Recent guidelines have focused on ejection fraction cut-off values to determine eligibility for primary-prevention implantable cardioverter-defibrillators (ICDs). Clinical trials that led to the guidelines used varying techniques for ejection fraction assessment, including echocardiography and multigated acquisition (MUGA) scan. A prospective cohort study to determine the economic attractiveness of repeated echocardiography and MUGA scanning during the evaluation process of patients referred for consideration of a primary-prevention ICD was undertaken. From January 2005 to December 2006, data were collected for patients aged >18 years with ejection fraction <30% referred for a primary-prevention ICD based on referral assessment of heart function in any form. Costs based on the 2006 Ontario Health Insurance Plan fee schedule were determined for clinical assessment, echocardiography, MUGA scanning, and ICD implantation in patients who remained eligible based on MUGA ejection fraction. The 100 patients (age 61.1 +/- 10.2 years; 78 men) assessed for primary-prevention ICD implantation had an ejection fraction of 28.9 +/- 12.3% using MUGA scan. Thirty-one of 100 patients (31%) had an ejection fraction >30% and were no longer eligible for an ICD. Although imaging increased preimplantation cost from dollars 130 to dollars 536 per patient, averted inappropriate ICDs decreased the overall per-patient cost from dollars 20,914 to dollars 14,877. Despite an additional testing cost of dollars 40,599, the overall cost savings was dollars 603,722 in the 100 patients, with a cost savings of dollars 6,037 per patient. In conclusion, verification of ejection fraction identified a significant proportion of patients who were not eligible for an ICD.