Biomedical Engineering Reference
In-Depth Information
First Refinement of DDD Mode
A pacemaker has a stimulation threshold measuring unit which measures a stimula-
tion threshold voltage value of heart and a pulse generator for delivering stimulation
pulses to the heart. The pulse generator is controlled by a control unit to deliver
the stimulation pulses with respective amplitudes related to the measured threshold
value under the safety margin. We introduce two new variables
Thr_A
and
Thr_V
to hold the sensing threshold value of the pacemaker's sensor from the atrial and
ventricular chambers. Similarly, next two variables
Thr_A_State
and
Thr_V_State
represent boolean states as TRUE or FALSE of the pacemaker's sensor to sense the
intrinsic activity from the atrial and ventricular chambers.
inv
1
:
Thr
_
A
∈ N
1
inv
2
:
Thr
_
V
∈ N
1
inv
3
:
Thr
_
A
_
State
∈
BOOL
inv
4
BOOL
inv
5
:
Pace
_
Int
_
flag
=
FA L S E
∧
PM
_
Actuator
_
A
=
ON
⇒
sp
≥
Pace
_
Int
−
FixedAV
:
Thr
_
V
_
State
∈
Invariants are given in Table
9.2
. An additional invariant (
inv
5) is introduced and
states that, when the pacemaker's actuator of the atrial chamber is ON, then the
current clock counter
sp
is greater than or equal to the ventriculoatrial (VA) interval
(
Pace_Int
−
FixedAV
).
EVENT Thr
_
Va l u e
_
V
ANY
Thr
_
V
_
val
WHERE
grd1
:
Thr
_
V
_
val
∈ N
grd2
:
PM
_
Sensor
_
V
=
ON
grd3
:
Thr
_
V
_
State
=
TRUE
grd4
:
Thr
_
V<STA
_
THR
_
V
grd5
:
(sp
≥
VRP
∧
sp < Pace
_
Int
−
FixedAV)
(sp
≥
Pace
_
Int
−
FixedAV
∧
sp < Pace
_
Int)
grd6
:
(Thr
_
A
_
State
=
FA L S E
∧
Thr
_
A<STA
_
THR
_
A)
(PM
_
Sensor
_
A
=
OFF
∧
AV
_
Count < FixedAV)
THEN
act1
:
Thr
_
V
:=
Thr
_
V
_
val
act2
:
Thr
_
V
_
State
:=
FA L S E
END
In this refinement, we introduce two new events (
Thr_Value_V
and
Thr_Value_A
)
for sensing the intrinsic activities from the ventricular and atrial chambers. These
events are synchronised with all other events of the operating mode under all the
Search WWH ::
Custom Search