Do epicardial electrogram and monophasic action potential techniques reflect similar electrical activity?

The authors tested whether: (1) epicardial monophasic action potential (MAP) and electrogram (EG) record different signals during the same tachyarrhythmia (TA); (2) the correlation between close and far bipolar signals is similar in TAs. Different TAs were induced in isolated perfused feline hearts. Two bipolar (close sites) epicardial EG and two MAP electrodes were attached to the left ventricle (10 mm apart). Bipolar EG electrodes were also attached to the right ventricle (far EG). 30" recordings were sampled at 200 Hz per channel. Coherence spectrum analysis (CSA) (scale 0-1) was used to assess correlation between electrical activity signals. The results (n=33) showed that mean CSA value was higher in MAP vs. close bipolar EG signals (0.6/spl plusmn/0.24 vs 0.54/spl plusmn/0.2 respectively) (p<0.04), due to high MAP prevalence on CSA>0.6. Lower CSA values were obtained with far (0.48/spl plusmn/0.21) vs. close EG sites (p<0.08). It is concluded that electrical activity during TA is displayed differently by MAP and EG. This is associated with the difference in correlation between close and far sites.