Clinical Severity of Noise in ECG

Abstract

Objective noise metrics such as the signal to noise ratio and the root mean squared value, are not always related to the actual impact that noise can have on the clinical evaluation of cardiac signals. This work is intended to design a database along with a set of criteria to be used as an initial solid gold-standard of noise severity within a scale created from the clinical point of view. Different from previous approaches, we used recordings from external cardiac event recorders, which have a signal morphology and characteristics typical for the usual Holter monitoring devices. These recorded events often correspond to noise segments, which makes simpler the retrieval of a variety of signal segments with real noise examples. We generated a database recordings from 8 patients (4 female and 4 male with a clinical indication for long-term monitoring, 64.75±25.44 years old). In a first attempt, a set of rules for clinical quality recording were initially defined by a cardiologist, so segments with clear clinical description were categorized into free, low, moderate, hard, or other noise. Segments with unclear description are set apart for revision. This process was iterated until convergence of expert opinion and labels. A specific software tool was created and modified for supporting the process for each iteration. The relative duration of the different kinds of noise in both leads according to their clinical severity was: 4h 14m 15s (free, 37.32%), 2h 54m 52s (moderated, 25.67%), 2h 21m 46s (hard, 20.81%), 1h 43m 13s (low, 15.15%) and 07m 07s -other-(1.05%). The generated database and criteria represent a valuable gold standard for clinical quality evaluation of noise impact on ECG signals.

Noise Maps for Quantitative and Clinical Severity Towards Long-Term ECG Monitoring

“…We defined and validated a set of noise severity criteria in real ECG signals obtained from EER devices in 10 patients (see [ 30 ] for details on the database). An expert cardiologist (A.G.A.)…”

“…We subsequently analyzed the noise clinical severity measurement for long-term recordings from ECG external event recorders (EER) in 10 patients and in one case from 7 day Holter monitoring on a detailed timeline. A preliminary version of this work has been previously introduced [ 30 ].…”

Characterization of noise in long-term ECG monitoring with machine learning based on clinical criteria

“…It has been shown in previous studies that there exist apparent differences on how the impact of noise affects to the interpretation of the ECG when it is assessed by quantitative means than when the interpretation is made by cardiologist [9,10], i.e., qualitatively. The former approach relies on quantitative noise severity, based on figures of merit.…”

“…In the current work we deal with the interpretation of the ECG as understood by cardiologist, so with clinical noise. In [9,10], a noise taxonomy in terms of clinical noise was proposed in a scale of 5 categories as follows:…”

“…Thus, clinical noise severity is assessed in a qualitative scale. In [9,10], a 5-level scale scoring the effect of clinical noise on the ECG was designed based on the recommendations given by a team of cardiologists. A methodology, based on noise maps, to evaluate how well qualitative severity correlates with quantitative severity was also developed.…”