Showing papers on "Cardiac arrhythmia published in 2011"

Atrial Fibrillation Pathophysiology Implications for Management

Abstract: Atrial fibrillation (AF), the most common sustained cardiac arrhythmia, is an important contributor to population morbidity and mortality. An arrhythmia that is particularly common in the elderly, AF is growing in prevalence with the aging of the population. Our understanding of the basic mechanisms that govern AF occurrence and persistence has been increasing rapidly. This article reviews the basic pathophysiology of AF over a broad range of levels, touching on the tissue mechanisms that maintain the arrhythmia, the relationship between clinical presentation and basic mechanisms, ion channel and transporter abnormalities that lead to ectopic impulse formation, basic models and tissue determinants of reentry, ion channel determinants of reentry, the nature and roles of electric and structural remodeling, autonomic neural components, anatomic factors, interactions between atrial and ventricular functional consequences of AF, and the basic determinants of atrial thromboembolism. We then review the potential implications of the basic pathophysiology of the arrhythmia for its management. We first discuss consequences for improved rhythm control pharmacotherapy: targeting underlying conditions, new atrium-selective drug targets, new targets for focal ectopic source suppression, and upstream therapy aiming to prevent remodeling. We then review the implications of basic mechanistic considerations for rate control therapy, AF ablation, and the prevention of thromboembolic events. We conclude with some thoughts about the future of translational research related to AF mechanisms.

Prolonged Rhythm Monitoring for the Detection of Occult Paroxysmal Atrial Fibrillation in Ischemic Stroke of Unknown Cause

Abstract: Atrial fibrillation (AF), commonly encountered in patients with ischemic stroke and transient ischemic attack (TIA), confers a 5-fold increased risk of ischemic stroke.1,2 AF-related strokes are associated with an ≈50% increased risk of disability and 60% increased risk of death at 3 months compared with strokes of other etiologies.3 Paroxysmal AF (PAF), a self-terminating recurrent form of cardiac arrhythmia that comprises between 25% and 62% of AF cases, may present as a brief single episode of arrhythmia or as clusters of abnormal rhythm of variable duration, sometimes evolving into a more persistent or permanent form.4 The self-terminating nature of PAF may lead to its underdiagnosis and consequent use of less effective treatment strategies (aspirin instead of oral anticoagulation) in poststroke patients. To address the underdiagnosis of PAF in patients with ischemic stroke and TIAs, several treatment guidelines have singled out the identification of PAF as an important goal after a stroke/TIA.5–8 The diagnosis of PAF, however, poses a challenge. Several features of AF (such as its brief duration, episodic frequency, and asymptomatic presentations) make its detection difficult and elusive to bedside screening measures, such as pulse monitoring and routine ECGs. To date, several studies have explored the use of prolonged noninvasive and invasive cardiac monitoring devices to identify AF but with variable success. After detection of AF, a cardioembolic mechanism is often inferred and anticoagulation occasionally prescribed for secondary stroke prevention. The routine use of cardiac monitoring to identify patients with PAF who will benefit from anticoagulation has been reported to be cost-effective.9 In this review, we provide an overview of the different methods of cardiac monitoring, summarize studies that investigated the incidence of PAF after stroke, and highlight gaps in our understanding of the pathogenic and prognostic significance of AF …

A Computational Model to Predict the Effects of Class I Anti-Arrhythmic Drugs on Ventricular Rhythms

Abstract: A long-sought, and thus far elusive, goal has been to develop drugs to manage diseases of excitability. One such disease that affects millions each year is cardiac arrhythmia, which occurs when electrical impulses in the heart become disordered, sometimes causing sudden death. Pharmacological management of cardiac arrhythmia has failed because it is not possible to predict how drugs that target cardiac ion channels, and have intrinsically complex dynamic interactions with ion channels, will alter the emergent electrical behavior generated in the heart. Here, we applied a computational model, which was informed and validated by experimental data, that defined key measurable parameters necessary to simulate the interaction kinetics of the anti-arrhythmic drugs flecainide and lidocaine with cardiac sodium channels. We then used the model to predict the effects of these drugs on normal human ventricular cellular and tissue electrical activity in the setting of a common arrhythmia trigger, spontaneous ventricular ectopy. The model forecasts the clinically relevant concentrations at which flecainide and lidocaine exacerbate, rather than ameliorate, arrhythmia. Experiments in rabbit hearts and simulations in human ventricles based on magnetic resonance images validated the model predictions. This computational framework initiates the first steps toward development of a virtual drug-screening system that models drug-channel interactions and predicts the effects of drugs on emergent electrical activity in the heart.

