PROJECT STRUCTURE

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 STANDARD FORMAT

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 then store the informations into a standard format. For this purpose 5 arrays, called standard arrays, are used :

1. RRTime : contains the time when each heart beat occurs in the format HH.MM.SS.
2. RRInterval : stores the duration of each heart beat (RR interval) in msec.
3. RRBeatType : contains the type of every heart beat (N = normal, S = sopraventricular ectopy, V = ventricular ectopy, A = artifact)
4. RRST : gives informations on the ST tract changes (presence of ischemia)
5. RRMarker : informs when Holter "event button" is pressed.

The methods ImportFromSource of the class RRManager performs these operations.

2) DATA STORAGE AND MANAGEMENT

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 class RRManager and they are :

1. LOAD 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.
   
2. ARCHIVE PATIENT DATA : informations, like sex, age, diseases and medications, can be added and stored in the file.
3. SELECT 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.
4. EXPORT 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

1. Time domain analysis : statistical functions are used to quantify the heart rate variability.
2. Frequency domain analysis : it uses the spectral analysis (FFT, AR and wavelet).
3. Non-linear dynamics : many  mathematic tools are used (Poincare plot, ApEn, DFA, etc.)