Localization of Ischemic Change during PTCA

An example of how we detect changes due to ischemia in patients undergoing coronary angioplasty. The top panel contains two isointegral maps from the QRST segment, and their difference. The left map (A) originates from signals measured before inflation of the PTCA balloon while the middle map (B) is the same integral from a beat recorded at the latter, peak phase of the inflation; the rightmost map is the difference (peak- minus pre-inflation). These maps have been projected onto a two-dimensional surface, with the anterior torso on the left of each map and the posterior on the right. In the lower part of the figure, all distributions shown are isopotential instant maps, also from the same pre-inflation (panel A) and peak-inflation (Panel B) beats. The torso maps were measured, but the epicardial maps in the lower right portion of each panel contain estimates based on inverse calculations. The red areas denote positive potential, the blue denote negative potential and the green/yellow colors span the region of small potential values near zero. The arrow indicates the approximate location of the angioplasty balloon. The presense of positive potentials in the epicardial maps identifies the zone of predicted ischemia, located downstream from the site of occlusion. This was work from my PhD research performed with Milan Horacek at Dalhousie University.

Last modified: Wed Sep 11 19:43:43 MD 2002