BACKGROUND
The management of STEMI has evolved over the past 30 years and the importance of timely reperfusion in STEMI by pharmacological or catheter-based measures has been well substantiated.5.9,10 Reperfusion of an occluded coronary artery remains a significant contributor to positive patient outcomes.4,5,8,11 D2B time is a recommended core quality measure for the Joint Commission on Accreditation of Health Care Organizations and the Centers for Medicare and Medicaid Services.12 Achieving an overall D2B time ≤90 minutes in Primary PCI centers is an important time target in acute STEMI care.3,13 The recommended minimal adherence score to a D2B ≤90 minutes is 75% of STEMI patients in the US.3,14There is evidence that D2B times are improving over time. An analysis of all STEMI patients demonstrated that D2B times < 90 minutes increased from 44.2% to 91.4% over a period from December 31, 2005 to September 30, 2010.15 Short D2B time is important because a delay in treatment for STEMI increases the likelihood and amount of cardiac muscle damage due to localized hypoxia.5
An ECG is the initial diagnostic indicator of STEMI.4,5 Delay in obtaining an ECG adversely influences D2B time and has commanded extensive investigation in the past. An important time target in acute STEMI management is to obtain an ECG in ≤10 minutes from time of admission.3-5,13 An integrated approach that includes chief-complaint-based ECG processes initiated by a triage nurse could improve the target rate of door-to-ECG time of < 10 minutes for potential STEMI patients.16 Both target rate of door-to-ECG < 10 minutes and D2B times< 90 were significantly increased. The integrated ECG approach remained a significant predictor of door-to-ECG time ≤10 minutes beyond the contribution of other covariates.
Current guidelines strongly recommend that all patients with STEMI symptoms seek emergency medical services (EMS) and arrive at the hospital via ambulance.10,17 EMS activation shortens the time to definitive treatment, facilitates obtaining an ECG early, allows for prompt activation of the STEMI team, and significantly improves D2B time.17-19 Prior studies regarding mode of transportation indicate low EMS use by STEMI patients (10-53%), use of private transportation (16% self-driving) and suboptimal improvement in EMS use (14-20%) despite extensive community campaigns to educate the public.19-22 Recent data demonstrated slightly better EMS use (60-62%) for STEMI patients directly presenting to PCI capable hospitals. 10,17 Wireless ECG transmission from the ambulance, and verification of probable STEMI from the ED physician or cardiologist prevents delays that occur in the ED.23 Although CCL pre-activation is recognized as an important factor in treating STEMI patients, it was found to occur in only 41% of patients with STEMI. 24 Mumma and associates found that a prehospital ECG was associated with a 10-minute reduction in first medical contact to balloon time.25Patients who have symptoms of ischemic chest pain and who have pre-hospital ECG changes consistent with STEMI should optimally bypass the ED and be transported directly to the CCL.26,27
Confounders may significantly contribute to a delay in reperfusion. Patient-related confounders are primarily comorbidities or an unstable clinical presentation, including inconclusive ECG findings, family interference, patient refusal, unstable hemodynamics, cardiac arrest and procedural difficulties.6,28 Non-patient-related confounders are generally system-related difficulties such as availability of the CCL, inadequate staff, holidays and after-hours procedures. Weather can impede EMS ability to transport patients to the hospital.7,29