The diagnostic accuracy of a shock advisory algorithm in automated external defibrillators in the presence of real-world artifacts.

BACKGROUND: The current standards for shock advisory algorithms in AEDs require performance testing on artifact-free ECGs. However, AED analysis in the real world is more challenging due to potential artifacts from various sources (e.g., patient handling, and electromagnetic interference). This retrospective data analysis reports the real-world performance and behavior of a shock advisory algorithm used in three AED models with the presence of artifacts. METHODS: ECG rhythm analyses recorded during the use of three AED models (HS1, FRx and FR3) were reviewed. The shock recommendations made in the AEDs were compared to the expert annotations of reviewers. The effects of real-world artifacts and the handling by the algorithm were analyzed. RESULTS: Among the 3,941 analyses, 619 were annotated as shockable rhythms, and 2,912 were non-shockable. The overall sensitivity and specificity were 97.1% (601/619), and 99.9% (2,908/2,912), respectively. Artifacts were detected by the algorithm in 23.3% (918/3,941) of the analysis periods. The algorithm performance for the analysis periods with artifacts detected was 95.2% (80/84) for sensitivity and 100.0% (687/687) for specificity. In the remaining analysis periods with no artifacts detected, the sensitivity was 97.4% (521/535), and specificity was 99.8% (2,221/2,225). CONCLUSIONS: The performance of this shock advisory algorithm during real-world resuscitations with or without artifacts, exceeded AHA recommendations and the requirements in international standards. The high sensitivity and specificity demonstrate the effectiveness and safety of this algorithm in all three AED models.

A user-friendly integrated monitor-adhesive patch for long-term ambulatory electrocardiogram monitoring.

BACKGROUND: Compliance to long-term ambulatory electrocardiogram monitoring is important for diagnosis in patients with cardiac arrhythmia. This requires a system with a minimal impact on daily activities. OBJECTIVE: The aim of this study was to investigate if a lightweight integrated adhesive monitor for long-term use without unacceptable adverse effects is feasible. METHODS: The participants wore either a prototype lightweight monitor or a control system for a total of up to 30 days, changing patches once (investigational device) or twice (control) weekly. Comfort, skin irritation, and impact on quality of life were recorded. RESULTS: The new monitor can be worn by most participants for periods of at least 6 days. Skin irritation and comfort rating were comparable, and impact on the quality of life was low compared with the control. Patients considered the device comfortable. CONCLUSION: An integrated adhesive monitor that can be worn on the skin up to 7 days with minimal side effects is feasible.

Detection of ventricular ectopy by a novel miniature electrocardiogram recorder.

BACKGROUND: The ability of a miniaturized, skin-attached, 3-channel electrocardiogram (ECG) recorder prototype to detect ventricular ectopic beats (VEBs) and ventricular fibrillation (VF) was compared with that of standard Holter ECG. METHODS: Concurrent 15-hour ECG recordings were made in 143 patients using an experimental device provided by Philips Healthcare (Seattle, WA) and a commercially available Holter recorder. In a consensus review process, 3 physicians (M.L., A.J., and A.G.), blinded for the recording device, analyzed 1804 seven-second strips for total number of VEBs, total number of their QRS configurations, and presence of VF. Agreement between the experimental and standard devices was calculated using Spearman correlation coefficients. RESULTS: There was 100% agreement regarding VF recognition. Spearman correlation coefficients were 0.98 (P < .001) for the total number of VEBs and 0.91 (P < .001) for the total number of QRS configurations. CONCLUSIONS: The accuracy of the experimental miniaturized ECG recorder for detecting ventricular activity was found to be high. This finding could be of clinical importance.

Quality of ECG monitoring with a miniature ECG recorder.

