AMI in LBBB Jeffrey Tabas, MD Professor of Emergency Medicine - - PDF document

AMI in LBBB

Jeffrey Tabas, MD

Professor 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 predictive

value of New LBBB

• 3. Describe the ST

segment changes that are diagnostic of AMI in LBBB

Case 1 65 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 1 65 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 1 65 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 QRS Bundle 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 leads
• r
• 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% AMI

New LBBB is not predictive of AMI Indications for PCI and Thrombolytics

• 1mm ST elevation in 2 contiguous leads
• r
• Left Bundle Branch not known to be old

2) Is this NEW LBBB?

2013 ACCF/AHA Guideline for the Management

• f 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

• f 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 for every lead

LBBB ACUTE MI in LBBB

CONCORDANT ST Elevation CONCORDANT ST Depression

ACUTE MI in LBBB

EXCESSIVE DISCONCORDANCE ST: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 Points Dx of AMI in LBBB

• 1. Determine if LBBB

– LBBB man

• 2. Do not use New LBBB to predict AMI

Take Home Points Dx of AMI in LBBB

• 3. Determine if AMI is present

Expected ST segments –Opposite terminal R or S wave –or isoelectric –in every lead

Take Home Points Dx of AMI in LBBB

• 3. Determine if AMI is present

Acute 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