Arrhythmia

Epidemiological, clinical and laboratory studies have yielded definitive evidence that physical activity is able to reduce the morbidity and mortality of cardiovascular diseases and to improve physical fitness and quality of life. Moreover, physical activ- ity seems to be capable of significantly reducing the risk of developing other chronic diseases, such as obesity, osteoporosis, diabetes, some neoplasms and depression. For

Therapy with bisphosphonates, including alendronate (ALN), is considered a safe and effective treatment for osteoporosis. However, recent studies have reported an unexpected increase in serious atrial fibrillation (AF) in patients treated with bisphosphonates. The mechanism that explains this side effect remains unknown. Since AF is associated with an altered sarcoendoplasmic reticulum calcium load, we studied how ALN affects cardiomyocyte calcium homeostasis and protein isoprenylation in vitro. Acute and long-term (48 h) treatment of atrial and ventricular cardiomyocytes with ALN (10 − 8 -10 − 6 M) was performed. Changes in calcium dynamics were determined by both fluorescence measurement of cytosolic free Ca 2+ concentration and western blot analysis of calcium-regulating proteins. Finally, effect of ALN on protein farnesylation was also identified. In both atrial and ventricular cardiomyocytes, ALN treatment delayed and diminished calcium responses to caffeine. Only in atrial cells, long-term exposure to ALN-induced transitory calcium oscillations and led to the development of oscillatory component in calcium responses to caffeine. Changes in calcium dynamics were accompanied by changes in expression of proteins controlling sarcoendoplasmic reticulum calcium. In contrast, ALN minimally affected protein isoprenylation in these cells. In summary, treatment of atrial cardiomyocytes with ALN-induced abnormalities in calcium dynamics consistent with induction of a self-stimulatory, pacemaker-like behavior, which may contribute to the development of cardiac side effects associated with these drugs.

Background: Although good prognosis and clinical long-term outcome have been commonly reported in minimally symptomatic adult patients with ASD, this information has been based on studies with a relatively small number of adult patients. We studied unoperated patients aged over 40 years to define the patterns of presentation, anatomical characteristics, outcome and predictive factors for free-event survival of major cardiovascular and pulmonary events. Methods and results: Two-hundred survivors of atrial septal defect aged over 40-yr attended from 1985 to 1998 were reviewed and followed-up from 1.6 to 22 years. Patients were classified in three groups according to age at entry: Group 1, between 40 and 49; Group 2; 50 and 59; and Group 3, z 60 years old. The mean age at presentation was 48.8 F 9.2 years, and the most common clinical presentations were arrhythmia and dyspnea (51.4%). There were 37 (18.5%) events: 7 heart failure-related, 5 sudden death, 13 severe pulmonary infections, 5 embolisms, and 4 strokes. According to Cox's regression analysis, predictors of primary end point included age group at presentation (hazard ratio 1.71, 95% confidence limits 1.16 to 2.54), and either pulmonary hypertension (mean pulmonary pressure > 35 mmHg; hazard ratio = 0.65 (4.6, confidence limits 2.2 to 9.5) or, arterial oxygen saturation < 80% (hazard ratio 1.71, 95% confidence limits 1.16 to 2.54). Conclusions: This study supports that long term outcome of patients aged >40 years with unoperated ASD is importantly determined by the mPAP (>35 mmHg), SaO2% (_80) and the age at diagnosis. Nevertheless we identified an inverse association between the mPAP level and SaO2% (interaction). The event-free survival expectancy may be estimated using the age at diagnosis and either SaO2% or mPAP. This prognostic stratification based on pathophysiological principles, may help in making decisions for therapeutic interventions. SaO2% should always be measured as a part of the initial clinical approach of those patients with atrial septal defect aged over 40 years. D

Dilated cardiomyopathy (DCM) is a major cause of morbidity and mortality in various dog breeds. The diagnosis of overt DCM is not normally problematic, although the importance of active exclusion of other causes of the dilated, hypokinetic heart is emphasised. Recent interest in human familial DCM has prompted a number of researchers to investigate the genetic basis of canine DCM. Prospective screening of dogs from lines with familial prevalence of DCM may identify dogs with pre-clinical ("occult") DCM. Dogs with other echocardiographic abnormalities or arrhythmias may also be identified. It is clear that dogs, like humans, have a prolonged pre-symptomatic phase of the disease extending over years. The ESVC DCM taskforce was established to provide the veterinary cardiology community with guidelines for the diagnosis of DCM, predominantly based on 2D and M-mode echocardiography. Diagnosis of DCM requires all of the following: (i) Left ventricular dilatation (ii) Reduced systolic function (iii) Increased sphericity of the left ventricle. We propose a scoring system for the identification of dogs in the pre-clinical stages. These include a number of major criteria and minor criteria. Future prospective longitudinal studies are required to test these in different breed populations to assess their predictive power and further refinements may be required. The importance of post mortem confirmation of disease is emphasised, and the two major histopathological features associated with DCM, the attenuated wavy fibre and the fibro-fatty infiltration-degenerative forms, require further investigation to identify the different aetiopathogenetic factors which may be involved.

