Termination of malignant ventricular arrhythmias with an implanted automatic defibrillator in human beings

Exact and fast automatic analyses of electrocardiogram (ECG) signal is critical for the computer based diagnosis of cardiac diseases, which has attracted many researches' attentions in recent years. In the present study, a novel QRS complex detection approach based on differential threshold method was proposed, which was designed as three analysis steps of an improved differential processor, a detector of the R wave, and a detector of the Q and S waves. The QRS complex detection performance of the proposed algorithm was further evaluated with clinical ECG records in patients coming from the widely recognized Massachusetts Institute of Technology Database (MIT-BIH DB). As a result, 67,167 beats were correctly determined with the proposed approach from a total of 67,197 QRS beats (30 ECG records in variant rhythms, 30 minutes for each), while the numbers of false positives and false negatives were 251 and 208, respectively. The summarized sensitivity and positive predictivity of the proposed method were obtained as 99.69% and 99.63%, respectively. Meanwhile, the computing time of the proposed algorithm for a ECG record of 30 min is only 1.40 seconds, which shows a distinct advantage on computation requirement compared with previous works. In conclusion, the proposed straightforward algorithm for QRS complex detection would potentially be implemented easily for portable monitoring applications with both a better performance and a lower computation requirement.

A real-time QRS complex detection algorithm based on differential threshold method

The differences in measured prostate material properties between probing and unconfined compression testing methods.

En este articulo se presenta un sistema portatil para el monitoreo ambulatorio del ritmo cardiaco y la deteccion temprana de las arritmias cardiacas de mayor riesgo . El sistema consta de un sensor con tres electrodos superficiales para la captura de la senal ECG, la cual se transmite via Bluetooth a un dispositivo movil con Android, en donde se realiza el analisis de la senal capturada durante lapsos de 5 s. El sistema propuesto distingue entre Ritmo Normal (Ritmo Sinusal - RS) , Taquicardia Ventricular (TV) , Fibrilacion Ventricular (FV) y Asistolia, con una precision del 100%, 55%, 75% y 90% respectivamente. Sin embargo, el sistema puede recuperarse de los errores rapidamente en el analisis de la trama subsecuente. Este trabajo se centra en el uso de dispositivos moviles de uso cotidiano, multitarea y de facil acceso, implementando algoritmos en el dominio del tiempo para la extraccion de parametros, los cuales son idoneos para ser usados en aplicaciones moviles principalmente por su baja carga computacional y posibilidad de ejecucion en tiempo real, permitiendo la deteccion de anomalias cardiacas de forma automatica y rapida sin la necesidad de una supervision constante por parte de un especialista para el analisis preliminar.

/pdf/monitoreo-ambulatorio-y-generacion-de-alertas-tempranas-ante-5z216gbqyo.pdf

Monitoreo ambulatorio y generación de alertas tempranas ante anomalías cardiacas usando dispositivos móviles

The purpose of the present study is to numerically analyze and optimize structural parameters effecting on the transmitting performance of piezoelectric micromachined ultrasonic transducers (PMUTs) with a vibration layer. Using the finite elements method (FEM), a planar and two curved (dome-shaped and concave) structures of PMUTs based on aluminum nitride (A1N) were modeled separately. By applied a sine excitation working on a frequency band ranged from 20 kHz to 25 MHz, resultant transmitting performances with various structural parameters of each PMUT model were estimated numerically in water. The obtained results clearly show that there is a relative higher transmitting performance both of the dome-shaped and concave structures comparing with that of the planar one. Importantly, the transmitting performance would be optimized with a diameter of 64 μm for the top electrode of the planar element, which is consistent with previous theoretic works, and a radius of 200 μm would be suggested for the curvature of the curved structures so as to launch a larger acoustic pressure. In conclusion, both the physical parameters and geometric structures of a PMUT-based ultrasound sensor combining its work frequency could be optimized efficiently with a numerical method.

Piezoelectric micromachined ultrasonic transducers: Modeling and simulation of structural parameters on transmitting performance

Since the inability of clinical approaches to measure the shock-induced electric field distribution of internal cardiac defibrillation, current clinical applications of the implantable cardioverter defibrillator (ICD) still stay largely empirical. In this study, a finite element modeling and simulation method for solving internal cardiac defibrillation field was proposed. Using this method, the defibrillation shock-induced potential field distribution was solved numerically in the torso of a patient implanted with a widely used transvenous ICD system. Moreover, the defibrillation energy threshold (DFT) for this patient was pre-surgically calculated using the critical mass hypothesis of cardiac defibrillation studies. The obtained results showed a high agreement between the predicted defibrillation thresholds with records observed in clinical. As a conclusion, the proposed method would be a feasible approach for using a further patient-specific optimization of ICD implantation, as part of preoperative planning.

Numerical modeling and simulation based on finite element method for internal cardiac defibrillation in a human torso

Piezoelectric Micromachined Ultrasonic Transducers for Photoacoustic Imaging: Modeling and Simulation of Structural Parameters on Receive Performance

Compared with clinical and experimental approaches, numerical modeling of defibrillation offers a great opportunity to optimize the defibrillation strategy in a more individualized way. Through numerical simulation of the shock-induce electric field distribution, the outcome of a certain defibrillation shock could be predicted according to several different metrics. In this paper, we propose a novel evaluation method, in which four defibrillation criteria are assigned with separate weighting factors to quantitatively assess the efficiency of a certain defibrillation shock. Three anatomically realistic finite element models of swine were constructed for the evaluation study of 8 electrode pairs in different placements. In addition, corresponding animal experiments were performed to determine the defibrillation threshold of 8 electrode placements. Both computational and experimental results suggest that the clinical recommended anterior-lateral position is the most efficient electrode displacement for transthoracic defibrillation in swine. In conclusion, the good agreement between stimulations and experiments indicates that the present multi-criteria evaluation method would be potentially useful for optimizations of cardiac defibrillation outcome.

A multi-criteria evaluation method for assessing the defibrillation outcome of different electrode placements in swine

To make automatic external defibrillators (AEDs) easy to use by the public who is not familiar with emergency treatment and electrocardiogram (ECG) analysis, it is critical to have an accurate shockable rhythm recognition algorithm. This paper presents a novel compositive algorithm by combining a slope variability analyzer with a band-pass digital filter so as to accurately distinguish shockable rhythms from non-shockable rhythms for automatic external defibrillators (AEDs). A total of 35 ECG records from the widely recognized Creighton University Ventricular Tachyarrhythmia Database (CUDB) were used to test the performance of the proposed algorithm. The obtained sensitivity of 94.2% and the specificity of 96.6% both satisfy requirements by the AHA rules on the arrhythmias detection for AEDs, and show a higher performance comparing with the previous HILB algorithm and the slope variability method only. As a conclusion, the proposed compositive algorithm would potentially provide a useful tool for AED systems with a higher accuracy and lower computation requirements.

A shockable rhythm detection algorithm for automatic external defibrillators by combining a slope variability analyzer with a band-pass digital filter

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Papers

Numerical modeling and simulation based on finite element method for internal cardiac defibrillation in a human torso

Piezoelectric Micromachined Ultrasonic Transducers for Photoacoustic Imaging: Modeling and Simulation of Structural Parameters on Receive Performance

A multi-criteria evaluation method for assessing the defibrillation outcome of different electrode placements in swine

A shockable rhythm detection algorithm for automatic external defibrillators by combining a slope variability analyzer with a band-pass digital filter