Identification of gender-related normality regions for T-wave alternans

Abstract

Background: T-wave alternans (TWA), a harbinger of sudden cardiac death, associates to a broad variety of pathologies. In a previous study, we observed the presence of unstable and low-amplitude TWA also in healthy subjects, and considered it as "physiological TWA." The possible existence of different TWA characteristics between males and female is investigated in the present work.

Methods: Resting ECG recordings from 142 control healthy subjects, 77 males and 65 females, were submitted to our adaptive match filter (AMF) based method for TWA detection and characterization in terms of duration, amplitude, and their product. The 99.5th percentile of these parameters distributions over the entire control population and over the male and female subgroups, were used to define thresholds which delimit a gender-independent and male- and female-related TWA normality regions, respectively, out of which abnormal TWA cases (TWA+) are expected to fall. Clinical usefulness of these regions was tested using a population of 151 coronary artery disease (CAD) patients, divided into 128 males and 23 females.

Results: In our control-female population, TWA duration was significantly longer than in control-male population (65 ± 13 beat vs 52 ± 14 beat; P < 10(-6) ). Our gender-related normality regions allowed identification of 36 (23.8%) TWA+ cases among the CAD patients, 17 more than those obtained from a gender-independent region. All these 17 patients were CAD males with over-threshold TWA duration.

Conclusions: TWA is a gender-related phenomenon. Definition of gender-related TWA normality regions improves identification of patients at increased TWA stability (i.e., prolonged TWA duration) and, thus, at increased risk of arrhythmic events.

Figure 1

TWA normality regions defined over the entire control population (panel A) or over the two genders separately (panels B and C), together with TWA levels measured in the control and CAD populations.

Figure 2

ECG tracing (X, Y, and Z leads from top to bottom panels) from a control subject.

Figure 3

Superimposition of 128 consecutive T‐waves (X, Y, and Z leads) from ECG tracings of the control subject of Figure 2 (TWA duration = 41 beat; TWA amplitude = 68 μV, TWA product = 2955 beat·μV), and a CAD patient (TWA duration = 76 beat; TWA amplitude = 105 μV, and TWA product = 8151 beat·μV). Both cases fall in the TWA+ region.

Figure 4

Superimposition of the TWA normality regions, respectively, defined over the entire control population (solid line), the control‐male subgroup (dashed line) and the control‐female subgroup (dotted line). Compared to the control‐population normality region, the control‐male normality region is characterized by a significant reduction of TWA duration threshold which gives rise to the shaded zone where 17 extra CAD‐male patients are identified as TWA+ with a gender‐related analysis.