Recent trends in clinical and telemedicine applications highly demand automation in (electrocardiogram) ECG signal processing and heart beat classification. A real-time patientadaptive cardiac profiling scheme using repetition detection is proposed in this paper. We introduce a novel local ECG beat classifier to profile each patient's normal cardiac behavior. As ECG morphologies vary from person to person, and even for each person, it can vary depending on the person's physical condition, having such profile is essential for various diagnosis (e.g. arrhythmia) purposes, and can successfully raise an early warning flag for the abnormal cardiac behavior of any individual. Experimental results show that our technique follows the MIT/BIH arrhythmia database annotations with high accuracy.

We have developed an automatic method for the analysis and identification of dynamical regimes in intracellular calcium patterns from confocal calcium images. The method allows the identification of different dynamical patterns such as spatially concordant and discordant alternans, irregular behavior or phase-locking regimes such as period doubling or halving. The method can be applied to the analysis of different cardiac pathologies related to anomalies at the cellular level such as ventricular reentrant arrhythmias.

Background-The anisotropy of cardiac tissue is a key determinant of 3D electric propagation and the stability of activation wave fronts in the heart. The electric properties of ventricular myocardium are widely assumed to be axially anisotropic, with activation propagating most rapidly in the myofiber direction and at uniform velocity transverse to this. We present new experimental evidence that contradicts this view. Methods and Results-For the first time, high-density intramural electric mapping (325 electrodes at Ϸ4ϫ4ϫ1-mm spacing) from pig left ventricular tissue was used to reconstruct 3D paced activation surfaces projected directly onto 3D tissue structure imaged throughout the same left ventricular volume. These data from 5 hearts demonstrate that ventricular tissue is electrically orthotropic with 3 distinct propagation directions that coincide with local microstructural axes defined by the laminar arrangement of ventricular myocytes. The maximum conduction velocity of 0.67Ϯ0.019 ms Ϫ1 was aligned with the myofiber axis. However, transverse to this, the maximum conduction velocity was 0.30Ϯ0.010 ms Ϫ1 , parallel to the myocyte layers and 0.17Ϯ0.004 ms Ϫ1 normal to them. These orthotropic conduction velocities give rise to preferential activation pathways across the left ventricular free wall that are not captured by structurally detailed computer models, which incorporate axially anisotropic electric properties. Conclusions-Our findings suggest that current views on uniform side-to-side electric coupling in the heart need to be revised. In particular, nonuniform laminar myocardial architecture and associated electric orthotropy should be included in future models of initiation and maintenance of ventricular arrhythmia. (Circ Arrhythmia Electrophysiol. 2009;2:433-440.)

Background: Heart rate variability (HRV) is a marker of cardiac autonomic tone. Depressed HRV has been reported in patients with AIDS. We conducted this study to find out if HRV is depressed in human immunodeficiency virus (HIV)-positive individuals without AIDS. Methods: We studied prospectively HRV by spectral analysis of short-term electrocardiography (ECG) monitoring in 21 HIVpositives (33F11 years) and in 18 healthy volunteers (31F9 years). None of the HIV-positives had any clinical evidence of autonomic or cardiac dysfunction. Echocardiography was also performed in HIV-seropositives to rule out left ventricular (LV) systolic dysfunction. All these individuals did not have any evidence of AIDS. Results: Mean CD4+ lymphocyte count was 426F166/mm 3 . The ejection fraction (EF%) of HIV patients was 62.4F6.4.The total power of HRV was reduced significantly in HIV-positive individuals ( p<0.00001). All the components of HRV were reduced. Conclusions: HRV is reduced in HIV-seropositive individuals in early stages of infection as well without any clinical evidence of autonomic dysfunction. This may serve as an early marker of future global sympathovagal imbalance. D

Epinephrine-induced arrhythmias (EPIA) are known to be associated with local cardiac cholinergic activation. The present study examined the development of QT prolongation and the effect on EPIA of whole-body exposure of animals to a potent acetylcholine esterase inhibitor. Freely moving rats were exposed to sarin vapor (34.2 ± 0.8 mg/liter) for 10 min. The electrocardiograms (ECG) of exposed and control animals were monitored every 2 weeks for 6 months. One and six months post exposure, rats were challenged with epinephrine under anesthesia, and the threshold for arrhythmias was determined. Approximately 35% of the intoxicated rats died within 24 h of sarin exposure. Additional occasional deaths were recorded for up to 6 months (final mortality rate of 48%). Surviving rats showed, agitation, aggression, and weight loss compared to non-exposed rats, and about 20% of them experienced sporadic convulsions. Sarin-challenged rats with severe symptoms demonstrated QT segment prolongation during the first 2-3 weeks after exposure. The EPIA that appeared at a significantly lower blood pressure in the treated group in the first month after intoxication lasted for up to 6 months. This decrease in EPIA threshold was blocked by atropine and methyl-atropine. Three months post exposure no significant changes were detected in either k D or B max values of 3 H-N-methyl scopolamine binding to heart homogenates, or in the affinity of carbamylcholine to cardiac muscarinic receptors. The increase in the vulnerability to develop arrhythmias long after accidental or terror-related organophosphate (OP) intoxication, especially under challenging conditions such as stress or intensive physical exercise, may explain the delayed mortality observed following OP exposure.

