Journal Feed Weekly Wrap-Up

We always work hard, but we may not have time to read through a bunch of journals. It’s time to learn smarter. 

Originally published at JournalFeed, a site that provides daily or weekly literature updates. 

Follow Dr. Clay Smith at @spoonfedEM, and sign up for email updates here.

#1: Compass MI – Taking the Guess Work Out of High-Sensitivity Troponin

Spoon Feed
The new tool, Compass MI, allows you to choose high-sensitivity troponin i or t (hsTni or hsTnt), initial cutoff, early/late delta troponin, and calculates the diagnostic performance you can expect.

Why does this matter?
The performance of hsTni and hsTnt is slightly different. Also, the time it is drawn and time interval of serial sampling makes a difference. How should an organization trying to add this test use hsTn? What will the diagnostic accuracy be at various cutoffs?

This was a multicenter study of 22,651 patients presenting to the ED with possible MI who had either hsTni or hsTnt drawn at various times. The diagnostic performance of a risk assessment tool was derived, internally validated, and externally validated. The gist is that the lower the hsTn on arrival and the lower the delta hsTn on serial sampling, the lower the risk of MI or death in the ED or at 30 days. But it depends on the assay, cutoff, and delta timing. And there are almost infinite combinations. To solve this, they made a web calculator that allows you to choose these variables and calculates the diagnostic performance based on your selections. It is a great tool called Compass MI. See it in action here. Here are some screenshots.

Application of High-Sensitivity Troponin in Suspected Myocardial Infarction. N Engl J Med. 2019 Jun 27;380(26):2529-2540. doi: 10.1056/NEJMoa1803377.

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#2: How to Not Miss Posterior Stroke

Spoon Feed
Follow these five steps to help avoid missing a posterior circulation stroke.

Why does this matter?
Posterior circulation strokes are misdiagnosed 30-60% of the time. Patients with delayed diagnosis may do worse due to extension of the stroke, brainstem compression from posterior fossa edema, or recurrent stroke.

Keeping Wallenberg straight makes my head spin
Collateral circulation and vascular anatomic variants make it hard to distinguish a lateral medullary stroke (Wallenberg) from a lateral pontine stroke (Marie-Foix).  Instead, this article ditches the eponyms and uses a symptoms-based approach to help you differentiate between a stroke and a non-stroke.

1) Establish an abrupt onset of symptoms.

2) Be cautious with non-specific presentations. Most strokes should present with cranial neuropathies, ocular symptoms, or language deficits. However, vertebral artery dissection can occur with pain only. Also, vomiting may be so severe that it distracts you from looking for associated symptoms.

3) Consider a basilar stroke in altered patients. These patients are obviously ill and will be admitted. But a CTA to expedite timely endovascular intervention may be life saving.  These patients may have involuntary movements that mimic seizure.

4) Use a modern approach to workup dizziness.

  • Asking “What do you mean by dizzy?” isn’t very helpful or evidence based. Instead, focus on “timing and triggers.” It is especially important to recognize that dizziness caused by movement (peripheral etiology) is not the same as dizziness exacerbated by movement, which is more likely to be a central etiology.

  • If dizziness is constant, think:

    • vestibular neuritis, or

    • posterior circulation stroke

  • If dizziness is episodic but triggered, think:

    • BPPV, or

    • orthostatic hypotension

  • If dizziness is episodic and spontaneous, think:

    • vestibular migraine (most common),

    • Meniere’s disease, or

    • TIA

  • A HINTS exam has been shown to be more sensitive than MRI acutely. However, since you’re not a neuro-otologist, supplement your exam with a careful evaluation of the posterior circulation by checking visual fields, cranial nerves, and limb/truncal/gait ataxia.  If anything is abnormal, assume a central etiology.

5) Do not rely over much on imaging. A good physical exam and high index of suspicion are critical.

  • DWI-MRI has a false negative rate of 6.8% among all acute ischemic strokes. This false negative rate increases among patients with posterior circulation strokes (12-18%). It is the highest in patients with small infarcts that are < 10mm in diameter (53%).

  • If you are considering a basilar stroke or vertebral artery dissection, CTA is more available in the ED and may be superior to MRA.

Another Spoonful
We also summarized all eight points of the article in a more detailed summary. It has some additional pearls you need to know.

Avoiding misdiagnosis in patients with posterior circulation ischemia. Acad Emerg Med. 2019 Jul 11. doi: 10.1111/acem.13830. [Epub ahead of print]

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For more on posterior strokes, see this emDocs post.

#3: tPA 4.5 to 9h or Wake-Up Stroke – New Meta-analysis

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Compared to the placebo group, patients who presented with ischemic stroke (4.5-9h from onset or wake-up stroke) with salvageable brain tissue identified on perfusion imaging and received tPA, had a slight improvement in functional outcome (mRS of 0-1) at 3 months (36% vs 29%) with higher rates of symptomatic intracerebral hemorrhage (5% vs <1%).

Why does this matter?
Ischemic stroke is a disease entity with significant morbidity and mortality. Prior to endovascular therapy, there was little we could offer patients if they fell outside of the 0-4.5h window. This is a meta-analysis and systematic review of the efficacy and safety of tPA outside of the window (4.5-9h or wake-up stroke) with evidence of salvageable brain on perfusion imaging.

tPA – I put that 💩on everything?
The authors identified three trials that met eligibility criteria (EXTEND, ECASS4-EXTEND, and EPITHET) for a total of 414 patients. The primary outcome of this meta-analysis was the proportion of patients with excellent functional outcome (mRS of 0-1) at 3 months adjusted for pre-treatment NIHSS. Safety outcomes included symptomatic intracerebral hemorrhage within 36h of treatment, neurological deterioration ≥4 NIHSS points, or death.

In the alteplase group, 76/211 (36%) achieved mRS of 0-1 at 3 months compared to 58/199 (29%) of the placebo group for an OR of 1.86 (95% CI 1.15-2.99). However, this was accompanied by a higher symptomatic ICH rate for the alteplase group 10/213 (5%) compared to placebo 1/201 (<1%) for an OR of 9.7, 95%CI 1.23-76.55. The authors note that the adjusted OR mentioned previously are slightly better than those achieved in the 0-3h tPA window or the 3-4.5h window (OR 1.75 and 1.26 respectively). The rate of ICH was 4.7% in this extended tPA window compared to 3.4% in the 0-4.5h tPA window.

It is important to note that the patients included in this meta-analysis were very carefully selected. 62% of the tPA group and 60% of the placebo group were identified to have large-vessel occlusions. The patients were also found to have a relatively small ischemic core with an area of salvageable brain. These should be the ideal patients for treatment, yet the effect of tPA was not very impressive. In the current practice environment, many of these patients will go for thrombectomy instead. I think this gives us some information about the risks and benefits of giving tPA to patients who are outside of the window without access to a center that does endovascular treatment.

Extending thrombolysis to 4·5-9 h and wake-up stroke using perfusion imaging: a systematic review and meta-analysis of individual patient data. Lancet. 2019 Jul 13;394(10193):139-147. doi: 10.1016/S0140-6736(19)31053-0. Epub 2019 May 22.

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