Myocardial Stimulation Research Articles

Pacing of the specialized His-Purkinje conduction system: 'back to the future'.

The conduction system of the human heart is composed of specialized cardiomyocytes that initiate and propagate the electric impulse with consequent rhythmic and synchronized contraction of the atria and ventricles, resulting in the normal cardiac cycle. Although the His-Purkinje system (HPS) was already described more than a century ago, there has been a recent resurgence of conduction system pacing (CSP), where pacing leads are positioned in the His bundle region and left bundle branch area to provide physiological cardiac activation as alternatives to the unnatural myocardial stimulation obtained with conventional right ventricular and biventricular pacing. In this review, we describe the fundamental anatomical and pathophysiological aspects of the specialized HPS along with the CSP technique's nuts and bolts to highlight its potential benefits in everyday clinical practice.

Causes of Failures and Complications in Stimulation of the Conduction System Pacing

Conductive system stimulation relies on the direct stimulation of His-Purkinje’s specialized cardiac conduction system for physiological activation of the ventricles, as opposed to asynchronous activation induced by conventional myocardial stimulation. Since the first report of permanent His bundle stimulation in 2000, the stylet-based technique has undergone significant advances in technology. Single-center observational studies have now been supported by large multicenter, international registries, meta-analysis and the first randomised controlled trials. New evidence has elucidated mechanisms of HBP and illustrated the nature and magnitude of its potential benefits for preventing pacing-induced cardiomyopathy and correcting bundle branch block. Left bundle branch pacing (LBBP) is a newer technique in which the lead is fixed deep into the left side of the intraventricular septum to allow capture of the left bundle, distal to the His bundle. LBBP holds promise as a method for physiological pacing that overcomes some of the fixation, threshold and sensing challenges of HBP.

Hypothalamic Norepinephrine Concentration and Heart Mass in Hypertensive ISIAH Rats Are Associated with a Genetic Locus on Chromosome 18.

The relationship between activation of the sympathetic nervous system and cardiac hypertrophy has long been known. However, the molecular genetic basis of this association is poorly understood. Given the known role of hypothalamic norepinephrine in the activation of the sympathetic nervous system, the aim of the work was to carry out genetic mapping using Quantitative Trait Loci (QTL) analysis and determine the loci associated both with an increase in the concentration of norepinephrine in the hypothalamus and with an increase in heart mass in Inherited Stress-Induced Arterial Hypertension (ISIAH) rats simulating the stress-sensitive form of arterial hypertension. The work describes a genetic locus on chromosome 18, in which there are genes that control the development of cardiac hypertrophy associated with an increase in the concentration of norepinephrine in the hypothalamus, i.e., genes involved in enhanced sympathetic myocardial stimulation. No association of this locus with the blood pressure was found. Taking into consideration previously obtained results, it was concluded that the contribution to the development of heart hypertrophy in the ISIAH rats is controlled by different genetic loci, one of which is associated with the concentration of norepinephrine in the hypothalamus (on chromosome 18) and the other is associated with high blood pressure (on chromosome 1). Nucleotide substitutions that may be involved in the formation or absence of association with blood pressure in different rat strains are discussed.

Cardiac power output accurately reflects external cardiac work over a wide range of inotropic states in pigs

