Long-term ECG Recordings Research Articles

Premature ventricular complexes on screening electrocardiogram and risk of ischemic stroke.

Premature ventricular complexes (PVCs) detected from long-term ECG recordings have been associated with an increased risk of ischemic stroke. Whether PVCs seen on routine ECG, commonly used in clinical practice, are associated with an increased risk of ischemic stroke remains unstudied. This analysis included 24 460 participants (aged, 64.5+9.3 years; 55.1% women; 40.0% blacks) from the Reasons for Geographic and Racial Differences in Stroke (REGARDS) study who were free of stroke at the time of enrollment. PVCs were ascertained from baseline ECG (2003-2007), and incident stroke cases through 2011 were confirmed by an adjudication committee. A total of 1415 (5.8%) participants had at least 1 PVC at baseline, and 591 developed incident ischemic stroke during an average (SD) follow-up of 6.0 (2.0) years. In a cox proportional hazards model adjusted for age, sex, race, geographic region, education, previous heart disease, systolic blood pressure, blood pressure-lowering medications, current smoking, diabetes mellitus, left ventricular hypertrophy by ECG, and aspirin use and warfarin use, the presence of PVCs was associated with 38% increased risk of ischemic stroke (hazard ratio [95% confidence interval], 1.38 [1.05-1.81]). PVCs are common on routine screening ECGs and are associated with an increased risk of ischemic stroke.

Heartbeat classification using decision level fusion

Purpose Automatic heartbeat classification is an important technique to assist doctors to identify ectopic heartbeats in long-term ECG recording. In this paper, we employed a multi-lead fused classification schema to improve the performance of heartbeat classification.

Heart rate variability--current diagnosis of the cardiac autonomic neuropathy. A review.

The autonomic nervous system is one of the major homeostatic regulatory systems of the body. Detection of cardiac autonomic neuropathy (CAN), reflected by reduced heart rate variability (HRV), is an independent adverse prognostic factor: sympathovagal balance failure with a sympathetic dominance is the main trigger for lethal arrhythmias and sudden death. PubMed database based on original articles from 1983 to 2013 and the author´s clinical experience. This review covers the current status of the methodology and the clinical uses of HRV, especially in the field of internal medicine. Heart rate variability is making a valuable contribution to the diagnosis of cardiovascular autonomic dysfunction and CAN. It can be assessed from short-term and long-term ECG recordings. It is one of the few methods that allow outpatient CAN diagnosis, monitoring the progress, therapeutic effect and evaluation of patient prognosis. It is used as an independent prognostic factor in combination with other recognized risk factors in risk stratifying after myocardial infarction. It is a unique method of CAN diagnosis particularly in diabetology. Its diagnostic and prognostic potential in other medical fields is being intensively explored.

Electrodes for Long-Term Esophageal Electrocardiography

The emerging application of long-term and high-quality ECG recording requires alternative electrodes to improve the signal quality and recording capability of surface skin electrodes. The esophageal ECG has the potential to overcome these limitations but necessitates novel recorder and lead designs. The electrode material is of particular interest, since the material has to ensure conflicting requirements like excellent biopotential recording properties and inertness. To this end, novel electrode materials like PEDOT and silver-PDMS as well as established electrode materials such as stainless steel, platinum, gold, iridium oxide, titanium nitride, and glassy carbon were investigated by long-term electrochemical impedance spectroscopy and model-based signal analysis using the derived in vitro interfacial properties in conjunction with a dedicated ECG amplifier. The results of this novel approach show that titanium nitride and iridium oxide featuring microstructured surfaces did not degrade when exposed to artificial acidic saliva. These materials provide low electrode potential drifts and insignificant signal distortion superior to surface skin electrodes making them compatible with accepted standards for ambulatory ECG. They are superior to the noble and polarizable metals such as platinum, silver, and gold that induced more signal distortions and are superior to esophageal stainless steel electrodes that corrode in artificial saliva. The study provides rigorous criteria for the selection of electrode materials for prolonged ECG recording by combining long-term in vitro electrode material properties with ECG signal quality assessment.

