Transcatheter ablation of arrhythmias associated with congenital heart disease

The improvement of surgical techniques resulted in significant life prolongation of many young patients with congenital heart disease (CHD). However, as these patients reach adulthood, their risk for late complications associated with surgery is also increased. One of the most difficult challenges associated with CHD is the high incidence of cardiac arrhythmias that arise from either the myocardial substrate created by abnormal physiology (pressure/volume changes, septal patches, and suture lines) or the presence of surgical scar. Catheter ablation is proven to be effective in treating atrial and ventricular arrhythmias in structurally normal hearts, and has also been used to treat arrhythmias in adults with congenital heart disease. In this review we provide an overview about diagnostic challenges, mapping and ablation techniques and outcome of patients undergoing transcatheter ablation procedures

Case report : synergetic effect of ischaemia and increased vagal tone inducing ventricular fibrillation in a patient with Brugada syndrome

Background Brugada syndrome (BS) is a hereditary channelopathy associated with syncope, malignant ventricular arrhythmia, and sudden cardiac death. Right ventricular ischaemia and BS have similar underlying substrates precipitating ventricular tachycardia or fibrillation (VF). Case summary A 72-year-old woman with BS and a stenosis on the proximal right coronary artery received several subsequent implantable cardioverter-defibrillator shocks due to VF during an episode of extreme nausea with vomiting. Discussion This case report emphasizes on the synergetic effect of mild ischaemia and increased vagal tone on the substrate responsible for BS to create pathophysiological changes precipitating VF

Shock and patient preimplantation type D personality are associated with poor health status in patients with implantable cardioverter-defibrillator

Background: Implantable cardioverter-defibrillator (ICD) shock is a critical event to patients associated with well-being after implantation, although other factors may play an equally important role. We compared the association of shock and the patient's preimplantation personality with health status, using a prospective study design. Methods and Results: Consecutively implanted ICD patients (n=383; 79% men) completed the Type D Scale at baseline and the Short-Form Health Survey 36 (SF-36) at baseline and 3, 6, and 12 months. Of all patients, 23.5% had a Type D personality and 13.8% received a shock during follow-up. Shocked patients reported significantly poorer health status, as did Type D patients. Health status patterns were poorest in patients with combined Type D personality and shock during follow-up. Shock during follow-up was a significant independent associate of poorer health status for 4 of 8 subscales of the SF-36 and the Mental Component Summary (all P<.05), with shocked patients scoring between 2.60 to 13.30 points lower than nonshocked patients. Type D personality was an independent associate of poor postimplantation health status for 6 of 8 of the SF-36 subscales and the Mental Component Summary, with Type D patients scoring between 2.12 to 8.02 points lower, adjusting for demographic and clinical characteristics. Conclusions: ICD shock and the patient's preimplantation personality disposition were equally important associates of health status 12 months after implantation. Identification of the patient's personality profile before ICD implantation may help identify subsets of patients who may need additional care, for example, with a psychosocial component

ICDs at higher age and clinical risk factors

Background The implantable cardioverter defibrillator (ICD) is effective in preventing sudden cardiac death. However, in elderly patients (aged 75 years or older) the role of ICDs is still not well-defined and controversial. Methods We retrospectively analysed all clinical and survival data of all ICD patients who were ≥75 years at the date of implantation in the Erasmus MC, Rotterdam, the Netherlands and the University Hospital, Basel, Switzerland. Kaplan- Meier survival analysis was performed, and mortality predictors were identified. Mortality of the cohort was compared with a random sample of patients aged 60-70 years originating from the same database and to an age- and sex-matched cohort of Dutch persons. Results The study cohort consisted of 179 patients aged 75 years or older who were implanted between February 1999 and July 2008. The median follow-up time was 2.0 (IQR 2.8) years. Survival rates after 1, 2 and 3 years were 87, 82, 75 %, respectively. Survival was similar for primary and secondary prevention. Mortality in this study population could be predicted by combining four clinical risk factors: QRS duration >120 ms, NYHA class > II, renal failure and atrial fibrillation (AF). Survival was worse compared with the group of ICD patients aged 60-70 years and to the age- and sex-matched group of elderly persons. However, survival was not significantly worse when comparing elderly ICD patients without additional risk factors to the general population. Conclusions Elderly patients still have an acceptable survival probability independent of prevention indication, certainly if there are no additional clinical risk factors. The presence or absence of additional clinical risk factors should be taken into account when making the decision for imp