Heart–brain interactions in cardiac arrhythmia

Abstract: This review examines current knowledge of the effects of higher brain centres and autonomic control loops on the heart with particular relevance to arrhythmogenesis. There is now substantial evidence that higher brain function (cortex), the brain stem and autonomic nerves affect cardiac electrophysiology and arrhythmia, and that these may function as an interactive system. The roles of mental stress and emotion in arrhythmogenesis and sudden cardiac death are no longer confined to the realms of anecdote. Advances in molecular cardiology have identified cardiac cellular ion channel mutations conferring vulnerability to arrhythmic death at the myocardial level. Indeed, specific channelopathies such as long QT syndrome and Brugada syndrome are selectively sensitive to either sympathetic or vagal stimulation. There is increasing evidence that afferent feedback from the heart to the higher centres may affect efferent input to the heart and modulate the cardiac electrophysiology. The new era of functional neuroimaging has identified the central neural circuitry in this brain-heart axis. Since precipitants of sudden fatal arrhythmia are frequently environmental and behavioural, central pathways translating stress into autonomic effects on the heart might be considered as therapeutic targets. These brain-heart interactions help explain the apparent randomness of sudden cardiac events and provide new insights into future novel therapies to prevent sudden death.

The Duration of Pacing-induced Atrial Fibrillation Is Reduced in Vivo by Inhibition of Small Conductance Ca2+-activated K+ Channels

Abstract: :Atrial fibrillation (AF) is associated with increased morbidity and is in addition the most prevalent cardiac arrhythmia. Compounds used in pharmacological treatment has traditionally been divided into Na+ channel inhibitors, β-blockers, K+ channel inhibitors, and Ca2+ channel inhibitors, w

Catheter systems for cardiac arrhythmia ablation

Abstract: A plurality of catheter-based ablation apparatus embodiments are provided that address several areas of atrial target tissue and which feature firm and consistent ablation element to tissue contact enabling the creation of effective continuous lesions.

Phenotypic Manifestations of Mutations in Genes Encoding Subunits of Cardiac Potassium Channels

Abstract: Since 1995, when a potassium channel gene, hERG (human ether-a-go-go-related gene), now referred to as KCNH2, encoding the rapid component of cardiac delayed rectifier potassium channels was identified as being responsible for type 2 congenital long-QT syndrome, a number of potassium channel genes have been shown to cause different types of inherited cardiac arrhythmia syndromes. These include congenital long-QT syndrome, short-QT syndrome, Brugada syndrome, early repolarization syndrome, and familial atrial fibrillation. Genotype-phenotype correlations have been investigated in some inherited arrhythmia syndromes, and as a result, gene-specific risk stratification and gene-specific therapy and management have become available, particularly for patients with congenital long-QT syndrome. In this review article, the molecular structure and function of potassium channels, the clinical phenotype due to potassium channel gene mutations, including genotype-phenotype correlations, and the diverse mechanisms underlying the potassium channel gene-related diseases will be discussed.

Coffee, caffeine, and risk of hospitalization for arrhythmias.

Abstract: Context: Population study data about relations of coffee drinking to arrhythmia are sparse.Objective: To study relations of coffee drinking to risk of cardiac arrhythmia in 130,054 persons with previous data about coffee habits.Design and Outcome Measure: We used Cox proportional hazards models with 8 covariates to study coffee-related risk in 3137 persons hospitalized for cardiac arrhythmia. We conducted a similar analysis of total caffeine-related risk in a subgroup with data about other caffeine intake (11,679 study participants; 198 hospitalized).Results: With non-coffee-drinkers as the referent, the adjusted hazard ratio (HR) for any arrhythmia at the level of Language: en

Atrial fibrillation: diagnosis and treatment.

