Anton Mateasik

Effect of changes in left ventricular anatomy and conduction velocity on the QRS voltage and morphology in left ventricular hypertrophy: a model study

UNLABELLED The increased QRS voltage is considered to be a specific electrocardiogram (ECG) sign of left ventricular hypertrophy (LVH), and it is expected that the QRS voltage reflects the increase in left ventricular mass (LVM). However, the increased QRS voltage is only one of QRS patterns observed in patients with LVH. According to the solid angle theory, the resultant QRS voltage is influenced not only by spatial (anatomic) but also by nonspatial (electrophysiologic) determinants. In this study, we used a computer model to evaluate the effect of changes in anatomy and conduction velocity of the left ventricle on QRS complex characteristics. MATERIAL AND METHODS The model defines the geometry of cardiac ventricles analytically as parts of ellipsoids and allows to change dimensions of the ventricles, as well as the conduction velocity in the individual layers of myocardium. Three types of anatomic changes were simulated: concentric hypertrophy, eccentric hypertrophy, and dilatation. The conduction velocity was slowed in the inner layer of the left ventricle representing the Purkinje fiber mesh and in the layers representing the working myocardium. The outcomes of the model are presented as the time course of the spatial QRS vector magnitude, the vectorcardiographic QRS loops (VCGs) in horizontal, left sagittal, and frontal planes, as well as derived 12-lead ECGs. The following indicators of the 12-lead ECG were evaluated: the left axis deviation, the intrinsicoid deflection in V6, Cornell voltage, Cornell voltage-duration product, and Sokolow-Lyon index. RESULTS The increase in LVM did not affect the QRS voltage proportionally, and the LVM and type of hypertrophy were not the only determinants of the QRS patterns. The conduction velocity slowing resulted in a spectrum of QRS patterns including increased QRS voltage and duration, left axis deviation, prolonged intrinsicoid deflection, VCG patterns of left bundle branch block, as well as pseudo-normal VCG/ECG patterns. The anatomic changes and conduction velocity slowing affected differently Sokolow-Lyon index and Cornell criteria. CONCLUSION We showed that the LVM is not the only determinant of the QRS complex changes in LVH, but it is rather a combination of anatomic and electric remodeling that creates the whole spectrum of the QRS complex changes seen in LVH patients. The slowed conduction velocity in the model heart produced QRS patterns consistent with changes described in LVH, even if the LVM was not changed.

Electrocardiographic patterns of left bundle-branch block caused by intraventricular conduction impairment in working myocardium: a model study.

UNLABELLED By definition, the electrocardiographic (ECG) patterns of left bundle-branch block (LBBB) represent distinctive changes in duration and shape of the QRS complex caused by intraventricular conduction delay in the left ventricle (LV) due to structural abnormalities in the His-Purkinje conduction system and/or ventricular myocardium. However, impaired conduction in the working myocardium is not taken into consideration in the practical ECG diagnosis. Because the degree of LV myocardium impairment could be of importance for clinical evaluation of patients, we studied the effects of blocked and of delayed onsets of activation in the LV to simulate complete and incomplete LBBBs and slowed conduction in the LV myocardium by applying an analytical computer model. We demonstrated that typical LBBB patterns were caused both by block or delay in the onset of the LV activation, as well as by impaired conduction in the myocardium itself while maintaining the location and onset of the LV activation. The most important difference was the absence of initial anteriorly oriented electrical forces in cases of the simulated complete LBBB and of incomplete LBBB if the onset of LV activation was delayed (≥ 6 milliseconds). Under the conditions defined in this model that did not consider myocardial infarction, the presence of initial anteriorly oriented electrical forces was indicative of preserved conduction in the left bundle and of impaired conduction in LV working myocardium. CONCLUSION The elucidation of the participation of working myocardium impairment in the intraventricular conduction delay in the LV could be of vital significance for the clinical management of patients with LBBB patterns, for example, indicated for resynchronization therapy.

High Level of Low-density Lipoprotein Receptors Enhance Hypericin Uptake by U-87 MG Cells in the Presence of LDL

The dependence of the uptake of hypericin (Hyp) by human glioma U‐87 MG cells on the level of expression of low‐density lipoprotein (LDL) receptors has been studied in this work. A special role of the LDL receptor‐pathway for Hyp delivery to U‐87 MG cells in the presence of LDL was revealed by the substantial increase of Hyp uptake in the situation, when the number of LDL receptors on the cell surface was elevated. Moreover, the colocalization experiments showed the lysosomal localization of Hyp following the uptake and that the concentration of Hyp in these organelles was enhanced in the cells with elevated number of LDL receptors when the incubation medium contained LDL. Both these findings suggest that LDL and LDL receptor‐pathway play an important role in the delivery and accumulation of Hyp into the cells.

