V posledních letech se do klinické praxe dostávají nové metody trvalé kardiostimulace, které se v literatuře nazývají fyziologickou stimulací či stimulací Hisova-Purkyňova převodního systému. Patří mezi ně stimulace Hisova svazku, přímá stimulace levého Tawarova raménka a stimulace myokardu levokomorového septa. Tyto stimulační techniky jsou spojeny se změnou přístupu k trvalé kardiostimulaci, jak ji známe v posledních desetiletích. Na rozdíl od myokardiální stimulace pravé komory srdeční je u nich stimulační elektroda fixována přímo do oblasti výskytu buněk převodního systému (Hisova svazku či levého Tawarova raménka), či do jejich těsné blízkosti. Dalším významným rozdílem je nutnost použití speciálního vybavení k dosažení optimálního místa stimulace a obvykle i využití speciálních manévrů k potvrzení uchvácení buněk převodního systému. Narůstající evidence o bezpečnosti a účelnosti těchto metod se odrazila v doporučených postupech některých národních společností pro kardiostimulaci. Fyziologická stimulace (především stimulace Hisova svazku) je ve specifických indikacích doporučována jako alternativa pro pravokomorovou nebo biventrikulární stimulaci. Tento přehledový článek popisuje jednotlivé typy fyziologické stimulace, techniku jejich provádění, způsoby potvrzení typu komorové aktivace a výhody či nevýhody jejich použití u pacientů s indikací k implantaci kardiostimulátoru pro bradykardii.
New methods of cardiac pacing are being adopted in clinical practice in recent years. They are called physiological pacing or conduction system pacing and include His bundle pacing, direct left bundle branch pacing, and left ventricular septal pacing. These methods differ significantly from a standard pacemaker implant procedure. The lead is fixed directly into or adjacent to the tissue of the conduction system of the heart as opposed to lead fixation in myocardial tissue of the right ventricle. Specialized tools and maneuvers for confirming conduction system capture are necessary during the implant procedure. Growing evidence on the safety and feasibility of these methods is reflected in latest guidelines on cardiac pacing of several national societies. They recommend physiological pacing (mainly His bundle pacing) in some specific indications as an alternative to right ventricular myocardial or biventricular pacing. This review describes types of physiological pacing, implant technique, methods of confirming conduction system capture, and its advantages and disadvantages in patients with bradycardia and indication for pacemaker implantation.
- MeSH
- blokáda Tawarova raménka terapie MeSH
- Hisův svazek fyziologie MeSH
- implantované elektrody MeSH
- kardiostimulace umělá * metody MeSH
- lidé MeSH
- myokard MeSH
- převodní systém srdeční * fyziologie MeSH
- srdce - funkce komor fyziologie MeSH
- srdeční septum fyziologie MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- práce podpořená grantem MeSH
- přehledy MeSH
This study investigates the impact of reduced transmural conduction velocity (TCV) on output parameters of the human heart. In a healthy heart, the TCV contributes to synchronization of the onset of contraction in individual layers of the left ventricle (LV). However, it is unclear whether the clinically observed decrease of TCV contributes significantly to a reduction of LV contractility. The applied three-dimensional finite element model of isovolumic contraction of the human LV incorporates transmural gradients in electromechanical delay and myocyte shortening velocity and evaluates the impact of TCV reduction on pressure rise (namely, (dP/dt)max) and on isovolumic contraction duration (IVCD) in a healthy LV. The model outputs are further exploited in the lumped "Windkessel" model of the human cardiovascular system (based on electrohydrodynamic analogy of respective differential equations) to simulate the impact of changes of (dP/dt)max and IVCD on chosen systemic parameters (ejection fraction, LV power, cardiac output, and blood pressure). The simulations have shown that a 50% decrease in TCV prolongs substantially the isovolumic contraction, decelerates slightly the LV pressure rise, increases the LV energy consumption, and reduces the LV power. These negative effects increase progressively with further reduction of TCV. In conclusion, these results suggest that the pumping efficacy of the human LV decreases with lower TCV due to a higher energy consumption and lower LV power. Although the changes induced by the clinically relevant reduction of TCV are not critical for a healthy heart, they may represent an important factor limiting the heart function under disease conditions.