Abstract: Atrial fibrillation is the most common cardiac arrhythmia. It impairs cardiac function and increases the risk of stroke. The incidence of atrial fibrillation increases with age. Key treatment issues include deciding when to restore normal sinus rhythm, when to control rate only, and how to prevent thromboembolism. Rate control is the preferred management option in most patients. Rhythm control is an option for patients in whom rate control cannot be achieved or who have persistent symptoms despite rate control. The current recommendation for strict rate control is a resting heart rate of less than 80 beats per minute. However, one study has shown that more lenient rate control of less than 110 beats per minute while at rest was not inferior to strict rate control in preventing cardiac death, heart failure, stroke, and life-threatening arrhythmias. Anticoagulation therapy is needed with rate control and rhythm control to prevent stroke. Warfarin is superior to aspirin and clopidogrel in preventing stroke despite its narrow therapeutic range and increased risk of bleeding. Tools that predict the risk of stroke (e.g., CHADS2) and the risk of bleeding (e.g., Outpatient Bleeding Risk Index) are helpful in making decisions about anticoagulation therapy. Surgical options for atrial fibrillation include disruption of abnormal conduction pathways in the atria, and obliteration of the left atrial appendage. Catheter ablation is an option for restoring normal sinus rhythm in patients with paroxysmal atrial fibrillation and normal left atrial size. Referral to a cardiologist is warranted in patients who have complex cardiac disease; who are symptomatic on or unable to tolerate pharmacologic rate control; or who may be candidates for ablation or surgical interventions.

Rationale and current perspective for early rhythm control therapy in atrial fibrillation

Abstract: Atrial fibrillation (AF) is the most common sustained arrhythmia and an important source for mortality and morbidity on a population level. Despite the clear association between AF and death, stroke, and other cardiovascular events, there is no evidence that rhythm control treatment improves outcome in AF patients. The poor outcome of rhythm control relates to the severity of the atrial substrate for AF not only due to the underlying atrial remodelling process but also due to the poor efficacy and adverse events of the currently available ion-channel antiarrhythmic drugs and ablation techniques. Data suggest, however, an association between sinus rhythm maintenance and improved survival. Hypothetically, sinus rhythm may also lead to a lower risk of stroke and heart failure. The presence of AF, thus, seems one of the modifiable factors associated with death and cardiovascular morbidity in AF patients. Patients with a short history of AF and the underlying heart disease have not been studied before. It is fair to assume that abolishment of AF in these patients is more successful and possibly also safer, which could translate into a prognostic benefit of early rhythm control therapy. Several trials are now investigating whether aggressive early rhythm control therapy can reduce cardiovascular morbidity and mortality and increase maintenance of sinus rhythm. In the present paper we describe the background of these studies and provide some information on their design.

Modular neural network based arrhythmia classification system using ecg signal data

Abstract: This research is on presenting a new approach for cardiac arrhythmia disease classification. The proposed method uses Modular neural network (MNN) model to classify arrhythmia into normal and abnormal classes. We have performed experiments on UCI Arrhythmia data set [8]. Missing attribute values of this data set are replaced by closest column value of the concern class. We have constructed neural network model by varying number of hidden layers from one to three and are trained by varying training percentage in data set partitions. In this study, we are mainly interested in producing high confident arrhythmia classification results to be applicable in diagnostic decision support systems. This data set is a good environment to test classifiers as it is incomplete and ambiguous bio-signal data collected from total 452 patient cases. The classification performance is evaluated using six measures; sensitivity, specificity, classification accuracy, mean squared error (MSE), receiver operating characteristics (ROC) and area under curve (AUC). The experimental results presented in this paper show that more than 82.22% testing classification accuracy may be obtained.

Triple threat: the Na+/Ca2+ exchanger in the pathophysiology of cardiac arrhythmia, ischemia and heart failure.

Abstract: The Na(+)/Ca(2+) exchanger (NCX) is the main Ca(2+) extrusion mechanism of the cardiac myocyte and thus is crucial for maintaining Ca(2+) homeostasis. It is involved in the regulation of several parameters of cardiac excitation contraction coupling, such as cytosolic Ca(2+) concentration, repolarization and contractility. Increased NCX activity has been identified as a mechanism promoting heart failure, cardiac ischemia and arrhythmia. Transgenic mice as well as pharmacological interventions have been used to support the idea of using NCX inhibition as a future pharmacological strategy to treat cardiovascular disease.