A Novel Method for Automatic Identification of Motion Artifact Beats in ECG Recordings

This paper presents a novel method for automatic identification of motion artifact beats in ECG recordings. The proposed method is based on the ECG complexes clustering, fuzzy logic and multi-parameters decision. Firstly, eight simulated datasets with different signal-to-noise ratio (SNR) were built for identification experiments. Results show that the identification sensitivity of our method is sensitive to SNR levels and acts like a low-pass filter that matches the cardiologists' recognition, while the Norm FP rate and PVB FP rate keep significantly low regardless of SNR. Furthermore, a simulated dataset including random durations of motion activities superimposed segments and two clinical datasets acquired from two different commercial recorders were adopted for the evaluation of accuracy and robustness. The overall identification results on these datasets were: sensitivity >94.69%, Norm FP rate <0.60% and PVB FP rate <2.65%. All the results were obtained without any manual threshold adjustment according to the priori information, thus dissolving the drawbacks of previous published methods. Additionally, the total cost time of our method applied to 24 h recordings is less than 1 s, which is extremely suitable in the situation of magnanimity data in long-term ECG recordings.

Heartbeat Time Series Classification With Support Vector Machines

In this study, heartbeat time series are classified using support vector machines (SVMs). Statistical methods and signal analysis techniques are used to extract features from the signals. The SVM classifier is favorably compared to other neural network-based classification approaches by performing leave-one-out cross validation. The performance of the SVM with respect to other state-of-the-art classifiers is also confirmed by the classification of signals presenting very low signal-to-noise ratio. Finally, the influence of the number of features to the classification rate was also investigated for two real datasets. The first dataset consists of long-term ECG recordings of young and elderly healthy subjects. The second dataset consists of long-term ECG recordings of normal subjects and subjects suffering from coronary artery disease.

Plötzlicher Herztod im Langzeit-EKG

An analysis has been made of long-term ECG recordings in 11 patients, 9 men and 2 women, mean age 69 +/- 7 years, who were carrying ECG recording equipment at the time of sudden death. Nine patients had coronary heart disease, one patient a dilatative cardiomyopathy and another one a combined aortic valve defect. Seven patients had a history of syncope. All patients had signs of cardiac insufficiency (NYHA index 3.0 +/- 0.6, heart-thorax quotient 0.55 +/- 0.05). Sudden death occurred predominantly whilst resting. In one patient it was due to bradyarrhythmia, in 10 to tachyarrhythmia, mostly ventricular tachycardia (initial heart rate 198 +/- 43/min; n = 8) which degenerated into ventricular fibrillation. Atrial fibrillation was present in 8 patients at the time of sudden death. Premonitory warning arrhythmias were not consistently detectable: comparison of arrhythmias in the first and last hour showed significant increases only in single ventricular extrasystoles (135 vs. 278 VES/h, P less than 0.05), not however in repetitive arrhythmias. An R-on-T phenomenon, as trigger mechanism of ventricular tachycardia, occurred in 5 cases. A synopsis of the published reports on approximately 110 patients with sudden death during long-term electrocardiographic monitoring confirmed that acute death is caused by bradyarrhythmias in approximately 15% (17 patients), and by tachyarrhythmias in 85% (94 patients). An increase in ventricular arrhythmias in the hour prior to death was observed in about 50% of patients and the R-on-T phenomenon, as the initiating mechanism for ventricular tachycardia, in 42%.

Frequent Atrial Premature Beats Predict Paroxysmal Atrial Fibrillation in Stroke Patients

