Intra-Individual Comparison of Sinus and Ectopic Beats Probing the Ventricular Gradient’s Activation Dependence

Figures

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  Figure 1. Relationship between VGe→ (the ventricular gradient of the ectopic beat) and VGp→ (the ventricular gradient of the predominant beat). VGe→ and VGp→ are the magnitudes of VGe→ and VGp→, respectively. |VGe|→−|VGp|→ is the magnitude of the difference between the magnitudes of VGe→ and VGp→, irrespective of which is the largest and which is the smallest. ΔVGep→ is the magnitude of the difference vector between VGe→ and VGp→. This difference vector magnitude depends on |VGe|→−|VGp|→ and on the angle α between the two ventricular gradient vectors. If ΔVGep→ equals |VGe|→−|VGp|→, the ventricular gradient vectors of the predominant and ectopic beat assume the same direction. A difference in spatial orientation of VGe→ and VGp→ increases the magnitude of the difference vector ΔVGep→, which is then larger than |VGe|→−|VGp|→. The larger the angle between VGe→ and VGp→, the larger the difference between ΔVGep→ and |VGe|→−|VGp|→. The figure illustrates this, including the invariance for the difference in magnitudes of VGe→ and VGp→: in the left panel VGe→ is smaller than VGp→, while in the right panel VGe→ is larger than VGp→.

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  Figure 2. Flowchart for ectopic beat categorization into beats of supposed supraventricular origin with and without aberrant conduction and beats of supposed ventricular origin. See text.

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  Figure 3. Examples of VCGs of subjects with a supraventricular ectopic beat with normal conduction (panel A, beat seven was analyzed), a supraventricular ectopic beat with similar initial 20 ms and aberrant conduction (panel B1), a supraventricular ectopic beat with strict LBBB configuration, and thus also aberrant conduction (panel B2, beat five was analyzed), and a ventricular ectopic beat (panel C), respectively.

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  Figure 4. Magnitudes of the ectopic ventricular gradient (VGe→) versus the ventricular gradient of the predominant beat (VGp→). The scatterplot displays the data from all patients (N = 118). The solid line shows the linear regression with constant (intercept = 13.23) and the dotted line shows the linear regression forced through the origin (intercept = 0). The correlation coefficients of both regressions differ statistically significantly from zero (p < 0.001).

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  Figure 5. Magnitude of the ventricular gradient difference vector (ΔVGep→) versus the magnitude of the difference between the ventricular gradient magnitudes (|VGe|→−|VGp|→). When VGe→ and VGp→ have the same spatial orientation, the magnitude of the difference vector equals the difference of the vector magnitudes. This situation is represented by the 45-degree line. When VGe→ and VGp→ have different spatial orientations, the magnitude of the difference vector is larger than the difference of the vector magnitudes (data points above the 45-degree line). The scatterplot shows that not only the magnitudes of the VGe→ and VGp→ differ, but that the spatial orientations differ as well. See also Figure 2.

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  Figure 6. Distribution of the planar angle α (see Figure 2) between the ventricular gradient vectors of the ectopic beat (VGe→) and of the predominant beat (VGp→).

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  Figure 7. Magnitudes of the ventricular gradient difference vectors as a function of prematurity for patients with normally conducted supraventricular ectopic beats (SN; N = 6), aberrantly conducted supraventricular ectopic beats (SA; N = 20), and ventricular ectopic beats (V; N = 92). Linear regressions were computed from the VG difference vectors of these three subgroups and of the entire study group (All; N = 118) on prematurity. All correlation coefficients were very low and none of the regression lines had a slope that was statistically significantly different from zero.