[Studies on intraoperative cardiac mapping]

Precise determination of the arrhythmogenic area by the intraoperative cardiac mapping procedure is a prerequisite to successful surgical therapy for tachyarrhythmias. Because of the limitation of time during operation, mapping should be performed precisely and quickly. For this purpose we have developed and used an on-line portable minicomputer system (modified HPM-6500; Fukuda Denshi Co., Ltd.). A ventricular epicardial excitation sequence map is acquired by measuring the conduction time difference for 51 predetermined points on the whole ventricular surface. The measured data are instantaneously digitized and computed to be displayed as an isochornous map in real time basis. Similar program is available for atrial excitation map. With this system it takes only about ten minutes to get an epicardial isochornous map. Recently a multi-channel signal-processing unit has been incorporated in the HPM-6500. With the use of a sock electrode or a card electrode, a map can be obtained on a few cardiac contractions. Multi-point simultaneous mapping has been proved to be especially important to get a VT isochornous map, for induced VTs during operation are usually unstable and transient.