BackgroundCardiac power output (CPO), derived from the product of cardiac output and mean aortic pressure, is an important yet underexploited parameter for hemodynamic monitoring of critically ill patients in the intensive-care unit (ICU). The conductance catheter-derived pressure-volume loop area reflects left ventricular stroke work (LV SW). Dividing LV SW by time, a measure of LV SW min− 1 is obtained sharing the same unit as CPO (W). We aimed to validate CPO as a marker of LV SW min− 1 under various inotropic states.MethodsWe retrospectively analysed data obtained from experimental studies of the hemodynamic impact of mild hypothermia and hyperthermia on acute heart failure. Fifty-nine anaesthetized and mechanically ventilated closed-chest Landrace pigs (68 ± 1 kg) were instrumented with Swan-Ganz and LV pressure-volume catheters. Data were obtained at body temperatures of 33.0 °C, 38.0 °C and 40.5 °C; before and after: resuscitation, myocardial infarction, endotoxemia, sevoflurane-induced myocardial depression and beta-adrenergic stimulation. We plotted LVSW min− 1 against CPO by linear regression analysis, as well as against the following classical indices of LV function and work: LV ejection fraction (LV EF), rate-pressure product (RPP), triple product (TP), LV maximum pressure (LVPmax) and maximal rate of rise of LVP (LV dP/dtmax).ResultsCPO showed the best correlation with LV SW min− 1 (r2 = 0.89; p < 0.05) while LV EF did not correlate at all (r2 = 0.01; p = 0.259). Further parameters correlated moderately with LV SW min− 1 (LVPmaxr2 = 0.47, RPP r2 = 0.67; and TP r2 = 0.54). LV dP/dtmax correlated worst with LV SW min− 1 (r2 = 0.28).ConclusionCPO reflects external cardiac work over a wide range of inotropic states. These data further support the use of CPO to monitor inotropic interventions in the ICU.

P6547The energy cost of His bundle pacing can be curtailed

Abstract Introduction His bundle pacing (HBP) allows physiological ventricular activation and prevents the electrical and mechanical desynchronization generally induced by myocardial stimulation, which can increase the risk of atrial fibrillation and heart failure. On the other hand, reliable HBP capture often requires higher energy than conventional myocardial pacing. This reduces the expected life of the stimulator and might limit the diffusion of HBP in the clinical practice. Purpose Decreasing HBP current drain by careful management of stimulation safety margin and pulse duration. Methods In 28 patients undergoing DDD pacing with HBP, a third lead was implanted in RV apex to provide back-up pacing on demand. HBP and apical leads were connected, respectively, to the V1 and V2 channels of a 3-chamber stimulator. When HBP was effective, apical sensing occurred within the VV delay and prevented V2 stimulation. In contrast, in case of HBP failure, V2 sensing was missing and apical back-up pacing was promptly delivered at the end of the VV delay. The availability of a back-up pulse on demand allowed reducing the HBP safety margin with no risk. Furthermore, the individual HBP strength-duration curve was derived in the aim of optimizing the Hisian pulse parameters, which are the major determinants of the device current drain. Results Correct back-up inhibition by successful HBP and stimulation in the event of capture loss was achieved in all the patients. The latency from Hisian pacing to apical sensing averaged 96±14 ms. According to the pacemaker counters, no back-up pulse was delivered in daily life in 59% of patients. In the remaining, the prevalence of back-up stimulation never exceeded 15% of paced ventricular cycles. The high HBP threshold was essentially due to an increased rheobase (1.2±0.6 V), while the chronaxie ranged from 0.30 to 0.53 ms in 71% of patients (median 0.44 ms), exceeding 0.6 ms only in 29% of the cases. An average current saving of 5.4±3.0 μA was obtained at the expense of a mild reduction in HBP safety margin (from 1.6±0.2 to 1.4±0.1 times). HBP and apical back-up Conclusions Back-up stimulation on demand is a reliable option to decrease HBP current drain and prolong the stimulator service life with full safety. In most of the cases, significant saving can be achieved by pulse shortening, as the chronaxie time is in the same range as with myocardial stimulation and longer pulses are not required. A pulse duration exceeding 0.6 ms is indicated in less than 1/3 of the implants.

