In this paper, we developed and evaluated a robust single-lead electrocardiogram (ECG) delineation system based on the wavelet transform (WT). In a first step, QRS complexes are detected. Then, each QRS is delineated by detecting and identifying the peaks of the individual waves, as well as the complex onset and end. Finally, the determination of P and T wave peaks, onsets and ends is performed. We evaluated the algorithm on several manually annotated databases, such as MIT-BIH Arrhythmia, QT, European ST-T and CSE databases, developed for validation purposes. The QRS detector obtained a sensitivity of Se=99.66% and a positive predictivity of P+=99.56% over the first lead of the validation databases (more than 980,000 beats), while for the well-known MIT-BIH Arrhythmia Database, Se and P+ over 99.8% were attained. As for the delineation of the ECG waves, the mean and standard deviation of the differences between the automatic and manual annotations were computed. The mean error obtained with the WT approach was found not to exceed one sampling interval, while the standard deviations were around the accepted tolerances between expert physicians, outperforming the results of other well known algorithms, especially in determining the end of T wave.

A wavelet-based ECG delineator: evaluation on standard databases

Electrocardiogram (ECG) compression techniques are compared, and a unified view of these techniques is established. ECG data compression schemes are presented in two major groups: direct data compression and transformation methods. The direct data compression techniques are ECG differential pulse code modulation (DPCM) and entropy coding, AZTEC, Turning-point, CORTES, Fan and SAPA algorithms, peak-picking, and cycle-to-cycle compression methods. The transformation methods include Fourier, Walsh, and Karhunen-Loeve transforms. The theoretical bases behind the direct ECG data compression schemes are presented and classified into three categories: tolerance-comparison compression, DPCM, and entropy coding methods. A framework for evaluation and comparison of ECG compression schemes is presented. >

ECG data compression techniques-a unified approach

QT interval duration, reflecting myocardial repolarization on the electrocardiogram, is a heritable risk factor for sudden cardiac death and drug-induced arrhythmias. We conducted a meta-analysis of three genome-wide association studies in 13,685 individuals of European ancestry from the Framingham Heart Study, the Rotterdam Study and the Cardiovascular Health Study, as part of the QTGEN consortium. We observed associations at P < 5 x 10(-8) with variants in NOS1AP, KCNQ1, KCNE1, KCNH2 and SCN5A, known to be involved in myocardial repolarization and mendelian long-QT syndromes. Associations were found at five newly identified loci, including 16q21 near NDRG4 and GINS3, 6q22 near PLN, 1p36 near RNF207, 16p13 near LITAF and 17q12 near LIG3 and RFFL. Collectively, the 14 independent variants at these 10 loci explain 5.4-6.5% of the variation in QT interval. These results, together with an accompanying paper, offer insights into myocardial repolarization and suggest candidate genes that could predispose to sudden cardiac death and drug-induced arrhythmias.

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Common variants at ten loci influence QT interval duration in the QTGEN Study.

A comparison of commonly used QT correction formulae: the effect of heart rate on the QTc of normal ECGs.

Criteria for intraventricular conduction disturbances and pre-excitation

A reference data base for multilead electrocardiographic computer measurement programs

Establishment of a reference library for evaluating computer ECG measurement programs

A four year concerted action project has been started in the European Communities (EC) with the aim of “Common Standards for Quantitative Electrocardiography” (CSE Project). Standards for computer derived ECG measurements are urgently required because more and more quantitative diagnostic ECG criteria are now being derived by ECG computer programs and in view of the existing differences, first of all with respect to time measurements of present computer programs.

Common Standards for Quantitative Electrocardiography : The CSE Pilot Study

Not only does the underlying mechanism(s) of atrial fibrillation defy our full understanding, but the cause and nature of the irregular ventricular response have been and still are to a large extent "terra incognita" [2]. In his editorial in 1970 Brody [3] raised the question: " ... what factors govern the response ofthe atrioventricular transmission system and the ventricles to the show er of impulses arriving from above?" For all practical and clinical purposes the ventricular response in patients with atrial fibrillation is considered to be random or, in other words, totally irregular. Lewis [4] left little doubt, when he stated that: "Amongst the distinguishing features [of auricular fibrillation] absolute irregularity of the ventricle is one of the most important." Again, Brody [3] called the question of the "absolute irregularity" perplexing. So it is, that nearly 80 years af ter Hering's [1] paper on the "Analyse des Pulsus irregularis perpetuus" the nature and degree of the ventricular irregularity in atrial fibrillation are still not fully understood.

Frits M.A. Harms

Papers

A reference data base for multilead electrocardiographic computer measurement programs

Establishment of a reference library for evaluating computer ECG measurement programs

Common Standards for Quantitative Electrocardiography : The CSE Pilot Study

Comparative atrioventricular conduction and its consequences for atrial fibrillation in man