Objective: To assess the clinical potential of 4D volume rendering of the atrioventricular (AV) junction in normal fetuses and in those with abnormalities of the AV valves, aiming to demonstrate new spatial views of the fetal heart and to provide clear representations of the underlying anatomy. Methods: This prospective study included 30 normal fetuses and 22 fetuses with CHD related to the AV junction (8 cases of AVSD, 4 HLHV, 2 tricuspid atresia, 2 Ebstein, 2 tricuspid valve dysplasia and 4 polyvalvular dysplasia). Volume datasets were acquired in apical or lateral isonation of the fetal heart, at the level of the four-chamber view and stored for later offline evaluation in a spatial volume rendering of the AV junction. The render box (RB) was systematically selected. Firstly, the RB included the AV valves and the reference dot was placed at the level of the crux of the heart. Then the reference dot was placed in the interventricular septum at the level of the distal opening of the tricuspid valve leaflet. The view obtained allowed the papillary muscles (PM) of the valve tension apparatus of the AV valves to be identified. Results: Successful acquisitions, rendering and evaluation of the AV valve were technically possible in all cases. The evaluation of the PM of the left ventricle(LV) was possible in 26/30 normal fetuses (86%) and in 20/30 (66%) for the right ventricle(RV). A dense fibrous tissue was seen in cases of atresia. A trifoliate left AV valve with a cleft in some cases of AVSD, with different arrangement of the PM within the LV. In Ebstein's anomaly, the mural and septal leaflets are displaced into the RV. Conclusion: Volume rendering of the AV valves is a reliable and useful complementary investigation for evaluation of congenital valvular lesions. The study provide a qualitative 3D assessment of some of the components of the AV valve complex that contribute to our understanding of normal and abnormal fetal AV valve function.

The incidence and nature of cardiac arrhythmias during static apnea were studied by monitoring the electrocardiogram (ECG) and oxygen saturation (SaO 2 ) of 16 recreational breath-hold divers. All subjects completed a maximal apnea with a mean ( §SD) breath-hold duration of 281 ( §73) s without clinical complications. Both heart rate (HR) and SaO 2 decreased signiWcantly with breath-hold duration. The decline in SaO 2 was inversely related to the decline in HR (r = ¡0.55, P < 0.05). Cardiac arrhythmias (supraventricular and ventricular premature complexes, right bundle branch block) occurred in 12/16 (77%) subjects and were related to breath-hold duration. Subjects with atrial premature complexes (n = 9) had a reduced BMI (P = 0.016) and a higher decline of the terminal SaO 2 (P = 0.01). In conclusion, ectopic arrhythmias were common during maximal static apneas for training purposes.

This study was designed to evaluate the feasibility of using cylindrical ultrasound transducers mounted on a catheter for the ablation of cardiac tissues. In addition, the effects of ultrasound frequency and power was evaluated both using computer simulations and in vitro experiments. Frequencies of 4.5, 6, and 10 MHz were selected based on the simulation studies and manufacturing feasibility. These transducers were mounted on the tip of 7-French catheters and applied in vitro to fresh ventricular canine endocardium, submerged in flowing degassed saline at 37 degree C. When the power was regulated to maintain transducer interface temperature at 90-100 degree C, the 10-, 6-, and 4.5-MHz transducers generated a lesion depth of 5.9 +/- 0.2 mm, 4.6 +/- 1.0 mm, and 5.3 +/- 0.9 mm, respectively. The 10-MHz transducer was chosen for the in vivo tests since the maximum lesion depth was achieved with the lowest power. Two dogs were anesthetized and sonications were performed in both the left and right ventricles. The 10-MHz cylindrical transducers caused an average lesion depth of 6.4 +/- 2.5 mm. In conclusion, the results show that cylindrical ultrasound transducers can be used for cardiac tissue ablation and that they may be able to produce deeper tissue necrosis than other methods currently in use.

Methods: In this study out of 380 planned off-pump coronary artery bypass procedures done between August 2002 to July 2006, 12 patients required emergency conversion, of which three patients were after haemodynamic collapse, and nine patients were semi elective conversions before haemodynamic collapse.