Oximetry-Guided normoxic resuscitation following canine cardiac arrest reduces cerebellar Purkinje neuronal damage

BackgroundAnimal studies indicate that maintaining physiologic O2 levels (normoxia) immediately after restoration of spontaneous circulation (ROSC) from cardiac arrest (CA) results in less hippocampal neuronal death compared to animals ventilated with 100% O2. This study tested the hypothesis that beneficial effects of avoiding hyperoxia following CA are apparent in the cerebellum and therefore not limited to one brain region. MethodsAdult beagles were anesthetized and mechanically ventilated. Ventricular fibrillation CA was induced by electrical myocardial stimulation and cessation of ventilation. Ten min later, dogs were ventilated with 100% O2 and resuscitated using 3 min of open chest CPR followed by defibrillation. Dogs were ventilated for 1 h with either 100% O2 or with O2 titrated rapidly to maintain hemoglobin O2 saturation at 94–96%. FiO2 was adjusted in both groups between one and 24 h post-arrest to maintain normoxic PaO2 of 80–120 mm Hg. Following 24 h critical care, dogs were euthanized and cerebellum analyzed for histochemical measures of neuronal damage and inflammation. Results and ConclusionsHyperoxic resuscitation increased the number of injured Purkinje cells by 278% and the number of activated microglia/macrophages by 18% compared to normoxic resuscitation. These results indicate that normoxic resuscitation promotes favorable histopathologic outcomes in the cerebellum (in addition to hippocampus) following CA/ROSC. These findings emphasize the importance of avoiding unnecessary hyperoxia following CA/ROSC.

The Effects of Helium-Generated Cold Plasma on the Parameters of Heart Rate Variability in Rats

Abstract—The goal of the present study was to evaluate the mechanism of the systemic response to helium-generated cold plasma based on heart rate variability indices in rats. The experiments were performed using 20 male Wistar rats. The animals were divided into two equal groups containing 10 rats per each group. In animals of the control group, a single measurement of the microcirculation indices was performed. The rats of the experimental group were exposed to helium-generated cold plasma applied onto the skin on the back (1 min) for 10 days. Helium-generated cold plasma was produced with a special device designed at the Institute of Applied Physics (Nizhny Novgorod, Russia) using the principle of microwave-induced ionization of the gas stream. The electrocardiograms were recorded using a Polyspectr diagnostic complex (Ivanovo, Russia). The statistical analysis of the electrocardiograms and calculation of spectral parameters was performed according to the standard algorithms. It has been found that the exposure to helium-generated cold plasma led to the formation of non-specific (adaptive) changes in heart rate. These changes manifested in the form of moderate tachycardia, the activation of sympathetic stimulation of myocardium, and a proportional decrease in the spectrum power within all frequency ranges.

Total polyphenol quantitation using integrated NIR and MIR spectroscopy: A case study of Chinese dates (Ziziphus jujuba).

Polyphenols are the foremost measure of phytochemicals in Chinese dates due to their many potential health benefits such as averting cancers, reducing the risk of coronary artery disease, diuretic activity, myocardial stimulant, coronary dilator and muscle relaxant. To quantitate the polyphenols in Chinese dates using a data fusion approach with near-infrared (NIR) and mid-infrared (MIR) spectroscopy. A total of 80 Chinese dates samples were used for data acquisition from both NIR and MIR spectroscopy. The efficient spectral intervals were extracted by the synergy interval partial least square (Si-PLS) algorithm as input variables for NIR-MIR fusion model. A genetic algorithm (GA) was used to construct the model based on NIR-MIR fusion. The performance of the developed models was evaluated using correlation coefficients of calibration (R2 ) and prediction (r2 ), root mean square error of prediction (RMSEP), bias and residual prediction deviation (RPD). The data fusion model based on the GA was superior compared to NIR and MIR build model. The optimal GA-fusion model yielded R2 =0.9621, r2 =0.9451, RPD=2.44, calibration set bias=0.004 and prediction set bias=0.061, computing only 15 variables. These findings reveal that integration of NIR and MIR is possible for the prediction of total polyphenol content in Chinese dates.

Multipoint pacing-more CRT or awaste of battery power?

