Quantitative effects of acute myocardial infarction on intracavitary potentials

The objective of this study was to quantify the features of intracavitary potential recordings before and after experimental myocardial infarction. Potentials were recorded within the left ventricular cavity in 10 dogs using a cylindrical [45mm × 10mm] probe with 40 evenly spaced unipolar recording electrodes on its surface, before and after acute occlusion of the left anterior descending coronary artery. Analysis of control and post-infarct waveforms was based on QRS and ST-T area, and maximum negative potential and maximum negative dV/dt during the QRS complex. Infarction resulted in significant [p<0.01] reductions in QRS area [521±132 vs. 398±181 mV·ms], maximum negative potential [20.8±3.6 vs. 16.6±5.3 mV], and maximum negative dV/dt [1.9±0.6 vs. 1.3±0.6 mV/ms], and significant increases in ST-T area [42±160 vs. 138±246 mV·ms]. The waveforms were evaluated using linear discriminant function and cross-validation procedures to determine if specific criteria from these measurements could distinguish waveforms recorded before from those recorded after acute coronary occlusion. Results indicated that the intracavitary waveforms distinguished pre-infarct from post-occlusion with 84% accuracy. Analysis of misclassified recordings indicates that 80% of the misclassified recordings were from electrodes distal to local endocardial events. The significance of this study is that simultaneous intracavitary recordings have been confirmed as a useful tool in detecting local endocardial events and could eliminate the need for sequential recordings in arrhythmia mapping, reducing errors due to non-steady state conditions during several minutes, rather than seconds, of recording time.