Preventing Sudden Cardiac Death after MI + Hyperacute T waves

Thanks to Leslie Suen and Meghan Lockwood for presenting a super interesting case of aborted sudden cardiac death (SCD) after MI. It was a great opportunity to review some bread and butter – my favorite carb and second favorite fat source, respectively.

SCD after MI is common

  • After an MI (STEMI or NSTEMI), overall incidence of SCD is up to 2-4% per year (that’s so high!!!)
  • Incidence is highest in the first month after MI.

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The cornerstone of prevention is revascularization and optimal medical management 

  • Incidence has decreased drastically with the advent of PCI and optimal medical management
  • The biggest risk factor for SCD is permanent LV dysfunction despite medical therapy.
  • Just a reminder below of how great optimal medical management is for heart failure. The table below shows how much each medication reduces mortality when optimally deployed
guideline-recommended therapy
relative risk reduction in RCTs (%)
NNT for mortality benefit
RRR in metanalysis
ACE or ARB
17%
77
20%
beta blocker 34%
28%
31%
aldosterone antagonist
30%
18
25%
hydral + nitrates
43%
24
29/22%
From Fonarow et al.
 

ICDs are recommended for primary prevention of SCD for people with persistent LV dysfunction >40 days after MI

  • The 2006 AHA/ACC/ESC guidelines (AKA all the cardiologist you most want guidelines from) recommend ICD implantation in the following circumstances
  • >40 days after MI + LVEF <30-40% OR NYHA Class II/III heart failure with reasonable expectation of survival + good functional status at 1 year.
  • There’s great evidence to support this – the MADIT I and MADIT II trials are the most often cited.
  • Despite arrest risk being highest in the 30 days after MI, there have been many, high quality RCTs that show no survival benefit to early ICD implantation unless patients have persistent, tough to control VT.
  • Much is still unknown here. There is definitely subpopulation who would benefit from more aggressive arrhythmia prevention vs a life vest, but we haven’t quite figured out who. If you are a future cardiologist and you would like to nerd out about this, check out the references.
Bonus pearl – hyperacute T waves!
We also discussed hyper acute T waves – The tall, broad based, peaked T waves that can herald a STEMI. They are extremely rare because they are so transient. You can distinguish them from hyperkalemia peaked T waves based on the base – narrow based in hyper K, broad based in a STEMI. There’s a great review of hyper acute T waves on the blog life in the fast lane

References

 Fonarow GC, Yancy CW, Hernandez AF, et al. Potential impact of optimal implementation of evidence-based heart failure therapies on mortality. Am Heart J 2011; 161:1024.
Kusumoto et al. HRS/ACC/AHA consensus statement on use of ICD therapy in patients who are not included or well represented in RCTs. Circulation 2014;130:94-125.
Zaman S, Kovoor P. Sudden Cardiac Death Early After MI: Pathogenesis, Risk Stratification and Primary Prevention. Circulation 2014;129:2426-2435.
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