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.

Twelve-lead electrocardiography in the young: physiologic and pathologic abnormalities.

UNLABELLED: BACKGROUND/ OBJECTIVE: The purpose of the present study was to analyze the prevalence of physiologic and pathologic ECG abnormalities in a cohort of young conscripts that represents the whole young generation of today. METHODS: ECGs of all Swiss citizens who underwent conscription for the army during a 29-month period were analyzed manually. RESULTS: ECGs of 43,401 conscripts (mean age 19.2 ± 1.1 years) were analyzed; 158 conscripts were female. Incomplete right bundle branch block was found in 5870 (13.5%) and left anterior fascicular block in 360 (0.83%). First-degree AV block was present in 329 (0.8%) and Mobitz type I (Wenckebach) second-degree AV block in 3 (0.01%). Early repolarization was observed in 1035 (2.4%), T-wave inversion in 39 (0.09%), and minor T-wave changes in 182 (0.42%). Brugada-like abnormalities were observed in 6 (0.01%). None of the conscripts had atrial fibrillation or flutter. CONCLUSION: ECG abnormalities can be found in a relatively large proportion of young individuals. Incomplete right bundle branch block, left fascicular block, and first-degree AV block are the most frequent findings. No conscript presented with atrial fibrillation or flutter.

Prevalence of preexcitation in a young population of male Swiss conscripts.

BACKGROUND: Sudden cardiac death can be the first clinical presentation of asymptomatic ventricular preexcitation. Recent data about prevalence of preexcitation in the electrocardiograms (ECG) of the general population are scarce. OBJECTIVE: The aim of the present study was to analyze the prevalence of preexcitation in a contemporary population of young conscripts. METHODS: We reanalyzed all consecutive ECGs of Swiss citizens who underwent conscription for the army between March 1, 2004, and July 31,2006. All ECGs with the diagnosis preexcitation were included in the present study. RESULTS: We analyzed ECGs of 41,699 male conscripts. Mean age was 19.2 ± 1.1 years. Preexcitation was found in 53 individuals. The length of the delta wave was 46 ± 10 ms. The most frequent localization of the accessory pathway was the left free wall. CONCLUSION: The prevalence of preexcitation in young, predominantly male conscripts is 0.13%. This is comparable with previous findings in children.

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. METHODS: A database of 41,806 young Swiss people, who underwent compulsory conscription for the Swiss Army, was compiled. Along with other medical data, an ECG was taken. Statistical analyses, such as linear regression and calculation of correlation coefficient, were carried out between LVH voltage criteria and BMI. RESULTS: The mean age in the studied population was 19.2 +/- 1.1 years with a median age of 19 years (range from 17 to 38 years). We found an overweight prevalence of 25.1%. The results showed that body habitus had significant association with Sokolow-Lyon voltages. A mean decrease of 13%, 5%, 19%, 14%, and 12% for the five studied Sokolow-Lyon indexes were found between normal range subjects (18.5 < or = BMI < 25) and obese subjects (25< or = BMI). CONCLUSIONS: Our study confirms the hypothesis that people with higher BMI, a growing section of the population, have lower ECG amplitudes. Therefore, the Sokolow-Lyon voltage criteria may underestimate the presence of LVH for subjects with higher BMI, which is not the case for the Cornell voltage. Our analysis suggests that computerized electrocardiography for the diagnosis of left ventricular hypertrophy based on Sokolow-Lyon voltages should incorporate the BMI factor.

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.

Prevalence of long and short QT in a young population of 41,767 predominantly male Swiss conscripts.

BACKGROUND: Abnormally long and short QT intervals are recognized to be associated with an increased risk for life-threatening ventricular arrhythmias. It is therefore important to define the upper and lower border of the normal QT. OBJECTIVE: The aim of this study was to describe the normal distribution of the QT interval in a contemporary population of young conscripts and to define long and short limits of the QT interval. METHODS: In Switzerland, all young male citizens must undergo compulsory conscription for the Swiss Army at the age of 18 to 19 years. In every conscript, an electrocardiogram (ECG) is performed. Retrospectively, 41,767 consecutive ECGs of Swiss citizens who underwent conscription for the army between March 1, 2004, and July 31, 2006, were analyzed. RESULTS: The mean QTc Bazett interval was 394 +/- 22 ms. One percent of the conscripts had a Bazett QTc shorter than 347 ms, and one percent had a Bazett QTc longer than 445 ms, respectively. None of the subjects presented a QTc Bazett < 300 ms; the prevalence of a QTc Bazett < 320 ms was 0.02%. CONCLUSION: The present study shows the distribution of QT intervals in an unselected young population. Because none of the subjects presented a QTc < 300 ms, it may be concluded that the short QT syndrome is a very rare entity in the population of young male adults.

Clinical experience with a low-energy pulsed biphasic waveform in out-of-hospital cardiac arrest.

The efficiency of a pulsed biphasic waveform (PBW) was compared with that of biphasic truncated exponential (BTE) waveforms. First defibrillation shock outcome was studied in a population of 104 out-of-hospital cardiac arrest patients in ventricular fibrillation as the presenting rhythm. The call to first shock time was 8.2+/-5.4 min. At 5s post-shock, defibrillation efficiency was 90%. The arrest was witnessed in only 50% of the patients and only 5% received bystander CPR. Despite these limitations 38% of the patients achieved restoration of a spontaneous circulation at departure from scene and 9.8% were discharged from the hospital. These observations demonstrate a rate of first shock success in termination of ventricular fibrillation comparable to that reported with biphasic truncated exponential waveforms in out-of-hospital cardiac arrest.