Cardiac arrhythmia detection using dynamic time warping of ECG beats in e-healthcare systems

Abstract: Automatic real-time detection and classification of ECG patterns is of great importance in early diagnosis and treatment of life-threatening cardiac arrhythmia. In this paper, we have presented dynamic time warping (DTW) distance based approach for classification of arrhythmic ECG beats, with an aim of using it in smart-phone/mobile environment. The performance of the proposed method is tested on ECG beats of various arrhythmia types selected from MIT-BIH arrhythmia database. We have compared the proposed DTW approach using naive Bayes classifier with relative band spectral power as feature. The DTW approach has shown superior performance compared to the naive Bayes classifier. Furthermore, we have verified the performance of the DTW approach on down-sampled ECG beats in order to improve speed of the DTW algorithm. It is observed that the performance of the DTW approach did not deteriorate even after subsampling of ECG beats. The DTW with subsampling has been aimed at real-time arrhythmia detection in wearable mobile healthcare systems in telemedicine scenario for continuous monitoring of ECG records from cardiac patients.

Atrial tachycardia/fibrillation in the connexin 43 G60S mutant (Oculodentodigital dysplasia) mouse

Abstract: Atrial fibrillation (AF), the most common cardiac arrhythmia seen in general practice, can be promoted by conduction slowing. Cardiac impulse conduction depends on gap junction channels, which are ...

Clasification Of Arrhythmic ECG Data Using Machine Learning Techniques

Abstract: In this paper we proposed a automated Artificial Neural Network (ANN) based classification system for cardiac arrhythmia using multi-channel ECG recordings. In this study, we are mainly interested in producing high confident arrhythmia classification results to be applicable in diagnostic decision support systems. Neural network model with back propagation algorithm is used to classify arrhythmia cases into normal and abnormal classes. Networks models are trained and tested for MIT-BIH arrhythmia. The different structures of ANN have been trained by mixture of arrhythmic and non arrhythmic data patient. The classification performance is evaluated using measures; sensitivity, specificity, classification accuracy, mean squared error (MSE), receiver operating characteristics (ROC) and area under curve (AUC). Our experimental results gives 96.77% accuracy on MIT-BIH database and 96.21% on database prepared by including NSR database also.

Cardiac ion channels and mechanisms for protection against atrial fibrillation

Abstract: Atrial fibrillation (AF) is recognised as the most common sustained cardiac arrhythmia in clinical practice. Ongoing drug development is aiming at obtaining atrial specific effects in order to prevent pro-arrhythmic, devastating ventricular effects. In principle, this is possible due to a different ion channel composition in the atria and ventricles. The present text will review the aetiology of arrhythmias with focus on AF and include a description of cardiac ion channels. Channels that constitute potentially atria-selective targets will be described in details. Specific focus is addressed to the recent discovery that Ca2+-activated small conductance K+ channels (SK channels) are important for the repolarisation of atrial action potentials. Finally, an overview of current pharmacological treatment of AF is included.

Method and system for identifying cardiac arrhythmia driver sites

Abstract: A method of identifying potential driver sites for cardiac arrhythmias includes acquiring a plurality of electrograms from a plurality of locations on at least a portion of a patient's heart. Using the acquired electrograms, at least one electrical activity map is generated. Desirable electrical activity maps include complex fractionated electrogram standard deviation and mean maps, dominant frequency maps, peak-to-peak voltage maps, and activation sequence maps. Using one or more of these maps (e.g., by analyzing one or more electrogram morphological characteristics represented by these maps), at least one potential driver site can be detected.

Impact of Fontan conversion with arrhythmia surgery and pacemaker therapy.

