03382nas a2200349 4500008004100000022001400041245008900055210006900144260001200213300001100225490000700236520236800243653002202611653001502633653001202648653003502660653001602695653002402711653002602735653002102761653004002782653002702822653001002849653002502859653002002884100001702904700001902921700001402940700001702954700001402971856004702985 1997 eng d a0090-696400aTechnical features of a CCD video camera system to record cardiac fluorescence data.0 aTechnical features of a CCD video camera system to record cardia c07/1997 a713-250 v253 a

A charge-coupled device (CCD) camera was used to acquire movies of transmembrane activity from thin slices of sheep ventricular epicardial muscle stained with a voltage-sensitive dye. Compared with photodiodes, CCDs have high spatial resolution, but low temporal resolution. Spatial resolution in our system ranged from 0.04 to 0.14 mm/pixel; the acquisition rate was 60, 120, or 240 frames/sec. Propagating waves were readily visualized after subtraction of a background image. The optical signal had an amplitude of 1 to 6 gray levels, with signal-to-noise ratios between 1.5 and 4.4. Because CCD cameras integrate light over the frame interval, moving objects, including propagating waves, are blurred in the resulting movies. A computer model of such an integrating imaging system was developed to study the effects of blur, noise, filtering, and quantization on the ability to measure conduction velocity and action potential duration (APD). The model indicated that blurring, filtering, and quantization do not affect the ability to localize wave fronts in the optical data (i.e., no systematic error in determining spatial position), but noise does increase the uncertainty of the measurements. The model also showed that the low frame rates of the CCD camera introduced a systematic error in the calculation of APD: for cutoff levels > 50%, the APD was erroneously long. Both noise and quantization increased the uncertainty in the APD measurements. The optical measures of conduction velocity were not significantly different from those measured simultaneously with microelectrodes. Optical APDs, however, were longer than the electrically recorded APDs. This APD error could be reduced by using the 50% cutoff level and the fastest frame rate possible.

10aAction Potentials10aAlgorithms10aAnimals10aBody Surface Potential Mapping10aCalibration10aComputer Simulation10aElectric Conductivity10aFluorescent Dyes10aImage Processing, Computer-Assisted10aModels, Cardiovascular10aSheep10aVentricular Function10aVideo Recording1 aBaxter, Bill1 aDavidenko, J M1 aLoew, L M1 aWuskell, J P1 aJalife, J uhttp://www.ncbi.nlm.nih.gov/pubmed/923698302348nas 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 a

Voltage-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