Accuracy of advanced versus strictly conventional 12-lead ECG for detection and screening of coronary artery disease, left ventricular hypertrophy and left ventricular systolic dysfunction.

BACKGROUND: Resting conventional 12-lead ECG has low sensitivity for detection of coronary artery disease (CAD) and left ventricular hypertrophy (LVH) and low positive predictive value (PPV) for prediction of left ventricular systolic dysfunction (LVSD). We hypothesized that a approximately 5-min resting 12-lead advanced ECG test ("A-ECG") that combined results from both the advanced and conventional ECG could more accurately screen for these conditions than strictly conventional ECG. METHODS: Results from nearly every conventional and advanced resting ECG parameter known from the literature to have diagnostic or predictive value were first retrospectively evaluated in 418 healthy controls and 290 patients with imaging-proven CAD, LVH and/or LVSD. Each ECG parameter was examined for potential inclusion within multi-parameter A-ECG scores derived from multivariate regression models that were designed to optimally screen for disease in general or LVSD in particular. The performance of the best retrospectively-validated A-ECG scores was then compared against that of optimized pooled criteria from the strictly conventional ECG in a test set of 315 additional individuals. RESULTS: Compared to optimized pooled criteria from the strictly conventional ECG, a 7-parameter A-ECG score validated in the training set increased the sensitivity of resting ECG for identifying disease in the test set from 78% (72-84%) to 92% (88-96%) (P < 0.0001) while also increasing specificity from 85% (77-91%) to 94% (88-98%) (P < 0.05). In diseased patients, another 5-parameter A-ECG score increased the PPV of ECG for LVSD from 53% (41-65%) to 92% (78-98%) (P < 0.0001) without compromising related negative predictive value. CONCLUSION: Resting 12-lead A-ECG scoring is more accurate than strictly conventional ECG in screening for CAD, LVH and LVSD.

Impacto de la naturaleza compensatoria de la masa ventricular izquierda sobre la labilidad temporal de la repolarización miocardica en pacientes con hipertensión arterial / Impact of the compensatory nature of left ventricular mass on myocardial repolarization lability in hypertensive patients

El propósito fue investigar si la naturaleza de la respuesta compensatoria de la masa ventricular izquierda (MVI) es un factor determinante del grado de labilidad temporal de la repolarización miocárdica. Se evaluaron 263 pacientes hipertensos y 52 sujetos controles normotensos mediante ecocardiografía y electrocardiografía de alta resolución. Se definió MVI inapropiada como un índice de compensación de la MVI (ICMVI) > 128%. El grado de labilidad temporal de la repolarización miocárdica se evaluó a través del índice de variabilidad del intervalo OT (IVQT) determinado en forma automatizada. Pacientes hipertensos con MVI inapropiada presentaron valores significativamente más altos del IVQT (-0,92 ± 0,25) en comparación con sujetos normotensos (-1,53 ± 0,21) y pacientes hipertensos con MVI apropiada (-1,24 2410,18) (P<0,001). El ICMVI se correlacionó en forma dirtecta con el IVQT (r=0,49, P<0,001). en el análisis multivariante de regresión lineal, el nivel de MVI inapropiada. medido a través del ICMVI, se comportó como un predictor independiente del grado de labilidad temporal de la repolarización miocárdica (ß=0,007; P<0,001). Los resultados de este estudio indican que, en pacientes con HTA-E, la presencia de MVI inapropiadamente alta para el estímulo hemodinámico del ventrículo izquierdo se relaciona con aumento de la variabilidad temporal del intervalo QT.

The goal of this study was to investigate whether the compensatory nature of left ventricular mass (LVM) is a determinant factor of the temporal lability of the myocardial repolarization. Two hundred and sixty three hypertensive patients and 52 normotensive control subjects were studied by Doppler echocardiography and high resolution electrocardiography. A compensatory index of LVM (CILVM) > 128% defined inapropiate LVM. The degree of myocardial repolarization lability was evaluated by the QT interval variability index (QTVI). Hypertensive patients with inapropiate LVM had QTVI values significantly higher (-0,92 ± 0,25) than those with appropriate MVI (-1.24 ± 0.18) and normotensive control subjects (-1.53 ± 0.21) (P<0.001). The CILVM was positively correlated with QTVI (r=0.49; P<0.001). A stepwise multivariate linear regtession analysis showed that the level of inappropriate LVM was an independent predictor of QTVI (ß=0.007; P<0.001). Our result indicate that inappropriately high LVM for hemodynamic stimuli are associated with increased QT temporal variability.

