No conflicts of interest or financial ties to disclose

False Positive ST Elevation in Patients Undergoing Direct Percutaneous Coronary Intervention David M. Larson MD, Katie M. Menssen, BS, Randall K Johnson MD, Scott W Sharkey MD, Nicholas Burke MD, James Harris MD, Robert Schwartz MD, Jay H Traverse MD, Barbara T Unger RN, Timothy D. Henry MD, Ridgeview Medical Center, Waconia, Minnesota and Minneapolis Heart Institute Foundation, Minneapolis, Minnesota

Introduction Previous data shows that up to 11% of STEMI patients treated with thrombolysis did not have a Myocardial Infarction (MI) ACC/AHA guidelines recommend that the Emergency physician make the decision regarding reperfusion therapy for STEMI There is limited data reporting the rate of “false positive” ECGs in STEMI patients treated with Percutaneous Coronary Intervention.

Objective 1)To determine the incidence and etiologies of “false positive” ECGs, defined as: no culprit coronary vessel and negative cardiac markers (no MI), from a non-selected cohort of STEMI patients. 2)To determine the incidence of “true false positive” ECGs defined as no culprit, no significant coronary disease and negative cardiac markers.

Methods Minneapolis Heart Institute/Abbott Northwestern Hospital (ANW) – a tertiary cardiac center with referral relationships with 30 community hospitals (CH) in Minnesota and Wisconsin – instituted the “MHI Level 1 MI Program” in 2003.

Methods Level 1 MI Protocol: Includes STEMI (ST elevation or new Left Bundle Branch Block) with symptom < 24hrs. Diagnosis and decision to activate the cath lab is made by the Emergency Physician at the presenting hospital. Transferred patients go directly to cath lab for Primary or Facilitated PCI Data obtained from a prospective registry of all “Level 1 MI” patients that includes clinical, laboratory, ECG, angiographic and follow up data.

Results From 3/03 to 6/06, 1121 STEMI patients enrolled in Level 1 MI program including 861 transferred from 28 rural or community hospitals. 13.6% of STEMI patients undergoing angiography did not have a clear culprit (fig 1) however, 27% of these had positive cardiac markers (Tables 1 and 2) and 35% had moderate to severe coronary disease.

STEMI Diagnosis N=1,121 Angiography N=1,114 5 died prior to angio 2 no angiogram Surgery N=37 (3.3%) Medical Management N=26 (2.3%) PCI N=899 (80.7%) No Angiographic Culprit N=152 (13.6%) Figure 1

No Culprit and Negative Cardiac Biomarkers (n=111) Nonspecific ECG30 (27%)Vasospasm3 (2.7%) Pericarditis20 (18%)Pacemaker2 (1.8%) Benign early repolarization/norm al variant 16 (14.8%)Cholecystitis2 (1.8%) Left Bundle Branch Block 12 (10.8%)Myocarditis1 (0.9%) Prior MI8 (7.2%)Aortic dissection1 (0.9%) Left Ventricular Hypertrophy 8 (7.2%)Atrial fib with rate related ST Elevation 1 (0.9%) Right Bundle Branch Block 6 (5.4%)Intraventricular Conduction Delay 1 (0.9%) Table 1

No Culprit and Positive Cardiac Biomarkers (n=41) Myocarditis14 (31.8%) Stress Cardiomyopathy9 (21.9%) NonSTEMI8 (19.5%) STEMI (embolic or spasm)6 (14.6%) Pulmonary embolus2 (4.8%) Post Cardiac Arrest1 (2.4%) Acute Mitral insufficiency1 (2.4%) Table 2

Results 11.2% had negative cardiac makers (no MI) 9.9% had no culprit and negative cardiac markers (no culprit + no MI) 6.4% had no culprit, normal Coronary arteries and negative cardiac markers (no culprit + normal CA + no MI) One year morality with a culprit was 7.4% vs 3.9% in those without (p=0.45) The rate of no culprit + no MI varied by Emergency department annual volume (Fig 2)

No culprit/Neg biomarkers by Hospital ED Volume ED visits/year Cochran-Armitage Trend Test p=0.01 Figure 2

Conclusions The incidence of “false positive” ECGs in STEMI patients treated with Primary PCI is similar to previous data in patients treated with thrombolytic therapy. Patients presenting with “False Positive” ST elevation are a heterogeneous group, many with other serious cardiac conditions.

Conclusions Emergency physicians from a variety of community and rural hospitals can make appropriate diagnostic decisions and activate the cath lab without excessive false positive diagnosis of STEMI, although there appears to be a relation to ED volume.