January 11, 2016

Background: Left Bundle Branch Block (LBBB) on the ECG makes accurate recognition of ST-Elevation Myocardial Infarction (STEMI) rather difficult. The 1996 and 2004 American College of Cardiology/American Heart Association (ACC/AHA) STEMI guidelines recommended immediate reperfusion therapy for patients with potentially ischemic symptoms and new, or presumed new, LBBB. In 2013, this recommendation was removed from the guidelines. Historically, reperfusion decisions in LBBB have been determined by the original Sgarbossa criteria published in 1996, but there are three key limitations to the original study by Sgarbossa et al:
  1. The original Sgarbossa criteria (i.e. the “weighted” Sgarbossa criteria) depends on a point system that rely on 3 findings, only 2 of which would provide enough points (i.e. 3) to make the diagnosis of AMI. Using the Sgarbossa criteria without the point system (i.e. the “unweighted” Sgarbossa criteria) increases sensitivity but decreases specificity.
  2. Sgarbossa et al diagnosed AMI by creatine kinase MB (CK-MB) elevations instead of angiographic evidence of acute coronary occlusion (ACO), which limits the sensitivity of the rule because it combines NSTEMI and STEMI patients in the outcome definition
  3. Finally, Sgarbossa et al used an absolute criterion (5mm) rather than a proportional criterion for excessively discordant ST elevation lowering the sensitivity of the criteria.
The modified Sgarbossa criteria replaces the absolute 5mm discordant ST elevation with a proportion (ST elevation/S-wave amplitude ≤ -0.25). In other words, the modified Sgarbossa criteria only changes the last of the original Sgarbossa criteria with the first two criteria staying intact. Now, if any of these criteria are met, the cardiac catheterization lab should be activated. We have written on REBEL EM before about the modified Sgarbossa criteria and one of our conclusions was this rule looked very promising, but needed an external validation study. Well that study is now here and for full disclosure I am one of the authors on the paper.

January 7, 2016

Background: The traditional standard workup for ruling out subarachnoid hemorrhage (SAH) has been a non-contrast head CT and, if negative, a lumbar puncture. The thought behind this is that the sensitivity of head CT to rule out SAH is not 100% and declines over time and missing a SAH is potentially devastating. There has been a series of studies published in the past few years looking at the value of a negative head CT scan performed within 6 hours of headache onset in ruling out SAH. I have heard many say that if they have a negative Head CT at 6 hours or less in a neurologically intact patient they would not perform a lumbar puncture.

December 10, 2015

Welcome to the December 2015 REBELCast, where Swami, Matt, and I are going to tackle a couple of topics in the world of Cardiology and Critical Care. First of all, we all know that the optimal treatment for STEMI is getting the patient to the cardiac catheterization lab, and time is muscle, but does it help to get patients to the catheterization lab even faster than 90 minutes? Or does speeding up the time have bad outcomes? Secondly, it has been drilled into our heads that high-quality CPR with minimal to no interruptions is key in OHCA.  This gives our patients the best chance of neurologically intact survival.  But a new study just published might beg to differ. So with that introduction today we are going to specifically tackle:

Topic #1: Reducing Door to Balloon (D2B) Times to <90 Minutes in STEMI Topic #2: Continuous vs Interrupted CPR in OHCA

November 30, 2015

Background: As emergency providers we must be smarter than our ECG machines. Many times subtle findings on ECGs are not read by the machine, but we must be the experts at making the distinction between findings that require emergent treatment versus more benign etiologies. One specific set of diagnoses that can be very difficult to distinguish from each other is inferior STEMI vs Pericarditis. ECG experts discuss strategies such as looking at morphology of ST-segments (i.e. concavity or convexity), but this is not always accurate. Another, frustrating fact is that ST-elevation in the inferior leads (II, III, aVF) is typically seen with inferior STEMI and pericarditis. We therefore need a finding that has both a high sensitivity and specificity for MI.

November 23, 2015

Background: We have already discussed the value of a good history in assessing patients with chest pain on REBEL EM. What is known about chest pain is that it is a common complaint presenting to EDs all over the world, but only a small percentage of these patients will be ultimately diagnosed with Acute Coronary Syndrome (ACS). This complaint leads to prolonged ED length of stays, provocative testing, potentially invasive testing, and stress for the patient and the physician. For simplicity sake, we will say that, looking at the ECG can make the diagnosis of STEMI. What becomes more difficult is making a distinction between non-ST-Elevation ACS (NSTEMI/UA) vs non-cardiac chest pain. ED physicians have different levels of tolerance for missing ACS with many surveys showing that a miss rate of <1% is the acceptable miss rate, but some have an even lower threshold, as low as a 0% miss rate. Over testing however, can lead to false positives, which can lead to increased harms for patients. In November 2015, a new systematic review was published reviewing what factors could help accurately estimate the probability of ACS.
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