Clinical experience with a novel subcutaneous implantable defibrillator system in a single center

Background: Implantable cardioverter-defibrillators (ICDs) reduce mortality in both primary and secondary prevention, but are associated with substantial short- and long-term morbidity. A totally subcutaneous ICD (S-ICD) system has been developed. We report the initial clinical experience of the first 31 patients implanted at our hospital. Methods: All patients had an ICD indication according to the ACC/AHA/ESC guidelines. The first 11 patients were part of the reported CE trial. The implantation was performed without fluoroscopy. The device was implanted subcutaneously in the anterior axillary line, with a parasternal lead tunneled from the xiphoid to the manubrial-sternal junction. Ventricular fibrillation (VF) was induced to assess detection accuracy and defibrillation efficacy using 65 J shocks. Results: Post-implant, 52 sustained episodes of VF were induced. Sensitivity was 100% and induced conversion efficacy was 100% (with standard polarity in 29 patients). Mean time to therapy was 13.9 ± 2.5 s (range 11-21.6 s). Late procedure-related complications were observed in 2 of the first 11 implantations (lead migration). During follow-up, spontaneous ventricular arrhythmias occurred in four patients, with accurate detection of all episodes. Inappropriate therapy was observed in five patients. Recurrences were prevented with reprogramming. Conclusions: The S-ICD system can be implanted without the use of fluoroscopy by using anatomical landmarks only. Episodes of VF were accurately detected using subcutaneous signals, and all induced and clinical episodes were successfully converted. The S-ICD system is a viable alternative to conventional ICD systems for selected patients

Unique Cardiac Purkinje Fiber Transient-Outward Current Beta-Subunit Composition: A Potential Molecular Link to Idiopathic Ventricular Fibrillation.

Rationale: A chromosomal-haplotype producing cardiac overexpression of dipeptidyl peptidase-like protein-6 (DPP6) causes familial idiopathic ventricular fibrillation (IVF). The molecular basis of transient-outward current (Ito) in Purkinje fibers (PFs) is poorly understood. We hypothesized that DPP6 contributes to PF Ito and that its overexpression might specifically alter PF Ito-properties and repolarization. Objective: To assess the potential role of DPP6 in PF-Ito. Methods and Results: Clinical data in 5 IVF-patients suggested arrhythmia-origin in the PF conducting-system. PF and ventricular-muscle (VM) Ito had similar density, but PF Ito differed from VM in having tetraethylammonium-sensitivity and slower recovery. DPP6-overexpression significantly increased, whereas DPP6-kockdown reduced, Ito-density and tetraethylammonium-sensitivity in canine PF, but not VM-cells. The K+-channel interacting beta-subunit KChIP2, essential for normal expression of transient outward current (Ito) in VM, was weakly-expressed in human PFs, whereas DPP6 and frequenin (NCS-1) were enriched. Heterologous expression of Kv4.3 in Chinese hamster ovary (CHO)-cells produced very small Ito; Ito-amplitude was greatly enhanced by co-expression with KChIP2 or DPP6. Co expression of DPP6 with Kv4.3 and KChIP2 failed to alter Ito versus Kv4.3/KChIP2 alone, but DPP6 expression with Kv4.3 and NCS-1 (to mimic PF Ito-composition), greatly enhanced Ito versus Kv4.3/NCS-1 and recapitulated characteristic PF kinetic/pharmacological properties. A mathematical model of cardiac PF action potentials showed that Ito-enhancement can greatly accelerate PF repolarization. Conclusions: These results point to a previously-unknown central role of DPP6 in PF Ito, with DPP6 gain-of-function selectively enhancing PF-current, and suggest that a DPP6-mediated PF early repolarization syndrome might be a novel molecular paradigm for some forms of IVF

Survival analysis and clinical medicine: an observational comparison of the implantable cardioverter defibrillator, amiodarone treatment, and heart transplantation

In clinical practice, observational studies remain necessary for evaluating accepted and new treatments. The comparison of results remains difficult and often controversial, because of a wide variation in clinical characteristics. Survival analysis and calculation of the standardized mortality ratio offer the possibility to compare outcomes in different study groups. We have applied these techniques to an observational comparison of outcomes in three groups of patients, followed in two university centres: (i) patients treated with an implantable cardioverter defibrillator; (ii) patients under amiodarone treatment and (iii) recipients of a heart transplant. There was no statistically significant difference in the cumulative survival from total mortality. The standardized mortality ratio revealed the different natural history of patients undergoing heart transplantation