Myocardial contractility assessed by dynamic electrical impedance measurements during dobutamine stress.

In this study, the electrical impedance of myocardial tissue is measured dynamically during the cardial cycle. The multisine-based approach used to perform electrical impedance spectroscopy (EIS) measurements allows acquiring complete spectral impedance information of the tissue dynamics during contraction. Measurements are performed in situ in the left ventricule of swines during contractility stress tests induced by dobutamine infusion. Additionally, the ECG and the left ventricular (LV) pressure are also acquired synchronously to the impedance signals. The calculated impedance magnitude exhibits a periodic behavior during tissue contraction. The amplitude (peak-to-peak) of this signal is quantified and the compared to the maximum first derivative of the LV pressure (dP/dtmax) that is used as an indicator of contractility variations. The results show a linear correlation between impedance amplitude and dP/dtmax during dobutamine-increased contractility. The present work demonstrates how fast EIS measurements during heart contraction can represent a feasible method to assess changes in myocardial contractility.

Determinantes del éxito de la revascularización de las oclusiones coronarias crónicas: estudio mediante tomografía computarizada con multidetectores / Factors determining success in percutaneous revascularization of chronic total coronary occlusion: multidetector computed tomography análisis

Introducción y objetivos. La revascularización percutánea de las oclusiones crónicas totales supone un desafío técnico, y tiene una tasa de éxito menor que las demás angioplastias. Conocer los predictores de fracaso permitiría mejorar la selección de pacientes con mayores posibilidades de éxito. Diseñamos un estudio para identificar los datos de la tomografía computarizada con multidetectores que podrían asociarse al fracaso del tratamiento percutáneo de las oclusiones crónicas totales. Métodos. Estudio prospectivo monocéntrico sobre 69 pacientes consecutivos, portadores de una oclusión crónica total, a los que se realizó una tomografía computarizada con multidetectores previa a la revascularización. Resultados. Se analizaron 77 lesiones, con una longitud ocluida media de 19,9±14,3 mm y una duración de la oclusión de 47±62 meses. El único factor predictor angiográfico independiente del fracaso de la revascularización fue la presencia de una fuerte curva entre la placa y el vaso proximal permeable (odds ratio=3,8; intervalo de confianza del 95%, 1,2-12; p=0,02). El único factor derivado de la tomografía computarizada con multidetectores asociado significativamente con fracaso fue la presencia de un arco de calcio que afectase a más del 50% de la circunferencia del segmento ocluido en la porción proximal (p=0,04) y media (p=0,03). Conclusiones. La tomografía computarizada con multidetectores identifica una variable no cuantificable por angiografía como predictora del fracaso de la revascularización de las oclusiones crónicas totales. En casos seleccionados podría ser útil para el cribado antes de la revascularización (AU)

Introduction and objectives. Percutaneous revascularization of chronic total coronary artery occlusion is a technical challenge and has a lower success rate than other angioplasty procedures. Identification of predictors of failure could lead to better selection of patients with the greatest possibility of success. In this study, we investigate the multidetector computed tomography features associated with failure of percutaneous treatment for chronic total coronary occlusion. Methods. This is a prospective, single-center study of 69 consecutive patients with chronic total occlusion in whom multidetector computed tomography study was performed before percutaneous coronary revascularization. Results. Seventy-seven lesions were analyzed. The mean length of the occlusion was 19.9 (14.3) mm and the estimated duration of occlusion was 47 (62) months. The only angiographic factor independently predictive of failure was a severe curve between the plaque and the proximal patent vessel (odds ratio 3.8, 95% confidence interval, 1.2-12; P=.02). On multidetector computed tomography, the only factor predictive of failure was an arc of calcium affecting more than 50% of the vessel circumference in the proximal (P=.04) and middle (P=.03) third of the occlusion. Conclusions. Multidetector computed tomography identified a variable that cannot be measured by angiography that can predict failure in percutaneous revascularization of chronic total coronary occlusions. In selected cases, this parameter could be useful for preprocedure screening (AU)

Factors determining success in percutaneous revascularization of chronic total coronary occlusion: multidetector computed tomography analysis.

INTRODUCTION AND OBJECTIVES: Percutaneous revascularization of chronic total coronary artery occlusion is a technical challenge and has a lower success rate than other angioplasty procedures. Identification of predictors of failure could lead to better selection of patients with the greatest possibility of success. In this study, we investigate the multidetector computed tomography features associated with failure of percutaneous treatment for chronic total coronary occlusion. METHODS: This is a prospective, single-center study of 69 consecutive patients with chronic total occlusion in whom multidetector computed tomography study was performed before percutaneous coronary revascularization. RESULTS: Seventy-seven lesions were analyzed. The mean length of the occlusion was 19.9 (14.3) mm and the estimated duration of occlusion was 47 (62) months. The only angiographic factor independently predictive of failure was a severe curve between the plaque and the proximal patent vessel (odds ratio 3.8, 95% confidence interval, 1.2-12; P=.02). On multidetector computed tomography, the only factor predictive of failure was an arc of calcium affecting more than 50% of the vessel circumference in the proximal (P=.04) and middle (P=.03) third of the occlusion. CONCLUSIONS: Multidetector computed tomography identified a variable that cannot be measured by angiography that can predict failure in percutaneous revascularization of chronic total coronary occlusions. In selected cases, this parameter could be useful for preprocedure screening.

In-cycle myocardium tissue electrical impedance monitoring using broadband impedance spectroscopy.

Measurements of myocardium tissue impedance during the cardiac cycle have information about the morphology of myocardium cells as well as cell membranes and intra/extra cellular spaces. Although the variation with time of the impedance cardiac signal has information about the myocardium tissue activity during the cardiac cycle, this information has been usually underestimated in the studies based on frequency-sweep Electrical Impedance Spectroscopy (EIS) technique. In these cases, the dynamic behavior was removed from the impedance by means of averaging. The originality of this research is to show the time evolution of in-vivo healthy myocardium tissue impedance during the cardiac cycle, being measured with a multisine excitation at 26 frequencies (1 kHz-1 MHz). The obtained parameters from fitting data to a Cole model are valid indicators to explain the time relation of the systolic and diastolic function with respect to the myocardium impedance time variation. This paper presents a successful application of broadband Impedance Spectroscopy for time-varying impedance monitoring. Furthermore, it can be extended to understand various unsolved problems in a wide range of biomedical and electrochemical applications, where the system dynamics are intended to be studied.