Anil Makam Profile picture
Aug 25, 2018 12 tweets 6 min read Twitter logo Read on Twitter
1| follow for my critical appraisal tweetorial of #SCOTHEART trial in @NEJM #ESCCongress

Basics: RCT of upfront CTA vs standard of care for stable CP referred to Scottish cardiology clinics. 1.6% fewer had primary outcome with CTA…
2| more basics: primary outcome is driven by nonfatal MI, not death. Authors did tremendous job at highlighting this

3| before diving in to methods/findings, how would a CTA first approach meaningfully change outcomes?

4| I would think CTA first strategy would work via both better revascularization and better medical therapies
5| hold onto that thought. 2 methods questions

Q: Was RCT blinded? A: no

Q: How were outcomes defined? A: dx codes, not adjudicated. See text below

6| major limitation is having a bias susceptible primary outcome of non fatal MI. 1 reason is with CTA result in hand, could more easily classify MI as demand mismatch than true plaque rupture if had low CAC score

7| even if believe MI outcome safe from bias, did intermediate pathways on causal pathway improve?

For revascularization, NO

8| for optimal medical management, MODEST INCREASE in CTA group. 97 more people started treatment precisely.

9| so with no real diff in PCI between groups, left to believe that 97 more ppl commencing therapy led to 29 fewer non fatal heart attacks. That would mean a NNT of 3 people after median follow up of 5 years!!!!

10| so to believe this result would mean having to believe medical therapy in a population with stable CP (many without CAD or angina) seen in an outpt carde clinic is far far more effective than ASA after STEMI (NNT in 40s)
11| my takeaway of #SCOTHEART trial: falls short due to: a)bias prone outcome of nonadjudicated nonfatal MI, b) CTA strategy without clear effect on necessary causal pathway for benefit, & c) implausible effect size of medical tx in low risk pop


Other takes?
12| 1 thing not reported is intensification of existing medical therapy. But dose dependent relationship only really strong for statins and not or nonexistent for BB, ACEi, or other antianginals.



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More from @AnilMakam

Aug 27, 2018
1| Good #cardiotwitter on #SCOTHeart. Others have tweeted reasons y believable. Here is my reply tweetorial

@khurramn1 @AChoiHeart @MarcDweck @JWeirMcCall @rwyeh @drjohnm @venkmurthy @DavidLBrownMD @RogueRad
Linking my original tweetorial:
2| Let's start with MI def. Billing codes less accurate than adjudicated MI outcomes, yes? Could be nondiff misclassification which bias to null. But could also be diff w/ ascertainment bias (look harder, anchoring) knowing CCTA result, since 2/3rds normal or nonobstruct.
3| It is conjecture. But basis of clinical reasoning is to factor in test results. The posterior probability for this theory moves up much higher when we try to figure out by what mechanism did a diagnostic testing strategy lead to better outcomes, since the radiation did zilch
Read 11 tweets

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