Abstract: Objective: In the long-term period after Fontan operation, atrial arrhythmia was one of the important factors to decide the postoperative quality of life. We reviewed the impact of Fontan conversion with arrhythmia surgery and pacemaker therapy. Methods: Thirty-eight patients underwent Fontan conversion using extracardiac conduit from 1992, and 22 patients with atrial arrhythmia underwent maze procedure simultaneously using cryoablation or radiofrequency ablation and epicardial DDD pacemaker implantation and 16 patients had regular ‘sinus’ rhythm before Fontan conversion. Mean follow-up period was 52 months. Pre- and postoperative clinical course were analyzed. Average weight, age at Fontan conversion, and years after first Fontan operation were 49.0 kg, 25.8 years old, 14.7 years, respectively. Nineteen percent of patients were in New York Heart Association class I (NYHA I), and 74% of patients were in NYHA II, and 7% were in NYHA III, respectively. Results: Except three early deaths, actual survival rate at 1 year and 5 years were 80% and 64%, respectively. In survivors, 80% of the patients obtained regular heart rhythm including artificial pacemaker rhythm, although only 43% of the patients had regular ‘sinus’ rhythm before the Fontan conversion. Postoperative average cardiothoracic ratio and oxygen saturation (SpO2) were 50% and 94%, and 74% of patients were in NYHA I and 26% were in NYHA II, respectively, after Fontan conversion. Conclusions: Mid-term results of Fontan conversion with arrhythmia surgery and pacemaker therapy were acceptable. Restoration of regular rhythm might improve the postoperative NYHA status and the activity of the daily life.

Transient ST-segment episode detection for ECG beat classification

Abstract: Sudden Cardiac Death (SCD) is an unexpected death caused by loss of heart function when the electrical impulses fired from the ventricles become irregular. Most common SCDs are caused by cardiac arrhythmias and coronary heart disease. They are mainly due to Acute Myocardial Infarction (AMI), myocardial ischaemia and cardiac arrhythmia. This paper aims at automating the recognition of ST-segment deviations and transient ST episodes which helps in the diagnosis of myocardial ischaemia and also classifying major cardiac arrhythmia. Our approach is based on the application of signal processing and artificial intelligence to the heart signal known as the ECG (Electrocardiogram). We propose an improved morphological feature vector including ST-segment information for heart beat classification by supervised learning using the support vector machine approach. Our system has been tested and yielded an accuracy of 93.33% for the ST episode detection on the European ST-T Database and 96.35% on MIT-BIH Arrhythmia Database for classifying six major groups, i.e. Normal, Ventricular, Atrial, Fusion, Right Bundle and Left Bundle Branch Block beats.

A Real-Time Cardiac Arrhythmia Classification System with Wearable Electrocardiogram

Abstract: Long term continuous monitoring of electrocardiogram (ECG) in a free living environment provides valuable information for prevention on the heart attack and other high risk diseases. A design of a real-time wearable ECG monitoring system with cardiac arrhythmia classification is proposed in this paper. One of the striking advantages is that ECG analog front-end and on-node digital processing are designed to remove most of the noise and bias. In addition, a novel layered hidden Markov model is seamlessly integrated to classify multiple cardiac arrhythmias in real time. Last, human activities by an accelerometer can be identified to reduce the chance of false alarm in classification due to the motion artifacts.

Synergism between arrhythmia and hyperhomo-cysteinemia in structural heart disease.

Abstract: Elevated levels of homocysteine (Hcy) known as hyperhomocysteinemia (HHcy) is associated with cardiac arrhythmia and sudden cardiac death (SCD). Hcy increases iNOS, activates matrix metalloproteinase (MMP), disrupts connexin-43 and increases collagen/elastin ratio. The disruption of connexin-43 and accumulation of collagen (fibrosis) interupt cardiac conduction and attenuate NO transport from endothelium to myocyte (E-M) causing E-M uncoupling. We hypothesize that Hcy increases mtNOS, metalloproteinase activity, disrupts connexin-43, exacerbates endothelial-myocyte uncoupling, and induces cardiac failure by activating NMDA-R1 in structural heart disease. Chronic volume overload heart failure was created by aorta-venacava (AV) fistula. HHcy was induced by adminstrering Hcy in drinking water. NMDA-R1 was blocked by dizocilpine (MK-801). EKG and M-mode Echocardiography was performed. The E-M coupling was determined in cardiac rings. LV mitochondria was isolated. Levels of NMDA-R1, peroxiredoxin, NOX4, and mtNOS were measured. The degradation of connexin-43, collagen and elastin was measured by Western blot analysis. Mouse cardiac endothelial cells were cultured with or without Hcy or MK-801. The results suggest systolic and diastolic heart failure in HHcy and AVF mice. The levels of connexin, collagen degradation and MMP-9 were increased. The elastin was decreased in HHcy and AVF hearts. The mitochondrial NOX4 increased and peroxiredoxin was decreased. The mtNOS activity was synergistically increased in HHcy, AVF and HHcy+AVF hearts. The cardiac contraction and endothelial dependent relaxation was attenutated in HHcy and AVF hearts. Interestingly, the treatment with MK-801 mitigated the contractile dysfunction. These studies delineated the mechanism of Hcy-dependent endothelial-myocyte uncoupling in cardiac arrhythmia and failure, and have therapeutic ramifications for sudden cardiac death.