Diseño e implementación de un instrumento virtual para la adquisición y procesamiento de señales fisiológicas

Se desarrolla e implementa un sistema basado en instrumentación virtual para la adquisición y procesamiento de señales fisiológicas para ser empleado como herramienta para mejorar el proceso de enseñanza-aprendizaje que se lleva a cabo en los laboratorios de fisiología de las facultades de Medicina de nuestro país. El hardware del sistema comprende un amplificador de bio-potenciales de cuatro canales, una tarjeta de adquisición de datos y un computador personal (PC) que permite la interfase con el usuario. Para el desarrollo del software se empleó el lenguaje de programación gráfico LABVIEW 6.1. Se implementaron prácticas de laboratorios empleando principalmente las señales fisiológicas: electrocardiográficas y electromiógraficas. Como resultado del trabajo se implementó un prototipo que funciona con los requerimientos técnicos exigidos para realizar prácticas docentes en un laboratorio de fisiología. Entre las conclusiones del trabajo podemos nombrar: es factible el diseño e implementación de instrumentos virtuales con fines educativos para ser empleados en laboratorios con las mismas capacidades de instrumentos equivalentes producidos en países desarrollados, y la necesidad de que estos instrumentos puedan producirse en serie para beneficiar a un mayor número de estudiantes de Medicina.

It is developed and it implemented a system based on virtual instrumentation for the acquisition and physiological signal processing to be used like tool to improve the education process learning that are carried out in the laboratories of physiology of the medicine faculties of our country. The hardware of the system includes/understands a bio-potential amplifier of 4 channels, a card of data acquisition, and a personal computer (PC) that the interphase with the user allows. For the development of software the graphical programming language LABVIEW 6.1 was used. Practices of laboratories were implemented mainly using the physiological signals: electrocardiograficas and electromiograficas. As resulting from the work implemented a prototype that works with the technical requirements demanded to make educational practices in a physiology laboratory. Between the conclusions of the work we can name: It is feasible the design and implementation of virtual instruments with educative aims to be used in laboratories with the same capacities of produced equivalent instruments in developed countries, and the necessity that these instruments can take place in series to benefit to a greater number of medicine students.

Sistema para digitalización del electrocardiograma e historia médica computarizada aplicada a cardiología

Este trabajo presenta el desarrollo de un sistema formado por dos partes. La primera parte consiste en un módulo hardware diseñado para digitalizar el electrocardiograma (ECG) de cualquier electrocardiógrafo con salida analógica, y transmitir los datos a un computador personal (PC). La segunda parte del sistema consiste en un software programado en el computador, que tiene por finalidad manipular y almacenar los datos del paciente y el registro del ECG obtenido, en un formato de historia médica computarizada aplicada a cardiología. Entre las tareas que realiza el sistema se pueden nombrar: adquisición y muestreo de la señal ECG proveniente del electrocardiógrafo analógico, transmisión en forma serial al computador, visualización de la señal en tiempo real, almacenamiento digital de la historia médica de cada paciente, así como de cada una de las consultas y registros de ECG realizados, y generación de reporte para la impresión en papel de las 12 derivaciones electrocardiográficas. Como resultado de este trabajo se construyó un prototipo, el cual se encuentra actualmente en validación clínica en el Hospital Universitario de Los Andes. Este sistema ayuda a modernizar los antiguos electrocardiógrafos analógicos, transformándolos en electrocardiógrafos digitales de bajo costo, con todas las ventajas de los equipos de última generación. Además, permite el almacenamiento ordenado de las historias médicas de los pacientes, con fácil acceso a cada una de las consultas y los registros de ECG realizados con anterioridad.

This work presents the development of a system formed by two parts. The first part consists on a module hardware designed to digitize the electrocardiogram (ECG) of any electrocardiograph with analog exit and to transmit the data to a personal computer (PC). The second part of the system consists on a software programmed in the computer that has the purpose of manipulate and store the patient’s data and also perform the registration of the obtained ECG, this data is taken in a format of on-line medical history applied to cardiology. Among the tasks that carries the system can be named: Acquisition and sampling of the sign ECG coming from the analog electrocardiograph, transmission in serial form to the computer, visualization of the sign in real time, digital storage of each patient’s medical history, as well as of each one of the consultations and registrations of carried ECG, and report generation for the impression in paper of the 12 derivations of ECG. As result of this work, a prototype was built, which is at the moment in clinical validation in the University Hospital of The Andes. This system helps to modernize the old analogical electrocardiographs, transforming them in digital electrocardiographs of low cost, with all the advantages of the teams of last generation. It also allows the orderly storage of the medical histories of the patients with easy access to each one of the consultations and the registrations of ECG carried out previously.

Markov random field modeling for three-dimensional reconstruction of the left ventricle in cardiac angiography.

This paper reports on a method for left ventricle three-dimensional (3-D) reconstruction from two orthogonal ventriculograms. The proposed algorithm is voxel-based and takes into account the conical projection geometry associated with the biplane image acquisition equipment. The reconstruction process starts with an initial ellipsoidal approximation derived from the input ventriculograms. This model is subsequently deformed in such a way as to match the input projections. To this end, the object is modeled as a 3-D Markov-Gibbs random field, and an energy function is defined so that it includes one term that models the projections compatibility and another one that includes the space-time regularity constraints. The performance of this reconstruction method is evaluated by considering the reconstruction of mathematically synthesized phantoms and two 3-D binary databases from two orthogonal synthesized projections. The method is also tested using real biplane ventriculograms. In this case, the performance of the reconstruction is expressed in terms of the projection error, which attains values between 9.50% and 11.78 % for two biplane sequences including a total of 55 images.