Cardiac resynchronization therapy (CRT) reduces morbidity and mortality in patients with broad QRS complex ≥130 ms and heart failure with reduced ejection fraction despite optimal guideline-directed medical therapy. However, approximately 30% of the patients implanted with aCRT system do not show clinical benefit. Reasons for nonresponse are complex and some aspects can be addressed during follow-up. Based on quadripolar lead technology, multipoint pacing (MPP) allows left ventricular stimulation at two different sites along the lead. In particular, in scarred and fibrotic ventricular myocardium stimulation at two different sites may overcome conduction barriers and lead to homogeneous ventricular depolarization. Especially for patients that do not respond to conventional CRT, activation of MPP may present an option to increase clinical response. On the other hand, MPP may significantly decrease battery longevity.This review offers an overview of the current knowledge and data on MPP balancing the potential clinical benefit and the possible disadvantages of this therapy.

5330A novel platform to maintain adult cardiac tissue in vitro: myocardial slices and electromechanical stimulation with physiological preload

5330A novel platform to maintain adult cardiac tissue in vitro: myocardial slices and electromechanical stimulation with physiological preload

073_16838-J4 Ventricular Excitability in Chronic Implants of a VDD Single-Pass Lead

Efficient myocardial stimulation ensures reliable pacing with restricted energy expense. We assessed the ventricular stimulation performance of a single-pass lead for VDD pacing (Phymos 4, Medico) in the chronic follow-up (28±14 months) of 29 implants. This lead is tined, non-steroid eluting and

Beating Heart Validation of Safety and Efficacy of a Percutaneous Pericardiotomy Tool.

Epicardial procedures frequently require pericardial manipulation. We aimed to develop a nonsurgical percutaneous pericardial modification tool that may (1) facilitate epicardial-based procedures by enabling adhesiolysis or (2) attenuate the myocardial constraining effect of the pericardium. Three novel devices were developed to enable pericardiotomy, all of which can be deployed in over-the-wire fashion following percutaneous epicardial access. The grasper permits us to seize the pericardial membrane providing leverage for incision. The scissors enables anterograde cutting maneuvers. The reverse-slitter allows retrograde incisions; in addition, this device has a deflectable tip that increases the potential cutting area. We optimized these tools for safety by including electrodes to test for phrenic nerve stimulation as well as myocardial stimulation to determine directionality of the cutting devices. The base of the scissors and reverse-slitter are also blunt ensuring that the cutting element is always away from the myocardium. Following 5 nonbeating heart bench test experiments for prototype development, 11 animal (9 canine, 2 swine) studies were performed. Of these 2 were proof-of-concept open chest studies; the remaining 9 were entirely closed-chest, percutaneous procedures allowing for remodification of the prototypes. The tools successfully permitted incision of the pericardium in all studies. Hemodynamic measurements were assessed postincision and showed no compromise of systolic function. No coronary artery or phrenic nerve damage was seen in any study. Percutaneous pericardiotomy is feasible and appears to be safe. It may provide leverage in epicardial-based procedures and offer treatment options in disease processes characterized by pericardial restraint.

Evaluation of tea and coffee products commercialized in Egypt using HPTLC

Tea and coffee have been consumed for hundreds of years ago for their flavour and stimulating properties. Nowadays, caffeine received an increasing interest in food and pharmaceutical industries due to its CNS stimulant properties, peripheral vasoconstriction, relaxation of the smooth muscle and myocardial stimulation. Caffeine constitutes an average of up to 4% of tea leaf and 1.5% of coffee bean. The aim of this study is to assess the quality of tea and coffee products present in the Egyptian market. Quality assessment was performed based on caffeine levels by using high performance thin layer chromatography (HPTLC). The results showed the quality variation among the products examined of both tea and coffee. With Ahmed tea London English breakfast showing the highest caffeine content (535 mg/ cup) and El Gawhara Green tea showing the lowest (3 mg/ cup). The used method is simple, rapid, reliable and suitable for evaluation of quality of caffeine containing preparations.

Echocardiographic and biochemical analysis of cardiac function and injury among female amateur runners post-marathon.

