“Late Potentials” and Delayed Intrinsic Deflections — Comparative Study in Acute Regional Ischemia in Isolated Porcine Hearts

Summary

Waveforms, occurring at the end of the QRS complex or during the ST segments, T wave, or diastolic intervals are defined as late potentials. Whether late potentials reflect delayed regional activiation is still under discussion. A correlation with electrophysiological parameters directly indicating delayed activation has yet not been done. - The present study was performed in isolated porcine hearts (n = 12) perfused according to the Langendortfmethod. An ischemic zone was produced by occluding the left anterior descending coronary artery. Unipolar electrograms were recorded by means of non polarizable electrodes using DC-amplifiers (0–1250 Hz) without signal averaging, filtering and high gain amplification. - We measured the intrinsic deflection of the ischemic zone electrogram, and compared it with deflections within the ST -segments of the normal zone. When the ischemic zone was activated more and more delayed, the intrinsic deflections and the deflections within the ST -segments were also progressively delayed. When 2: I block into the ischemic zone occurred deflections within ST -segments showed the same sequence. When premature stimuli were applied both deflections could be delayed until they outlasted the ST-segment duration. If the delay was sufficient, ventricular tachycardia developed. - Our data demonstrate a definite correlation between late potentials and delayed intrinsic deflections and suggest, that late potentials in acute regional ischemia are due to extracellular current flow that might be sufficient to induce malignant ventricular dysrhythmia.

Supported by the Deutsche Forschungsgemeinschaft.