Analysis of mice with genetically altered expression of cardiac connexins can provide insights into the role of individual gap junction channel proteins in cell-to-cell communication, impulse propagation, and arrhythmias. However, conflicting results have been reported regarding conduction velocity slowing in mice heterozygous for a null mutation in the gene encoding connexin43 (Cx43). Methods: High-resolution optical mapping was used to record

This paper introduces a real-time data compression and transmission algorithm between e-health terminals for a periodic ECGsignal. The proposed algorithm consists of five compression procedures and four reconstruction procedures. In order to evaluate the performance of the proposed algorithm, the algorithm was applied to all 48 recordings of MIT-BIH arrhythmia database, and the compress ratio (CR), percent root mean square difference (PRD), percent root mean square difference normalized (PRDN), rms, SNR, and quality score (QS) values were obtained. The result showed that the CR was 27.9:1 and the PRD was 2.93 on average for all 48 data instances with a 15% window size. In addition, the performance of the algorithm was compared to those of similar algorithms introduced recently by others. It was found that the proposed algorithm showed clearly superior performance in all 48 data instances at a compression ratio lower than 15:1, whereas it showed similar or slightly inferior PRD performance for a data compression ratio higher than 20:1. In light of the fact that the similarity with the original data becomes meaningless when the PRD is higher than 2, the proposed algorithm shows significantly better performance compared to the performance levels of other algorithms. Moreover, because the algorithm can compress and transmit data in real time, it can be served as an optimal biosignal data transmission method for limited bandwidth communication between e-health devices.

A robust multi-lead ECG wave detection-delineation algorithm is developed in this study on the basis of discrete wavelet transform (DWT). By applying a new simple approach to a selected scale obtained from DWT, this method is capable of detecting QRS complex, P-wave and T-wave as well as determining parameters such as start time, end time, and wave sign (upward or downward). First, a window with a specific length is slid sample to sample on the selected scale and the curve length in each window is multiplied by the area under the absolute value of the curve. In the next step, a variable thresholding criterion is designed for the resulted signal. The presented algorithm is applied to various databases including MIT-BIH arrhythmia database, European ST-T Database, QT Database, CinC Challenge 2008 Database as well as high resolution Holter data of DAY Hospital. As a result, the average values of sensitivity and positive predictivity Se = 99.84% and P+ = 99.80% were obtained for the detection of QRS complexes, with the average maximum delineation error of 13.7 ms, 11.3 ms and 14.0 ms for P-wave, QRS complex and T-wave, respectively. The presented algorithm has considerable capability in cases of low signal-to-noise ratio, high baseline wander, and abnormal morphologies. Especially, the high capability of the algorithm in the detection of the critical points of the ECG signal, i.e. the beginning and end of T-wave and the end of the QRS complex was validated by cardiologists in DAY hospital and the maximum values of 16.4 ms and 15.9 ms were achieved as absolute offset error of localization, respectively.

The purpose of this article is to review the nerve sprouting hypothesis of sudden cardiac death. It is known that sympathetic stimulation is important in the generation of sudden cardiac death. For example, there is a diurnal variation of sudden death rate in patients with myocardial infarction. Beta blockers, or drugs with beta blocking effects, are known to prevent sudden cardiac death. It was unclear if the cardiac nerves in the heart play only a passive role in the mechanisms of sudden death. To determine if nerve sprouting and neural remodeling occur after myocardial infarction, we performed immunocytochemical studies of cardiac nerves in explanted native hearts of transplant recipients. We found that there was a positive correlation between nerve density and a clinical history of ventricular arrhythmia. Encouraged by these results, we performed a study in dogs to determine whether or not nerve growth factor (NGF) infusion to the left stellate ganglion can facilitate the development of ventricular tachycardia (VT), ventricular fibrillation (VF), and sudden cardiac death (SCD). The results showed that augmented myocardial sympathetic nerve sprouting through NGF infusion plus atrioventricular (AV) block and MI result in a 44% incidence (four of nine dogs) of SCD and a high incidence of VT in the chronic phase of MI. In contrast, none of the six dogs (with AV block and MI) without NGF infusion died suddenly or had frequent VT episodes. Based on these findings, we propose the nerve sprouting hypothesis of ventricular arrhythmia and SCD. The hypothesis states that MI results in nerve injury, followed by sympathetic nerve sprouting and regional (heterogeneous) myocardial hyperinnervation. The coupling between augmented sympathetic nerve sprouting with electrically remodeled myocardium results in VT, VF and SCD. Modification of nerve sprouting after MI may provide a novel opportunity for arrhythmia control.

This paper presents an ECG compressor based on optimized quantization of Discrete Cosine Transform (DCT) coefficients. The ECG to be compressed is partitioned in blocks of fixed size, and each DCT block is quantized using a quantization vector and a threshold vector that are specifically defined for each signal. These vectors are defined, via Lagrange multipliers, so that the estimated entropy is minimized for a given distortion in the reconstructed signal. The optimization method presented in this paper is an adaptation for ECG of a technique previously used for image compression. In the last step of the compressor here proposed, the quantized coefficients are coded by an arithmetic coder. The Percent Root-Mean-Square Difference (PRD) was adopted as a measure of the distortion introduced by the compressor. To assess the performance of the proposed compressor, 2-minute sections of all 96 records of the MIT-BIH Arrhythmia Database were compressed at different PRD values, and the corresponding compression ratios were computed. We also present traces of test signals before and after the compression/decompression process. The results show that the proposed method achieves good compression ratios (CR) with excellent reconstruction quality. An average CR of 9.3:1 is achieved for PRD equal to 2.5%. Experiments with ECG records used in other results from the literature revealed that the proposed method compares favorably with various classical and state-of-the-art ECG compressors. 

