%0 Journal Article %J Biophys J %D 2001 %T Visualizing excitation waves inside cardiac muscle using transillumination. %A Baxter, Bill %A Mironov, S F %A Zaitsev, A V %A Jalife, J %A Pertsov, A V %K Animals %K Biophysical Phenomena %K Biophysics %K Electrophysiology %K Endocardium %K Fluorescent Dyes %K Heart %K Models, Cardiovascular %K Myocardium %K Optics and Photonics %K Perfusion %K Pericardium %K Pyridinium Compounds %K Sheep %X

Voltage-sensitive fluorescent dyes have become powerful tools for the visualization of excitation propagation in the heart. However, until recently they were used exclusively for surface recordings. Here we demonstrate the possibility of visualizing the electrical activity from inside cardiac muscle via fluorescence measurements in the transillumination mode (in which the light source and photodetector are on opposite sides of the preparation). This mode enables the detection of light escaping from layers deep within the tissue. Experiments were conducted in perfused (8 mm thick) slabs of sheep right ventricular wall stained with the voltage-sensitive dye di-4-ANEPPS. Although the amplitude and signal-to-noise ratio recorded in the transillumination mode were significantly smaller than those recorded in the epi-illumination mode, they were sufficient to reliably determine the activation sequence. Penetration depths (spatial decay constants) derived from measurements of light attenuation in cardiac muscle were 0.8 mm for excitation (520 +/- 30 nm) and 1.3 mm for emission wavelengths (640 +/- 50 nm). Estimates of emitted fluorescence based on these attenuation values in 8-mm-thick tissue suggest that 90% of the transillumination signal originates from a 4-mm-thick layer near the illuminated surface. A 69% fraction of the recorded signal originates from > or =1 mm below the surface. Transillumination recordings may be combined with endocardial and epicardial surface recordings to obtain information about three-dimensional propagation in the thickness of the myocardial wall. We show an example in which transillumination reveals an intramural reentry, undetectable in surface recordings.

%B Biophys J %V 80 %P 516-30 %8 01/2001 %G eng %U http://www.ncbi.nlm.nih.gov/pubmed/11159422 %N 1 %R 10.1016/S0006-3495(01)76034-1 %0 Journal Article %J Ann Biomed Eng %D 1997 %T Technical features of a CCD video camera system to record cardiac fluorescence data. %A Baxter, Bill %A Davidenko, J M %A Loew, L M %A Wuskell, J P %A Jalife, J %K Action Potentials %K Algorithms %K Animals %K Body Surface Potential Mapping %K Calibration %K Computer Simulation %K Electric Conductivity %K Fluorescent Dyes %K Image Processing, Computer-Assisted %K Models, Cardiovascular %K Sheep %K Ventricular Function %K Video Recording %X

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.

%B Ann Biomed Eng %V 25 %P 713-25 %8 07/1997 %G eng %U http://www.ncbi.nlm.nih.gov/pubmed/9236983 %N 4 %R 10.1007/BF02684848 %0 Journal Article %J J Electrocardiol %D 1992 %T Spatiotemporal irregularities of spiral wave activity in isolated ventricular muscle. %A Davidenko, J M %A Pertsov, A V %A Salomonsz, R %A Baxter, Bill %A Jalife, J %K Animals %K Cardiac Pacing, Artificial %K Fluorescent Dyes %K Heart Conduction System %K Membrane Potentials %K Optics and Photonics %K Pericardium %K Signal Processing, Computer-Assisted %K Tachycardia %K Ventricular Function %X

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.

%B J Electrocardiol %V 24 Suppl %P 113-22 %8 1992 %G eng %U http://www.ncbi.nlm.nih.gov/pubmed/1552240 %R 10.1016/s0022-0736(10)80029-9