Subcutaneous chronic implantable defibrillation systems in humans

The recent introduction of subcutaneous implantable cardioverter defibrillator (S-ICD) has raised attention about the potential of this technology for clinical use in daily clinical practice. We review the methods and results of the four studies conducted in humans for approval of this innovative technology for daily practice. Two studies using a temporary S-ICD system (acute human studies) were conducted to search for an appropriate lead configuration and energy requirements. For this purpose, 4 S-ICD configurations were tested in 78 patients at the time of transvenous (TV)-ICD implantation. The optimal configuration was tested in 49 more patients to comparatively assess the subcutaneous defibrillation threshold (S-DFT) versus the standard TV-ICD. Long-term implants were evaluated in 55 patients using an implanted system (chronic human study). The acute humans studies led to an optimal S-ICD configuration comprising a parasternal electrode and left anterolateral thoracic pulse generator. Both configurations successfully terminated 98% of induced ventricular fibrillation (VF), but significantly higher energy levels were required with S-ICD than with TV-ICD systems (36.6?±?19.8 J vs. 11.1?±?8.5 J). In the chronic study, all 137 VF episodes induced at time of implant were detected with a 98% conversion rate. Two pocket infections and four lead revisions were required during 10?±?1 months of follow-up. During this period, survival was 98%, and 12 spontaneous ventricular tachyarrhythmias were detected and treated by the device. These data show that the S-ICD systems here consistently detected and converted VF induced at time of implant as well as sustained ventricular tachyarrhythmias occurring during follow-up (248).     

Beyond the cardiorenal anaemia syndrome: recognizing the role of iron deficiency

Growing awareness that heart failure, renal impairment, and anaemia are frequent co‐morbidities which can exacerbate one another in a vicious circle of clinical deterioration has led to the concept of the cardiorenal anaemia syndrome (CRAS). The role of iron deficiency within this complex interplay has been less well examined. Scrutiny of data from the recent FAIR‐HF trial raises a new hypothesis: is it time for ‘CRAS’ to be supplemented with new acronyms such as CRIDS (cardiorenal–iron deficiency syndrome) or even CRAIDS (cardiorenal–anaemia–iron deficiency syndrome)? Iron deficiency occurs frequently in heart failure patients with or without anaemia. It not only impairs oxygen transport through reduced erythropoiesis, but adversely affects oxidative metabolism, cellular energetics, and immune mechanisms, and the synthesis and degradation of complex molecules such as DNA. One large observational study in patients with heart failure found iron deficiency to be an independent predictor of death or urgent heart transplantation (hazard ratio 1.58, 95% confidence interval 1.14–2.17, P = 0.005). In the FAIR‐HF trial, i.v. iron therapy was associated with significant improvements in physical functioning in iron‐deficient patients with heart failure, even in non‐anaemic patients in whom haemoglobin levels did not change following i.v. iron administration. Key questions regarding the use of i.v. iron supplementation in the setting of heart failure merit exploration and could readily be answered by appropriately designed clinical trials. It is to be hoped that these important clinical trials are conducted, to permit a more subtle characterization of the patient's pathological condition and interventional requirements.