Developmental aspects of cardiac arrhythmogenesis

Abstract: The transcriptional regulation orchestrating the development of the heart is increasingly recognized to play an essential role in the regulation of ion channel and gap junction gene expression and consequently the proper generation and conduction of the cardiac electrical impulse. This has led to the realization that in some instances, abnormal cardiac electrical function and arrhythmias in the postnatal heart may stem from a developmental abnormality causing maintained (epigenetic) changes in gene regulation. The role of developmental genes in the regulation of cardiac electrical function is further underscored by recent genome-wide association studies that provide strong evidence that common genetic variation, at loci harbouring these genes, modulates electrocardiographic indices of conduction and repolarization and susceptibility to arrhythmia. Here we discuss recent findings and provide background insight into these complex mechanisms.

Estimating the risk of fatal arrhythmia in patients in methadone maintenance treatment for heroin addiction

Abstract: Aims. To estimate risk of death due to cardiac arrhythmia during methadone maintenance treatment. Background. There is evidence that methadone prolongs the QT interval, and has been associated with ventricular tachycardia in some individuals. Methods. We identified 51 deaths occurring during methadone treatment, occurring in a cohort with a defined exposure to methadone treatment. We obtained consent to access coronial records to investigate these in-treatment deaths in detail, to identify potential cases of fatal arrhythmia—those cases in which sudden death occurred without clear evidence of an alternate cause of death. We obtained consent to access clinic records of dosing. Two physicians reviewed the coronial files and circumstances of death. The total number of person-years exposure to methadone treatment was calculated. Results. There were extensive missing data in coronial and clinic files, making definitive assessment difficult in many cases. No definite case of death due to cardiac arrhythmia was identified. There were two cases in which arrhythmia seemed possible, and 10 cases in which arrhythmia could not be excluded. The study covered 14 500 patient-years (pys) in methadone treatment, yielding an estimate from 0 to 0.069 deaths per 100 pys, with a best estimate of fatal arrhythmia occurring at a rate of 0.014 per 100 pys. Overdose is a more common cause of death. Both potential arrhythmias and overdoses were associated with use of other drugs in addition to methadone—usually, prescription drugs or methamphetamine. Conclusions. The risk of fatal cardiac arrhythmia in methadone maintenance patients appears to be low. The major risk factor for death was use of prescription drugs, and methamphetamine, in addition to methadone.[Butler B, Rubin G, Lawrance A, Batey R, Bell J. Estimating the risk of fatal arrhythmia in patients in methadone maintenance treatment for heroin addiction. Drug Alcohol Rev 2010]

Current pacemaker and defibrillator therapy.

Abstract: Bradyarrhythmias (i.e., cardiac arrhythmias with a ventricular rate below 50/min) and especially tachyarrhythmias (those with a ventricular rate above 100/min) are often life-threatening. In Germany, some 100 000 persons sustain a cardiac arrest each year, caused in 65% to 80% of cases by a ventricular tachyarrhythmia (1). Bradycardia is a less common cause of cardiac arrest, accounting for only 5% to 20% of cases. Pacemakers have been available for 50 years, and implantable defibrillators for 25 years, as electrotherapy for cardiac arrhythmia.

