ARUP; ISBN: 978-0-9562121-5-3 - CMBBE 2012 - Cardiff University

mobile cart for easy recording in cardiology clinics and elsewhere. All sounds were
recorded using the Goldwave software (Version 5.55), which includ es tools for
recording, playing, filtering, and analyzing sounds. Using this software, we also deleted
any electrical utility frequency (50 Hz) from the ECG recordings. We used MATLAB in
conjunction with the signal processing and real-time data acquisition toolboxes as the
computational heart of the system. Two time-adjacent phonocardiogram cycles, PCG-1
and PCG-2,
are obtained using the QRS complex of the ECG as a marker for the start of
each cardiac cycle. The difference of the two PCG cycles is a murmurgram.
Figure 2
illustrates the PCG subtraction method.
Amplit ude
0 . 2
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0
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C y c l e A
Amplit ude
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S a m p l e s
0 . 2
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1
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Amplit ude
0 . 2
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8 C y c l e A - C y c l e B
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S a m p l e s
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C y c l e B
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2 3 S a m p l e s
Figure 2. The schematic of result of subtracting two successive heartbeats to construct a
“murmurgram”.
4. RESULTS
Figure 4 shows samples of simulated PCGs (first & second panels) from a simulated
healthy heart. The murmurgram and the corresponding color spectrogram are shown in
the bottom two panels. Each simulated PCG is of 1 cardiac cycle covering an elapsed
time of 0.7 second. Note that murmurgram is "flat" and has frequency components
largely
under 200 Hz. Two successive heartbeats of data for a simulated VSD case are
shown in the first and second panels in Figure 5. The murmurgram (third panel)
between S1and S2 isn`t "flat". The spectrographic graph, shown at the bottom of the
figure, indicates
that the murmur has frequency components extending to 700 Hz.
Figure 6 shows PCGs from a simulated ASD case. The murmurgram and corresponding
color spectrogram are shown in the bottom two panels. The simulated PCG is of 1
cardiac cycle covering an elapsed
time of 0.7 seconds. Note that the murmurgram isn`t
"flat" between S1and S2. The mid systolic murmur in the murmurgram in this case has
frequency components that extend to around 600 Hz.
3 8 5
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3 2 0
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3 7 8