AMI in LBBBJeffrey Tabas, MDProfessor of Emergency Medicine
UCSF School of Medicine
Goals: Widen Your Understanding of the Wide QRS!1. Describe an approach to diagnosis of
LBBB
2. Describe the predictivevalue of New LBBB
3. Describe the ST segment changes thatare diagnostic of AMIin LBBB
Case 165 y.o F with fatigue
• 65 y.o. F with the sugar diabetes BIBA w/ fatigue and vomiting for a few hours.
• Vital signs and physical exam are unremarkable
1) 65 y.o. F with fatigue
Case 165 y.o F with fatigue
• No Old ECG available
• Called for records to another hospital and faxed consent
• While awaiting response, patient went into Vfib, was resuscitated, rushed to cath and found to have 100% LAD
Case 165 y.o F with fatigue
3 Questions
1. Is this LBBB?
2. Is this NEW LBBB?
3. Can we read ST segment abnormalities?
1) Is this LBBB?
6 CAUSES - WIDE QRSBundle branch block
Ventricular rhythm
Hyperkalemia
Medications
Paced rhythm
WPW
1) Is this LBBB?
The QRS is wide, usually > 0.14
Look at TERMINAL portions of the QRS in Lead V1 and Lead 1 (V6) LBBB = Terminal R in 1 (V6) and Slurred S in V1
Left Bundle Branch
Man
LBBB Man
Left hand is up for LBBB
Left hand represents left side - lateral leads
Right hand represents right side – V1
Hand points in direction of the final wave of the QRS (i.e. R wave points up, Q and S waves point down
LBBB
2) Is this NEW LBBB?
Indications for PCI and Thrombolytics
•1mm ST elevation in 2 contiguous leadsor
•Left Bundle Branch not known to be old
Predictive Value of New or Presumed New LBBB
Chang, Am JEM, 2009• 55 with New LBBB = 7.3% AMI• 136 with Old LBBB = 5.2% AMI• 7746 with no LBBB = 6.1% AMINew LBBB is not predictive of AMI
Indications for PCI and Thrombolytics
•1mm ST elevation in 2 contiguous leadsor
•Left Bundle Branch not known to be old
2) Is this NEW LBBB?
2013 ACCF/AHA Guideline for the Management of ST-Elevation Myocardial Infarction
“New or presumably new LBBB at presentation occurs infrequently, may
interfere with ST-elevation analysis, and should not be considered diagnostic of
acute MI in isolation.”
3) Can we read the ST segments (i.e. Dx AMI) in LBBB?
2013 ACCF/AHA Guideline for the Management of ST-Elevation Myocardial Infarction
•Criteria for ECG diagnosis of acute STEMI in the setting of LBBB have been proposed (see Online Data Supplement 1)
LBBB: Normal ST Segments
Iso-electric or
Discordant (ST segment opposite the terminal QRS)
This is true forevery lead
LBBB
ACUTE MI in LBBB
CONCORDANTST Elevation
CONCORDANTST Depression
ACUTE MI in LBBB
EXCESSIVE DISCONCORDANCEST:S wave = 0.25 or more
Acute MI in LBBB
Annals of EM, October 2008
Acute MI in LBBB
• 1 mm Concordant ST elevation –10 studies with 1,614 patients
–Sensitivity = 20% (NLR = 0.8)
–Specificity of 98% (PLR = 7.9)
• 5 mm Discordant ST elevation–Specificity of 80% (PLR = 4.5)
Acute MI in LBBB
Annals of EM, August 2012
ST segments in AMI/LBBB
• Excessive Discordance –ST elevation: S wave >= 1:4
–ST depression: R wave >= 1:4
–Significant improvement in sensitivity and specificity
1) 65 y.o. F with fatigue
1) 65 y.o F with fatigue – baseline LBBB
Another pt with LBBB and Chest Pain
c
Yet another pt with LBBB and Chest Pain
c
ACUTE MI in Paced Rhythms
Same as with LBBB!
80 y.o. M with CP and pacer
Prior ECG
Take Home PointsDx of AMI in LBBB
1. Determine if LBBB – LBBB man
2. Do not use New LBBB to predict AMI
Take Home PointsDx of AMI in LBBB
3. Determine if AMI is presentExpected ST segments –Opposite terminal R or S wave –or isoelectric–in every lead
Take Home PointsDx of AMI in LBBB
3. Determine if AMI is presentAcute MI• 1 mm Concordant ST segments (in same
direction as last wave of QRS) in any lead
• Excessive Discordance of ST segments (opposite to terminal R or S wave)– ST:S wave ratio > = 1:4
Treatment of Chest Pain with LBBB or a Paced Rhythm
• If ST changes diagnostic of AMI then – Reperfuse immediately (Lytics or Cath Lab) if
• If no concerning ST changes then– Involve cardiology consultant early if possible– Reperfuse for high suspicion of STEMI (> 50%?)– Use cardiac markers or formal echo to rule out AMI
in the rest