Numerous studies with male amateur runners have determined negative changes in their cardiac function/of their myocard following long endurance loads. This study aims to examine such potential changes in women, specifically, after running a marathon. A total of 18 female amateur runners (39.5 ± 10.5 years) were examined before (T1), immediately after (T2) and 24 h post-marathon (T3). An echocardiography was performed using Tissue Doppler (TD) imaging. In addition, the concentration of cardiac troponin T (cTnT) and the activity of the myocardial muscle creatine kinase (CK-MB) were determined at T1 and T2. The echocardiographic parameters revealed impairment of the diastolic function, without, however, documenting a diastolic dysfunction (in accordance with the classification of Nagueh (J Am Soc Echocardiogr, 22:107-33, 2009)). The ratio of blood flow velocity through the mitral valve during early versus late diastole (MV E/A ratio), for example, decreased. The values measured at T3 were similar to those measured at T1. The ratio of early transmitral diastolic filling velocity and of the transmitral diastolic filling velocity by TD imaging (MV E/E') did not indicate any change from T1 to T2, but a significant increase at T3 (in comparison with T1). The systolic function (measured by the left ventricular ejection fraction) did not change significantly. The cTnT concentration and CK-MB activity were significantly higher in T2 than in T1. The data collected does not provide any solid evidence of pathological changes in the cardiac function of female amateur runners post-marathon, although the lab values indicate a strongly increased myocardial stimulation.

Impact myocardial cytoprotection and inotropic stimulation at the annual prognosis in patients with myocardial infarction lifting segment ST, complicated heart failure

The article analyzes the effectiveness and safety of treatment cytoprotectant meldonium dihydrate and inotropic stimulator of levosimendan on an annual prognosis in patients with myocardial infarction complicated by acute heart failure II-III class Killip, subjected to percutaneous transluminal coronary angioplasty.

Rabbit models of post-cardiac arrest syndrome induced by transcutaneous electrical stimulation on the myocardium

Objective To establish a simple and convenient model of post-cardiac arrest syndrome (PCAS) in rabbits.Methods The experiment site in Xiamen university animal experiment center.Twenty five New Zealand rabbits were selected,male and female unlimited.Two acupuncture needles connected to the anode and cathode of a stimulator were transcutaneously inserted into the myocardium as electrode.The stimulating current was steered to the myocardium and maintained for 3 minutes to induce cardiac arrest (CA).Cardiopulmonary resuscitation (CPR) was performed at 6 minutes after a period of nonintervention.The levels of white blood cell (WBC),alanine aminotransferase (ALT),creatinine (Cr),troponin Ⅰ (Tn Ⅰ),brain natriuretic peptide (BNP),partial pressure of oxygen (PaO2),partial pressure of carbon dioxide (PaCO2) in arterial blood and the heart rate,body temperature,blood pressure were measured before CA and 0,24,48,72 hours after ROSC.Rabbits were sacrificed and microstructure injury was observed using electric microscope after ROSC 72 h.Comparisons among two groups were studied by using IndependentSamples t Test.Statistical comparisons within groups were analyzed by using paired t-test.Results The rate of ROSC in rabbits was 22/25.Twenty rabbits were survived in systemic inflammatory response syndrome (SIRS) and myocardial injury and dysfunction at 24 h after ROSC.Eleven rabbits were survived in post-resuscitation multiple organ dysfunction syndrome (PR-MODS) at 72 h after ROSC.TNF-α level peaked at 24 h after ROSC,and then decreased gradually.The procalcitonin (PCT) concentration significantly increased after ROSC 24 h.Conclusions The model of CA in rabbits induced by transcutaneous electrical myocardial stimulation required low-intensity current and showed typical pathophysiological process of PCAS,the model had high success rate and long survival time.The model appeared typical brain injury,myocardial dysfunction,ischemia-reperfusion injury.It may be an ideal animal model for investigation on PCAS. Key words: Electrical stimulation; Cardiac muscle; Cardiopulmonary resuscitation; Post-cardiac arrest syndrome; Animal models

Recurrent transient apical cardiomyopathy (Tako-Tsubo-like left ventricular dysfunction) in a postmenopausal female with diffuse esophageal spasms

Transient apical cardiomyopathy, also known as Takot-tsubo-like left ventricular dysfunction, is a clinical syndrome characterized by reversible left ventricular dysfunction at the apex with preserved basal contractility, in the setting of new ST and T wave changes suggestive of ischemia but no evidence of obstructive coronary artery disease on angiography. The main mechanism appears to be intense neuroadrenergic myocardial stimulation with endothelial dysfunction of the coronary vasculature. It has been noted that patients with esophageal spasms also have a tendency for coronary spasms. We present the case of a postmenopausal female with documented severe esophageal spasms who presented with atypical angina and recurrent Tako-tsubo cardiomyopathy.

