Epicardial Isochrones From a New High-Frequency ECG Imaging Technique

The aim of this study is to compare epicardial isochrone maps (EIM) derived from electrocardiographic (ECG) imaging with a new technique based on high-frequency ECG isochrone maps (HFEIM) computation. We analyzed three subjects - normal, left bundle branch block (LBBB) and right bundle branch block (RBBB). Body surface potentials were measured: 5-minute supine, 2KHz sampling, 184 electrodes. These potentials were used for inverse reconstruction of EIM using patient-specific torso-heart geometry (CT). HFEIM was determined as follows: averaged body surface QRS amplitude envelopes 150-400 Hz (HFQRS) were projected onto the epicardium, the time delay from the onset of the QRS complex to centers of mass of projected HFQRS was computed. The EIM and HFEIM pattern of electrical activation was similar, especially for LBBB and RBBB subjects. The correlation between EIM and HFEIM activation times was 0.42, 0.82 and 0.83 for the NORMAL, LBBB and RBBB subjects respectively. Maximal dyssynchrony was about 40 ms lower for HFEIM than for EIM. EIM and HFEIM provide comparable distribution of electrical delays but different reference values. Lower HFEIM dyssynchrony may reflect the electrical activation in an entire ventricular wall segment and may better correlate with local electro-mechanical function.