Biomedical Engineering Reference
In-Depth Information
-15V
C1
-15V
0.01uF
IC1B
TL082
4
J2
1
2
4
IC1A
6
-
2
R1
R2
R3
7
J1
1
2
-
1
5
VOUT
+
3
+
VIN
10M
10M
100
TL082
8
8
C3
1uF
+15V
C2
0.01uF
+15V
D1
D2
1N4148
1N4148
D5
6.2V
1N709A
D3
D4
1N4148
1N4148
Figure 2.32
This slew-rate limiter filters fast transients such as MRI artifacts from ECG signals that can be used to filter ECG signals from
fast transients. The circuit around IC1A acts as a precision-rectified zener diode. R2 converts the voltage of the bridge into a current that is
limited by the zener voltage and which charges C3. The change in voltage across this capacitor is limited by its capacitance, thus limiting
the slew rate of signals at the input of buffer IC1B.
ECG AMPLIFIER WITH PACEMAKER PULSE DETECTION
AND ARTIFACT REJECTION
Patients with cardiac pacemakers may have di
culties, especially just after implantation
of the pacemaker and lead system, from failure of the pacing system to properly sense the
heart's intrinsic signals or to evoke heartbeats (capture the myocardium). This may re
ect
problems in the electronics, the leads, the placement of the leads, or the myocardium itself.
The most catastrophic event is failure of the pacemaker to capture the heart when the
patient's intrinsic rate is slow or nonexistent. To ensure that pacing therapy is being deliv-
ered in an appropriate manner, patients must be monitored to determine if the pacemaker
is functioning properly and if appropriate bene
fl
fi
t is being derived from the therapy.
Speci
fi
cally, it is important to know how often and why a pacemaker is activated, whether
it is
firing at appropriate times, and whether it is, in fact, capturing the heart to produce a
heartbeat in response to the electrical stimulation.
fi
Search WWH ::
Custom Search