Abstract 306: Proinflammatory Prostaglandin E Impairs Adrenergic Contractility in Animal Hearts

Introduction: Inflammation is a major risk factor for heart failure; inflammatory prostaglandin E is elevated in myocardium, and has been associated with development of heart failure via cardiac LV remodeling, but the mechanisms remain unclear. Hypothesis: We hypothesize that proinflammatory prostaglandin signaling might affect Left ventricular contractility by directly impairing β-adrenergic (βAR) signaling. Methods and Results: Pretreatment with Prostaglandin E impairs intracellular PKA phosphorylation of substrates in myocardium and cardiac contractile responses under β-adrenergic stimulation. Both prostaglandin E and β-adrenergic agonist isoproterenol induce intracellular cAMP activities in myocytes. However, the cAMP signal under prostaglandin stimulation is confined along the plasma membrane whereas the cAMP signal under isoproterenol stimulation is distributed throughout the cells, including the intracellular sarcoplasmic reticulum (SR), a calcium storage compartment critical for myocyte calcium signaling and contractile response. Interestingly, the prostaglandin E-induced cAMP signal is sufficient for PKA activation, leading phosphorylation and activation of phosphodiesterase 4 on the plasma membrane, a group of enzymes associated with membrane βARs for cAMP degradation. Moreover, pretreatment of prostaglandin E prevents dissociation of phosphodiesterase 4 from βAR induced by isoproterenol, a step necessary for cAMP diffusion from the plasma membrane to the intracellular SR. Together, prostaglandin E induces activation of phosphodiesterase 4 in βAR complex and prevents the cAMP diffusion from the plasma membrane to the SR under isoproterenol stimulation, and inhibits calcium signaling and contractile response in myocytes and animal hearts. Conclusions: This study provides a novel mechanism underlying the phosphodiesterase-mediated signaling crosstalk between two neurohormonal stimulation in myocardium under chronic conditions, and suggests that proinflammatory prostaglandin signaling may impair β-adrenergic contractile in the development of heart failure.

HPLC and HPTLC Determination of Caffeine in Raw and Roasted Date Seeds (Phoenix Dactylifera L)

Caffeine-containing products have been consumed for hundreds of years for their pleasant flavor and stimulating effects. In recent years, caffeine received increasing attention in food and pharmaceutical industries, due to its pharmacological properties which comprise stimulation of the central nervous system, peripheral vasoconstriction, relaxation of the smooth muscle and myocardial stimulation. The aim of this study was to determine the content of caffeine in raw and roasted date seeds. The caffeine content was determined by HPTLC-UV densitometric analysis. The highest caffeine content in the roasted date seed was determined by employing the HPTLC analysis (34.72 mg/ gm). The content of the flavonoids of raw date seeds and roasted date seeds were determined using HPLC methods. The highest content of flavonoids was determined in roasted date seeds gallic acid (0.1mg/gm), Rutin (2.2mg/gm), and Quercetin (0.52 mg/gm and raw date seeds contains gallic acid (0.1mg/gm), Rutin (0.4mg/gm), and Quercetin (0.9mg/gm).

254 Comparison of Chest Position and Distance to the Heart in the Induction of Cardiac Stimulation From an Electronic Control Device Using Steel versus Carbon Fiber Darts in Pigs

254 Comparison of Chest Position and Distance to the Heart in the Induction of Cardiac Stimulation From an Electronic Control Device Using Steel versus Carbon Fiber Darts in Pigs