For patients having suffered ischemic stroke, the current diagnostic strategies often fail to detect atrial fibrillation as a potential cause of embolic events. The aim of the study was to identify paroxysmal atrial fibrillation in stroke patients. We hypothesized that patients with frequent atrial premature beats (APBs) recorded in 24-hour ECG will show more often atrial fibrillation when followed by repeated long-term ECG recordings than patients without or infrequent APBs. 127 patients with acute ischemic stroke and without known AF were enrolled in a prospective study to detect paroxysmal AF. Patients were stratified according to the number of APBs recorded in a 24-hour ECG (> or =70 APBs versus <70 APBs). Subsequently, they all underwent serial 7-day event-recorder monitoring at 0, 3, and 6 months. Serial extended ECG monitoring identified AF in 26% of patients with frequent APBs but only in 6.5% when APBs were infrequent (P=0.0021). A multivariate analysis showed that the presence of frequent APBs in the initial 24-hour ECG was the only independent predictor of paroxysmal AF during follow-up (odds ratio 6.6, 95% confidence intervals 1.6 to 28.2, P=0.01). In patients with acute ischemic stroke, frequent APBs (> or = 70/24 hours) are a marker for individuals who are at greater risk to develop or have paroxysmal AF. For such patients, we propose a diagnostic workup with repeated prolonged ECG monitoring to diagnose paroxysmal AF.

Phase-rectified signal averaging for the detection of quasi-periodicities and the prediction of cardiovascular risk

We present the phase-rectified signal averaging (PRSA) method as an efficient technique for the study of quasi-periodic oscillations in noisy, nonstationary signals. It allows the assessment of system dynamics despite phase resetting and noise and in relation with either increases or decreases of the considered signal. We employ the method to study the quasi-periodicities of the human heart rate based on long-term ECG recordings. The center deflection of the PRSA curve characterizes the average capacity of the heart to decelerate (or accelerate) the cardiac rhythm. It can be measured by a central wavelet coefficient which we denote as deceleration capacity (DC). We find that decreased DC is a more precise predictor of mortality in survivors of heart attack than left ventricular ejection fraction, the current "gold standard" risk predictor. In addition, we discuss the dependence of the DC parameter on age and on diabetes.

Discovering dangerous patterns in long-term ambulatory ECG recordings using a fast QRS detection algorithm and explorative data analysis

The next two decades will see dramatic changes in the health needs of the world's populations with chronic diseases as the leading causes of disability, according to recent World Health Organization reports. Increases in the senior population living “confined” in domestic area are also expected producing a steep increase in the need for long-term monitoring and home care services. Independently of the particular features and specific architectures, long-term monitoring systems usually produce a large amount of data to be analyzed and inspected by the practitioners and in particular by the cardiologists dealing with ECG recordings analysis. This problem is well known and regards also the traditional holter-based practice. In this paper we present a program for discovering patterns in ECG recordings, to be considered as a medical decision-making support. Computational methods are based on a QRS detector especially designed for noisy applications followed by a parameters space reduction operated by the KL transform modified on a “user-fit” basis. Events characterization is based on a recently introduced clustering method, called KHM (K-harmonic means). The most representative beat families and the corresponding prototypes (physiological and pathological) are then presented to the user through appropriate graphics to facilitate an easy and fast interpretation. We tested the QRS detection algorithm using the MIT-BIH arrhythmia database. Our method produced 565 false positive beats and 379 false negative beats and a total detection failure of 0.85% considering all the 109.809 annotated beats in the database. While a clinical experimentation of our program is on the way, we used the VALE Database to perform a preliminary evaluation of the methods used for data exploration (PCA, KHM). Considering the entire database, we succeeded in identifying pathological clusters in 97% of the cases.

Comparison of RR-interval scaling exponents derived from long and short segments at different wake periods

Heartbeat fluctuations show fractal-like correlations that are associated with highly adaptive cardiovascular regulatory systems. Moreover, the short-range fractal or scaling exponent α1 extracted from these correlations has been found to be a predictor of mortality for subjects with an impaired left ventricular function. In general, the RR-interval data required for this analysis are derived from long-term ECG recordings during free-running conditions. Yet short-term recordings are more likely to be obtained in some practical circumstances, so becoming relevant to assess the possibility of obtaining representative α1 exponents from these recordings. Here, we compare the α1 exponents extracted from the RR-interval series (9:00 am–6:00 pm) of 51 healthy adults in normal sinus rhythm and the α1 calculated from three shorted segments of only 700 beats obtained from the same series at 9:00 am, 1:30 pm and 5:00 pm. We found no significant differences between the scaling exponents derived from the whole 9 h series and the short segments at 9:00 am and 5:00 pm, but did find significant differences when comparing the whole series with the short segment at 1:30 pm. Thus, only if the time of day is taken into consideration can short segments of heartbeat fluctuation data be used to obtain representative α1 exponents.

