Universal programmer for operating implantable device reed switch

There is disclosed on external programmer for use with heart pacers of two different types. Depending on the reed orientations in the two types of pacers, the magnetic flux generated by the programmed has to be in one of two orthogonal directions through the pacers. A pair of parallel coils is provided. A switching circuit switches the current direction through one of the coils so that the two coil fluxes aid or oppose each other, thus giving rise to orthogonal fluxes through pacers to be adjusted. A pacer of either type can thus be adjusted without the physician having any concern for the reed/programmer orientations.

DESCRIPTION 
This invention relates to programmers for use with heart pacers and other 
programmable medical prostheses, and more particularly to a programmer 
which can adjust the operating characteristics of different types of 
prostheses. 
It is customary in the heart pacer art to provide a pacer whose operating 
characteristics such as rate and sensitivity can be adjusted, even 
following implantation, by operating an external programmer. Typically, 
the programmer is provided with a magnetic coil which is pulsed in a 
predetermined sequence in accordance with the new desired parameter 
values. A reed switch in the pacer opens and closes in accordance with the 
resulting pulsating flux, and the pacer decodes the reed operations to 
adjust its operating characteristics, for example, by counting the total 
number of pulsations. Programmers per se and reed/decoder circuits are 
well known in the art. 
Pacer manufacturers, however, do not all place the reed switch in the same 
position within their pacers. Even if the pacers have the same overall 
shape and are placed in the same position within a human body, in one case 
the axis of the switch might be parallel with the patient's chest in a 
head-to-toe orientation, and in another case the axis of the reed switch 
might be perpendicular to the plane of the patient's chest, extending in a 
front-to-back direction. Each manufacturer therefore provides its own 
programmer for use with its line of pacers. Even assuming that the 
programmers of two different manufacturers have the same overall shape and 
that they are both placed flat on the chest of a patient when they are to 
be operated, the coils within the programmers generally have different 
orientations. In one case the axis of the coil, when the programmer is 
placed on the chest of a patient, will be in the plane of the patient's 
chest so that the generated flux will be parallel with the patient's chest 
and pass along the head-to-toe axis of the reed switch within the pacer to 
be controlled. Another manufacturer, on the other hand, might provide a 
coil whose axis is perpendicular to the plane of the patient's chest in 
order that the resulting flux will be directed through a reed switch which 
has a front-to-back orientation. Even if the pulse sequences for two 
different types of pacers happen to be the same, it may be necessary to 
provide two different programmers for adjusting them, the coils of the two 
different programmers having different orientations. Alternatively, if the 
same programmer is to be used for both pacers, the physician has to hold 
it "out of place" by 90 degrees in order to program one of the two pacers, 
a cumbersome and unreliable procedure. 
It is a general object of my invention to provide a programmer for a heart 
pacer or the like which, while always operated in the same position, can 
control closure of reeds which may have different orientations in a 
patient's body. It is another object of my invention to allow use of the 
same programmer, in the same operating position, with pacers which have 
not only different reed orientations but also different pulse sequence 
requirements. 
Briefly, in accordance with the principles of my invention and in the 
illustrative embodiment thereof, the programmer is designed to work with 
pacers whose reed axes are either vertical within the patient's body or 
extend through the patient's body from front to back. Flux flows along two 
paths, the two paths controlling closures of the two differently oriented 
reeds. Two different pulse burst circuits can be provided, each for 
generating a pulsating flux sequence for a different one of the two flux 
paths; each pulsing circuit can control a pulse sequence for a respective 
type of pacer. In this manner, operation of the programmer can result in 
pacer adjustments no matter which type of pacer is adjusted (as long as it 
is a pacer type for which the programmer is designed for use). Preferably, 
the two pulse sequences, each controlling flux along a respective path, 
are generated automatically in succession each time that the pacer is 
operated; in this manner, the physician need not even concern himself with 
setting a switch on the programmer to identify the particular type of 
pacer to be programmed. In the case of a programmer designed to adjust two 
different types of pacers, one of the pulse bursts will have no effect and 
the other will control reed closures.

The numeral 10 in FIG. 1 depicts a prior art programmer. Since the detailed 
construction of such a programmer is well known to those skilled in the 
art, all that is shown in FIG. 1, as well as FIGS. 2, 3A and 3B, are the 
coil and reed orientations necessary for an understanding of the present 
invention. Programmer 10 has a face 10a which is placed on the chest of 
the patient. The programmer includes an internal coil 14 which has an 
orientation such that when the programmer is placed on the chest of a 
patient, the coil axis is in the head-to-toe direction. 
The pacer to be programmed has a reed switch 12, or some other magnetically 
actuated device, whose operation adjusts the characteristics of the pacer 
or otherwise effects changes in it. For example, the use of a permanent 
field to hold the switch closed may disable the pacer operation, while a 
pulsating field which passes through the switch may control changes in 
pacer rate, etc. When the pacer is implanted in its recommended position, 
reed switch 12 also has a head-to-toe orientation. It is thus apparent 
that when a current flows through coil 14 in the programmer, whether the 
current be direct or pulsating, the path 16 of the magnetic flux which is 
generated passes through the reed switch along its axis; a flux in this 
direction causes the reed to close. 
