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Background: There is no currently available technology to accurately predict ablation lesion size within seconds of onset of delivery of radiofrequency (RF) energy., Methods: Changes in several biophysical characteristics of cardiac tissue in vitro within 5-15 seconds of the onset of RF energy were evaluated to predict lesion formation at 120 seconds. RF energy was applied with a 50% duty cycle to measure heating and cooling behavior of the electrode temperature sensor. Changes in impedance, phase angle, and the resulting resistance and capacitance, power, and electrode temperature variation during RF ablation were analyzed., Results: A combination of electrical-based parameters measured online as early as 5, 10, and 15 seconds after onset of RF energy in vitro was found to explain 63, 75, and 76% of variability (R(2) ) of lesion volume. These correlations were better than any single parameter, particularly impedance and target temperature., Conclusions: A combination of electrical-based parameters provides better correlation with lesion formation than a single parameter and may be useful to predict lesion size during RF ablation in vivo. These parameters appear to represent changes in the tissue during heating., (©2010, The Authors. Journal compilation ©2010 Wiley Periodicals, Inc.)

Introduction: Changes due to biventricular pacing have been documented by shortening of QRS duration and echocardiography. Compared to normal ventricular activation, the presence of left bundle branch block (LBBB) results in a significant change in cardiac cycle time intervals. Some of these have been used to quantify the underlying cardiac dyssynchrony, assess the effects of biventricular pacing, and guide programming of ventricular pacing devices. This study evaluates a simple noninvasive method using accelerometers attached to the skin to measure cardiac time intervals in biventricularly paced patients., Methods: Ten patients with biventricular pacemakers previously implanted for congestive heart failure were paced in the AAI mode, then in atrioventricular (AV) sequential mode from the right and left ventricles followed by biventricular pacing. Simultaneous recordings were obtained by 2D, Doppler echocardiography as well as by accelerometers. Similar recordings were obtained from 10 gender, aged matched, normal controls during sinus rhythm., Results: Compared to normals, heart failure patients paced in AAI mode had prolonged isovolumetric contraction time (IVCT), shorter ventricular ejection time (LVET), and prolonged isovolumetric relaxation (IVRT). With biventricular pacing the IVCT decreased, but the LVET and IVRT did not change significantly. There was excellent correlation between the echo and accelerometer-measured intervals., Conclusions: Shortening of the IVCT measured by an accelerometer is a consistent time interval change due to biventricular pacing that probably reflects more rapid acceleration of left ventricular ejection. The accelerometer may be useful to assess immediate efficacy of biventricular pacing during device implantation and optimize programmable time intervals such as AV and interventricular (VV) delays.

We report our experience with a system that utilizes changes in several biophysical characteristics of cardiac tissue to determine lesion formation and to estimate lesion size both on and off-line in vitro during radio frequency (RF) energy delivery. We analyzed the reactive and resistive components of tissue impedance and tracked the change of phase angle during RF ablation. We correlated the amount of tissue damage with these and other biophysical parameters and compared them with off-line analysis. We found that there are irreversible changes in the reactive and resistive components of impedance that occurred during tissue ablation. The irreversible changes of these components are greater in magnitude, and correlate better with the size of lesions than that of impedance alone that is currently used. Numerically, the best single on-line and off-line correlation for combined perpendicular and parallel electrode orientation was with phase angle. On-line and off-line capacitance and susceptance correlations were essentially similar suggesting that they may be useful as lesion size predictors, given these parameter's persistent change without temperature sensitivity. This study indicates that it is technically feasible to assess lesion formation using biophysical parameters.

Aims: The aim of this study was to determine if the bio-battery signal can predict myocardial lesion formation and depth., Methods: Fresh bovine ventricular myocardium was immersed in a temperature-controlled bath of circulating blood. RF energy was delivered with a custom generator to a catheter electrode. RF energy, electrode temperature, bio-battery signal and tissue impedance were displayed and recorded. A copper return plate was placed in the bath., Results: When 50 volts of constant RF energy was terminated at a 20, 40, or 60% decline from the maximum bio-battery signal, the lesion depth was 4 +/- 0.4 mm. When RF energy application was terminated later, at a point characterized by a brief change of slope of the bio-battery signal, the lesions measured 7.8 +/- 1.4 mm in depth. This "bump" occurred before a rapid impedance rise., Conclusion: The depth of lesions created at the "bump" point was almost two-fold deeper than those at the termination points of 20, 40 and 60% bio-battery decrease (p = 0.0001). When RF energy was terminated at the rapid impedance rise the lesions were similar in depth, 8.2 +/- 0.9 mm, to those obtained when RF energy was stopped at the "bump" (p = 0.28). The bio-battery signal provides a unique marker that might be useful to obtain maximum lesion depth while avoiding rapid impedance rise.