New or Presumed New LBBB As STEMI?

A Debate

Dr. Chew Keng Sheng, MD, MMED Universiti Sains Malaysia

Five Compelling Reasons Why New or Presumed New LBBB Should Not Be Treated as STEMI

1.  Recent evidences 2.  Questionable historical origin 3.  Confounding pathogenetic mechanisms 4.  Ethical issue of giving fibrinolytics when it is not

needed 5.  Unnecessary PCIs.

1. Recent Evidences

•  Chang et al (2009) (observational, n = 7937): –  rate of MI is the same (~7%) whether new, old or no

LBBB •  Jain et al (2011) (retrospective, n = 892):

–  Only 1/3rd of new or presumed new LBBB have AMI •  Kontos et al (2011) (observational, n = 401):

–  rate & size of MI is the same in new, old or no LBBB •  Wong et al (2005) HERO-2 Trial (n = 15640; 300

LBBB): –  rate of MI is the same whether new or old; unless there is

concordant ST changes

2. Questionable Historical Origin

•  First recognized in 1917 by Oppenheimer & Rothschild

•  Bauer (1965): many confounders

•  Sgarbossa 2000: Timing of ECG recording?

“In the prethrombolytic era, the management of patients with myocardial infarction consisted only of pain relief,

observation, and treatment of complications. In patients with ECG confounders, such as LBBB, the diagnosis of MI was confirmed through biochemical determinations over several

hours or days after admission. Because there was no incentive to collect information on early ECG signs of MI,

most studies on the diagnosis of MI in the presence of LBBB included ECGs with old infarctions as well as recordings obtained at widely scattered time-points

after acute infarction”

-­‐ Elena  Sgarbossa  MD  J  Electrocardiol  2000;33  Suppl:87-­‐92.  

The FTT Data

•  Pooled data of 9 trials in the FTT group (1991) •  STEMI with BBB treated with fibrinolytics - lower

mortality rate than placebo (18.7% vs 23.6%) –  increased major bleeding risk (1.3% vs 0.3%) –  increase in stroke (2.1% vs 1.1%)

•  3 caveats: •  Is it LBBB or RBBB? •  Is it new or old? •  Small BBB cohort (3.6% of 58,000)

3. Confounding Pathogenetic Mechanisms

•  De novo LBBB due to MI •  Or LBBB secondary to pre-

existing structural heart disease

•  Is the LBBB a cause or consequence?

•  Bauer (1965): true AMI-related LBBB has very high mortality

Neeland et al (2012)

4. Ethical Issues

•  Giving fibrinolytic when it is not necessary? •  Bleeding risk

–  FTT data 1.1 – 1.3% compared to 0.4% in control •  NNT for streptokinase 25 •  STEMI with LBBB – higher co-morbidities

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5. Unnecessary PCIs

•  Larson et al (2007) –  N = 1335 –  overall false +ve cath lab activation: 14%, –  in the LBBB cohort: 44%!

•  Lopes et al (2011) –  N = 98 –  39% new LBBB (including with concordant ST-changes)

have no +ve angio findings

Cost? PCI availability?

Reflection

•  What if it is your own family member: Subject to fibrinolysis if: A. New or presumed new LBBB? B. New or presumed new LBBB with concordant ST

changes? Subject to PCI if: A. New or presumed new LBBB? B. New or presumed new LBBB with concordant ST

changes?

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Five Compelling Reasons Why New or Presumed New LBBB Should Not Be Treated as STEMI

1.  Recent evidences (the scientific lens) 2.  Questionable historical origin (the historical lens) 3.  Confounding pathogenetic mechanisms (the basic

science lens) 4.  Ethical issue of giving fibrinolytics when it is not

needed (the bioethical lens) 5.  Unnecessary PCIs (the socioeconomic lens)

•  Download a copy of my 6-page notes in pdf at URL: http://tinyurl.com/pern38t

THANK YOU