Rate-correction technique for QT interval in long-term telemetry ECG recording in beagle dogs.

The establishment of a new rate-correction method for the QT interval is presented for long-term telemetry ECG recording in free-moving beagle dogs. First, in order to define the QT-RR relation to derive the correction formula, the diurnal variations of the QT and RR intervals and the influencing factors were analyzed, and the QT-RR regression coefficient beta was estimated under various conditions: steady and non-steady states of animal, light and dark periods, and over 24 h. In the results, the diurnal rhythm of the QT interval was synchronized with the RR interval reflecting the physical and emotional states of the animal. The coefficient beta had considerable variation during the day: beta; 0.276 +/- 0.052 (maximum to minimum: 0.495 to 0.153). Thus, it was considered that the ideal rate-correction technique for telemetry ECG requires the selection of a flexible coefficient beta adjusted to the condition of the measurement. Therefore, rate-correction utilizing analysis of covariance estimating the coefficient beta for each dog, was compared with previously proposed formulas which fix the rate-correction coefficient, based on the capacity to dissociate the effects of heart rate on the QT interval. This was then tested by the levels of discrimination apparent in the QT prolongation caused by a class III antiarrhythmic drug, which ranked the formulas on the levels of correction achieved as follows: covariance adjustment > Matsunaga > Van de Water > Bazett. Thus, the rate-correction method utilizing analysis of covariance is proven adequate for data from telemetry ECG recordings.

Frequency-domain heart rate variability in 24-hour holter recordings: Role of spectral method to assess circadian patterns and pharmacological

Different spectral methodologies for heart rate variability were recently shown to provide the same qualitative results in the context of passive tilt test. However, the impact of the method and the use of normalized power units in long-term ECG monitoring is still debated. Autoregressive and Fast Fourier transform (FFT) spectral approaches were applied to assess circadian modulation and the effect of beta-blocker administration in mild hypertensive patients who underwent continuous ambulatory ECG recording (n=44, 51±12 years, 30 men). Spectral analysis was applied to 5-minute sequences and spectral parameters representative of each circadian period (24 hour, day, night) were calculated. In baseline recordings, FFT spectral method provided a smaller estimate of total and very low frequency powers. On the contrary, low-and high-frequency components were systematically larger with FFT. Circadian variations were in favor of an increased overall nocturnal variability but of a reduced low frequency normalized power with both spectral methods. Chronic oral administration of beta-blocker induced an increase of all spectral components except for an unchanged low-frequency normalized power, independently from the spectral approach. In spite of quantitative differences, the qualitative assessment of circadian patterns and beta-blockade effect by autoregressive- and FFT-based spectral analyses is equivalent. The low-frequency component of heart rate variability cannot be considered a reliable direct marker of sympathetic activity in long-term ambulatory ECG recording.