- MeSH
- fibrilace síní patofyziologie MeSH
- hemodynamika fyziologie MeSH
- lidé MeSH
- modely kardiovaskulární * MeSH
- počítačová simulace * MeSH
- převodní systém srdeční fyziologie MeSH
- srdce - funkce komor fyziologie MeSH
- srdeční komory patofyziologie MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
Purpose To develop a deep learning-based method for fully automated quantification of left ventricular (LV) function from short-axis cine MR images and to evaluate its performance in a multivendor and multicenter setting. Materials and Methods This retrospective study included cine MRI data sets obtained from three major MRI vendors in four medical centers from 2008 to 2016. Three convolutional neural networks (CNNs) with the U-NET architecture were trained on data sets of increasing variability: (a) a single-vendor, single-center, homogeneous cohort of 100 patients (CNN1); (b) a single-vendor, multicenter, heterogeneous cohort of 200 patients (CNN2); and (c) a multivendor, multicenter, heterogeneous cohort of 400 patients (CNN3). All CNNs were tested on an independent multivendor, multicenter data set of 196 patients. CNN performance was evaluated with respect to the manual annotations from three experienced observers in terms of (a) LV detection accuracy, (b) LV segmentation accuracy, and (c) LV functional parameter accuracy. Automatic and manual results were compared with the paired Wilcoxon test, Pearson correlation, and Bland-Altman analysis. Results CNN3 achieved the highest performance on the independent testing data set. The average perpendicular distance compared with manual analysis was 1.1 mm ± 0.3 for CNN3, compared with 1.5 mm ± 1.0 for CNN1 (P < .05) and 1.3 mm ± 0.6 for CNN2 (P < .05). The LV function parameters derived from CNN3 showed a high correlation (r2 ≥ 0.98) and agreement with those obtained by experts for data sets from different vendors and centers. Conclusion A deep learning-based method trained on a data set with high variability can achieve fully automated and accurate cine MRI analysis on multivendor, multicenter cine MRI data. © RSNA, 2018 See also the editorial by Colletti in this issue.
- MeSH
- deep learning * MeSH
- interpretace obrazu počítačem metody MeSH
- lidé MeSH
- magnetická rezonance kinematografická metody MeSH
- retrospektivní studie MeSH
- srdce - funkce komor fyziologie MeSH
- srdeční komory diagnostické zobrazování MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
Recent studies have shown that left ventricle (LV) exhibits considerable transmural differences in active mechanical properties induced by transmural differences in electrical activity, excitation-contraction coupling, and contractile properties of individual myocytes. It was shown that the time between electrical and mechanical activation of myocytes (electromechanical delay: EMD) decreases from subendocardium to subepicardium and, on the contrary, the myocyte shortening velocity (MSV) increases in the same direction. To investigate the physiological importance of this inhomogeneity, we developed a new finite element model of LV incorporating the observed transmural gradients in EMD and MSV. Comparative simulations with the model showed that when EMD or MSV or both were set constant across the LV wall, the LV contractility during isovolumic contraction (IVC) decreased significantly ((dp/dt)max was reduced by 2 to 38% and IVC was prolonged by 18 to 73%). This was accompanied by an increase of transmural differences in wall stress. These results suggest that the transmural differences in EMD and MSV play an important role in physiological contractility of LV by synchronising the contraction of individual layers of ventricular wall during the systole. Reduction or enhancement of these differences may therefore impair the function of LV and contribute to heart failure.
- MeSH
- kontrakce myokardu fyziologie MeSH
- lidé MeSH
- modely kardiovaskulární * MeSH
- počítačová simulace * MeSH
- srdce - funkce komor fyziologie MeSH
- srdeční komory * MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
Hodnocení srdeční funkce je klíčový prvek pro odhad prognózy srdečních onemocnění. Posouzení srdeční funkce in vivo je však ovlivněno mnoha faktory, univerzální parametr, který by definoval status „mechanicky zdravého srdce“, proto neexistuje. V přehledu jsou nové i stávající ukazatele srdeční funkce rozděleny podle toho, zda vyjadřují kontraktilitu nebo mechanickou energii srdeční činnosti. Je diskutována jejich role v hodnocení srdeční fyziologie, způsoby stanovení, možné klinické využití i nevýhody.
