Figure 2.

Implantable cardioverter defibrillators (ICDs) implanted and missingness of ICD indication over time. Cardiac Services BC collected data on ICD implantations in its Cardiac Device Registry (CDC) from 1995 to 2013 (blue shading), and then in the Heart Information System (HEARTis) database from October of 2013 until 2019 (red shading). Hawkins et al.¹⁴ performed a chart review of all ICD implantations between 2003 and 2012; however, the portion of this indication data available for the current study begins in 2004 (green shading). The solid line depicts the number of ICDs implanted per quarter with missing indication, and the dashed line depicts the total number of ICDs implanted per quarter. The main finding is that only a small proportion of patients have missing data on indication for implantation during the Hawkins or HEARTis period.