David R. Hampton

Effect on Treatment Delay of Prehospital Teletransmission of 12-Lead Electrocardiogram to a Cardiologist for Immediate Triage and Direct Referral of Patients With ST-Segment Elevation Acute Myocardial Infarction to Primary Percutaneous Coronary Intervention

Prehospital electrocardiogram (ECG) transmission to hospitals was shown to reduce time to treatment in patients with acute myocardial infarction. However, new technologies allow transmission directly to a mobile unit so an attending physician can respond irrespective of presence within or outside the hospital. The primary study purpose was to determine whether delays could be decreased in an urban area by transmitting a prehospital 12-lead ECG directly to the attending cardiologists mobile telephone for rapid triage and transport to a primary percutaneous coronary intervention (PCI) center, bypassing local hospitals and emergency departments. A secondary purpose was to describe whether transport would be safe despite longer transport times. During a 2-year period, patients with acute nontraumatic chest pain had their prehospital ECG transmitted directly to a cardiologists mobile telephone. Time to treatment was compared with historic controls. After ECG evaluation, 168 patients (30%) were referred directly for PCI, and 146 of these (87%) underwent emergent catheterization. In referred patients, median time from 911 call to PCI was significantly shorter than in the control group (74 vs 127 minutes; p <0.001). Accordingly, door-to-PCI time was 63 minutes shorter for referred patients versus controls (34 vs 97 minutes; p <0.001). During transport, 7 patients (4%) experienced ventricular fibrillation; 3 patients (2%), ventricular tachycardia; and 1 patient (0.5%), pulseless electrical activity, including 2 deaths (1%) caused by treatment-resistant arrhythmia. In conclusion, transmission of a prehospital 12-lead ECG directly to the attending cardiologists mobile telephone decreased door-to-PCI time by >1 hour when patients were transported directly to PCI centers, bypassing local hospitals. Ambulance transport seems safe despite longer transport times.

Improving sensing and detection performance in subcutaneous monitors

Implantable loop recorders (ILRs) are used for continuous assessment of patients at risk for syncope and arrhythmia. Device accuracy depends on appropriate sensing of the patients electrocardiogram (ECG) signal. However, current methods for sensing cardiac electrical activity rely on simple threshold detectors that are computationally efficient but nonspecific. We test the hypothesis that better ILR implant positions will increase detection accuracy. Ten healthy subjects were studied as they assumed 12 different postures. Body surface potential map (BSM) recordings were used to estimate bipolar R-wave amplitudes for 64 potential implant sites at 360 orientations per site. Optimal sites were identified as the combination of position and orientation that consistently gave the largest signal and the lowest variability during posture changes. Results showed that posture impacts the R-wave amplitude in both BSM and derived bipolar ECGs in healthy subjects. Specific postures are associated with significant drops in R-wave signal amplitude that could cause loss of signal detection in ILRs, especially in positions likely to displace the diaphragm. R-wave changes occurred abruptly as posture was changed. Optimal implant locations cluster near the center of the chest, aligned with the cardiac axis, consistent with the steeper isoelectric gradients known to be associated with these positions.

Evaluation of age and sex dependent criteria for ST elevation myocardial infarction

An evaluation of the Glasgow ECG analysis program criteria for acute ST elevation myocardial infarction (STEMI) was undertaken using two Board Certified cardiologists as the reference. Out of a data base of 1220 patients presenting with chest pain, 248 cases of confirmed MI were available for evaluation and 52 control cases were added from the remainder. The age and sex based Glasgow criteria were also assessed against existing ESC/ACC criteria. Irrespective of whichever way the criteria were evaluated, the Glasgow age and sex based criteria proved to have a superior performance compared to the non age and sex based criteria. The overall sensitivity of the Glasgow criteria was 89% in a set of 219 patients with an MI, of whom 113 had a cardiologist reported STEMI. Evaluation of specificity in this population is not meaningful. The corresponding ESC/ACC criteria evaluated by computer were 75% sensitive.

Effect of age and gender on diagnostic accuracy of ECG diagnosis of acute myocardial infarction

Recently published ACUESC criteria for acute MI were nor age and gender dependent. The aim of this study was to modifv the criteria by incorporating age and gender based limits of ST amplitude, together with other ST-T measures, and to assess the effect on sensitiviry erc. A database of 789 ECGs from patients presenting with acute chest pain was used to develop criteria along with 1498 ECGs from normal individuals whose ECGs were used to control specijkity. A third database of 1220 ECGs was also available as a test set. The sensitivity of the new criteria increased from 41.5% to 46.8% while specificity improved from 96% to 98.5%. Similar improvements were seen for males and females. With respect to age, specificity improved in all deciles. Sensitivity decreased slightly in the middle deciles but improved dramatically for the remainder. Age and gender based criteria markedly improved sensitivity and specificity of ECG criteria fur acute MI.

Steps required to inclusion in commercial ECG analysis systems — the new ECG indices for quantitating extent, acuteness and severity of acute myocardial ischemia for facilitating emergency triage decisions

Clinically useful diagnostic methods for chest pain triage often fail to reach everyday practice where they can improve patient outcomes. One means to bridge the gap is through adoption of ECG interpretive algorithms with enhanced accuracy or expanded features into established commercial products. The transition from innovation to industry can be facilitated if researchers consider three factors aiding a successful handoff to companies. First, they should assess their algorithm to assure that it meets a real market need and can be easily assimilated by commercial partners. Second, their design documentation and databases should support the regulated development processes required of manufacturers. Finally, they should hold appropriate expectations for the structure of commercial partnerships that lead to release of a marketed product.