The aim of this population-based study was to (1) describe living conditions and actual health care utilization among 85 year olds; (2) determine factors that affect hospital admissions in this age. The study was conducted on 85-year-old residents in Linköping municipality, Sweden. The data collected included medical records, health care utilization during the preceding 12 months and a postal questionnaire on assistance, assistive technology, functional impairment, feelings of loneliness, worries and health-related quality of life measured by the EQ-5D. Out of 650 eligible individuals, 496 (78% of those alive) participated. Despite the prevalence of multi-morbidity (68%) and mental discomfort, the majority managed self-care (85%), usual activities (74%) and had high (&gt;60/100) self-rated health evaluated by a visual analog scale (VAS). The non-hospitalized group reported a better health status than the hospitalized group in terms of medical aspects, living conditions and subjectiv...

Secundum atrial septal defects (ASD) are the commonest congenital cardiac abnormality. They are often identified incidentally, or in conjunction with an acquired cardiac abnormality. Untreated they may lead to significant morbidity and mortality, with consequences including right ventricular overload and right heart failure, pulmonary arterial hypertension, shunt reversal and cyanosis, and arrhythmias. Deciding whether to close an ASD can consume as much clinical time as finding them or indeed closing them. In the past when surgical closure was the only option, the morbidity of the procedure, including the need for sternotomy or thoracotomy, limited its use to large defects considered likely to result in shunt reversal or heart failure. Smaller defects were often managed conservatively. However within the past 2 decades percutaneous closure has come to the fore and is now considered first line when morphology allows. With lower morbidity, this has "lowered the bar" in terms of who is considered for closure, although the absolute mortality risk of either procedure is low. However, even though mortality is low, morbidity is still significant after percutaneous closure. Despite this, the utilisation of ASD closure has dramatically increased in the last decade with a sudden rise from 2001, owing largely to growth in percutaneous closures. Instead of looking for symptoms, which are subjective, or evidence of large shunt/RV failure, an objective measure of exercise capacity might help identify other patients who would benefit from closure. This review will look at the current evidence of cardiopulmonary exercise testing (CPET) in ASD closure.

A novel algorithm for real-time detection and prediction of the dicrotic notch from aortic pressure waves was evaluated in arrhythmic aortic pressure signals from heart failure patients. A simplified model of the arterial tree was used to calculate real-time aortic flow from aortic pressure. The dicrotic notch was detected at the first negative dip from the calculated flow, prediction of the notch was performed using a percentage of the decreasing flow. The performance of the real-time dicrotic notch detection algorithm (RTDND) was evaluated during severe arrhythmia from aortic pressure signals of 12 patients. The RTDND was able to detect the dicrotic notch in 98.1%. No false positive dicrotic notch identifications were observed. Prediction of the dicrotic notch was tested at 40%, 20%, and 0% of the decreasing calculated aortic flow. The mean time-delays to the notch were 68 +/- 14 ms, 55 +/- 12 ms, and 43 +/- 8 ms, respectively. Given these small variability, intra-beat prediction ...

The illicit use of supraphysiological doses of androgenic steroids (AAS) has been suggested as a cause of arrhythmia in athletes. The objectives of the present study were to investigate the time-course and the cellular, ionic and molecular processes underlying ventricular repolarization in rats chronically treated with AAS. Male Wistar rats were treated weekly for 8 weeks with 10 mg/kg of nandrolone decanoate (DECA n = 21) or vehicle (control n = 20). ECG was recorded weekly. Action potential (AP) and transient outward potassium current (I to ) were recorded in rat hearts. Expression of KChIP2, Kv1.4, Kv4.2, and Kv4.3 was assessed by real-time PCR. Hematoxylin/eosin and Picrosirius red staining were used for histological analysis. QTc was greater in the DECA group. After DECA treatment the left, but not right, ventricle showed a longer AP duration than did the control. I to current densities were 47.5% lower in the left but not in the right ventricle after DECA. In the right ventricle the I to inactivation time-course was slower than in the control group. After DECA the left ventricle showed lower KChIP2 (∼ 26%), Kv1.4 (∼ 23%) and 4.3 (∼ 70%) expression while the Kv 4.2 increased in 4 (∼ 250%) and diminished in 3 (∼ 30%) animals of this group. In the right ventricle the expression of I to subunits was similar between the treatment and control groups. DECA-treated hearts had 25% fewer nuclei and greater nuclei diameters in both ventricles. Our results strongly suggest that supraphysiological doses of AAS induce morphological remodeling in both ventricles. However, the electrical remodeling was mainly observed in the left ventricle.

Objetivos: O objetivo deste estudo foi o de analisar morbidade e mortalidade pós-cirúrgicas em pacientes submetidos à cirurgia de aneurisma da aorta torácica e aneurisma toracoabdominal no Departamento de Cirurgia Vascular do IRCCS San Raffaele, Milão.

