Low Voltage Technology

Stimulation and Sensing

Pacing

Pulse-amplitude(Volt)

Pulse width (ms)

Pacemaker pulse

To stimulate the heart...

pulse amplitude [Volts]

0.5 1.0 1.50

Strength Duration Curve

pulse width [ms]

1.0

2.0

Strength Duration Curve

Rheobasethe minimum pulse amplitude at which capture results at an infinitely wide pulse duration (1.0 ms)

Chronaxiethe pulse duration for which the pulse amplitude is twice the rheobase (0.4 -0.6 ms)

pulse amplitude [Volts]

0.5 1.0 1.50

Rheobase

Strength Duration Curve

pulse width [ms]

1.0

2.0

2 x Rheobase

Chronaxie

Fibrous tissue around the lead tip resulting in high threshold.(Low current density)

Fibrous tissue around the lead tip resulting in high threshold.(Low current density)

Fibrous tissue

Implantation

2-3 months2 weeks Time

Threshold (Volts)

Threshold

Output

Classic Threshold Development over Time

Implantation

2-3 months2 weeks Time

Output

Threshold (Volts)

Today’s Threshold Development over Time

Threshold

0 0.5 1.5 2.5 3.5 4.5 5.5 6.5 7.51.0 2.0 3.0 4.0 5.0 6.0 7.0

0.05 0.6 1.5…0.4 1.0 1.2 1.40.8

Amplitude (V)

Pulse width (ms)

1.31.10.90.70.5

Example of programmability

Sensing

Cell- potential

SurfaceECG

IEGM

Electrical recordings

Note that both have the same rate!

Signal Frequency Content

T-wave P- or R-wave Myopotentials

8 mV

0,2 mV1 mV

The Band-Pass Filter

Sensitivity5.0 mV

Sensitivity 1.0 mV

Sensitivity10.0 mV

Choosing Sensitivity

0.50.30.1 2.0 3.0 4.01.51.0

P-wave~3 mV

Atrial fibrillation~0.2-1.0 mV

Sensitivity 1.5 mV

Sensitivity 0.3 mV

Noise~0.1 mV

Sensitivity, Atrial Channel

5.0

0.5 2.0 3.01.0 4.0 7.0 9.05.0 12.5

R-wave~9 mV

PVC~3.5 mV

Sensitivity 4.5 mV

Sensitivity 2.0 mV

Noise~0.5 mV

Sensitivity, Ventricular Channel

A B

C

D

Point A

Point C

Point B

Point D

A B

C D

Depolarisation spread/ sensing points