Pre-hospital body surface potential mapping improves early diagnosis of acute coronary artery occlusion in patients with ventricular fibrillation and cardiac arrest

Aims: To determine whether 80-lead body surface potential mapping (BSPM) improves detection of acute coronary artery occlusion in patients presenting with out-of-hospital cardiac arrest (OHCA) due to ventricular fibrillation (VF) and who survived to reach hospital. Methods and results: Of 645 consecutive patients with OHCA who were attended by the mobile coronary care unit, VF was the initial rhythm in 168 patients. Eighty patients survived initial resuscitation, 59 of these having had BSPM and 12-lead ECG post-return of spontaneous circulation (ROSC) and in 35 patients (age 69±13 yrs; 60% male) coronary angiography performed within 24. h post-ROSC. Of these, 26 (74%) patients had an acutely occluded coronary artery (TIMI flow grade [TFG] 0/1) at angiography. Twelve-lead ECG criteria showed ST-segment elevation (STE) myocardial infarction (STEMI) using Minnesota 9-2 criteria - sensitivity 19%, specificity 100%; ST-segment depression (STD) =0.05. mV in =2 contiguous leads - sensitivity 23%, specificity 89%; and, combination of STEMI or STD criteria - sensitivity 46%, specificity 100%. BSPM STE occurred in 23 (66%) patients. For the diagnosis of TFG 0/1 in a main coronary artery, BSPM STE had sensitivity 88% and specificity 100% (c-statistic 0.94), with STE occurring most commonly in either the posterior, right ventricular or high right anterior territories. Conclusion: Among OHCA patients presenting with VF and who survived resuscitation to reach hospital, post-resuscitation BSPM STE identifies acute coronary occlusion with sensitivity 88% and specificity 100% (c-statistic 0.94). © 2012 Elsevier Ireland Ltd

The effects of electrode misplacement on clinicians’ interpretation of the standard 12-lead electrocardiogram

IntroductionThis study investigates how a particular incorrect electrode configuration affects the 12-lead Electrocardiogram (ECG).MethodsA correct and an incorrect 12-lead ECG were extracted from a 192-lead BSPM. This was done for 232 BSPMs yielding 464 12-lead ECGs. The particular incorrect ECG involved displacing electrodes V1 and V2 in the second intercostal space whilst also offsetting the remaining electrodes. These ECGs were examined in two stages: (a) analysis of the effects of electrode misplacement on signal morphology and (b) analysis of how often the incorrect electrode configuration changed the diagnosis of two clinicians in a random sample of 75 patients.ResultsAccording to the Root Mean Square Error (RMSE) of the difference between PQRST intervals in the correct and incorrect ECGs, lead V2 is the most affected lead (mean: 185 μV ± 82 μV), followed by lead V4 (mean: 114 μV ± 59 μV) and lead V1 (mean: 100 μV ± 47 μV). It was found that if the incorrect electrode configuration is applied, there is a 17% to a 24% chance the diagnostic interpretation will be different. Quantified using Similarity Coefficient (SC) leads V1 and V2 were found to be more alike when misplaced in the second intercostal space. The average SC between these leads when correctly placed was 0.08 (± 0.65), however when incorrectly placed, the average SC was 0.43 (± 0.3).ConclusionThere is a reasonable chance this particular incorrect electrode configuration will change the diagnosis of the 12-lead ECG. This highlights the importance of developing algorithms to detect electrode misplacement along with better education regarding ECG acquisition

Assessing perception of new methods that represent ST deviation

The ST Map is a new method to assess acute myocardial infarction (AMI). Although variations of the ST Map do exist, Philips Healthcare has been the first to integrate its approach into clinical practice. This study assessed student perception of the Philips ST Map when seen for the first time