1. CVRTI Effects of Heart Position on the Body-Surface ECG Rob MacLeod, Quan Ni, Bonnie Punske, Phil Ershler, Bulent Yilmaz, Bruno Taccardi Cardiovascular Research and Training Institute University of Utah

2. CVRTI An Old Question Sigler (1938) –body position Olbrich & Woodward- Williams (1953) –body position Dougherty (1970) –heart position Shapiro, Berson, and Pipberger (1976) –body position Sutherland et al.: (1983) –body position and respiration Green et al.: (1985) –body habtitus MacLeod et al.: (1997) Hoekema (1999) –heart/torso geometry

3. CVRTI Sources of Variation Geometry variation: –anatomic differences –body position –respiration –electrode placement Physiologic variation: –pathology –beat to beat changes –rate effects –central control (ANS) –…..

4. CVRTI Relevant Questions for ECG? How much variation is there? Where does it come from? How can we isolate the sources? Is compensation possible?

5. CVRTI Some New Approaches Clinical –BSPM –medical imaging Simulations –forward/inverse solutions Experimental –isolated heart –electrolytic torso tank –three-dimensional digitizer

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

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

8. CVRTI Shifting Heart Location Y Y Z Z X X

9. CVRTI Pacing Protocols RV LV Apex Atrial Post Anterior

10. CVRTI Parameter Extraction QRS STT Shift (x, y, z) Ref.1 cm5 cm4 cm3 cm2 cm6 cm ATDR RV Ant. LV Post. Apex Pacing QRS STT

11. CVRTI X-shift; QRS; RV Pacing Y Y Z Z X X

12. CVRTI Y-Shift; STT; Ant. Pacing

13. CVRTI Z-Shift; QRS; Atrial Pacing Y Y Z Z X X

14. CVRTI Y Y Z Z X X Y Y Z Z X X

15. Changes in Amplitudes

16. CVRTI Peak Amplitudes: Y-shift 12345 0 1 2 3 4 5 6 Shift in cm QRS-max on the tank [abs. mV] Peak QRS-max atrial RV anterior left lat. posterior apex 12345 0 1 2 3 4 5 Shift in cm ST-max on the tank [abs. mV] Peak ST-max atrial RV anterior left lat. posterior apex

17. CVRTI Peak Amplitudes: Z-shift 12345 0 1 2 3 4 5 Shift in cm QRS-max on the tank [abs. mV] Peak QRS-max atrial RV anterior left lat. posterior apex Shift in cm 12345 0 1 2 3 4 5 ST-max on the tank [abs. mV] Peak ST-max atrial RV anterior left lat. posterior apex

18. CVRTI Variability Index: X shift Sutherland et al. STT: 1.5--3.5QRS: 2.2--6.8 Var = RMS(  i  ref )

19. CVRTI Variability Index: Y shift 12345 Shift in cm Variability [mV] QRS atrial RV anterior left lat. posterior apex 0 0.5 1 1.5 2 2.5 Sutherland et al. STT: 1.5--3.5QRS: 2.2--6.8

20. CVRTI Relative Variability Pacing SiteRel. Var. Atrial 0.224 RV 0.209 Anterior 0.419 LV 0.111 Post. 0.112 Apex 0.113 Isolated HeartHoekema (1999) SourceRel. Var. Physiol. 0.33 Geomtry 0.40 Total 0.52 RelVar = Stnd. Dev. RMS ref

21. CVRTI Shift Y; QRS; Ant. Pacing Measured Heart Shift (1 cm) Electrode Shift (1 cm) Y Y Z Z X X

22. CVRTI What Did We Learn? Experiments replicated clinical results –Sutherland: patterns, amplitudes, variability –Hoekema: relative variation index The role of geometry is complex Geometry errors could affect diagnosis Future: –mimic changes in body position –compare with electrode placement errors –recognize and compensate for geometry errors –simulations Bicycling is essential for good research