Performance assessment of standard algorithms for dynamic R-T interval measurement: comparison between R-Tapex and R-Tend approach

Three automatic approaches to ventricular repolarisation duration measurement (R-Tapex, R-Tend threshold and R-Tend fitting methods) are compared on computer-generated and real ECG signals, in relation to their reliability in the presence of the most common electrocardiographic artefacts (i.e. additive broadband noise and additive and multiplicative periodical disturbances). Simulations permit the evaluation of the amount of R-T beat-to-beat variability induced by the artefacts. The R-Tend threshold method performs better than the R-Tend fitting one, and, hence, the latter should be used with caution when R-Tend variability is addressed. Whereas the R-Tapex method is more robust with regard to broadband noise than the R-Tend threshold one, the reverse situation is observed in the presence of periodical amplitude modulations. A high level of broadband noise does not prevent the detection of the central frequency of underlying R-T periodical changes. Comparison between the power spectra of the beat-to-beat R-T variability series obtained from three orthogonal ECG leads (X,Y,Z) is used to assess the amount of real and artefactual variability in 13 normal subjects at rest. The R-Tapex series displays rhythms at high frequency (HF) with a percentage power on the Z lead (57.1±4.9) greater than that on the X and Y leads (41.9±4.6 and 46.1±4.9, respectively), probably because of respiratory-related artefacts affecting the Z lead more remarkably. More uniform HF power distributions over X,Y,Z leads are observed in the R-Tend threshold series (31.8 ±3.8, 39.2±4.1 and 35.1±4.2, respectively), thus suggesting minor sensitivity of the R-Tend threshold measure to respiratory-related artefacts.