FIG. 2 depicts another conventional arrangement. In this case the implanted 
pacer includes a reed switch 18 whose axis is in the front-to-back 
direction. Coil 22 in programmer 20 has a direction such that when face 
20a of the programmer is placed on the chest of the patient and a current 
is made to flow through the coil, the flux which is generated is directed 
perpendicularly out of the face of the programmer. The resulting flux path 
24 passes along the axis of the reed switch. 
Each of programmers 10 and 20 is designed for use with pacers (or other 
medical prostheses) which are contained in one of two groups. A first 
group includes reed switches, such as switch 12, which are closed when 
flux passes through them in a head-to-toe direction. The second group 
includes reed switches, such as switch 18, which are closed when flux 
passes through them in a front-to-back direction. (It is assumed, of 
course, that the medical prostheses in both groups are placed in the human 
body in the same position.) It is apparent that in the examples of FIGS. 1 
and 2 the two directions are orthogonal to each other. Because each reed 
switch responds to flux in one of two orthogonal directions and not to 
flux in the other, a different programmer must be used for each group of 
devices--unless the "wrong" programmer is rotated 90 degrees so that its 
coil faces in the "right" direction for a particular reed switch, a 
procedure which is hardly recommended. It should be noted that the same 
remarks apply to devices which are programmed even before implantation, 
and to devices which are not even implantable; if two devices are held in 
the same position, two different programmers will be required to program 
them unless the programmer is held rotated when programming one of the two 
devices. 
As depicted in FIGS. 3A and 3B, the programmer 30 illustrative embodiment 
of my invention is provided with two parallel coils whose axis are 
perpendicular to face 30a of the programmer. FIG. 3A depicts programmer 30 
operating on prior art reed switch 12 of FIG. 1, and FIG. 3B depicts the 
programmer operating on prior art reed switch 18 of FIG. 2. In both cases, 
it is assumed that a current flows through the upper coil such that its 
left side is a north pole and its right side is a south pole. The current 
through the lower coil in the two cases, however, is in opposite 
directions. In the case of the FIG. 3A, the current through the lower coil 
results in a north pole at the right end and a south pole at the left end. 
The flux which leaves one coil at one end thus flows directly into the 
pole of the other coil at the same end, the overall flux path being shown 
by the numeral 32. It is apparent that the flux path passes through reed 
switch 12 in a head-to-toe direction to control the reed closure. In the 
case of FIG. 3B the current through the lower coil causes the left end of 
the coil to be a north pole and the right end to be a south pole. The 
fluxes generated by the two coils thus oppose each other and the overall 
flux follows paths 34a, 34b. It is apparent that the flux from each coil 
passes through reed switch 18 in a front-to-back direction to control a 
closure. 
Thus simply by controlling the fluxes through the two parallel coils to aid 
or oppose each other, it is possible to cause the fluxes to follow paths 
which pass through the reed switches in orthogonal directions. When 
programming a pacer, for example, pulsating fluxes are required in order 
to control the opening and closing of a reed switch. This means that 
current pulses have to flow through each coil so that the flux can 
pulsate. When programming a pacer which contains a reed switch 12, and 
assuming that the two coils are wound in the same direction, all that is 
required is to ensure that any current which flows through the two coils 
flows through them in opposite directions. When programming a pacer which 
contains a reed switch 18, the currents must always flow in the same 
direction through the coils. Of course, if the coils are wound in opposite 
directions, then the currents in the case of FIG. 3A have to be in the 
same direction and the currents in the case of FIG. 3B have to be in 
opposite directions. Each coil is wound on an iron core which exhibits 
magnetic properties so that when current flows through the coil a large 
magnetic flux is generated. The key to the operation is that the poles at 
the ends of the coils on either side of the programmer are the same or 
opposite, depending upon the orientation of the reed switch which is to be 
controlled. 
With respect to any programmer which utilizes the technique of my invention 
for generating fluxes which can follow multiple paths, in its most 
elementary form it may be provided with a switch for selecting between the 
two paths. After the programming switches are set, as is known in the art, 
a pulsating current may be caused to flow through the two coils generating 
poles of the same or opposite type at face 30a of the programmer, 
depending upon the setting of the switch which controls the selection of 
the flux path. If the programmer is designed for use with two different 
types of pacers which require different reed closure sequences to effect 
programming of the pacers, the programmer may be provided with two pulsing 
circuits for generating one of two pulse sequences depending upon the 
setting of the same switch which selects the flux path. In this way, the 
physician can identify the pacer to be programmed by brand name, e.g., by 
setting a two-position switch, and then set the programming switches to 
reflect the desired operating characteristics. When the programmer is 
operated, not only will the generated flux follow the correct path for the 
identified pacer, but the pulse sequence for programming that type of 
pacer will also be the correct sequence. 
