Information about the programs for detecting the waves of the QRS complex

The main function is limits.m :

Input parameters: 
o	dirhea: directory where the signal header file is
o	dirsig: directory where the signal data file is
o	dirann: directory where the signal annotation file is
o	ecgnr: name of the signal
o	anot: name of the annotation file (if the annotator used is Aristotle anot=’ari’)
o	typerec: type of signal format (0=MIT format, 1=Lund format)

The former input parameters are obliged, the following input parameters are optional, if they are not given, default values are given inside the program:

o	res: results format (0=structure, 1=text), (default value, res=0)
o	nl: number corresponding to the processing lead, (nl=1)
o	ti: beginning of the processing, (ti=’0:00’)
o	tf: end of the processing, (tf=’end’)
o	nbo_flag: rejection of non-normal beats, (0=not applied, 1=applied), (nbo_flag=0)
o	Kq: threshold for Q wave beginning, (Kq=1.5)
o	Kr : threshold for R wave beginning and end, (Kr=5)
o	Ks: threshold for S wave end, (Ks=3)
o	Krr: threshold for R’ wave end in case of QRS complexes with RSR’ morphology, (Krr=5)
o	Kpb: threshold for P wave beginning, (Kpb=1.35)
o	Kpe: threshold for P wave end, (Kpe=2)
o	Ktb: threshold for T wave beginning, (Ktb=2)
o	Kte: threshold for T wave end, (Kte=3.5)
o	pco: threshold for T wave morphology classification, (pco=8)

Output parameters: 
o	banot: structure with the annotations
§	banot.time: position of the annotation (in samples)
§	banot.anntyp: type of annotation: ‘(’ :wave beginning, ‘)’: wave end, ‘p’: P peak, ‘N’: position of the QRS given by Aristotle, ‘Q’: Q peak, ‘R’: R peak, ‘S’: S peak, ‘t’: T peak
§	banot.subtyp: reserved field
§	banot.chan: channet to which annotations correspond
§	banot.num: 0: beginning or end of P wave, 1: beginning or end of QRS, 2: beginning or end of T wave, 0: P wave peak, 0: QRS position, 0: normal T wave, 1: inverted T wave, 2: up T wave, 3: down T wave, 4: biphasic negative-positive T wave, 5: biphasic positive-negative T wave.  
o	QT: structure with the value of QT interval (QT.val) and the position of the corresponding beat (QT.pos)
o	QTC: structure with the values of the QT interval corrected by Bazzett’s formula ant the position of the corresponding beat (QTC.val,QTC.pos)
o	QW: structure with Q wave amplitude (QW.val) and peak position (QW.pos)
o	RW: structure with R wave amplitude (RW.val) and peak position (RW.pos)
o	SW: structure with S wave amplitude (SW.val) and peak position (SW.pos)
o	QRS: structure with the value of the QRS interval (QRS.val) and the position of the corresponding beat (QRS.pos)

The function limits.m can be divided in the following blocks:

1) First, it reads the signal header and data from the corresponding directories. Two kinds of formats are supported:
MIT format: the functions readheader.m, opensig.m and getvec.m are used for that
Lund format: the functions gethdsig.m and getsig.m (from Lund’s toolbox) are used for that

2) Second, it reads the annotation file from its corresponding directory to obtain the QRS position given by an external annotator. If the annotator used is Aristotle, the input parameter anot=’ari’. If there is not annotation file, the program runs basicECG.m, which performs QRS detection by means of qrsdet.m (basicECG.m and qrsdet.m are from Lund’s toolbox).

3) The detection of the beginning, peak and end of the ECG waves is accomplished with the following functions:
- lynfilt.m: it filters the ECG signal to obtain intermediate signals
- proces.m: it process the intermediate signal to obtain the wave limits; it makes use of the following functions:
- qrsbound.m: it classify QRS complexes based on their morphology and obtains the position and limits of the different QRS waves using buscaR.m, buscaQ.m and buscaS.m.
- buscaR.m: it determines the morphology of the QRS complex, if it is of RSR’ type it obtains the significant points, if not, it gives the position of the R wave
- buscaQ.m: it obtains the beginning of the Q wave
- buscaS.m: it obtains the end of the S wave
- pbound.m: it detects P wave, giving its position, beginning and end, and its classification in normal or inverted
- tbound.m: it classifies the T wave based on its morphology (normal, inverted, upward, downward, biphasic negative-positive, biphasic positive-negative); it obtains the position, beginning and end of the T wave
- buscacero.m: it returns the first zero-crossing in a signal segment
- buscapic2.m: it returns the position and value of the peaks in a signal segment, avoiding peaks of only one sample
- buscaruido.m: it returns the mean level of noise in an signal segment 
- calc_rr.m: it computes the mean RR interval for each beat
- crearumbral.m: it gives the position of the first sample of a signal segment that crosses an specific threshold
- testpic.m: it checks if the position of a wave peak obtained by the derivative criterion corresponds to a peak in the ECG signal