN interval) and total power were significantly lower in DM1 patients than in healthy controls (p < 0.05). However, other parameters of HRV, such as SDANN (SD of the mean NN, 5-minute interval), low frequency (LF), high frequency (HF) power and the LF/HF ratio were somewhat lower in patients with DM1 than in controls, but this was not statistically significant. There was no significant relationship between autonomic dysfunction and the severity of the disease or CTG repeat length. There was also no correlation between HRV and age. Our findings suggest that sympathetic dysfunction and vagal predominance may both occur in patients with DM1.

[Prognostic value of Poincare plot as nonlinear parameter of chaos theory in patients with myocardial infarction]

INTRODUCTION

There are different proofs about association of autonomic nervous system dysfunction, especially nonlinear parameters, with higher mortality after myocardial infarction.

OBJECTIVE

The objective of the study was to determine predictive value of Poincaré plot as nonlinear parameter and other significant standard risk predictors: ejection fraction of the left ventricle, late potentials, ventricular arrhythmias, and QT interval.

METHOD

The study included 1081 patients with mean follow-up of 28 months (ranging from 0-80 months). End-point of the study was cardiovascular mortality. The following diagnostic methods were used during the second week: ECG with commercial software Schiller AT-10: short time spectral analysis of RR variability with analysis of Poincaré plot as nonlinear parameter and late potentials; 24-hour ambulatory ECG monitoring: QT interval, RR interval, QT/RR slope, ventricular arrhythmias (Lown > II); echocardiography examinations: systolic disorder (defined as EF < 40%).

RESULTS

There were 103 (9.52%) cardiovascular deaths during the follow-up. In univariate analysis, the following parameters were significantly correlated with mortality: mean RR interval < 800 ms, QT and RR interval space relationship as mean RR interval < 800 ms and QT interval > 350 ms, positive late potentials, systolic dysfunction, Poincaré plot as a point, ventricular arrhythmias (Lown > II). In multivariate analysis, the significant risk predictors were: Poincaré plot as a point and mean RR interval lower than 800 ms.

CONCLUSION

Mean RR interval lower than 800 ms and nonlinear and space presentation of RR interval as a point Poincaré plot were multivariate risk predictors.

[Early risk predictors of sudden cardiac death after myocardial infarction: results of follow up of 881 patients]

INTRODUCTION

It has been shown that depolarization disorders, autonomic dysfunction, and systolic dysfunction of the left ventricle are associated with sudden cardiac death after myocardial infarction.

OBJECTIVE

The objective of study was to examine the prognostic value of the most important predictors in the first week after myocardial infarction.

METHOD

Study included 881 patients who were followed up from 1 to 60 months. During the first week after myocardial infarction, following examination were performed: ECG with standard leads and X, Y, Z orthogonal leads, vectorcardiogram, QT interval, late potentials, short-time spectral analysis of RR variability, nonlinear (Poincaré plot) analysis and echocardiogram.

RESULTS

In univariate analysis, the following parameters measured on the first day were important predictors of sudden cardiac death: lower LF/HF ratio (<1.5) (p = 0.000), T wave inversion in X lead (p = 0.000), high P wave in D2 lead (p=0.030), and diminished systolic function (p = 0.000). In multivariate analysis, the following parameters were significant risk predictors: T wave inversion in X lead, lower LF/HF ratio, positive late potentials and the left ventricle systolic dysfunction.

CONCLUSION

The parameters of the left ventricle systolic disfunction with sympathicovagal imbalance and electric instability are the key risk predictors in the first few days after myocardial infarction.

[An unusual cause of complete atrioventricular block--a case report]

INTRODUCTION

Complete atrioventricular block is a serious disorder, since patients may be asymptomatic. However, it is an important risk for sudden cardiac death.

CASE REPORT

A 48-year old male patient was admitted to the coronary care unit, due to recurring substernal chest pain. It was followed by fatigue, weakness and confusion, it lasted more than half an hour and occurred twice. Loss of consciousness did not occur. The patient had a tick bite two months earlier. Physical examination was unremarkable, except for low heart rate (50/minute) electrocardiogram showed a complete atrioventricular block with narrow QRS complexes and good ventricular function. Elevation of ST segment was observed in the inferior ECG leads, with reciprocal ST depression in precordial leads; it was highly suspicious for acute myocardial infarction, but markers of myocardial necrosis (Troponin, Creatine kinase-MB) were normal. The chest pain recurred without evolutive changes in the electrocardiogram or increase in markers of myocardial necrosis. Tests for Lyme disease were negative, too. The cause of atrioventricular conduction disturbance was found by transthoracic echocardiography. A giant tumor was found in the right atrium and right ventricle. Further examinations excluded its secondary cause and the patient was sent to surgery. The tumor was inoperable and bled excessively. Although permanent pacing was performed, the patient died suddenly after dismisal.

CONCLUSION

We can conclude that a giant primary tumor of the heart can be asymptomatic for a long time causing complete atrioventricular block, and in this case it clinically presented as acute myocardial infarction. Echocardiographic examination was the main diagnostic tool in our case.