Artificial Neural Network Based Cardiac Arrhythmia Disease Diagnosis

Abstract: Changes in the normal rhythm of a human heart may result in different cardiac arrhythmias, which may be immediately fatal or cause irreparable damage to the heart sustained over long periods of time. The ability to automatically identify arrhythmias from ECG recordings is important for clinical diagnosis and treatment. In this paper we proposed an Artificial Neural Network (ANN) based cardiac arrhythmia disease diagnosis system using standard 12 lead ECG signal recordings data. In this study, we are mainly interested in classifying disease in normal and abnormal classes. We have used UCI ECG signal data to train and test three different ANN models. In arrhythmia analysis, it is unavoidable that some attribute values of a person would be missing. Therefore we have replaced these missing attributes by closest column value of the concern class. ANN models are trained by static backpropagation algorithm with momentum learning rule to diagnose cardiac arrhythmia. The classification performance is evaluated using measures such as mean squared error (MSE), classification specificity, sensitivity, accuracy, receiver operating characteristics (ROC) and area under curve (AUC). Out of three different ANN models Multilayer perceptron ANN model have given very attractive classification results in terms of classification accuracy and sensitivity of 86.67% and 93.75% respectively while Modular ANN have given 93.1% classification specificity.

Wavelet-based features for characterizing ventricular arrhythmias in optimizing treatment options

Abstract: Ventricular arrhythmias arise from abnormal electrical activity of the lower chambers (ventricles) of the heart. Ventricular tachycardia (VT) and ventricular fibrillation (VF) are the two major subclasses of ventricular arrhythmias. While VT has treatment options that can be performed in catheterization labs, VF is a lethal cardiac arrhythmia, often when detected the patient receives an implantable defibrillator which restores the normal heart rhythm by the application of electric shocks whenever VF is detected. The classification of these two subclasses are important in making a decision on the therapy performed. As in the case of all real world process the boundary between VT and VF is ill defined which might lead to many of the patients experiencing arrhythmias in the overlap zone (that might be predominately VT) to receive shocks by the an implantable defibrillator. There may also be a small population of patients who could be treated with anti-arrhythmic drugs or catheterization procedure if they can be diagnosed to suffer from predominately VT after objectively analyzing their intracardiac electrogram data obtained from implantable defibrillator. The proposed work attempts to arrive at a quantifiable way to scale the ventricular arrhythmias into VT, VF, and the overlap zone arrhythmias as VT-VF candidates using features extracted from the wavelet analysis of surface electrograms. This might eventually lead to an objective way of analyzing arrhythmias in the overlap zone and computing their degree of affinity towards VT or VF. A database of 24 human ventricular arrhythmia tracings obtained from the MIT-BIH arrhythmia database was analyzed and wavelet-based features that demonstrated discrimination between the VT, VF, and VT-VF groups were extracted. An overall accuracy of 75% in classifying the ventricular arrhythmias into 3 groups was achieved.

Coronary angiography and intervention during hypothermia can be performed safely without cardiac arrhythmia or vasospasm.

Abstract: Mild therapeutic hypothermia is a neuroprotective procedure after cardiac arrest. Therefore, it is increasingly used. Likewise, there is a growing demand for coronary angiography and percutaneous coronary interventions under hypothermia. Case studies suggested that hypothermia may be associated with coronary vasospasm, heart rhythm events and platelet dysfunction. In this study, it was evaluated whether vasospasm, arrhythmia or bleeding occur to a relevant degree during cardiac catheterization under concomitant hypothermia. In this prospective, single-center, open-label, non-interventional study, 29 patients after resuscitation for cardiac arrest were treated with mild hypothermia and underwent cardiac catheterization (coronary angiography n = 11, coronary angiography plus percutaneous intervention n = 18). The incidence of vasospasm, cardiac arrhythmia and relevant bleeding at the puncture site were evaluated. Mean temperature at cardiac catheterization was 33.9 ± 0.76°C. The mean heart rate was 82 ± 26 bpm at hospital admission and 67 ± 17 bpm under hypothermia (p < 0.05). There was no patient with relevant bradycardia beyond the expected hypothermia-induced rate reduction during the procedure. There were no unexpected ventricular tachycardias or episodes of ventricular fibrillation which might have been attributed to hypothermia. Twenty-nine of 29 patients (100%) were free from coronary vasospasm. There was no patient with a relevant bleeding at the puncture site. Potassium levels were low in 52% of the patients, even after resuscitation, which was partially attributed to hypothermia. Coronary angiography and percutaneous coronary interventions under mild therapeutic hypothermia were safe in this small cohort and were performed without hypothermia-induced vasospasm, relevant rhythm events or bleeding complications. This result has to be confirmed in a large series of patients.