Heart function evaluation is a key element in predicting heart disease prognosis. However, in vivo cardiac function assessment is influenced by many factors, and therefore there is no universal parameter defining the status of a "mechanically healthy heart". In this review, new and existing parameters of heart function are divided according to whether they express contractility or mechanical energy of cardiac function. Their role in the evaluation of cardiac physiology, methods of assessment, possible clinical use and disadvantages are discussed.
- Klíčová slova
- systolická elastance, srdeční kontraktilita, endsystolická elastance, preload recruitable stroke work, srdeční výkon, ejekční frakce,
- MeSH
- funkční vyšetření srdce metody MeSH
- infarkt myokardu diagnóza MeSH
- kontrakce myokardu * fyziologie MeSH
- lidé MeSH
- minutový srdeční výdej fyziologie MeSH
- srdce - funkce komor * fyziologie MeSH
- srdeční frekvence fyziologie MeSH
- systola fyziologie MeSH
- tepový objem * MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- přehledy MeSH
The poikilothermic heart has been suggested as a model for studying some of the mechanisms of early postnatal mammalian heart adaptations. We assessed morphological parameters of the carp heart (Cyprinus carpio L.) with diastolic dimensions: heart radius (5.73mm), thickness of the compact (0.50mm) and spongy myocardium (4.34mm), in two conditions (systole, diastole): volume fraction of the compact myocardium (20.7% systole, 19.6% diastole), spongy myocardium (58.9% systole, 62.8% diastole), trabeculae (37.8% systole, 28.6% diastole), and cavities (41.5% systole, 51.9% diastole) within the ventricle; volume fraction of the trabeculae (64.1% systole, 45.5% diastole) and sinuses (35.9% systole, 54.5% diastole) within the spongy myocardium; ratio between the volume of compact and spongy myocardium (0.35 systole, 0.31 diastole); ratio between compact myocardium and trabeculae (0.55 systole, 0.69 diastole); and surface density of the trabeculae (0.095μm(-1) systole, 0.147μm(-1) diastole). We created a mathematical model of the carp heart based on actual morphometric data to simulate how the compact/spongy myocardium ratio, the permeability of the spongy myocardium, and sinus-trabeculae volume fractions within the spongy myocardium influence stroke volume, stroke work, ejection fraction and p-V diagram. Increasing permeability led to increasing and then decreasing stroke volume and work, and increasing ejection fraction. An increased amount of spongy myocardium led to an increased stroke volume, work, and ejection fraction. Varying sinus-trabeculae volume fractions within the spongy myocardium showed that an increased sinus volume fraction led to an increased stroke volume and work, and a decreased ejection fraction.
- MeSH
- diastola fyziologie MeSH
- kapři anatomie a histologie fyziologie MeSH
- modely kardiovaskulární * MeSH
- srdce - funkce komor fyziologie MeSH
- srdce anatomie a histologie MeSH
- srdeční komory anatomie a histologie MeSH
- systola fyziologie MeSH
- tepový objem fyziologie MeSH
- zvířata MeSH
- Check Tag
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- MeSH
- lidé MeSH
- mezikomorová přepážka anatomie a histologie fyziologie MeSH
- srdce - funkce komor fyziologie MeSH
- srdce - funkce síní fyziologie MeSH
- srdce * anatomie a histologie fyziologie MeSH
- srdeční chlopně anatomie a histologie fyziologie MeSH
- srdeční komory * anatomie a histologie MeSH
- srdeční septum anatomie a histologie fyziologie MeSH
- srdeční síně * anatomie a histologie MeSH
- Check Tag
- lidé MeSH
AIMS: To assess the acute side-effects of right ventricular (RV) stimulation applied in apex and mid-septum, in order to establish the optimal lead location in clinical practice. METHODS: During pacemaker implantation, the ventricular lead was temporarily fixed in the apex and then moved to mid-septum. In both positions, surface and endocardial electrograms and transvalvular impedance (32 cases), left ventricular (LV) pressure (23), and transthoracic echocardiography (10) were acquired with intrinsic activity and VDD pacing. RESULTS: A larger increase in QRS duration was noticed with apical than septal pacing (65±25 vs. 45±29 ms; P<10(-4)). The proportion of cases where RV stimulation affected the transvalvular impedance waveform was higher with apical lead location (56% vs. 20%; P<0.02). VDD pacing at either site reduced the maximum dP/dt by 6% with respect to intrinsic AV conduction (IAVC; P<0.005). The maximum pressure drop taking place in 100 ms was reduced by 6 and 8%, respectively, with apical and septal pacing (P<0.01 vs. IAVC). Apical VDD decreased mitral annulus velocity in early diastole (E') from 7.5±1.4 to 5.9±0.9 cm/s (P<0.02) and prolonged the E-wave deceleration time (DT) from 156±33 to 199±54 ms (P<0.02), while septal pacing induced non-significant modifications in E' and DT. CONCLUSION: Ventricular stimulation acutely impairs LV systolic and diastolic performance, independent of the pacing site. Septal lead location preserves RV contraction mechanics and reduces the electrical interventricular delay.
