What's cardiac
electrophysiological mapping?
Gallagher defined cardiac mapping as "a method by which
potentials recorded directly from the surface of the heart are
spatially depicted as a function of time in an integrated manner.
The location of recording electrodes (epicardial, intramural, or
endocardial), the recording mode used (unipolar vs. bipolar), as
well as the method of display (isopotential vs. isochrone maps)
depends upon the problem under consideration." Universal Mapping goes a little bit
farther than this for it can also analyze fluorescent signals
emitted by potential-sensitive dyes such as di-4-ANNEPs and other
kinds of maps such as derivative maps of potential. In addition Universal Mapping can create moving displays of potential
and first derivative of potential, too.
What's wrong with
your current mapping software?
Traditional programs for the display and analysis of
multi-channel mapping data typically suffer from several of the
following limitations:
- Implementation in a low-level language, which makes
source code laborious to write and difficult to maintain
- Restriction to a specific mapping system and a single
type of mapping data (such as unipolar electrograms)
- rigid user-interface, with either a cryptic command-line
or an inflexible menu hierarchy
- inflexible display engine: just one or two views of your
data at any one time
- lack of documentation.
Universal Mapping avoids the
above-mentioned 5 limitations of traditional mapping programs:
- The program is implemented under Research Systems, Inc.
IDL 4.0.1, which provides all the medium-level
building block for building powerful graphical
applications. The initial program development time was
only 4 weeks, and so far the code, which since went
through many incremental stages of development, has
proved to be easy and straightforward to maintain.
- The program is "universal",
i. e. mapping-system independent, allowing up to 9999
channels in any arrangement on the screen, and .
Algorithms can analyze unipolar and bipolar electrograms
and optical action potentials.
- The user interface is fully graphical with no
modal dialogs that would impose needless restrictions on
the user.
- The program can, on the same screen, display a selected single signal,
a map of all
signals, color-coded,
contour and movie maps of
activation, repolarization and action potential duration,
potential distribution and first derivative of potential.
A mouse click on any of these maps will update the
single-signal window with the selected channel.
- The program is fully documented on over 30 pages of
documentation. There is even support.
The mapping-system independent design. Universal
Mapping is designed to be hardware and mapping system
independent from the ground up. Therefore, Universal
Mapping can:
- read
data from files in any binary data format that
you have had or will have (1 or 2-byte encoding,
byte-swap, up to 9999 data channels, no limit on the
number of frames),
- display
electrogram and external signal channels in any
pattern on the screen
- analyze
all kinds of mapping data (body surface
electrocardiograms, unipolar and bipolar electrograms,
fluorescent signals for optical mapping)
What does the program cost?
Currently, Universal Mapping is
available for free.
Contact the developer for the software evaluation agreement, sign
the agreement and send or fax it back to receive the distribution
archive with software and documentation.
Do I have to dump my old data?
No, Universal Mapping can read them
all. Once you have worked out the correct settings for the import
of your existing data files (or anybody else's data files), you
can save them to disk and re-use them. If you contact the developer and
send him a sample file with documentation and a print-out of your
data your import filter can even be included in the next release
of Universal Mapping.
What happens if I ever get a new mapping system?
No problem, Universal Mapping will
be able to read your
data.
What happens if I get a new mapping electrode array?
No problem, all you need to do is to
write a new matrix file for the display of your data by Universal Mapping. Take an existing matrix
file and open it with a text editor. Update the number of rows
and columns of channels that you want to be displayed on the
screen. Then list the channel numbers one by one as they are to
be arranged on the screen, starting with the left upper corner of
the screen. Assuming you have n data channels, the number for the
first channel is 0 and for the last channel is n-1. Encode
external data channels by negative numbers (if 0 is an external
channel, it will be -1, 1 will be -2 and so on until -n for the
last channel) and missing channels by the number 9999. Assign a
code to each thumbnail plot on the screen. Save your work as an
ANSI file under a new file name with the extension
".OMX" and you are done. The process of generating
matrix files can be considerably speeded up if you set up the
codes in a spreadsheet program, using their built-in drag and
copy functions, and export the values in the spreadsheet as a
space-delimited text file and add a header from an existing OMX
file.
