Electrocardiography in Wistar rat experimental model: analysis and characterization

El modelo experimental de rata Wistar es ampliamente utilizado por la comunidad científica para la evaluación de xenobióticos y estresantes ambientales. Sin embargo, a pesar de su gran uso, pocas publicaciones ´ han reportado explícitamente las diferencias entre los parámetros obtenidos del delineamiento del ECG para las distintas variables que intervienen en la configuración de un experimento con rata Wistar. Variables como la anestesia suministrada, el sexo, la edad, el peso, la restricción del movimiento y la derivación utilizada influyen significativamente ´ en los parametros electrocardiográficos analizados, tales como, los intervalos RR, QT y PR, las duraciones P y QRS, y las amplitudes pico de las ondas P, Q, R, S y T. El primer objetivo específico de este trabajo es organizar los parámetros electrocardiográficos que ya han sido publicados por la comunidad científica según su setup experimental. El segundo objetivo específico es aportar nuevos parámetros, como los intervalos JTend y Tpe, al estado del arte de ´ la caracterizacion del ECG de rata Wistar. Para ello, una base de datos de 48 ratas Wistar categorizadas por sexo y edad, medida en la derivación II, fue procesada y delineada.The experimental model of Wistar rat(WR) is widely used by the scientific community for the evaluation of xenobiotics and environmental stressors. However, in spite of its great use,few publications have explicitly reported the differences between the parameters obtained from the ECG delineation and the different variables involved in the settings of a Wistar rat experiment. Variables such as supplied anesthesia, sex, age, weight, movement restriction and lead used influence the electrocardiographic parameters analyzed, such as RR, QT, PR intervals, P and QRS durations and peak amplitudes of P, Q, R, S, and T-waves. The first specific objective of this work is to organize the electrocardiographic parameters that have already been published by the scientific community according to their experimental setup. The second specific objective is to provide new parameters, such as the JTend and Tpe intervals, to the state of the art of Wistar rat ECG characterization. For this purpose, a database of 48 Wistar ratscategorized by sex and age, measured in lead II, was processed and delineated.Fil: Caracciolo, Santiago Federico. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Saavedra 15. Instituto Argentino de Matemática Alberto Calderón; Argentina. Universidad de Buenos Aires. Facultad de Ingeniería; ArgentinaFil: Bertran, Guillermo Claudio. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Investigaciones Médicas. Universidad de Buenos Aires. Facultad de Medicina. Instituto de Investigaciones Médicas; ArgentinaFil: Arini, Pedro David. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Saavedra 15. Instituto Argentino de Matemática Alberto Calderón; Argentina. Universidad de Buenos Aires. Facultad de Ingeniería; Argentin

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

Es bien conocida la existencia de diferencias en la actividad eléctrica cardíaca asociadas al sexo. Si bien estas diferencias habitualmente se relacionan al efecto de la madurez y de las hormonas sexuales gonadales, todavía existen controversias al respecto. El objetivo de este trabajo fue evaluar el efecto que la madurez sexual y la castración producen sobre los distintos parámetros del electrocardiograma de superficie y de la duración de los potenciales de acción (DPA). Se utilizaron conejos jóvenes (menores de un mes de edad) y adultos (mayores de seis meses de edad). Las diferencias obtenidas en las hembras se observan en la repolarización tardía, mientras que en los machos ocurren en la repolarización temprana. Existiría una relación entre las diferencias observadas en la duración desde el pico máximo hasta el fin de la onda T (Ttpf) y las observadas en la DPA al 90% de la repolarización (DPA90) en las hembras, mientras que en los machos la relación existe entre la duración desde el punto J hasta el pico máximo de la onda T (JTp) y la DPA al 30 y 50% de la repolarización (DPA30 y DPA50). Si bien existen diferencias que podrían ser debidas a factores hormonales otras serían debidas a factores no hormonales.Sex-associated differences in cardiac electrical activity have already been documented. 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. The differences obtained in females were observed in late repolarization, whereas in males took place in early repolarization. There was a relationship between the differences observed in the duration from the peak to the end of the T wave and those observed in the duration of the action potential to 90% of repolarization in females, whereas in males the relationship exists between the duration from the point J to the peak of the T wave and the duration of the action potential at 30 and 50% of repolarization. Differences could be related to hormonal or non-hormonal factors.Fil: Eizikovits, Gabriela Yael. Universidad de Buenos Aires. Facultad de Medicina. Instituto de Investigaciones Médicas; ArgentinaFil: Casal, Carolina. Universidad de Buenos Aires. Facultad de Medicina. Instituto de Investigaciones Médicas; ArgentinaFil: Arini, Pedro David. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Saavedra 15. Instituto Argentino de Matemática Alberto Calderon; ArgentinaFil: Bertran, Guillermo Claudio. Universidad de Buenos Aires. Facultad de Medicina. Instituto de Investigaciones Médicas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Beat-to-beat ventricular repolarization variability evaluated during acute myocardial ischemia