- MeSH
- echokardiografie MeSH
- elektrická impedance škodlivé účinky terapeutické užití MeSH
- elektrokardiografie MeSH
- hemodynamika fyziologie MeSH
- kardiostimulace umělá škodlivé účinky metody MeSH
- lidé MeSH
- srdce - funkce komor fyziologie MeSH
- srdeční komory patofyziologie MeSH
- tepový objem MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
Cardiac repolarization is prolonged in diabetes mellitus (DM), however the distribution of repolarization durations in diabetic hearts is unknown. We estimated the ventricular repolarization pattern and its relation to the ECG phenomena in diabetic mice. Potential mapping was performed on the anterior ventricular surface in healthy (n=18) and alloxan-induced diabetic (n=12) mice with the 64-electrode array. Activation times, end of repolarization times, and activation-recovery intervals (ARIs) were recorded along with limb lead ECGs. ARIs were shorter in the left as compared to right ventricular leads (P<0.05). The global dispersion of repolarization, interventricular and apicobasal repolarization gradients were greater in DM than in healthy animals (P<0.03). The increased dispersion of repolarization and apicobasal repolarization gradient in DM correlated with the prolonged QTc and Tpeak-Tend intervals, respectively. The increased ventricular repolarization heterogeneity corresponded to the electrocardiographic markers was demonstrated in DM.
- MeSH
- akční potenciály MeSH
- alloxan farmakologie MeSH
- diabetes mellitus patofyziologie MeSH
- elektrokardiografie MeSH
- experimentální diabetes mellitus patofyziologie MeSH
- myši MeSH
- srdce - funkce komor fyziologie MeSH
- srdeční komory metabolismus MeSH
- zvířata MeSH
- Check Tag
- mužské pohlaví MeSH
- myši MeSH
- ženské pohlaví MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
OBJECTIVE: To develop models of various cardiac loading conditions in an experimental study. MATERIALS AND METHODS: A total of 78 piglets, average weight 24 kg were divided into 4 groups under different cardiac loading conditions: Group A were spontaneously breathing pigs without haemodynamic changes, Group B were ventilated animals with increased left ventricular afterload, Group C ventilated with increased right ventricular preload and Group D ventilated with increased afterload of both heart ventricles. Haemodynamic parameters were invasively measured at 60 and 120 minutes. RESULTS: Groups B, C and D demonstrated higher preload of both ventricles, compared with Group A. Group C demonstrated higher preload and afterload of both ventricles in comparison with Groups B and D. CONCLUSION: Haemodynamic measured data confirmed the expected changes in cardiac loading and corresponded to human clinical situations. These models may be used for future experimental haemodynamic studies (Tab. 1, Fig. 3, Ref. 8).
- MeSH
- hemodynamika MeSH
- minutový srdeční výdej MeSH
- monitorování fyziologických funkcí MeSH
- srdce - funkce komor fyziologie MeSH
- Sus scrofa MeSH
- Swanova-Ganzova katetrizace MeSH
- termodiluce MeSH
- umělé dýchání MeSH
- zvířata MeSH
- Check Tag
- mužské pohlaví MeSH
- ženské pohlaví MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
