Source: record aami-ec13/aami3a
val has 1 row (signal) and 43081 columns (samples/signal)
Duration:     0:59
Sampling frequency: 720 Hz  Sampling interval: 0.001388888889 sec
Row	Signal	Gain	Base	Units
1	ECG	130	0	mV

To convert from raw units to the physical units shown
above, call the 'rdmat.m' function from the wfdb-matlab
toolbox: https://physionet.org/physiotools/matlab/wfdb-app-matlab/