Resveratrol has been demonstrated to produce a variety of biological actions. Accumulating line of evidence supported the view that resveratrol may exert protective effect on the cardiovascular system. The aim of the study was to assess the antiarrhythmic profile as well as electrophysiological properties of resveratrol. We observe the antiarrhythmic effect of resveratrol on aconitine induced rat arrhythmia, ouabain induced guinea pig arrhythmia, and coronary ligation induced rat arrhythmia animal models. Resveratrol significantly and dose-dependently increased the doses of aconitine and ouabain required to induce the arrhythmia indexes. In coronary ligation induced rat arrhythmia model, resveratrol shortened duration of arrhythmia, decreased incidence of ventricular tachycardia and mortality. Electrophysiological experiment revealed that resveratrol could shorten APD through inhibition of I Ca and selective enhancement of I Ks without an effect on I Kr .

Impedance cardiography (ICG) charts the rises and falls of thoracic impedance as the fluid content of the chest changes with each heartbeat. Breathing, arrhythmia, movements and posture interfere with the ICG. Modern pattern recognition software can now produce a composite signalaveraged ICG that considerably simplifies interpretation. The first derivative velocity waveform shows a smooth S wave that corresponds with systole, while the second derivative acceleration waveform (dZ /dt) contains several reference points that outline the A, S and O waves. Normally, the A wave follows atrial contraction and occurs in late diastole. It can, therefore, be abnormal in both atrial and ventricular arrhythmias and is abnormally increased when there is diastolic dysfunction. The S wave reflects ventricular contractility and is deformed by ventricular dyssynchrony. The O wave is associated with mitral valve opening and is abnormally enlarged in heart failure. These different patterns of ICG waveform are relatively easy to recognise and can be cost-effectively and quickly obtained to reliably distinguish between normal and abnormal cardiac function.

Among the most compelling challenges facing cardiologists today is identification of which patients are at highest risk for sudden death. Automatic implantable cardioverter-defibrillators are now indicated in many of these patients, yet the role of noninvasive risk stratification in classifying patients at high risk is not well defined. The purpose of this review is to evaluate the various electrocardiographic (ECG) techniques that appear to have potential in assessment of risk for arrhythmia. The resting ECG (premature ventricular contractions, QRS duration, damage scores, QT dispersion, and ST segment and T wave abnormalities), T wave alternans, late potentials identified on signal-averaged ECGs, and heart rate variability are explored. Unequivocal evidence to support the widespread use of any single noninvasive technique is lacking; further research in this area is needed. It is likely that a combination of risk evaluation techniques will have the greatest predictive power in enabling identification of patients most likely to benefit from device therapy. (Curr Probl Cardiol 2004;29:357-432.) O ver the past decade advances in technology have provided cardiologists with improved therapeutic options for patients at risk for sudden cardiac death (SCD). The automatic implantable cardioverter-defibrillator (ICD) has changed the landscape of electrophys-

As the number of cancer survivors grows because of advances in therapy, it has become more important to understand the longterm complications of these treatments. This article presents the current knowledge of adverse cardiovascular effects of radiotherapy to the chest. Emphasis is on clinical presentations, recommendations for follow-up, and treatment of patients previously exposed to irradiation. Medline TM literature searches were performed, and abstracts related to this topic from oncology and cardiology meetings were reviewed. Potential adverse effects of mediastinal irradiation are numerous and can include coronary artery disease, pericarditis, cardiomyopathy, valvular disease and conduction abnormalities. Damage appears to be related to dose, volume and technique of chest irradiation. Effects may initially present as subclinical abnormalities on screening tests or as catastrophic clinical events. Estimates of relative risk of fatal cardiovascular events after mediastinal irradiation for Hodgkin's disease ranges between 2.2 and 7.2 and after irradiation for left-sided breast cancer from 1.0 to 2.2. Risk is life long, and absolute risk appears to increase with length of time since exposure. Radiation-associated cardiovascular toxicity may in fact be progressive. Long-term cardiac follow-up of these patients is therefore essential, and the range of appropriate cardiac screening is discussed, although no specific, evidencebased screening regimen was found in the literature. #

Inotropes are pharmacological agents that affect the force or energy of ventricular muscle contraction, and which often have effects on other variables such as heart rate, preload and afterload, and peripheral vascular tone. The use of such agents is commonplace in perioperative or critical care, and the indications for their use are multiple and not confined to their inotropic actions. No inotrope exerts its effect purely by altering myocardial contractility, therefore the potentially useful effects on heart rate, systemic and pulmonary vascular tone and the side effects of these agents must be taken into account when choosing an appropriate agent. The choice of inotrope is influenced by the therapeutic goal, which is seldom an elevation in systemic blood pressure alone. The purpose of manipulating a patient's haemodynamics in the acute situation is to ensure the adequate delivery of oxygen to vital tissues (to avoid or treat shock). The causes of inadequate oxygen delivery are: • a cardiac output insufficient to meet the demands of the body or organ • low perfusion pressure despite an adequate cardiac output.

