CVRTI Inverse Electric Imaging of Myocardial Ischemia: Getting the Most from What we Know? Robert S. MacLeod, Bonnie Punske, Shibaji Shome, Bulent Yilmaz, and Bruno Taccardi Cardiovascular Research and Training Institute University of Utah Do

CVRTI Origins Occlusion Pre-PTCAPeak-PTCA

CVRTI Biophysics of Acute Ischemia mV

CVRTI Cardiac Mapping of Ischemia Source of Electrocardiographic ST Changes in Subendocardial Ischemia Li et al. Circ. Res. 82: , 1998 Epicardium Endocardium LADLCx

CVRTI Research Questions ST elevation or (transient) depression? Acute occlusion versus graded flow? How do ST changes image on the body surface?

CVRTI Technical Apparatus “Andy III” 370 electrodes R = 500  cm Homogeneous 1024 channel acquisition

CVRTI Isolated Heart Preparation TorsoTank Electrodes Epicardial Sock Electrodes Support Dog Flow Regulators Heat Exchange C J Electrolytic Torso Tank

CVRTI Flow Control

CVRTI Epicardial Electrode Sock Nylon stocking material 490 recording wires 24 pacing wires Reference markers for geometry

CVRTI Acquisition Hardware

CVRTI Protocols Acute, complete occlusion –3-minute duration –measurements each 30 s Graded flow –2-minute intervals at each flow rate –measurement at end of each interval Graded heart rate –constant flow rate –increase rate in 2-minute intervals –measurement at end of each interval

CVRTI Data Processing Signals (Everett) –gain correction, windowing, baseline correction –global fiducials (Q on, S off, T off ) Geometry –location of sock in tank –coronaries Maps (Matlab, Map3d) –integrals: QRS, QRST, ST, STT, ST80

CVRTI Signal Processing T off Q on S off 3/85/8 ST off 80ms ST 80

CVRTI Comparison to Li et al. Dog (versus Sheep) Short (versus long) occlusions High spatial resolution, heart and tank surfaces Coronary cannulation (versus occluder) ST Depression required increased rate Localization of ST changes

CVRTI Nothing New Under the Sun Guyton et al. : Significance of Subendocardial S-T Segment Caused by Coronary Stenosis in the Dog, Am. J. Cardiol. 40: , Normal coronary flow is homogeneous But vulnerability to limited flow is not

CVRTI What Do We Know? Ischemia in the heart is complicated ST depression requires limited flow (not occlusion) and time ST depression requires load Body surface images reflect ST segment changes Think We

CVRTI The Rest We Still Have to Figure Out

CVRTI Bike News Bicyclist fatality rates [deaths/million pop]: –Florida: 8.14 –Louisiana: 6.63 –Wyoming: 6.25 –Utah: 3.29 –Maine: 0.80 –Hawaii:0.84