117 Rate of Inappropriate Catheterization Laboratory Activation Using An Automated System of Pre-Hospital STEMI Diagnosis

Abstract

Door-to-balloon times (DtB) for ST elevation myocardial infarction (STEMI) frequently exceed the recommended delay of less than 90 minutes. Automated STEMI diagnosis at first medical contact and pre-hospital cardiac catheterization laboratory (CCL) activation have been suggested as a viable options for significantly reducing DtB, but there is little data regarding the rate of inappropriate CCL activation in such a system. ECG's were performed by first-responders in the field for all patients with a complaint of chest pain or dyspnea. An electrographic diagnosis of STEMI (Zoll Medical Corporation) resulted automatically in CCL activation and direct transfer without physician interpretation of the ECG. Patient data were collected for all pre-hospital CCL activation between January 2010 and January 2012. Inappropriate activation was defined as any activation resulting from a non-diagnostic ECG (No ST-elevation, judged independently by 2 cardiologist reviewers). Identified inappropriate activations were then analyzed for the reasons for erroneous CCL activation. Human error was defined as an improper application of the referral algorithm by the ambulance technician. Machine error was defined as an incorrect automated diagnosis of STEMI for a tracing of adequate quality. We identified 155 patients with sufficiently complete data for analysis, of whom, 136 (88%) presented ST-elevation on the ECG. The remaining 19 activations (12%) were considered inappropriate. Compared to appropriate activations, these 19 patients had a significantly higher rate of hypertension (84% vs. 52%, p= 0.0026), known CAD (47% vs. 13%, p=0.0001), and prior CABG (16% vs. 4%, p= 0.047). Human error was implicated in 9 cases (47.3%), including acting on poor quality tracings in two thirds. Machine error occurred in 10 cases (53%), of which half were due to supraventricular tachyarrhythmia >140bpm. Pre-hospital automated STEMI diagnosis resulted in an acceptable rate of inappropriate CCL activation. Moreover, the present analysis suggests that simple modifications of the CCL activation algorithm, such as excluding patients with tachycardia >140 bpm, and first-responder education initiatives, such as ensuring proper quality tracings prior to CCL activation, may further reduce rates of inappropriate activation.