Signal integral for optimizing the timing of defibrillation

OBJECTIVE

The possibility of successful defibrillation decreases with an increased duration of ventricular fibrillation (VF). Futile electrical shocks are inversely correlated with myocardial contractile function and long-term survival. Previous studies have demonstrated that various ECG waveform analyses predict the success of defibrillation. This study investigated whether the absolute amplitude of pre-shock VF waveform is likely to predict the success of defibrillation.

METHODS

ECG recordings of 350 out-of-hospital cardiac arrest (OOHCA) patients were obtained from the automated external defibrillator (AED) and analyzed by the method of signal integral. Successful defibrillation was defined as organized rhythm with heart rate ≥40beat/min commencing within one min of post-shock period and persisting for a minimum of 30s.

RESULTS

Signal integral was significantly greater in successful defibrillation than unsuccessful defibrillation (81.76±32.3mV vs. 34.9±15.33mV, p<0.001). The intersection of the sensitivity and specificity curve provided a threshold value of 51mV. The corresponding values of sensitivity, specificity, positive predictive and negative predictive values for successful defibrillation were 90%, 86%, 80% and 93%, respectively. The receiver operator curve further revealed that signal integral predicted the likelihood of successful defibrillation (area under the curve=0.949).

CONCLUSIONS

Signal integral predicted successful electrical shocks on patients with ventricular fibrillation and have potential to optimize the timing of defibrillation and reduce the number of electrical shocks.

On boundary stimulation and optimal boundary control of the bidomain equations

The bidomain equations with Neumann boundary stimulation and optimal control of these stimuli are investigated. First an analytical framework for boundary control is provided. Then a parallel finite element based algorithm is devised and its efficiency is demonstrated not only for the direct problem but also for the optimal control problem. The computations realize a model configuration corresponding to optimal boundary defibrillation of a reentry phenomenon by applying current density stimuli.

Police AED programs: a systematic review and meta-analysis

BACKGROUND

Approximately 359,400 out-of-hospital cardiac arrests occur in the United States every year, and around 60% of them are treated by emergency medical services (EMS) personnel. In order to alleviate the impact of this public health burden, some communities have trained police officers as first responders so that they can provide cardiopulmonary resuscitation and defibrillation to cardiac arrest patients. This paper is a review of the current literature on the impact of police automated external defibrillators (AEDs) programs in these communities.

METHODS AND RESULTS

A literature search of electronic journal databases was conducted to identify articles that evaluated police AED programs and quantified survival rates. The 10 articles that met the inclusion criteria were very heterogeneous in terms of study design, controlling for confounders, outcome definitions, and comparison groups. Two communities found a statistically significant difference in survival and 6 studies reported a statistically significant difference in time to defibrillation after the implementation of these programs. The weighted mean survival rate of the study groups was higher than that of the control groups (p<0.001), as was the weighted mean survival rate of the group first shocked by police compared to those first shocked by EMS (39.4% vs. 28.6%, p<0.001). The pooled relative risk of survival was 1.4 (95% CI: 1.3-1.6).

CONCLUSIONS

Though there are many challenges in initiating these programs, this literature review shows that time to defibrillation decreased and survival from out-of-hospital cardiac arrests increased with the implementation of police AED programs.

Intrapericardial implantation of an implantable cardioverter-defibrillator in a child

Implantable cardioverter defibrillator (ICD) can be a crucial therapeutic modality for pediatric patients with congenital heart disease, Brugada syndrome, long QT syndrome and cardiomyopathy. Because transvenous implantation of ICD is mostly unfeasible for pediatric patients due to anatomical and technical limitations, epicardial patch type or subcutaneous type ICD have been used. Implantation of these alternative ICDs, however, was reported to be frequently associated with significant complications. We report a case of successful intrapericardial implantation of a single coil-type ICD through the transverse sinus in a 27 month-old child weighing lesser than 10 kg, and it was inferred from this experience that this alternative technique may decrease complications and morbidities after ICD implantation in children.

Defibrillation in children

Defibrillation is the only effective treatment for ventricular fibrillation (VF). Optimal methods for defibrillation in children are derived and extrapolated from adult data. VF occurs as the initial rhythm in 8-20% of pediatric cardiac arrests. This has fostered a new interest in determining the optimal technique for pediatric defibrillation. This review will provide a brief background of the history of defibrillation and a review of the current literature on pediatric defibrillation. The literature search was performed through PubMed, using the MeSH headings of cardiopulmonary resuscitation, defibrillation and electric countershock. The authors’ personal bibliographic files were also searched. Only published articles were chosen. The recommended energy dose has been 2 J/kg for 30 years, but recent reports may indicate that higher dosages may be more effective and safe. In 2005, the European Resuscitation Council recommended 4 J/kg as the initial dose, without escalation for subsequent shocks. Automated external defibrillators are increasingly used for pediatric cardiac arrest, and available reports indicate high success rates. Additional research on pediatric defibrillation is critical in order to be able to provide an equivalent standard of care for children in cardiac arrest and improve outcomes.

Cardiac pacemaker battery discharge after external electrical cardioversion for broad QRS Complex Tachycardia

External electrical cardioversion or defibrillation may be necessary in patients with implanted cardiac pacemaker (PM) or implantable cardioverter defibrillator (ICD). Sudden discharge of high electrical energy employed in direct current (DC) transthoracic countershock may damage the PM/ICD system resulting in a series of possible device malfunctions. For this reason, when defibrillation or cardioversion must be attempted in a patient with a PM or ICD, some precautions should be taken, particularly in PM dependent patients, in order to prevent damage to the device. We report the case of a 76-year-old woman with a dual chamber PM implanted in the right subclavicular region, who received two consecutive transthoracic DC shocks to treat haemodynamically unstable broad QRS complex tachycardia after cardiac surgery performed with a standard sternotomic approach. Because of the sternal wound and thoracic drainage tubes together with the severe clinical compromise, the anterior paddle was positioned near the pulse generator. At the following PM test, a complete battery discharge was detected.