Non-invasive imaging of arrhythmogenic left-ventricular myocardium after

A wide range of cardiac imaging procedures is available to assess left-ventricular function, geometry, perfusion, and altered metabolism. There is no non-invasive imaging procedure to detect electrically unstable myocardium. We assessed the electrical function of the myocardium by biomagnetic imaging of high-frequency depolarisation signals in a patient aged 70 years who had non-sustained ventricular tachycardia that developed after anterior left-ventricular myocardial infarction and apical aneurysm. Imaging was done on the basis of magnetic-field measurement and inverse computation of the magnitudes of 1200 left-ventricular endocardial dipoles regularly spaced (mean distance 3 mm). Such endocardial activity images have been computed for the unfiltered depolarisation signal (QRS) and for the last 40 ms of the bidirectional 30 Hz highpass filtered depolarisation signal (LP). In theory, three types of QRS/LP image pairs could appear. If areas of high dipole magnitude of LP and QRS images match, LP generators can be taken to lie in the intact myocardium. If areas of high dipole magnitude in LP images match areas of low dipole magnitude in QRS images, LP generators may belong to the area infarcted and, therefore, display properties of the surviving subendocardial layer. If no correlation of LP and QRS is seen, it will not fit into the concepts of arrhythmogenesis after infarction. By comparison of LP and QRS images (figure), we observed regional mismatch of dipole magnitudes. The QRS image shows low dipole magnitudes in the apical segment of the left ventricle (the apical aneurysm) with a loss of electrically active myocardium. The opposite has appeared in the LP image with high dipole magnitudes in the segments infarcted. This finding could be an indication of fragmented delayed intraventricular conduction in this region. We conclude that this method supports the imaging of delayed high-frequency depolarisation signals, which are known to correlate with conduction disturbances and, therefore, risk of arrhythmia. 1 Our findings may help in