Non-Sustained Microvolt Level T-Wave Alternans in Congenital Long Qt Syndrome Types 1 and 2

The Relationship between T-Wave Alternans and Adverse Cardiac Events in Patients with Congenital Long QT Syndrome: A Systematic Review and Meta-Analysis

“…In the time-domain Modified Moving Average (MMA) method, peak TWA ≥ 42 μV in the 12 leads with HR < 120 bpm were determined positive, otherwise, negative [12,13]. The frequency domain (SM) method was used in three studies [14][15][16]. Schmitt' research defined MTWA as positive when sustained alternans was present at rest or at an onset HR < 110 bpm; MTWA was defined as negative if the criteria for positivity were not met and at least 1 min of artifact-free data without significant alternans was identified while the HR was maintained at either a level <105 bpm or within 5 bpm of the maximum HR; otherwise, indeterminate [14].…”

“…Schmitt' research defined MTWA as positive when sustained alternans was present at rest or at an onset HR < 110 bpm; MTWA was defined as negative if the criteria for positivity were not met and at least 1 min of artifact-free data without significant alternans was identified while the HR was maintained at either a level <105 bpm or within 5 bpm of the maximum HR; otherwise, indeterminate [14]. In Kannampuzha's study [16], MTWA tests were defined as positive if MTWA appeared at or below a patient-specific onset HR threshold of 110 bpm, if the MTWA appeared with a magnitude of over 1.9 µV and had an alternans ratio (to noise) over 3, and if the MTWA was sustained for at least a minute during the time that the heart remained over the HR threshold; The MTWA test was negative if significant alternans was not elicited until after the HR ≥ 105 bpm, and it did not meet criteria for being positive; otherwise, indeterminate. While in Nemec's study, MTWA tests were defined as positive if MTWA (power at the alternans frequency > 4 µV 2 and ratio of the alternans frequency power to mean noise band power > 4) was recorded at HR < 150 bpm.…”

“…The characteristics of included studies were summarized in Table 1. Among these studies, five studies [12][13][14][15][16] focused on the relationship between MTWA and ACE (Tdp, syncope, aborted cardiac arrest or SCD), and only two studies [11,17] analyzed the relationship between macroscopic TWA and ACE (Tdp or cardiac arrest). On the other hand, four [11][12][13]17] discussed TWA without stress (transient 12-lead ECG or 24 h continuous ECG), and three [14][15][16] with exercise or catecholamine.…”

“…Among these studies, five studies [12][13][14][15][16] focused on the relationship between MTWA and ACE (Tdp, syncope, aborted cardiac arrest or SCD), and only two studies [11,17] analyzed the relationship between macroscopic TWA and ACE (Tdp or cardiac arrest). On the other hand, four [11][12][13]17] discussed TWA without stress (transient 12-lead ECG or 24 h continuous ECG), and three [14][15][16] with exercise or catecholamine. Finally, a total of 625 patients were included, 273 (43.68%) suffered ACE, 132 (21.12%) had non-negative TWA, and 58 (43.94%) suffered ACE in patients with non-negative TWA.…”

“…Studies and meta-analyses have indicated that both macroscopic TWA and MTWA are risk factors of ventricular arrhythmias or SCD in patients with ischemic cardiomyopathy (ICM) [7][8][9][10]. However, controversial results were obtained in patients with congenital LQTS [11][12][13][14][15][16][17]. To further clarify the relationship between TWA and ACE in patients with LQTS, we performed a meta-analysis of currently available medical literature.…”