However, rather than to require the physician to select one of two (or 
more) possible modes of operation, in the preferred embodiment of my 
invention the programmer operates in both (or more) modes in succession, 
so that the physician need not even concern himself with identifying a 
particular type of pacer by operating a switch on the device. A unit 
designed, for example, to program the pacers of two different 
manufacturers, will always program either type of pacer without the 
physician having to identify one of them. All the physician has to do is 
to set the programming switches in accordance with the desired operating 
characteristics and to then press the "start" button. The programming 
switches set up the desired pulse sequence in each of two burst pulsers, 
one for each type of pacer. When the programmer is triggered, the first 
burst pulser operates to generate a pulse sequence which is designed to 
program one of the two types of pacers in accordance with the settings of 
the programming switches. When this first pulser operates, the path of the 
flux which is generated is that which is the correct path for programming 
the respective type of pacer. Immediately thereafter, the second burst 
pulser operates and generates a pulse sequence which is designed to 
program the second type of pacer. When this second burst pulser operates, 
however, the generated flux follows the other path so that the pacer of 
the second type can be programmed. 
In the circuit of FIG. 4, the numeral 40 represents the programming 
switches which are manipulated by the physician to adjust the values of 
various parameters, such as pacer rate, sensitivity, etc. In a 
conventional programmer these switches control only one type of pulse 
sequence, but in the illustrative embodiment of the invention the switches 
control two sequences. Accordingly, the outputs of the programming 
switches are extended to the inputs of burst pulser 42 and burst pulser 
44. 
When "start" switch 48 is depressed, the positive potential at the trigger 
input of burst pulser 42 causes it to generate a series of pulses at its 
output whose sequence depends on both the setting of programming switches 
40 and the format necessary to program a pacer of the first type. After a 
short delay introduced by delay element 50, burst pulser 44 is triggered 
and it generates a series of pulses at its output whose sequence depends 
upon both the setting of programming switches 40 and the format necessary 
to program a pacer of the second type. The delay of element 50 is 
sufficient so that pulser 44 begins to operate only after pulser 42 has 
stopped pulsing. 
As soon as switch 48 is operated, the positive potential applied to the 
reset input of flip-flop 46 causes its Q output to go low. The low 
potential is applied to one input of NAND gate 56 so that its output 
remains high to enable one input of gate 58. The low output of the 
flip-flop is inverted by inverter 54 to enable one input of gate 52. 
Consequently, it is pulses at the output of pulser 42 which are 
transmitted through enabled gates 52 and 58 to the input of pulser 60 
which controls pulsating currents through coils 64 and 66. Pulser 60 
simply follows the pulses at the output of burst pulser 42 to close switch 
62, thus causing a current flow through the two coils in accordance with 
the pulse sequence generated by pulser 42. The directions of the currents 
through the two coils will be described below. 
At the end of the delay introduced by delay element 50, not only is burst 
pulser 44 triggered, but flip-flop 46 is set since the output of the delay 
element is connected to the set input of the flip-flop. The Q output now 
goes high so that inverter 54 causes the output of gate 52 to remain high; 
thus it is now gates 56 and 58 which are enabled and the pulses extended 
to pulser 60 are those derived from the output of burst pulser 44. In this 
way, pulser 60 is controlled to generate two different pulse sequences, 
for the two types of pacer for which use of the programmer is designed, in 
two successive parts of an overall pacing cycle. 
The flux path during each part of the overall cycle is controlled by the 
state of flip-flop 46. Whenever pulser 60 causes switch 62 to close, a 
current flows through coil 64 in the direction of arrow 68. The current 
then flows through coil 66, in a direction determined by the positions of 
ganged switches 76a, 76b. The positions of the switches are controlled by 
relay 74. 
During the first part of the overall programming cycle, the Q output of 
flip-flop 46 is low in potential and relay 74 is not energized. Switches 
76a, 76b remain in the positions shown in the drawing, and thus the 
current which flows through coil 66 flows in the direction of arrow 70. 
During the second part of the overall programming cycle, when the Q output 
of flip-flop 46 is high, relay 74 is energized and switches 76a, 76b 
change positions. The current which now flows through coil 66 is in the 
direction of arrow 72. With reference to FIGS. 3A and 3B, it will be 
apparent that during the first half of the overall programming cycle the 
flux follows the path shown in FIG. 3B (assuming that the coils are wound 
identically), and during the second half of the cycle the flux follows the 
path shown in FIG. 3A. 
It is thus apparent that in the illustrative embodiment of the invention 
current pulses through coil 64 are always in the same direction. It is by 
connecting the right end of coil 64 to different ends of coil 66, during 
the two halves of each overall cycle of operation, that the current pulses 
through coil 66 flow in opposite directions. 
Although the invention has been described with reference to a particular 
embodiment, it is to be understood that this embodiment is merely 
illustrative of the application of the principles of the invention. 
Numerous modifications may be made therein and other arrangements may be 
devised without departing from the spirit and scope of the invention.