Determinants of arrhythmogensis in right ventricular dysplasia

In the syndrome arrhythmogenic right ventricular dysplasia cardiomyopathy, little is known to date about the mechanism for the development of arrhythmias. In a group of 54 patients with documented ventricular tachycardia during longterm ECG recordings, the determinants for the development of VT and the relationship between signal-averaged ECG and the morphological characteristics of the disease are investigated. The analysis of the long-term electrocardiographic data includes the measurement of RR-intervals 30, 15, 5, 1min and immediately before onset of the VT, the determination of the morphology of the previous ventricular premature beats, and the frequency of the atrial arrhythmias. Normal values for the analysis of late potentials in the ECG signal accquisition with bidirectional filters between 40 and 300Hz were defined a maximum of 113ms for a QRS width, LAS of 38ms, and RMS40 of 16uV. The analysis of the long-term ECG produced monomorphic VT in all cases without previous atrial arrhythmia and in only 4 cases with previous polymorphic ventricular premature beats. A long-short phenomenon could only be proven in 4VT episodes. In 84% of all tachycardias, no arrhythmia were found immediately before onset of the arrhythmic event. According to the circadian clock, two peaks, mornings between 6 and 9h and evenings between 6 and 9h, could be determined. In patients, who were recently diagnosed with ARVD, a significant shortening of the RR intervals before the onset of VT as an indication of an acceleration of the sinus rhythm was observed. This effect could not be observed in patients with a past medical history of AVRD. Late potentials were determined with a prevalence of 74% overall. Increasingly, late potentials were observed with morphologically diffuse forms of the ARVD. A correlation to the severity of spontaneous arrhythmias (ventricular, sustained or not sustained VT) could not be established. In comparison to the origin of VT in coronary heart disease, previous arrhythmias play a less important role in arrhymogenic right ventricular dysplasia cardiomyopathy. Most importantly, an intensified sympathetic tone before onset of VT and an increased prevalence of positive late potentials are observed.

Prognosis and risk stratification after myocardial infarction.

In order to assess prognosis after myocardial infarction, various methods have been used: estimation of ejection fraction, Holter monitoring, detection of ventricular late potentials using signal-averaging techniques, programmed ventricular stimulation of the heart to test the inducibility of ventricular tachyarrhythmias, and parameters that assess heart rate variability. Left ventricular dysfunction is the major determinant for prognosis after myocardial infarction, but left ventricular end-systolic volume may be better than overall ejection fraction. The presence of an 'arrhythmogenic substrate' may be detected by recording low-amplitude, fractionated activity or by artificially introducing premature ventricular extrasystoles using programmed ventricular stimulation. The signal-averaged ECG represents an independent tool for risk assessment. In some studies, signal-averaging and programmed ventricular stimulation proved to be more sensitive for the prediction of sustained ventricular tachycardia than for sudden death. The risk of an arrhythmic event in patients with an abnormal signal-averaged ECG or an abnormal result of programmed ventricular stimulation is increased, although the majority of these patients still do not experience a fatal or life-threatening arrhythmia. This high number of false-positive results limits the practical applicability of the signal-averaged ECG but also of other techniques such as long-term ECG recording. Recent interest has focussed on heart rate variability, which is considered an index of sympatho-vagal interaction after acute myocardial infarction. Patients with decreased heart rate variability have a poorer prognosis than those with normal parameters. Patency of the infarct-related artery is a major factor that governs the potentially beneficial effects of thrombolytic therapy. Many, but not all, studies have shown a reduced prevalence of late potentials after successful thrombolysis or in the presence of an open infarct-related artery. Effective thrombolytic therapy may prevent the development of an abnormal electrophysiological milieu after myocardial infarction. Finally, neurological factors such as depression have been shown to be independent risk factors for mortality after acute myocardial infarction. The role of psycho-social factors and their mechanisms of action need further attention since they open the door for behavioural modification. In conclusion, there are several promising new techniques for identification of patients at risk of ventricular tachyarrhythmias. These techniques seem to be superior to more conventional methods such as long-term ECG monitoring as well as exercise testing. Methods which determine the arrhythmogenic substrate might be combined with a parameter of left ventricular ejection fraction because of the paramount importance of left ventricular pump function. However, due to the large proportion of false-positive results obtained with any of these methods, it seems unlikely that they will clearly surpass the others and be sufficiently accurate for risk assessment in the individual patient.

Clinical significance and management of ventricular arrhythmias in heart failure.

