Reproducibility of global electrical heterogeneity measurements on 12-lead ECG: The Multi-Ethnic Study of Atherosclerosis

Abstract

Objective: Vectorcardiographic (VCG) global electrical heterogeneity (GEH) metrics showed clinical usefulness. We aimed to assess the reproducibility of GEH metrics.

Methods: GEH was measured on two 10-s 12‑lead ECGs recorded on the same day in 4316 participants of the Multi-Ethnic Study of Atherosclerosis (age 69.4 ± 9.4 y; 2317(54%) female, 1728 (40%) white, 1138(26%) African-American, 519(12%) Asian-American, 931(22%) Hispanic-American). GEH was measured on a median beat, comprised of the normal sinus (N), atrial fibrillation/flutter (S), and ventricular-paced (VP) beats. Spatial ventricular gradient's (SVG's) scalar was measured as sum absolute QRST integral (SAIQRST) and vector magnitude QT integral (VMQTi).

Results: Two N ECGs with heart rate (HR) bias of -0.64 (95% limits of agreement [LOA] -5.68 to 5.21) showed spatial area QRS-T angle (aQRST) bias of -0.12 (95%LOA -14.8 to 14.5). Two S ECGs with HR bias of 0.20 (95%LOA -15.8 to 16.2) showed aQRST bias of 1.37 (95%LOA -33.2 to 35.9). Two VP ECGs with HR bias of 0.25 (95%LOA -3.0 to 3.5) showed aQRST bias of -1.03 (95%LOA -11.9 to 9.9). After excluding premature atrial or ventricular beat and two additional beats (before and after extrasystole), the number of cardiac beats included in a median beat did not affect the GEH reproducibility. Mean-centered log-transformed values of SAIQRST and VMQTi demonstrated perfect agreement (Bias 0; 95%LOA -0.092 to 0.092).

Conclusion: GEH measurements on N, S, and VP median beats are reproducible. SVG's scalar can be measured as either SAIQRST or VMQTi.

Significance: Satisfactory reproducibility of GEH metrics supports their implementation.

Keywords: Global electrical heterogeneity; QRS-T angle; Reproducibility; Spatial ventricular gradient; Vectorcardiogram.

Figure 1.

GEH measurements. (A) Spatial ventricular gradient (SVG) vector (blue) obtained as a vector sum of QRS (green) and T vector (red). Spatial QRS-T angle is the 3D angle between QRS and T vector. (B) Orientation of the angles (azimuth and elevation) in 3D space. (C) Sum absolute QRST integral (SAIQRST). (D) Vector magnitude QT integral.

Figure 2.

Study flowchart.

Figure 3.

Bland-Altman plots demonstrating agreement of spatial area QRS-T angle on two ECGs. Median beats were constructed in (A) normal sinus (N) rhythm, (B) atrial fibrillation/flutter, (C) ventricular pacing, including (D) ≤6 N beats, (E) 7–9 N beats, (F) ≥10 N beats. The scatterplot presents paired differences (Y-axis), plotted against pair-wise means (X-axis). The reference line indicates the perfect average agreement, Y = 0. The central green line indicates the mean difference between the two measurements, or mean bias. Upper and lower lines represent the mean ± 2 standard deviations (SD), or 95% limits of agreement.

Figure 4.

(A). Bland-Altman plot demonstrating agreement of mean-centered log-transformed SAIQRST and VMQTi. Definitions given in Figure 3 legend. (B). Concordance scatterplot of the mean-centered log-transformed SAIQRST and VMQTi. The reduced major axis of the data (green) goes through the intersection of the means and has the slope given by the sign of Pearson’s r and the ratio of the standard deviations. The reference red line shows the perfect concordance, Y = X.