(1) Background: Receiving the first internal electric shock is a turning point for patients with an implantable cardioverter defibrillator (ICD) for primary prevention. However, no study has investigated whether patients who receive a first device-delivered electric shock have a poor prognosis even at the time of ICD implantation. (2) Methods: We retrospectively identified 55 patients with ischemic (n = 31) or dilated (n = 24) cardiomyopathy who underwent ICD implantation for primary prevention with exercise test at the time of implantation. We recorded baseline characteristics, exercise test parameters, and clinical events. (3) Results: After a median follow-up of 5 years, we observed an association between an appropriate device-delivered electric shock, the occurrence of death or heart transplant, and the occurrence of the composite endpoint. There was also a significant relation between a VE/VCO2 slope >35 and the occurrence of the composite endpoint. Conversely, there was no significant association between negative outcomes on the exercise test and the occurrence of a device-delivered electric shock. (4) Conclusions: The exercise test performed at the time of ICD implantation do not predict the occurrence of device-delivered electric shock. The exercise test and the first electric shock are two independent markers of poor prognosis.
Keywords: exercise test; heart failure; implantable cardioverter defibrillator; oxygen uptake.