Session P87.2

Influence of Ischemia and Reperfusion Duration on Left Ventricular Depolarization in Isolated Rabbit Hearts Registered by Optical Method

J Kolárová*, O Janoušek, I Provazník, M Nováková, K Fialová

Brno University of Technology
Brno, Czech Repub.

The influence of ischemia and reperfusion duration on left ventricular depolarization is studied from electrograms (ECG) and monophasic action potentials (MAPs). Three orthogonal ECG signals and MAPs are recorded simultaneously during ischemia in isolated rabbit hearts perfused according to Langendorff. MAPs are recorded by an optical method via fluorescence measurement from the heart surface at appointed place. The principle of optical measurement of MAP is an application of voltage-sensitive dye (VSD), di-4-ANEPPS in our experimental set-up, into the heart tissue. The optical signal therefore depends on the cardiac action potential. The ratiometric fluorescence method, based on emitted light detection by a segment narrow-band photodiode at two different wavelengths, is used. MAPs are recorded with high signal-to-noise ratio and at 2kHz sampling frequency.
The speed of depolarization propagation in ventricular tissue is derived from activation time (AT), which is defined as the distance from the earliest QRS deflection to MAP upstroke.
6 isolated New Zealand rabbit hearts were included in this study. The hearts were perfused in a Langendorff set-up. The study of ischemia and reperfusion effect on the left ventricular depolarization in isolated rabbit hearts is possible due to long-time MAPs and ECG recordings, which last at least 60 minutes.
The excitement propagation and conduction in an ischemic heart takes a longer time in comparison to non-ischemic myocardium. Speed of propagation decreases with ongoing ischemia, and the activation time increases proportionally to ischemia duration. During reperfusion, the speed of propagation increases immediately with the first minute of reperfusion and remains at the same value until the end of the examined period.
The measurement of activation time from MAPs recorded by a touchless optical method is comparable with records obtained by a classical microelectrode technique.

(Abstract Control Number: 77)