Risk Stratification of Ventricular Arrhythmias in Implantable Cardioverter Defibrillator Patients

Aim of this thesis is to provide strategies for improvement patient selection for ICD implantation for primary prevention and secondary prevention of SCD. SCD is a multifactorial and dynamic process and the risk of SCD can vary over time due to the dynamic interplay between a substrate, modulator and trigger. Hence, risk stratification of SCD for improvement of ICD therapy remains challenging and we are aware that there is not just a single answer available to describe the patient that will benefit most of ICD implantation. Acknowledging the complexity of SCD is the first step in improved patient selection of ICD therapy. Nonetheless, several main conclusions can be drawn from this thesis. First, we investigated the current eligibility criteria of prophylactic ICD implantation primary prevention. We showed that CMR-specific LVEF cut-off values are needed to improve patient selection. When similar LVEF cut-off values are used for different imaging modalities, a CMR-guided LVEF assessment will result in more patients eligible for prophylactic ICD implantation. Importantly, increased numbers of ICD implantations due to CMR-LVEF assessment will not result in improved patients selection, because the additional patients are at low risk of appropriate device therapy. Second, we showed that the absence or presence of heart failure symptoms at time of ICD implantation is not an adequate parameter to determine which patient will develop VA during follow-up. Consequently, we propose that asymptomatic heart failure patients with a reduced LVEF should be considered for primary prevention ICD implantation. Third, we aimed to improve patient selection using advanced imaging techniques before ICD implantation. We showed that improved patient selection by advanced non-invasive imaging with PET-derived perfusion and sympathetic innervation and scar core quantification by LGE-CMR remains challenging for the individual patient with an ischemic cardiomyopathy and reduced LVEF. Fourth, we showed that the risk of VA between female and male ICD patients is different, however, we were not able to derive sex-specific risk models based on clinical parameters. Fifth, we demonstrated that signs of depression and anxiety were correlated with multiple cardiac parameters in ICD patients, which may influence the risk of VA during follow-up. Finally, we explored the risk of VA recurrence in cardiac arrest survivors with a reversible and correctable cause. We demonstrated that the recurrence risk of VA varies between different reversible causes of SCA and that this patient group should not be evaluated as one entity. Different groups of SCA survivors with a reversible cause might be at different risk of recurrent VA and selected patients may benefit from ICD implantation.