Objective. We present a concept for processing 6-lead
electrocardiography (ECG) signals which can be applied to
various use cases in quantitative electrocardiography.

Approach. Our work builds upon the mathematics of the well-
known Cabrera sequence which is a re-sorting of the six limb
leads (I, II, III, aVR, aVL, aVF) into a clockwise and
physiologically-interpretable order. By deriving correction
factors for harmonizing lead strengths and choosing an
appropriate basis for the leads, we extend this concept towards
what we call the “Cabrera Circle” based on a mathematically
sound foundation.

Main results. To demonstrate the practical effectiveness and
relevance of this concept, we analyze its suitability for
deriving interpolated leads between the six limb leads and a
“radial” lead which both can be useful for specific use cases.
We focus on the use cases of i) determination of the electrical
heart axis by proposing a novel interactive tool for
reconstructing the heart’s vector loop and ii) improving
accuracy in time of automatic R-wave detection and T-wave
delineation in 6-lead ECG. For the first use case, we derive an
equation which allows projections of the 2-dimensional vector
loops to arbitrary angles of the Cabrera Circle. For the second
use case, we apply several state-of-the-art algorithms to a
freely- available 12-lead dataset (Lobachevsky University
Database). Out-of-the-box results show that the derived radial
lead outperforms the other limb leads (I, II, III, aVR, aVL,
aVF) by improving F1 scores of R-peak and T-peak detection by
0.61 and 2.12, respectively. Results of on- and offset
computations are also improved but on a smaller scale.

Significance. In summary, the Cabrera Circle offers a
methodology that might be useful for quantitative
electrocardiography of the 6-lead subsystem—especially in the
digital age.