Can Body Surface Microvolt T‐Wave Alternans Distinguish Concordant and Discordant Intracardiac Alternans?

Abstract

MTWA is a potent technique to detect subtle and isolated intracardiac APD alternans that is artificially induced by alternating pacing. In the same model, discordant activation alternans can only be discriminated from concordant when using a quantifying approach of MTWA analysis.

Cardiac myocyte alternans in intact heart: Influence of cell–cell coupling and β-adrenergic stimulation

“…Ca 2+ alternans can be seen within regions of a myocyte [7, 8] as well as myocyte-wide alternans and both regional and whole heart alternans. Clinically, T-wave alternans (TWA) is an important marker for the risk of ventricular arrhythmia and is associated with Ca 2+ and APD alternans [9, 10], and small changes in Ca 2+ cycling can cause reentrant arrhythmias [11]. In disease models, CaT alternans can be observed long before arrhythmias or heart failure occurs [12].…”

T‐Wave Morphology in a Model of Paced Action Potential Duration Alternans

“…We appreciate the interest for our article recently published in the journal . With great interest, we have read the stimulating suggestions done by Dr. Madias.…”

TWA Regionality and ECG Lead Dependence

“…Also they refer to the regionality of the MTWA phenomenon, as done previously, in the setting of myocardial ischemia, or chronic myocardial infarction . The authors, in the section of their paper subtitled “Precordial leads have the highest sensitivity for discordant repolarization alternans,” refer to the precordial leads as “only picking up the local heterogeneity of the T‐wave vector” and thus reflecting only local MTWA, whereas in general it is accepted that precordial leads reflect both local (near‐field) (primarily) and global (far‐field) (to lower degree) potentials. Recently, Verrier et al reported that MTWA was regionally specific, with larger values noted in lead V5 than in V1 in patients with ST‐elevation myocardial infarction prior to percutaneous coronary interventions, prompting this author to suggest a way to differentiate between MTWA regionality and MTWA dependence on the corresponding T‐wave (or more correct J–T interval) amplitude by calculating ratios of the magnitude of MTWA over amplitude of the J–T interval area under the curve for leads V1 and V5, and compare the two ratios.…”

“…I read with great interest the study of Floré et al published online on April 24, 2013, ahead of print, in the Journal about the feasibility of distinguishing concordant and discordant microvolt T‐wave alternans (MTWA) using body surface maps in a porcine animal model . The authors emphasized the importance of quantitative assessment of MTWA regardless of the technique (frequency or time domain) employed.…”

“…Recently, Verrier et al reported that MTWA was regionally specific, with larger values noted in lead V5 than in V1 in patients with ST‐elevation myocardial infarction prior to percutaneous coronary interventions, prompting this author to suggest a way to differentiate between MTWA regionality and MTWA dependence on the corresponding T‐wave (or more correct J–T interval) amplitude by calculating ratios of the magnitude of MTWA over amplitude of the J–T interval area under the curve for leads V1 and V5, and compare the two ratios. Accordingly in the authors’ model, one wonders whether the regionality of MTWA can be differentiated from the J–T interval amplitude dependence by considering the magnitudes of MTWA, and the corresponding amplitudes of JT intervals in the orthogonal and the precordial leads. Perhaps, comparisons of ratios of MTWA and the corresponding JT interval area under the curve, from the three orthogonal leads and some (or all) of the body surface leads, or between various precordial leads, may discriminate between possible regionality of MTWA and/or a possible confounding influence of J–T interval amplitude dependence on the MTWA magnitude.…”