Ventricular arrhythmias are a frequent finding in patients with heart failure, and heart failure is a major underlying condition which is correlated to sudden death. Therefore, both sudden death and death from progression of heart failure strongly overlap. Besides long-term ECG recording, newer diagnostic techniques have been developed. The prognostic significance of the signal-averaged ECG in patients with advanced left ventricular dysfunction in the presence of coronary artery disease has been demonstrated; however, in patients with dilated cardiomyopathy, signal-averaging for detection of late potentials has not yet been clearly established as a useful diagnostic tool. Furthermore, heart period variability has been shown to correlate to overall mortality but not to a specific mechanism. Finally, programmed ventricular stimulation, though useful in patients with left ventricular dysfunction and/or heart failure in the setting of coronary artery disease, is of questionable significance in patients with dilated cardiomyopathy. With increasing degrees of left ventricular dysfunction, the efficacy of antiarrhythmic drugs decreases. On the other hand, with increasing degrees of heart failure, antiarrhythmic drugs demonstrate a greater negative inotropic effect, more frequent proarrhythmic effects, and more frequent bradyarrhythmias. Currently, several ongoing amiodarone trials are assessing different approaches of antiarrhythmic treatment in patients with heart failure.(ABSTRACT TRUNCATED AT 250 WORDS)

Influence of social support on cardiac event rate in men with ischaemic type ST segment depression during ambulatory 24-h long-term ECG recording: The prospective population study 'Men born in 1914', Malmo, Sweden

To the list of authors of the above, B. HEDBLAD, P.-O. ÖSTERGREN, B. S. HANSON AND L. JANZON, should be added B. W. JOHANSSON AND S. JUUL-MÖLLER

Ambulatory Electrocardiography Evaluation of Supraventricular Tachyarrhythmias and Brady arrhythmias

Long-term ECG recordings are of great value in the diagnosis and management of patients with cardiac arrhythmias. Information from programmed stimulation studies and intracardiac recordings has markedly improved the diagnostic abilities of the person examining the long-term ECG recording. This article discusses how knowledge from intracardiac electrophysiologic studies has resulted in much better recognition of the type and mechanisms of a supraventricular arrhythmia on the Holter record.

Influence of social support on cardiac event rate in men with ischaemic type ST segment depression during ambulatory 24-h long-term ECG recording. The prospective population study 'Men born in 1914', Malmö, Sweden.

Three-hundred and ninety-four 68-year-old men, representing 60.3% of a cohort of men born in 1914, were examined with ambulatory ECG during 24 h in 1982-83. Ninety-eight (24.8%) men had one or more episodes of ischaemic type ST segment depression (greater than or equal to 0.10 mV), 79 of whom had no history of previous ischaemic heart disease (IHD). During 63 months follow-up, 17 of the 98 suffered a cardiac event, i.e. fatal or non-fatal myocardial infarction (MI) or death due to chronic IHD. The objective of this study was to assess the influence of psychosocial factors, such as social network and social support, on cardiac event rate in men with ischaemic ST segment depression. A higher risk was found among men with little material and informational support (i.e. access to practical services and material resources and access to guidance, advice and information (crude relative risk 4.8; 95% CI; 1.6-14.8) and men with low availability of emotional support (i.e. opportunity for care, encouragement of personal value and feelings of confidence and trust) (crude relative risk 4.3; 95% CI: 1.4-13.3). This association was independent of history of IHD and other known risk factors for myocardial infarction (MI).

An update to silent myocardial ischemia: Pathophysiological, diagnostic, and therapeutic approaches

Silent myocardial ischemia (SMI) is a common ischemia process which can be defined as objective evidence of myocardial ischemia without chest pain or other equivalent indications. SMI can occur in totally asymptomatic patients, as well as in patients who have documented coronary artery disease (CAD) and who, on exercise and/or during Holter monitoring, may show ischemic changes. The precise mechanism for pathogenesis and pathophysiology of SMI remains to be clarified. A great deal has been learned about the role of beta-adrenergic receptors, adenylyl cyclase, and guanine nucleotide binding proteins (G proteins) in the myocardial ischemic process of SMI. Moreover, standard exercise test and long-term ECG recordings have proved to be of great value, especially when performed jointly, however, in this field there is still room for expanded knowledge. Pharmacological interventions to date have demonstrated the beneficial effects of beta-adrenergic receptor antagonists and/or calcium antagonists as contributing substantially to reducing both frequency and duration of SMI episodes. However, therapeutic options to improve the prognosis of SMI appear to be limited.