Reconstruction of the surface electrocardiogram (EKG) from voltage recordings from implanted leads is not performed by current pacemakers or cardioverter-defibrillators. We investigated the feasibility and accuracy of reconstruction of a full 12-lead surface EKG from an implanted biventricular device. Methods and results We applied three techniques for surface EKG reconstruction from multiple intracardiac (IC) vector recordings from implanted cardiac leads: single fixed dipole modelling via

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... t solution, exhaustive best-fit solution, and time-independent association using a transfer matrix. Recordings were performed at biventricular generator change in 10 patients. Overdetermined projection transformation resulted in high fidelity surface EKG reproduction for left-sided implanted devices (correlation coefficient 0.84 + 0.13) with computationally lightweight reconstruction. Conclusion After individual post-implantation correlation with the surface EKG, reconstruction using a time-independent transfer matrix accurately reproduces the surface EKG, is free from gating requirements, and retains validity during aberrant depolarization. These findings have significant implications for further study relating IC electrogram to surface tracings. The techniques may be used for real-time or remote monitoring and diagnosis of rhythm disturbances, cardiac ischaemia, and lead integrity and stability.