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Effects of Heart Position on Body-Surface ECG Variability Study

Explore sources of variation in ECG due to heart position, body habits, and more. Discuss new approaches and technical apparatus for ECG research.

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Effects of Heart Position on Body-Surface ECG Variability Study

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  1. 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 InstituteUniversity of Utah

  2. 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 An Old Question

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

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

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

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

  8. Z X Y Shifting Heart Location

  9. Atrial Post Anterior LV RV Apex Pacing Protocols

  10. STT QRS Shift (x, y, z) STT QRS Ref. 1 cm 2 cm 3 cm 4 cm 5 cm 6 cm QRS ATDR RV Ant. Pacing LV Post. Apex Parameter Extraction

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

  12. Z-Shift; QRS; Atrial Pacing Y Z X

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

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

  15. QRS STT 3 atrial atrial RV RV 3 anterior anterior left lat. left lat. 2.5 posterior posterior 2.5 apex apex 2 2 Variability [mV] Variability [mV] 1.5 1.5 1 1 0.5 0.5 0 0 1 2 3 4 5 1 2 3 4 5 Shift in cm Shift in cm Variability Index: X shift Var = RMS(Fi - Fref) Sutherland et al. QRS: 2.2--6.8 STT: 1.5--3.5

  16. QRS STT atrial atrial RV RV 2.5 2.5 anterior anterior left lat. left lat. posterior posterior apex apex 2 2 Variability [mV] Variability [mV] 1.5 1.5 1 1 0.5 0.5 0 0 1 2 3 4 5 1 2 3 4 5 Shift in cm Shift in cm Variability Index: Y shift Sutherland et al. QRS: 2.2--6.8 STT: 1.5--3.5

  17. Isolated Heart Hoekema (1999) Pacing Site Rel. Var. Source Rel. Var. Atrial Physiol. 0.224 0.33 RV Geomtry 0.209 0.40 Anterior Total 0.419 0.52 LV 0.111 Post. 0.112 Apex 0.113 Relative Variability Stnd. Dev. RelVar = RMSref

  18. 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

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