Mitochondrial membrane fluidity, potential, and calcium transients in the myocardium from acute diabetic rats

In this study, we report for the first time concurrent measurements of membrane potential and dynamics and respiratory chain activities in rat heart mitochondria, as well as calcium transients in the hearts of rats in an early phase of streptozotocin diabetes, not yet accompanied with diabetes-induced complications. Quantitative relationships among these variables were assessed. The mitochondria from diabetic rats exhibited decreased fluorescence anisotropy values of diphenylhexatriene. This indicates that hydrophobic core of the membranes was more fluid compared with controls (p<0.05). We discuss the changes in fluidity as having been associated with augmented energy transduction through the diabetic membranes. Reduced ratio of JC-1 fluorescence (aggregates to monomers) in the mitochondria from diabetic hearts reflected descendent transmembrane potential. A significant negative association between membrane fluidity and potential in the diabetic group was found (p<0.05; r=0.67). Further, we observed an increase in calcium transient amplitude (CTA) in the diabetic cardiomyocytes (p=0.048). We conclude that some of the calcium-induced regulatory events that dictate fuel selection and capacity for ATP production in diabetic heart occur at the membrane level. Our findings offer new insight into acute diabetes-induced changes in cardiac mitochondria.

The Dipolar ElectroCARdioTOpographic (DECARTO)-like method for graphic presentation of location and extent of area at risk estimated from ST-segment deviations in patients with acute myocardial infarction

A graphic method was developed for presentation of the location and extent of the myocardium at risk in patients with acute myocardial infarction (AMI). This method is based on a mathematical processing of ST-segment deviations of standard 12-lead electrocardiogram following the concept of Titomir and Ruttkay-Nedecky in their dipolar electrocardiotopographic method. The center of the location of the area at risk is given by the spatial orientation of the resultant spatial ST vector, and the extent of the area at risk is derived from the Aldrich score. The areas at risk are projected on a spherical image surface, on which a texture of the anatomical quadrants of the ventricular surface and its coronary artery supply are projected. The method was tested in 10 patients with AMI with single-vessel disease, including 6 patients with an occlusion in the proximal left anterior descending coronary artery (LAD), 3 patients with an occlusion in the right coronary artery, and one patient with occlusion in the left circumflex coronary artery. The estimated areas at risk were compared with myocardial perfusion single photon emission computed tomography. Eight (80%) patients of 10 were correctly localized according to the Aldrich decision rules for the location of AMI. The areas at risk in patients with LAD occlusion correctly localized by the Aldrich score were situated in the anteroseptal and anterosuperior quadrants. In the inferior AMI group, the area at risk was localized in the posterolateral and inferior quadrants. The visual comparison with myocardial perfusion single photon emission computed tomography (SPECT) showed best agreement in patients with LAD involvement. The initial testing showed that this method allows a graphic presentation of estimated area at risk using clinically defined diagnostic rules. The area at risk can be displayed in images that are familiar for clinicians and can be compared with or superimposed on results of other imaging methods used in cardiology.

Effect of ouabain on metabolic oxidative state in living cardiomyocytes evaluated by time-resolved spectroscopy of endogenous NAD(P)H fluorescence

Abstract. Time-resolved spectrometry of endogenous nicotinamide dinucleotide phosphate [NAD(P)H] fluorescence is a useful method to evaluate metabolic oxidative state in living cells. Ouabain is a well-known pharmaceutical drug used in the treatment of cardiovascular disease, the effects of which on myocardial metabolism were recently demonstrated. Mechanisms implicated in these actions are still poorly understood. We investigate the effect of ouabain on the metabolic oxidative state of living cardiac cells identified by time-resolved fluorescence spectroscopy of mitochondrial NAD(P)H. Spectral unmixing is used to resolve individual NAD(P)H fluorescence components. Ouabain decreased the integral intensity of NAD(P)H fluorescence, leading to a reduced component amplitudes ratio corresponding to a change in metabolic state. We also noted that lactate/pyruvate, affecting the cytosolic NADH gradient, increased the effect of ouabain on the component amplitudes ratio. Cell oxidation levels, evaluated as the percentage of oxidized NAD(P)H, decreased exponentially with rising concentrations of the cardiac glycoside. Ouabain also stimulated the mitochondrial NADH production. Our study sheds a new light on the role that ouabain plays in the regulation of metabolic state, and presents perspective on a noninvasive, pharmaceutical approach for testing the effect of drugs on the mitochondrial metabolism by means of time-resolved fluorescence spectroscopy in living cells.

