An initial exploration of subtraction electrocardiography to detect myocardial ischemia in the prehospital setting.

BACKGROUND: In the prehospital triage of patients presenting with symptoms suggestive of acute myocardial ischemia, reliable myocardial ischemia detection in the electrocardiogram (ECG) is pivotal. Due to large interindividual variability and overlap between ischemic and nonischemic ECG-patterns, incorporation of a previous elective (reference) ECG may improve accuracy. The aim of the current study was to explore the potential value of serial ECG analysis using subtraction electrocardiography. METHODS: SUBTRACT is a multicenter retrospective observational study, including patients who were prehospitally evaluated for acute myocardial ischemia. For each patient, an elective previously recorded reference ECG was subtracted from the ambulance ECG. Patients were classified as myocardial ischemia cases or controls, based on the in-hospital diagnosis. The diagnostic performance of subtraction electrocardiography was tested using logistic regression of 28 variables describing the differences between the reference and ambulance ECGs. The Uni-G ECG Analysis Program was used for state-of-the-art single-ECG interpretation of the ambulance ECG. RESULTS: In 1,229 patients, the mean area-under-the-curve of subtraction electrocardiography was 0.80 (95%CI: 0.77-0.82). The performance of our new method was comparable to single-ECG analysis using the Uni-G algorithm: sensitivities were 66% versus 67% (p-value > .05), respectively; specificities were 80% versus 81% (p-value > .05), respectively. CONCLUSIONS: In our initial exploration, the diagnostic performance of subtraction electrocardiography for the detection of acute myocardial ischemia proved equal to that of state-of-the-art automated single-ECG analysis by the Uni-G algorithm. Possibly, refinement of both algorithms, or even integration of the two, could surpass current electrocardiographic myocardial ischemia detection.

The impact of post-resuscitation feedback for paramedics on the quality of cardiopulmonary resuscitation.

PURPOSE: The Guidelines place emphasis on high-quality cardiopulmonary resuscitation (CPR). This study aims to measure the impact of post-resuscitation feedback on the quality of CPR as performed by ambulance personnel. MATERIALS AND METHODS: Two ambulances are dispatched for suspected cardiac arrest. The crew (driver and paramedic) of the first arriving ambulance is responsible for the quality of CPR. The crew of the second ambulance establishes an intravenous access and supports the first crew. All resuscitation attempts led by the ambulance crew of the study region were reviewed by two research paramedics and structured feedback was given based on defibrillator recording with impedance signal. A 12-months period before introduction of post-resuscitation feedback was compared with a 19-months period after introduction of feedback, excluding a six months run-in interval. Quality parameters were chest compression fraction (CCF), chest compression rate, longest peri-shock pause and longest non-shock pause. RESULTS: In the pre-feedback period 55 cases were analyzed and 69 cases in the feedback period. Median CCF improved significantly in the feedback period (79% vs 86%, p<0.001). The mean chest compression rate was within the recommended range of 100-120/min in 87% of the cases in the pre-feedback period and in 90% of the cases in the feedback period (p=0.65). The duration of longest non-shock pause decreased significantly (40s vs 19s, p<0.001), the duration of the longest peri-shock pause did not change significantly (16s vs 13s, p=0.27). CONCLUSION: Post-resuscitation feedback improves the quality of resuscitation, significantly increasing CCF and decreasing the duration of longest non-shock pauses.