Effects of Heart Position on the BodySurface ECG

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
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

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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

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Isolated Heart Preparation
Electrolytic Torso Tank
Flow Regulators
Heat Exchange
C
J
Support Dog
Epicardial Sock Electrodes
TorsoTank Electrodes
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Shifting Heart Location
9
Pacing Protocols
10
Parameter Extraction
11
X-shift QRS RV Pacing
Z
Y
X
12
Y-Shift STT Ant. Pacing
13
Z-Shift QRS Atrial Pacing
Y
Z
X
14
Y
Z
Z
X
Y
X
15
Changes in Amplitudes
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Peak Amplitudes Y-shift
Peak QRS-max
Peak ST-max
5
6
atrial
atrial
RV
RV
anterior
anterior
left lat.
4
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
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Peak Amplitudes Z-shift
Peak QRS-max
Peak ST-max
5
5
atrial
atrial
RV
RV
anterior
anterior
4
4
left lat.
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
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Variability Index X shift
Var RMS(Fi - Fref)
Sutherland et al.
STT 1.5--3.5
QRS 2.2--6.8
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Variability Index Y shift
Sutherland et al.
STT 1.5--3.5
QRS 2.2--6.8
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Relative Variability
Stnd. Dev.
RelVar
RMSref
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Shift Y QRS Ant. Pacing
Z
Heart Shift(1 cm)
Measured
Y
X
Electrode Shift(1 cm)
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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