Experimental and clinical studies have shown that beat-to-beat variability of ventricular repolarization morphology, which can be measured by T-wave spectral variance (TSV) index based on the 2D-FFT, is associated with an increased risk for developing malignant ventricular arrhythmias.In the present study we tested TSV index during percutaneous coronary intervention (PCI) procedure in the 12 standard ECG leads and in the orthogonal X, Y and Z leads. In addition, we analyzed the intraindividual and interindividual variations of TSV index, in order to determine reliable limits of significant repolarization variability due to an ischemic cardiac process. The study group consisted of 62 patients, in which two ECG controls and one ECG recording during PCI procedure were obtained. Results indicate that TSV index showed significant differences during PCI procedure respect to control situation in all ECG leads(p<0.0001).The relative change between PCI procedure and control situation increased up to almost 5 times in the precordial v3 lead. Moreover, TSV index presented a high stability in each patient and a significant larger variability between patients. Finally, we conclude that TSV index offers a robust tool for evaluating beat-to-beat repolarization variability during acute myocardial ischemia.Fil: Valverde, Esteban Raul. Universidad de Buenos Aires. Facultad de Ingenieria. Instituto de Ingeniería Biomédica; ArgentinaFil: Bertran, Guillermo Claudio. Universidad de Buenos Aires. Facultad de Medicina. Instituto de Investigaciones Médicas; ArgentinaFil: Arini, Pedro David. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Saavedra 15. Instituto Argentino de Matemática; Argentina. Universidad de Buenos Aires. Facultad de Ingenieria. Instituto de Ingeniería Biomédica; Argentin

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. We analyzed the role played by the dipolar and nondipolar components in determining TWR. Methods and Results: Singular value decomposition was applied to the repolarization signals obtained from isolated rabbit hearts using a 5 × 8 array multielectrode recording system during premature beats (N = 11) and after d-sotalol (N = 9) exposure. Both the dipolar and nondipolar components of the T wave increased significantly during premature stimulation and after d-sotalol exposure. The relative TWR decreased significantly during premature stimulation but did not change after d-sotalol. Changes in the dipolar and nondipolar components of the second half of the T wave were significantly greater than those corresponding to the first half during premature stimulation, and a significant correlation was observed between the nondipolar components of the second half of the T wave and the Tpeak?end interval. Conclusion: Conditions exist during which both the dipolar and nondipolar components can change simultaneously. Under these conditions, the relative TWR may not reflect regional heterogeneity of repolarization with accuracy. The nondipolar components of the second half of the T wave can be linked to assessment of the transmural dispersion of repolarization.Fil: Biagetti, Marcelo. Universidad Favaloro; ArgentinaFil: Arini, Pedro David. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Saavedra 15. Instituto Argentino de Matemática Alberto Calderón; Argentina. Universidad Favaloro; ArgentinaFil: Valverde, Esteban Raul. Universidad Favaloro; ArgentinaFil: Bertran, Guillermo Claudio. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Investigaciones Médicas. Universidad de Buenos Aires. Facultad de Medicina. Instituto de Investigaciones Médicas; ArgentinaFil: Quinteiro, Ricardo Alberto. Universidad Favaloro; Argentin

Effect of the Electrode Impedance in Improved Buffer Amplifier for Bioelectric Recordings

We analyzed the effects of the electrode impedance on the transfer response of a one-stage improved buffer amplifier. The electrode DC resistance (Rd) modifies the one-stage buffer transfer response. We found a limit electrode resistance (Rd(lim)) which depends on the transfer damping factor (∈). If Rd is lower than 86.5 kW, the transfer response of the buffer fulfils the American Heart Association, AHA, recommendations, but when Rd is greater than Rd(lim) it must be cautiously weighted-up because its influence in the transfer response becomes appreciable. The maximum Rd that can be driven by the buffer is 1.2 MW. Higher values never fulfil the AHA recommendations. Therefore, electrodes with higher impedance should not be used with this kind of buffer. On the other hand, when this buffer is used to build-in an instrumentation amplifier (IA) for bipolar recording, the common-mode rejection ratio (CMRR) is sensitive to the electrode type used.Fil: Valverde, Esteban Raul. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Favaloro; ArgentinaFil: Arini, Pedro David. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Saavedra 15. Instituto Argentino de Matemática Alberto Calderón; Argentina. Universidad Favaloro; ArgentinaFil: Biagetti, Marcelo. Universidad Favaloro; ArgentinaFil: Bertran, Guillermo Claudio. Universidad Favaloro; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Quinteiro, Ricardo Alberto. Universidad Favaloro; Argentin