effects of heart position on the body-surface ecg

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Effects of Heart Position on the Body-Surface ECG

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

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An Old QuestionAn 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 VariationSources of Variation

• Geometry variation: – anatomic differences– body position– respiration– electrode placement

• Physiologic variation: – pathology– beat to beat changes– rate effects– central control (ANS)– …..

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Relevant Questions for ECG?Relevant Questions for ECG?

• How much variation is there?• Where does it come from?• How can we isolate the sources?• Is compensation possible?

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Some New ApproachesSome New Approaches

• Clinical– BSPM– medical imaging

• Simulations– forward/inverse solutions

• Experimental– isolated heart– electrolytic torso tank– three-dimensional digitizer

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Technical ApparatusTechnical Apparatus

• “Andy III”• 370 electrodes• R = 500 cm• Homogeneous• 1024 channel

acquisition

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Isolated Heart PreparationIsolated Heart Preparation

TorsoTank Electrodes

Epicardial Sock Electrodes

Support Dog

Flow Regulators

Heat ExchangeC J

ElectrolyticTorso Tank

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Shifting Heart LocationShifting Heart Location

YY

ZZ

XX

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Pacing ProtocolsPacing Protocols

RV LV

Apex

Atrial Post

Anterior

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Parameter ExtractionParameter ExtractionQRS STT

Shift (x, y, z)

Ref. 1 cm 5 cm4 cm3 cm2 cm 6 cm

ATDR

RV

Ant.

LV

Post.

Apex

Pac

ing

QRSQRS

STT

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X-shift; QRS; RV Pacing X-shift; QRS; RV Pacing

YYZZ

XX

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Z-Shift; QRS; Atrial PacingZ-Shift; QRS; Atrial Pacing

YYZZ

XX

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Peak Amplitudes: Y-shiftPeak Amplitudes: Y-shift

1 2 3 4 50

1

2

3

4

5

6

Shift in cm

QR

S-m

ax o

n t

he

tan

k [a

bs.

mV

]

Peak QRS-max

atrialRVanteriorleft lat.posteriorapex

1 2 3 4 50

1

2

3

4

5

Shift in cm

ST

-max

on

th

e ta

nk

[ab

s. m

V]

Peak ST-max

atrialRVanteriorleft lat.posteriorapex

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Peak Amplitudes: Z-shiftPeak Amplitudes: Z-shift

1 2 3 4 50

1

2

3

4

5

Shift in cm

QR

S-m

ax o

n t

he

tan

k [a

bs.

mV

]

Peak QRS-max

atrialRVanteriorleft lat.posteriorapex

Shift in cm

1 2 3 4 50

1

2

3

4

5

ST

-ma

x o

n t

he

ta

nk

[a

bs

. m

V]

Peak ST-max

atrialRVanteriorleft lat.posteriorapex

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Variability Index: X shiftVariability Index: X shift

1 2 3 4 50

0.5

1

1.5

2

2.5

3

Shift in cm

Va

ria

bil

ity

[m

V]

QRS

atrialRVanteriorleft lat.posteriorapex

1 2 3 4 50

0.5

1

1.5

2

2.5

3

Shift in cm

Va

ria

bil

ity

[m

V]

STT

atrialRVanteriorleft lat.posteriorapex

Sutherland et al.

STT: 1.5--3.5QRS: 2.2--6.8

Var = RMS(iref)

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Variability Index: Y shiftVariability Index: Y shift

1 2 3 4 5

Shift in cm

Va

ria

bil

ity

[m

V]

QRS

atrialRVanteriorleft lat.posteriorapex

0

0.5

1

1.5

2

2.5

0

0.5

1

1.5

2

2.5

1 2 3 4 5

Shift in cm

Va

ria

bil

ity

[m

V]

STT

atrialRVanteriorleft lat.posteriorapex

Sutherland et al.

STT: 1.5--3.5QRS: 2.2--6.8

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Relative VariabilityRelative Variability

Pacing Site Rel. Var.Atrial 0.224RV 0.209Anterior 0.419LV 0.111Post. 0.112Apex 0.113

Isolated Heart Hoekema (1999)

Source Rel. Var.Physiol. 0.33Geomtry 0.40Total 0.52

RelVar = Stnd. Dev.

RMSref

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What Did We Learn?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