Johann-Jakob Schmid

Bench study of the accuracy of a commercial AED arrhythmia analysis algorithm in the presence of electromagnetic interferences.

This paper presents a bench study on a commercial automated external defibrillator (AED). The objective was to evaluate the performance of the defibrillation advisory system and its robustness against electromagnetic interferences (EMI) with central frequencies of 16.7, 50 and 60 Hz. The shock advisory system uses two 50 and 60 Hz band-pass filters, an adaptive filter to identify and suppress 16.7 Hz interference, and a software technique for arrhythmia analysis based on morphology and frequency ECG parameters. The testing process includes noise-free ECG strips from the internationally recognized MIT-VFDB ECG database that were superimposed with simulated EMI artifacts and supplied to the shock advisory system embedded in a real AED. Measurements under special consideration of the allowed variation of EMI frequency (15.7-17.4, 47-52, 58-62 Hz) and amplitude (1 and 8 mV) were performed to optimize external validity. The accuracy was reported using the American Heart Association (AHA) recommendations for arrhythmia analysis performance. In the case of artifact-free signals, the AHA performance goals were exceeded for both sensitivity and specificity: 99% for ventricular fibrillation (VF), 98% for rapid ventricular tachycardia (VT), 90% for slow VT, 100% for normal sinus rhythm, 100% for asystole and 99% for other non-shockable rhythms. In the presence of EMI, the specificity for some non-shockable rhythms (NSR, N) may be affected in some specific cases of a low signal-to-noise ratio and extreme frequencies, leading to a drop in the specificity with no more than 7% point. The specificity for asystole and the sensitivity for VF and rapid VT in the presence of any kind of 16.7, 50 or 60 Hz EMI simulated artifact were shown to reach the equivalence of sensitivity required for non-noisy signals. In conclusion, we proved that the shock advisory system working in a real AED operates accurately according to the AHA recommendations without artifacts and in the presence of EMI. The results may be affected for specificity in the case of a low signal-to-noise ratio or in some extreme frequency setting.

Correlation relationship assessment between left ventricular hypertrophy voltage criteria and body mass index in 41,806 Swiss conscripts.

Introduction: Electrocardiographic criteria for left ventricular hypertrophy (LVH) have been limited by low sensitivity at acceptable levels of specificity. A number of studies have demonstrated that body mass index (BMI) is associated with decreased sensitivity of ECG LVH classification in hypertensive patients. The objective of this study is to investigate the correlation relationship between LVH voltage criteria and BMI in Swiss conscripts.

New Methods to Induce Localized Brain and General Hypothermia

Sudden Cardiac Death is a major concern in industrialized countries. In France, it is the cause of death of 40–60,000 cases per year. Despite efforts made over decades to promote cardiac resuscitation science, education, and the arrival of automatic external defibrillators, less than 50 % of cardiac arrest victims are likely to reach recovery of stable circulation and this percentage decreases even for patients who suffer a severe rhythm disorder that cannnot be defibrillated or patients living in rural areas. The vast majority of patients leaving alive from the hospital after outdoor cardiac arrest bear irreversible brain damage. However, the authors are convinced of the possibility of improving this situation through a better understanding of sudden death by screening high-risk individuals and a better organization of care through cooperation skills of the first responders. One of the most promising methods involves therapeutic hypothermia. This chapter will review the main historical steps and will propose a new method of brain protection by localized hypothermia produced by adiabatic carbon dioxide expansion, now under development on animal models and the first fortuitous clinical case.

Updates to IEC/AAMI ECG standards, a new hybrid standard

The current set of IEC particular standards that pertain to electrocardiograph (ECG) devices, namely, 60601-2-25, 60601-2-27, and 60601-2-47, which define requirements and testing for the essential performance and basic safety of diagnostic ECG, ECG monitoring and ambulatory ECG systems, respectively. These standards have been harmonized with the corresponding AAMI standards, namely EC11, EC13 and EC38. Together these standards have been in existence for decades and have evolved separately even though the technology used in these three clinical applications is very similar. A work proposal was initiated in the ISO/IEC Joint Work Group 22 (JWG22), which over sees the revision of these standards, to update the standards by creating a single new hybrid standard. The goal of this work is a joint endeavor between ISO and IEC to combine the three separate particular standards that cover ECG device and to harmonize the similar requirements that are common across all three types of devices into one set of general requirements. The requirements that separate specific to meeting the intended use and essential performance for each of the 3 types of devices (diagnostic, patient monitoring, and ambulatory ECG recording) will continue to remain as separate requirements. Furthermore, manufactures of ECG devices have also been required to meet standards for disposable electrodes (AAMI EC12), ECG cables and leadwires (AAMI EC53), and arrhythmia analysis performance reporting (AAMI EC57). In addition to the primary goal, a secondary goal for the JW22 work is to also incorporate these three AAMI standards into the ECG hybrid standard. This paper describes the work being done and highlights key updates, and explains the rationale for approaches and changes being made. The Joint Work Group is currently in the process of updating the committee draft of the new hybrid standard before requesting comments from National Standard Committees participating in JWG22.