03253nas a2200301 4500008004100000022001400041245009200055210006900147260001200216300001200228490000700240520238200247653001702629653001202646653003102658653002402689653001702713653002402730653002702754653001002781653002902791100001902820700001702839700001702856700001702873700001402890856004702904 1995 eng d a0009-733000aEffects of pacing on stationary reentrant activity. Theoretical and experimental study.0 aEffects of pacing on stationary reentrant activity Theoretical a c12/1995 a1166-790 v773 a
It is well known that electrical pacing may either terminate or change the rate and/or ECG appearance of reentrant ventricular tachycardia. However, the dynamics of interaction of reentrant waves with waves initiated by external pacing are poorly understood. Prevailing concepts are based on simplistic models in which propagation occurs in one-dimensional rings of cardiac tissue. Since reentrant activation in the ventricles occurs in two or three dimensions, such concepts might be insufficient to explain the mechanisms of pacing-induced effects. We used numerical and biological models of cardiac excitation to explore the phenomena, which may take place as a result of electrical pacing during functionally determined reentry. Computer simulations of a two-dimensional array of electrically coupled FitzHugh-Nagumo cells were used to predict the response patterns expected from thin slices of sheep ventricular epicardial muscle, in which self-sustaining reentrant activity in the form of spiral waves was consistently initiated by premature stimulation and monitored by means of video mapping techniques. The results show that depending on their timing and shape, externally induced waves may collide with the self-sustaining spiral and result in one of three possible outcomes: (1) direct annihilation of the spiral, (2) multiplication of the spiral, or (3) shift of the spiral center (ie, core). Multiplication and shift of the spiral core were attended by changes in rate and morphology of the arrhythmia as seen by "pseudo-ECGs." Furthermore, delayed termination (ie, termination of the activity one to three cycles after the stimulus) occurred after both multiplication and shift of the spiral center. Both numerical predictions and experimental results support the hypothesis that whether a pacing stimulus will terminate a reentrant arrhythmia or modify its ECG appearance depends on whether the interactions between the externally induced wave and the spiral wave result in the de novo formation of one or more "wavebreaks." The final outcome depends on the stimulus parameters (ie, position and size of the electrodes and timing of the stimulus) as well as on the position of the newly formed wavebreak(s) in relation to that of the original wave.
10aAcceleration10aAnimals10aCardiac Pacing, Artificial10aComputer Simulation10aDeceleration10aElectrocardiography10aModels, Cardiovascular10aSheep10aTachycardia, Ventricular1 aDavidenko, J M1 aSalomonsz, R1 aPertsov, A V1 aBaxter, Bill1 aJalife, J uhttp://www.ncbi.nlm.nih.gov/pubmed/758623002348nas a2200313 4500008004100000022001400041245009000055210006900145260000900214300001100223490001300234520141700247653001201664653003101676653002101707653002801728653002401756653002501780653001601805653004101821653001601862653002501878100001901903700001701922700001701939700001701956700001401973856004701987 1992 eng d a0022-073600aSpatiotemporal irregularities of spiral wave activity in isolated ventricular muscle.0 aSpatiotemporal irregularities of spiral wave activity in isolate c1992 a113-220 v24 Suppl3 aVoltage-sensitive dyes and high resolution optical mapping were used to analyze the characteristics of spiral waves of excitation in isolated ventricular myocardium. In addition, analytical techniques, which have been previously used in the study of the characteristics of spiral waves in chemical reactions, were applied to determine the voltage structure of the center of the rotating activity (ie, the core). During stable spiral wave activity local activation occurs in a periodic fashion (ie, 1:1 stimulus: response activation ratio) throughout the preparation, except at the core, which is a small elongated area where the activity is of low voltage and the activation ratio is 1:0. The voltage amplitude increases gradually from the center of the core to the periphery. In some cases, however, regular activation patterns at the periphery may coexist with irregular local activation patterns near the core. Such a spatiotemporal irregularity is attended by variations in the core size and shape and results from changes in the core position. The authors conclude that functionally determined reentrant activity in the heart may be the result of spiral waves of propagation and that local spatiotemporal irregularities in the activation pattern are the result of changes in the core position.
10aAnimals10aCardiac Pacing, Artificial10aFluorescent Dyes10aHeart Conduction System10aMembrane Potentials10aOptics and Photonics10aPericardium10aSignal Processing, Computer-Assisted10aTachycardia10aVentricular Function1 aDavidenko, J M1 aPertsov, A V1 aSalomonsz, R1 aBaxter, Bill1 aJalife, J uhttp://www.ncbi.nlm.nih.gov/pubmed/1552240