What happens if I need a new module for some special task?
As the full version of the program includes the source code,
you can write the code yourself if you want to. Alternatively,
you can ask the developer
to write it for you.
What kind of a mapping
system do you use?
My mapping system is set up for recording fluorescent signals
emitted by isolated cardiac preparations that are vital-stained
with potential-sensitive dyes such as di-4-ANEPPs. My mapping
system is more or less entirely based on the laboratory designed
by Igor Efimov at the
Cleveland Clinic Foundation with the exception that I am using
the amplifier circuits developed by Vladimir Fast at the
University of Bern/Switzerland. The centerpiece of the system is
a 16 x 16 element Hamamatsu photodiode array, which comes with
256 built-in current-to-voltage converters in a neat enclosure.
Each of the 256 signal channels is then individually amplified
with a user-selectable gain and then passed to a MicroStar
Laboratories acquisition board, which performs the
analog-to-digital conversion.
Is there a data acquisition module?
Yes, there is, and it is available from
the developer as a free add-on to the Universal
Mapping program. The mapping data display and analysis
program Universal Mapping was designed
to be mapping-system independent from the ground up. That's why
the developer decided to implement his data acquisition program,
which is by necessity highly dependent on the underlying
hardware, as a separate task completely independent of the Universal Mapping program. It is even
programmed on a different platform, National Instruments LabView
4.0.1 which provided easy access to National Instrument's digital
timer board. The data acquisition program has a fully graphical
user-friendly interface and includes a fully-featured
programmable stimulator (up to three premature stimuli, a forth
premature stimulus from a second output channel) and freely
configurable timing pulses for the control of an optical mapping
system (one pulse for the electric shutter of the light source to
protect the preparation from photobleaching and phototoxicity,
one pulse for the control of the offset subtraction of the
amplifiers and a third pulse to trigger data acquisition by the
analog to digital conversion board.) You can have the data
acquisition program, but no support
can be provided for this particular program.
Can Universal Mapping interact with
my own data acquisition software?
Yes, it can. Any external data acquisition program can
communicate with the Universal Mapping
mapping data analysis program. All that the data acquisition
program has to do is to prefix the binary data file with Universal Mapping's ANSI file header. The
ANSI file header can contain all kinds of information on the data
file, such as the number of data channels, the sample rate, the
amplifier gain(s), the matrix file to be loaded by Universal Mapping defining the arrangement
of the data channels on its screen, time and date of the
recording, the stimulation protocol at the time of the recording,
a comment on the experimental protocol and many more. To prompt Universal Mapping to read the latest data
file, just let your data acquisition program write a dummy file
called AUTOLOAD.TXT into the data directory, and Universal Mapping will automatically open
the latest data file, read its file header and load and display
the data according to the information found in the file header.
Do I have to use Windows NT?
No. The same version of IDL also runs under Windows 95.
However, I strongly advise users to upgrade to Windows NT 4.0
(Service Pack 1 - don't try Service Pack 2), which is a
rock-solid multitasking operating system. I don't say that there
aren't some nasty programs that can lock up an NT machine, but
once you got your NT system set up with decent software, crashes
of NT will be as rare as 286-computers running MS Windows 1.0. If
you are planning to do serious experiments - as I hope you do -
you don't want your lab computer to lock up any minute while the
arrhythmia that you set out to map occurs and can't be
re-induced. This once happened to Igor Efimov and it steeled his
resolve to port his data acquisition to Windows NT.
Windows NT is fine, but what happens if I ever switch to a
new OS?
No problem, Research Systems,
Inc. IDL supports essentially every operating system on any
hardware platform currently available (e. g. NT both on Intel and
on Alpha, Mac OS, all major UNIX flavors including LINUX) with
the exception of IBM OS/2. Should NT fall in disuse, IDL will be
sure to support your next platform of choice. The
platform-specific code in Universal Mapping
is kept to a minimum and clustered in a few routines that can
easily be adapted to the new environment. The only thing that's
bound to happen is that IDL will run even faster!
What if all this didn't answer my questions?
Just contact the
developer and try out the program for yourself.
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