Velocity tracking of cardiac vector loops to identify signs of stress-induced ischaemia.

Coronary artery disease (CAD) is among the leading causes of death worldwide. Initial studies require an electrocardiogram stress test often followed by cardiac imaging procedures. However, conventional indices still show insufficient diagnostic performance.

Modelling of the electrocardiographic signal during an angioplasty procedure in the right coronary artery.

Dynamical models are useful tools to generate sets of varied morphological signals by synthesizing human electrocardiograms (ECGs). These signals are used for testing and improving algorithms of ECG delineation, patient monitoring and heart disease detection. This work presents a procedure based on the ECGSYN model to synthesize ECG morphological changes induced by a percutaneous transluminal coronary angioplasty (PTCA) procedure in the right coronary artery.

Dynamic features of cardiac vector as alternative markers of drug-induced spatial dispersion.

Introduction: The abnormal amplification of ventricular repolarization dispersion (VRD) has long been linked to proarrhythmia risk. Recently, the measure of VRD through electrocardiogram intervals has been strongly questioned. The search for an efficient and non-invasive surrogate marker of drug-induced dispersion effects constitute an urgent research challenge.

Biomarkers of pre-existing risk of Torsade de Pointes under Sotalol treatment.

Introduction: Antiarrhythmic drugs therapies are currently going through a turning point. The high risk that exists during the treatments has led to an ongoing search for new non-invasive toxicity risk biomarkers.

Methods: We propose the use of spatial biomarkers obtained through the quaternion algebra, evaluating the dynamics of the cardiac electrical vector in a non-invasive way in order to detect abnormal changes in ventricular heterogeneity.

Classification of ischemic and non-ischemic cardiac events in Holter recordings based on the continuous wavelet transform.

Holter recordings are widely used to detect cardiac events that occur transiently, such as ischemic events. Much effort has been made to detect early ischemia, thus preventing myocardial infarction. However, after detection, classification of ischemia has still not been fully solved.

Electrocardiogram Delineation in a Wistar Rat Experimental Model.

Background And Objectives: The extensive use of electrocardiogram (ECG) recordings during experimental protocols using small rodents requires an automatic delineation technique in the ECG with high performance. It has been shown that the wavelet transform (WT) based ECG delineator is a suitable tool to delineate electrocardiographic waveforms. The aim of this work is to implement and evaluate the ECG waves delineation in Wistar rats applying WT.

Quaternion-based study of angular velocity of the cardiac vector during myocardial ischaemia.

Background: Early detection of acute ischaemia through non-invasive methods remains a challenge in health research. Ischaemic condition caused by a decrease in the blood supply in a cardiac region induces hypoxia and metabolic abnormalities that contribute to the electrical instability of the heart and to the development of slow conduction in damaged tissue.

Methods: Herein, a percutaneous transluminal coronary angiography (PTCA) is considered as a model of supply ischaemia.

Deconvolution: It Fans Back, Out, and Ahead [Retrospectroscope].

The origins of convolution and its further and rather complex historical development were dealt with in detail by Alejandro Dominguez in a previous article [1]. We saw there that it can be traced back to the middle of the 18th century; however, its modern form and use are not more than 50 or 60 years old.

Identification of Patients with Myocardial Infarction. Vectorcardiographic and Electrocardiographic Analysis.

Background: The largest morbidity and mortality group worldwide continues to be that suffering Myocardial Infarction (MI). The use of vectorcardiography (VCG) and electrocardiography (ECG) has improved the diagnosis and characterization of this cardiac condition.

Objectives: Herein, we applied a novel ECG-VCG combination technique to identifying 95 patients with MI and to differentiating them from 52 healthy reference subjects.

Beat-to-beat electrocardiographic analysis of ventricular repolarization variability in patients after myocardial infarction.

Several studies have shown that the beat-to-beat variability of ventricular repolarization, which can be computed by T-wave spectral variance (TSV) index, constitutes a marker of cardiac risk. Moreover, the fact that properties of action potential duration are altered during the healing (days, weeks) and healed (months) infarct stages, have been reported. However, no data exist regarding the influence of the time elapsed after myocardial infarction (MI) on modulation of the beat-to-beat ventricular repolarization variability.

Novel technique for ST-T interval characterization in patients with acute myocardial ischemia.

Background: The novel signal processing techniques have allowed and improved the use of vectorcardiography (VCG) to diagnose and characterize myocardial ischemia. Herein, we studied vectorcardiographic dynamic changes of ventricular repolarization in 80 patients before (control) and during Percutaneous Transluminal Coronary Angioplasty (PTCA).

Methods: We propose four vectorcardiographic ST-T parameters, i.

Evaluation of ventricular repolarization dispersion during acute myocardial ischemia: spatial and temporal ECG indices.

In this work, we studied the evolution of different electrocardiogram (ECG) indices of ventricular repolarization dispersion (VRD) during acute transmural myocardial ischemia in 95 patients undergoing percutaneous coronary intervention (PCI). We studied both temporal indices of VRD (T-VRD), based on the time intervals of the ECG wave, and spatial indices of VRD (S-VRD), based on the eigenvalues of the spatial correlation matrix of the ECG. The T-wave peak-to-end interval I(TPE) index showed statistically significant differences during left anterior descending artery and right coronary artery (RCA) occlusion for almost the complete time course of the PCI procedure with respect to the control recording.