The EASI lead system, which is based on the dipole hypothesis of vectorcardiography, offers the possibility of deriving the standard 12-lead electrocardiogram (ECG) and other desired leads from ECGs recorded at only 4 sites; it uses the Frank E, A, and I electrode locations, a fourth electrode location (S) at the manubrium, and a reference electrode. Accordingly, the electrodes of this system can be applied rapidly on easy-to-locate, stable anatomical sites that leave the precordium free for other diagnostic procedures. In early EASI implementations, the derived leads differed from actual leads by more than some clinicians found acceptable. As these differences were thought to be caused by the fact that the coefficients that were used had been derived from a limited data set, we have calculated a new set of EASI coefficients for the standard 12 leads, and several other leads, by using a data set of 983 adult subjects with 120-lead ECGs and well-documented diagnoses. This database is a concatenation of 2 previously described ones: one consisting of 892 persons (normal subjects, postmyocardialinfarction patients with and without arrhythmias, and patients with ventricular arrhythmias but no history of myocardial infarction) and the other consisting of 91 patients with single-vessel coronary artery disease who underwent coronary balloon-inflation angioplasty. In addition to the coefficients for the standard 12 leads (derived for standard limb leads as well as for Mason-Likar leads), we derived coefficients for six additional unipolar leads (posterior V 7 -V 9 , and right-sided V 3 R-V 5 R), the Frank orthogonal leads, and three bipolar, vessel-specific leads that have been previously shown to exhibit optimal sensitivity for acute myocardial ischemia. We also derived coefficients for the modified electrode locations of the EASI system that must be used with patients who have undergone a midline sternotomy. Optimal coefficients for lead transformations were determined by maximizing the ensemble average (over the entire data set) of the correlation between the derived and the true lead for the chosen interval of the averaged complex. For derived standard limb leads, the amplitude was adjusted to give the best root-mean-square fit over the entire PQRST interval, whereas for derived Mason-Likar leads it was adjusted to give the best ST-segment fit. The entire set of coefficients and their corresponding goodness-of-fit measures are presented.

Background: Mitral annular disjunction (MAD) consists of an altered spatial relation between the left atrial wall, the attachment of the mitral leaflets, and the top of the left ventricular (LV) free wall, manifested as a wide separation between the atrial wall-mitral valve junction and the top of the LV free wall. Originally described in association with myxomatous mitral valve disease, this abnormality was recently revisited by a surgical group that pointed its relevance for mitral valve reparability. The aims of this study were to investigate the echocardiographic prevalence of mitral annular disjunction in patients with myxomatous mitral valve disease, and to characterize the clinical profile and echocardiographic features of these patients.

Although expression of numerous ion channels is altered in heart failure (HF), mechanisms by which dysfunction at the ionic and molecular levels lead to ventricular tachyarrhythmias in HF are unknown. Previously, we found that transmural heterogeneities of repolarization play a critical role in the genesis of polymorphic ventricular tachycardia (PVT) when QT interval was prolonged in LQT2. Because QT interval is also prolonged in HF, we hypothesized that transmural heterogeneities are a mechanism of PVT in HF. Optical action potentials were measured simultaneously from cells spanning the entire transmural wall of arterially perfused canine wedge preparations. Wedges were isolated from dogs without (control, nϭ5) and with HF (nϭ8) produced by rapid ventricular pacing. In HF, action potential duration (APD) prolongation was markedly heterogeneous across the transmural wall, and was characterized by disproportionate APD prolongation of midmyocardial (M) cells. APD prolongation of M cells accounted for QT-interval prolongation, and caused significant increases (PϽ0.01) in spatial gradients of repolarization across the ventricular wall from 4.3Ϯ2.1 (control) to 12.4Ϯ3.5 ms/mm (HF). Enhanced gradients were directly responsible for development of functional conduction block, leading to PVT in 63% of HF wedges but in no controls (PϽ0.03). Moreover, intramural decremental conduction and block of the premature impulse, preceded each episode of PVT, and always occurred at the border between M-cell and subepicardial zones, where repolarization gradients were highest. Selective prolongation of APD within M cells underlies several key features of the HF phenotype, including QT-interval prolongation, transmural heterogeneity of repolarization, and susceptibility to conduction block and reentrant PVT. (Circ Res. 2003;93:638-645.)

This paper introduces a real-time data compression and transmission algorithm between e-health terminals for a periodic ECGsignal. The proposed algorithm consists of five compression procedures and four reconstruction procedures. In order to evaluate the performance of the proposed algorithm, the algorithm was applied to all 48 recordings of MIT-BIH arrhythmia database, and the compress ratio (CR), percent root mean square difference (PRD), percent root mean square difference normalized (PRDN), rms, SNR, and quality score (QS) values were obtained. The result showed that the CR was 27.9:1 and the PRD was 2.93 on average for all 48 data instances with a 15% window size. In addition, the performance of the algorithm was compared to those of similar algorithms introduced recently by others. It was found that the proposed algorithm showed clearly superior performance in all 48 data instances at a compression ratio lower than 15:1, whereas it showed similar or slightly inferior PRD performance for a data compression ratio higher than 20:1. In light of the fact that the similarity with the original data becomes meaningless when the PRD is higher than 2, the proposed algorithm shows significantly better performance compared to the performance levels of other algorithms. Moreover, because the algorithm can compress and transmit data in real time, it can be served as an optimal biosignal data transmission method for limited bandwidth communication between e-health devices.