Characterization of the interaction of hypericin with protein kinase C in U-87 MG human glioma cells.

Abstract A fluorescence imaging technique was used to monitor intracellular localization of protein kinase C (PKC) in U-87 MG human glioma cells in the presence of hypericin (Hyp) and phorbol 12-myristate-13-acetate (PMA). It is shown that PKC localization, which reflects its activity, is influenced by Hyp and this influence is different from that observed for PMA which acts as PKC activator. Fluorescence binding experiments were used to determine the binding constants of Hyp to several isoforms of PKC. The obtained values of Kds (∼100 nM) suggest that Hyp binds with high affinity to PKC. Finally, molecular modeling was used to compare structural models of the interaction of C1B domain of PKC (PKC isoforms α, δ, γ) with Hyp and our previously published model of the (C1B domain PKCγ)/PMA complex. The influence of Hyp on PKC translocation in U-87 MG cells in comparison with PMA, colocalization fluorescence pattern of Hyp and PKC, the higher binding affinity of Hyp to PKC in comparison with known binding constants of phorbol esters, as well as the binding mode of Hyp and PMA to the C1B domain of PKC suggested by molecular modeling, support the idea that Hyp and PMA might competitively bind to the regulatory domain of PKC.

Interaction of merocyanine 540 with charged membranes

In this work, phospholipid liposomes were used to investigate the influence of lipid negative charge on the interaction of merocyanine 540 (MC540) with model membranes. Liposomes were prepared from a mixture of neutral dimyristoyl lecithin (DMPC) and negatively charged dimyristoyl phosphatidic acid (DMPA). A strong dependence between the presence of charges on the membrane and dye association was found. The affinity of the dye to liposomes was decreased with an increasing content of DMPA in liposomes. Changes in absorption spectra of MC540 suggest that the decrease in affinity of MC540 to charged membranes is accompanied by a hypsochromic solvatochromic shift and changes in monomer/dimer equilibrium of MC540 incorporated in the membrane.

Rejection of transplanted hearts in patients evaluated by the component analysis of multi-wavelength NAD(P)H fluorescence lifetime spectroscopy

Rejection of transplanted hearts remains one of the principal reasons for death of paediatric patients, but an appropriate diagnostic tool for the mild rejection in early stages is still missing. Tissue autofluorescence (AF) is one of the most versatile non-invasive tools for mapping the metabolic state in living tissues. Increasing interest in the imaging and diagnosis of living cells and tissues based on their intrinsic fluorescence rather than fluorescence labelling is closely connected to the latest developments in high-performance spectroscopy and microscopy techniques. In this contribution, we investigate individual components in spectrally- and time-resolved NAD(P)H fluorescence, revealed by linear unmixing, responsible for increased fluorescence in patients presenting mild rejection of transplanted hearts. Application of such approach has the potential to improve the diagnostics of the cardiac transplant rejection by helping currently used histological analysis.

Time-resolved fluorescence spectroscopy investigation of the effect of 4-hydroxynonenal on endogenous NAD(P)H in living cardiac myocytes

Abstract. Lipid peroxidation is a major biochemical consequence of the oxidative deterioration of polyunsaturated lipids in cell membranes and causes damage to membrane integrity and loss of protein function. 4-hydroxy-2-nonenal (HNE), one of the most reactive products of n-6 polyunsaturated fatty acid peroxidation of membrane phospholipids, has been shown to be capable of affecting both nicotinamide adenine dinucleotide (phosphate) reduced [NAD(P)H] as well as NADH production. However, the understanding of its effects in living cardiac cells is still lacking. Our goal was to therefore investigate HNE effects on NAD(P)H noninvasively in living cardiomyocytes. Spectrally resolved lifetime detection of endogenous fluorescence, an innovative noninvasive technique, was employed. Individual fluorescence components were resolved by spectral linear unmixing approach. Gathered results revealed that HNE reduced the amplitude of both resolved NAD(P)H components in a concentration-dependent manner. In addition, HNE increased flavoprotein fluorescence and responsiveness of the NAD(P)H component ratio to glutathione reductase (GR) inhibitor. HNE also increased the percentage of oxidized nucleotides and decreased maximal NADH production. Presented data indicate that HNE provoked an important cell oxidation by acting on NAD(P)H regulating systems in cardiomyocytes. Understanding the precise role of oxidative processes and their products in living cells is crucial for finding new noninvasive tools for biomedical diagnostics of pathophysiological states.