Cardiac repolarization analysis using the surface electrocardiogram

Abstract

Sudden cardiac death (SCD) is a challenging health problem in the western world. Analysis of cardiac repolarization from the electrocardiogram (ECG) provides valuable information for stratifying patients according to their risk of suffering from arrhythmic events that could end in SCD, as well as for assessing efficacy of antiarrhythmic therapies. In this paper, we start by exploring the cellular basis of ECG repolarization waveforms under both normal and pathological conditions. We then describe basic preprocessing steps that need to be accomplished on the ECG signal before extracting repolarization indices. A comprehensive review of techniques aimed to characterize spatial or temporal repolarization dispersion is provided, together with a summary of their usefulness for clinical risk stratification. Techniques that describe spatial dispersion of repolarization are based on either differences in repolarization duration or T-wave loop morphology. Techniques that evaluate temporal dispersion of repolarization include the analysis of QT interval adaptation to heart rate changes, QT interval and T-wave variability, and T-wave alternans.

Acquired Long QT Syndrome: Frequency, Onset, and Risk Factors in Intensive Care Patients

“…[13][14][15][16] The estimated annual incidence of sudden cardiac death is 1 per 1000 deaths in Western populations, or approximately 20% of all deaths. 3,17,18 The incidence of aLQTS is unknown, but the syndrome most likely is more unrecognized than rare. 19 According to estimates, 20 3000 to 4000 patients die each year of sudden cardiac death caused by long QT syndromes, highlighting the importance of developing strategies for early identification and prevention of the syndromes.…”

Variability of Ventricular Repolarization Dispersion Quantified by Time-Warping the Morphology of the T-Waves

“…Previous techniques developed to investigate cardiac repolarization from the surface ECG were based on interval repolarization durations and have been shown to reflect spatiotemporal repolarization heterogeneity [11,12], such as the QT interval, its corrected version [13], T-wave width [14], the distance from the peak to the end of the T wave (T pe interval) [15], the dynamic changes in the T pe interval with respect to the heart rhythm [16], the variability of the QT interval [3], the T-wave alternans [17], or the ST elevation [18]. However, these markers might not be able to capture both linear and non-linear T-wave morphological variations, and extracting such information may provide improved ventricular arrhythmic risk.…”

Techniques for Ventricular Repolarization Instability Assessment From the ECG

“…Instabilities in ventricular repolarization have been documented to be tightly linked to arrhythmia development [5], thus justifying the interest in the analysis and review of methods dealing with T wave characterization and quantification. The present paper follows from a previous review on cardiac repolarization analysis by the same authors [6]. Sudden cardiac death (SCD) is a major cause of death in developed countries, where 1 out of 1000 subjects die every year due to SCD [7].…”

“…Repolarization analysis based on the ECG is a low-cost, non-invasive approach that has been shown to be useful for risk assessment [6] and can be applied to the general population. Currently, challenges in this matter involve better understanding of the electrophysiological bases responsible for or secondary to the development of an arrhythmogenic substrate.…”