PhysioBank, PhysioToolkit, and PhysioNet : Components of a New Research http://circ.ahajournals.org/cgi/content/full/101/23/e215 located on the World Wide Web at: The online version of this article, along with updated information and services, is http://www.lww.com/reprints Reprints: Information about reprints can be found online at Abstract-The newly inaugurated Research Resource for Complex Physiologic Signals, which was created under the auspices of the National Center for Research Resources of the National Institutes of Health, is intended to stimulate current research and new investigations in the study of cardiovascular and other complex biomedical signals. The resource has 3 interdependent components. PhysioBank is a large and growing archive of well-characterized digital recordings of physiological signals and related data for use by the biomedical research community. It currently includes databases of multiparameter cardiopulmonary, neural, and other biomedical signals from healthy subjects and from patients with a variety of conditions with major public health implications, including life-threatening arrhythmias, congestive heart failure, sleep apnea, neurological disorders, and aging. PhysioToolkit is a library of open-source software for physiological signal processing and analysis, the detection of physiologically significant events using both classic techniques and novel methods based on statistical physics and nonlinear dynamics, the interactive display and characterization of signals, the creation of new databases, the simulation of physiological and other signals, the quantitative evaluation and comparison of analysis methods, and the analysis of nonstationary processes. PhysioNet is an on-line forum for the dissemination and exchange of recorded biomedical signals and open-source software for analyzing them. It provides facilities for the cooperative analysis of data and the evaluation of proposed new algorithms. In addition to providing free electronic access to PhysioBank data and PhysioToolkit software via the World Wide Web (http://www.physionet.org), PhysioNet offers services and training via on-line tutorials to assist users with varying levels of expertise. (Circulation. 2000;101:e215-e220.)

Heart structure is a unique system that can generate ECG signals independently via heart contraction and expansion. Basically, an ECG signal consists of PQRST waves. All these waves represent different heart functions. Normal healthy heart can be simply recognized by normal ECG signal while heart disorder or arrhythmias signals contain differences in terms of features and morphological attributes in their corresponding ECG waveform. This paper describes about the analysis of electrocardiogram (ECG) signals using different pattern recognition approaches: 1) template matching, 2) statistical classification, 3) syntactic or structural matching, and 4) neural networks. This paper also presents various application areas in which pattern recognition is used.

In this paper, we proposed a kernel differenceweighted k-nearest neighbor classifier (KDF-WKNN) for the diagnosis of cardiac arrhythmia based on the standard 12 lead ECG recordings. Different from classical KNN, KDF-WKNN defines the weighted KNN rule as the constrained least-squares optimization of sample reconstruction from its neighborhood, and then uses the Lagrangian multiplier method to compute the weights of different nearest neighbors by introducing the kernel Gram matrix G. In arrhythmia analysis, it is unavoidable that some attribute values of a person would be missing. Thus, this paper further introduces a modified PCA method to address this problem. To evaluate the performance of KDF-WKNN, Experimental results on the UCI cardiac arrhythmia database indicate that, KDF-WKNN is superior to the nearest neighbor classifier, and is very competitive while compared with several state-ofthe-art methods in terms of classification accuracy.

It is often reported that clinical symptoms are useful in differentiating cardiac from non-cardiac syncope. Studies in the young are rare. This study was designed to capture the symptoms and signs reported by patients with cardiac syncope before the patients or their attending clinicians knew the final diagnosis. Retrospective case-note review of 35 consecutive unrelated gene-positive probands with a proven cardiac channelopathy. The presentation leading to diagnosis of cardiac channelopathy was resuscitated sudden cardiac death in 7 patients; syncope in 20; collapse with retained consciousness in 2; palpitations in 1 and an incidental finding in 5. For the 20 patients with syncope (LQTS 18, Brugada syndrome 2), median age at presentation was 13.9 years (1.8 day to 40.8 years). Of the 17 patients able to describe the onset of syncope, 11 (65%) had at least one symptom prior to collapse, though none reported nausea. Dizziness or lightheadedness was the most frequent symptom, being experienced by 8 (47%). Nine (of 20) patients (45%) had witnessed seizure-like activity and 8 (40%) had urinary incontinence. Nineteen patients were capable of describing the post-syncopal period, of whom 15 (79%) reported symptoms, the most common (12; 65%) being drowsiness or exhaustion. Cardiac syncope in the young frequently presents with symptoms and signs that are typically associated with other causes of transient loss of consciousness, including vasovagal syncope and seizure disorders. The presence of symptoms may not be as helpful in differentiating arrhythmic from non-arrhythmic events as is often supposed. A thorough history, appropriate investigations and a high index of suspicion remain essential in the assessment of syncope.