ISCE2000 rob

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 Institute University of Utah

An Old Question: 

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

Sources of Variation: 

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

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?

Some New Approaches: 

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

Technical Apparatus: 

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

Isolated Heart Preparation: 

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

Shifting Heart Location: 

Shifting Heart Location

Pacing Protocols: 

Pacing Protocols

Parameter Extraction: 

Parameter Extraction

X-shift; QRS; RV Pacing : 

X-shift; QRS; RV Pacing Y Z X

Y-Shift; STT; Ant. Pacing: 

Y-Shift; STT; Ant. Pacing

Z-Shift; QRS; Atrial Pacing: 

Z-Shift; QRS; Atrial Pacing Y Z X

Slide14: 

Y Z X Y Z X

Changes in Amplitudes: 

Changes in Amplitudes

Peak Amplitudes: Y-shift: 

Peak Amplitudes: Y-shift 1 2 3 4 5 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 1 2 3 4 5 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

Peak Amplitudes: Z-shift: 

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

Variability Index: X shift: 

Variability Index: X shift Sutherland et al. STT: 1.5--3.5 QRS: 2.2--6.8 Var = RMS(Fi - Fref)

Variability Index: Y shift: 

Variability Index: Y shift Sutherland et al. STT: 1.5--3.5 QRS: 2.2--6.8

Relative Variability: 

Relative Variability RelVar = Stnd. Dev. RMSref

Shift Y; QRS; Ant. Pacing: 

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

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