Electrophysiology testing and the National Cardiovascular Data Registry: stimulating, yet inconclusive

In this issue of PACE, Cheng et al. do an impressive job in evaluating clinical variables associated with electrophysiology studies (EPS) performed within 1 month before implantable cardioverter defibrillator (ICD) placement in 33,786 individuals entered into the National Cardiovascular Data Registry for Implantable Cardioverter Defibrillators (NCDR®-ICD) over a 3-year period. Although of great interest, most of the conclusions are by necessity based on conjecture drawn from observations alone, since the inherent, point-in-time structure of the Registry limits the ability to assess accurate longitudinal clinical correlations and outcomes. The fact is, we really do not know why these patients underwent EPS or how the data from these tests were used. In addition to stimulating speculation on the role of EPS in ICD recipients, the present report should promote caution regarding what conclusions can and should be drawn from the NCDR®-ICD in its present format. As constructed, the Registry provides demographic data and clinical elements up to only a fixed point in time. Hence, the ability to draw conclusions is limited by the abundance of disconnected variables and snapshot quality of data in the NCDR.