Participants will only receive body-surface potential mapping (BSPM) with an extensive electrode set (256 electrodes).

Participants will receive body-surface potential measurements (BSPM) and a CT scan. These data will allow for non-invasive reconstruction of electrical potentials at the heart surface.

A CT scan of thorax and heart will be performed in the CT+BSPM group.

Primary outcome data include reconstructed electrical heart activity such as:

- epicardial potentials (units: millivolts [mV])

These outcome data are obtained at the moment of inclusion.

The primary outcome measures are a comparison of the primary outcome data with invasive outcome data available from clinical records:

- Reconstructed epicardial potentials (mV) will be compared to selected invasive epicardial potentials (mV) obtained from catheter-based recordings or pacemaker-based recordings available as clinical data

Primary outcome data include reconstructed electrical heart activity such as:

- epicardial electrograms (units: millivolts [mV] over milliseconds [ms])

These outcome data are obtained at the moment of inclusion.

The primary outcome measures are a comparison of the primary outcome data with invasive outcome data available from clinical records:

- Reconstructed electrograms (mV) will be compared to selected invasive epicardial electrograms (mV) obtained from catheter-based recordings or pacemaker-based recordings available as clinical data

Primary outcome data include reconstructed electrical heart activity such as:

- epicardial activation and recovery isochrones (units: milliseconds [ms])

These outcome data are obtained at the moment of inclusion.

The primary outcome measures are a comparison of the primary outcome data with invasive outcome data available from clinical records:

- Reconstructed activation and recovery sequences (ms) will be compared to recorded catheter-based sequences from clinical data (ms).

The secondary study endpoints include disease-specific differences of the primary outcome measures, which may include abnormal (low-amplitude, fractionated) electrograms and abnormal activation and recovery sequences. Depending on the primary measure, these differences will be expressed in absolute units (mV, ms) or relative differences (%).