Acute myocardial ischemia monitoring before and during angioplasty by a novel vectorcardiographic parameter set.

Background: This work evaluates the vectorcardiographic dynamic changes in ischemic patients before and during Percutaneous Transluminal Coronary Angioplasty (PTCA).

Methods: Four QRS-loop parameters were computed in 51 ischemic and 52 healthy subjects with the objective of assessing the vectorcardiographic differences between both groups: maximum vector magnitude (QRS(mVM)), planar area (QRS(PA)), maximum distance between centroid and loop (QRS(mDCL)) and perimeter (QRS(P)).The conventional ST-change vector magnitude (STC(VM)), QRS-vector difference (QRS(VD)) and spatial ventricular gradient (SVG) were also calculated.

The allometric model in chronic myocardial infarction.

Background: An allometric relationship between different electrocardiogram (ECG) parameters and infarcted ventricular mass was assessed in a myocardial infarction (MI) model in New Zealand rabbits.

Methods: A total of fifteen animals were used, out of which ten underwent left anterior descending coronary artery ligation to induce infarction (7-35% area). Myocardial infarction (MI) evolved and stabilized during a three month-period, after which, rabbits were sacrificed and the injured area was histologically confirmed.

Novel set of vectorcardiographic parameters for the identification of ischemic patients.

New signal processing techniques have enabled the use of the vectorcardiogram (VCG) for the detection of cardiac ischemia. Thus, we studied this signal during ventricular depolarization in 80 ischemic patients, before undergoing angioplasty, and 52 healthy subjects with the objective of evaluating the vectorcardiographic difference between both groups so leading to their subsequent classification. For that matter, seven QRS-loop parameters were analyzed, i.

Probability of ventricular fibrillation: allometric model based on the ST deviation.

Background: Allometry, in general biology, measures the relative growth of a part in relation to the whole living organism. Using reported clinical data, we apply this concept for evaluating the probability of ventricular fibrillation based on the electrocardiographic ST-segment deviation values.

Methods: Data collected by previous reports were used to fit an allometric model in order to estimate ventricular fibrillation probability.

Prediction of ventricular fibrillation based on the ST-segment deviation: allometric model.

Based on some reported clinical data, we attempt to apply the allometric law for evaluating the probability of ventricular fibrillation when electrocardiographic ST-segment deviations are determined. The deviation is measured in millimeters at the standard calibration of 1mV = 10mm and the probability in percent. Using the equation VF(P) = δ + β (ST) in log-log representation, the fitting procedure produced the following overall coefficients: Average β = 1.

[Influence of sexual maturity and gonadectomy on cardiac electrical activity in male and female rabbits].

Sex-associated differences in cardiac electrical activity have already been document noted. Even though these differences are usually associated with the effect of maturity and sex hormones, there are still some controversial points to this respect. The aim of this study was to evaluate the effects of maturity and gonadectomy on the different parameters of surface electrocardiogram and the duration of the action potential in young and adult rabbits.

Role of dipolar and nondipolar components of the T wave in determining the T wave residuum in an isolated rabbit heart model.

Introduction: Repolarization heterogeneity has been shown to constitute a substrate for malignant ventricular arrhythmias. Noninvasive measurement of abnormal repolarization through assessment of QT interval dispersion from the resting standard 12-lead ECG initially had shown promise in assessing arrhythmia risk but was challenged recently. The relative T wave residuum (TWR) has been proposed recently to reflect regional repolarization dispersion more accurately.

Developmental changes of cardiac repolarization in rabbits: implications for the role of sex hormones.

Objectives: Firstly, to compare gender-dependent differences of cardiac repolarization in both adult and young rabbits. Secondly, to analyze the effect of gonadectomy on these gender differences in cardiac repolarization.

Methods: We evaluated potential gender differences in cardiac repolarization with both microelectrode and ECG recordings.

Beat-to-beat repolarization variability measured by T wave spectral variance index in chronic infarcted animals.

Background: Recent experimental and clinical studies have shown that beat-to-beat variability of repolarization morphology is associated with an increased risk for developing malignant ventricular arrhythmias. However, few data exist on the relationship between beat-to-beat repolarization variability and myocardial infarction itself.

Methods And Results: In the present work we tested the algorithm of T wave spectral variance (TWSV) using the two dimension fast Fourier transform, in an animal model of myocardial infarction to extend the evidences that support the existence of beat-to-beat alteration in repolarization during the chronic stage of myocardial infarction.

Lack of effect of conduction direction on action potential durations in anisotropic ventricular strips of pig heart.

Introduction: The influence of activation sequence on the rate of rise of the depolarization phase of action potentials in atrial or ventricular muscles has been well established. However, whether myocardial fiber orientation is important in modulating the repolarization process is unclear.

Methods And Results: We examined the influence of activation sequence on the repolarization phase of action potentials in epicardial tissues from the right and left ventricles of domestic pigs.