BACKGROUND: Long-term monitoring of patients at risk of arrhythmias would benefit from a miniaturized device. This study evaluated the quality of electrocardiogram (ECG) signals recorded by a miniaturized ECG recorder. METHODS: ECG data were concurrently recorded with an investigational device (Philips Medical Systems, Seattle, WA, USA) and a Holter recorder from patients with cardiac-related symptoms at the emergency department of a tertiary care university hospital. The device was attached in one of four locations (L1: below left clavicle, L2: midsternal, L3: below left breast, L4: left anterior axillary line in 5th intercostal space). Selected ECG strips were analyzed for atrial activity, QRS width, and basic rhythm by two physicians. Patients were divided into groups based on their number of strips (A 2-5, B 6-9, C 10-21) for descriptive presentation of the data. For statistical analyses, nonlinear mixed-effects models were used. RESULTS: In 90 patients, 574 pairs of strips were analyzed. In L1 (n = 37), agreement between the device and the Holter recorder on presence of P wave was 58-80% in groups A-C and in L2 (n = 28):94-98%, L3 (n = 12):30-72%, and L4 (n = 13):0-70%; on PR interval in L1:58-80%, L2:94-98%, L3:30-62%, and L4:0-70%; on rhythm in L1:56-79%, L2:94-98%, L3:30-62%, and L4:0-70%; on QRS width in L1:86-100%, L2:88-98%, L3:100%, and L4:96-100%. The agreement of L2 in the parameters P wave, PR interval, and rhythm diagnosis was better than in the other locations (P < 0.01). CONCLUSIONS: A miniature ECG monitor provided accurate assessment of atrial beats and rhythm diagnosis at a midsternal location and of QRS width at all locations.

Early experience with a novel ambulatory monitor.

Ambulatory electrocardiographic (ECG) monitoring has addressed a wide variety of clinical needs with a wide variety of technical solutions, all with significant shortcomings and limitations. Common technical issues include patient discomfort and susceptibility to motion artifact related to lead wires, and limited data capacity leading to dependence on patient activation for selection of pertinent ECG rhythms for storage. We have been developing a novel ambulatory ECG monitor that addresses several of these issues. Small size and absence of lead wires improve patient comfort and reduce motion artifact but require novel, short ECG vectors. An integral motion sensor assists interpretation of remnant motion artifact. Large storage capacity permits recording of all ECG signals for a day at a time. Simple human factors design permit easy daily replacement of monitors for extended recording. Highly sensitive amplifiers and low artifact provide good-quality signal images, but the short vectors and close proximity to the heart, particularly the atria, result in ECG morphologies that appear different from more familiar recording technologies. We present some examples to illustrate the issues and generate productive discussion.

Amplitude spectrum area: measuring the probability of successful defibrillation as applied to human data.

OBJECTIVE: The objective of our study was to examine the effectiveness of an electrocardiographic predictor, amplitude spectral area (AMSA), for the optimal timing of defibrillation shocks in human victims of cardiac arrest. Based on the spectral characteristics of ventricular fibrillation potentials, we examined the probability of successful conversion to an organized viable rhythm, including the return of spontaneous circulation. The incentive was to predict the likelihood of successful defibrillation and thereby improve outcomes by minimizing interruptions in chest compression and minimizing electrically induced myocardial injury due to repetitive high-current shocks. DESIGN: Observational study on human electrocardiographic recordings during cardiopulmonary resuscitation. SETTING: Medical research laboratory of a university-affiliated research and educational institute. PATIENTS: Victims of out-of-hospital cardiac arrest. INTERVENTIONS: Iteration of electrocardiographic records, representing lead 2 equivalent recordings on 108 defibrillation attempts with an automated external defibrillator, of 46 victims of cardiac arrest due to ventricular fibrillation. MEASUREMENTS AND MAIN RESULTS: Three seconds of ventricular fibrillation, recorded immediately preceding delivery of a shock, were analyzed utilizing the AMSA algorithm. AMSA represents a numerical value based on the sum of the magnitude of the weighted frequency spectrum between 3 and 48 Hz. The greater the AMSA value, the greater was the probability of reversal of ventricular fibrillation. At an AMSA value of >13.0 mV-Hz, successful defibrillation yielded a sensitivity of .91 and a specificity of .94. CONCLUSION: AMSA predicts the success of electrical defibrillation with high specificity. AMSA therefore serves to minimize interruptions of precordial compression and the myocardial damage caused by delivery of repetitive and ineffective electrical shocks.