The aim of this project is to acquire data from ECG recordings and
to calculate the HRV parameters from them. Therefore the project works
in three steps :
1) DATA ACQUISITION AND CONVERSION IN
The first step of this software is to acquire ECG data from
different sources (ECG recorder, monitor, ECG Holter analysis software)
and therefore different conversion modules are necessary. These modules
store the informations into a standard format. For this purpose 5
arrays, called standard arrays,
are used :
- RRTime : contains the time
when each heart beat occurs in the format HH.MM.SS.
- RRInterval : stores the
duration of each heart beat (RR interval) in msec.
- RRBeatType : contains the
type of every heart beat (N = normal, S = sopraventricular ectopy, V =
ventricular ectopy, A = artifact)
- RRST : gives informations on
the ST tract changes (presence of ischemia)
- RRMarker : informs when
Holter "event button" is pressed.
The methods ImportFromSource of the
class RRManager performs
2) DATA STORAGE
This is the second step of the project : the data are now in the standard arrays in a format common
to all sources and therefore can be easily used for the analysis in the
third step of the project. However there are some functions that the
software have to perform before data can be analyzed. These functions
are performed by an object derived from the
and they are :
AND SAVE DATA : the method SaveHRVFile
allows to save the data,
stored in the standard arrays,
in a file with extension "hrv". The method LoadHRVFile can read
easily and quickly this file and load the data in the standard arrays.
PATIENT DATA : informations, like sex, age, diseases and
medications, can be added and stored in the file.
DATA FOR ANALYSIS : the data analysis (step 3) is not performed
directly on stored data (standard arrays), but on a copy, called selected
arrays. The method SelectPeriod copy the selected period (e.g.
night, day or all recording) from the standard to the selected arrays.
RR AND NN INTERVALS : validation process is important during the
design phase of the project, to detect the presence of bugs in the
algorithms. The function ExportRRintervas extracts the RR intervals and save
them in a file with extension ".RR"; the function
ExportNNintervals filters the
RR intervals, removing non-synus beat (ectopies and artifacts), then
saves the data (NN intervals or normal intervals) in a file with
extension ".NN". These files can be then read by an analysis software
(e.g. Matlab) to confirm the results obtained with HRV Analyser.
3) DATA ANALYSIS
This is the final step of the project. The data contained in the selected arrays are analyzed with :
domain analysis : statistical functions are used to quantify the
heart rate variability.
domain analysis : it uses the spectral analysis (FFT, AR and
dynamics : many mathematic tools are used (Poincare plot,
ApEn, DFA, etc.)