5/23/14 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 McCabe et al. JAHA, 2014 65 y.o F with fatigue • 65 y.o. F with the sugar diabetes BIBA w/ • “Based on the ECG above, is there a fatigue and vomiting for a few hours. blocked coronary artery present causing a STEMI?” • Vital signs and physical exam are • 36 STEMI activations unremarkable – Overall 65% sensitivity, 79% specificity – No difference in accuracy between EP’s, Cardiologists, Interventional Cardiologists – Years of experience was only predictor of accuracy 1
5/23/14 Case 1 1) 65 y.o. F with fatigue 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? 2
5/23/14 Left Bundle • The QRS is wide, usually > 0.14 Branch • Look at TERMINAL QRS wave in Lead V1 and Lead 1 (V6) Man • LBBB = Terminal R in 1 (V6) and Slurred S in V1 LBBB • 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 3
5/23/14 Predictive Value of 2) Is this NEW LBBB? New or Presumed New LBBB Indications for PCI and Thrombolytics • 1mm ST elevation in 2 contiguous leads or • Left Bundle Branch not known to be old 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 2) Is this NEW LBBB? 3) Can we read the ST segments (i.e. Dx AMI) in LBBB? Indications for PCI and Thrombolytics • 1mm ST elevation in 2 contiguous leads 2013 ACCF/AHA Guideline for the Management of ST-Elevation Myocardial Infarction or 2013 ACCF/AHA Guideline for the Management • Left Bundle Branch not known to be old of ST-Elevation Myocardial Infarction • Criteria for ECG diagnosis of acute STEMI in “New or presumably new LBBB at the setting of LBBB have been proposed presentation occurs infrequently, may (see Online Data Supplement 1 ) interfere with ST-elevation analysis, and should not be considered diagnostic of acute MI in isolation.” 4
5/23/14 LBBB • Iso-electric or • Discordant (ST segment opposite the terminal QRS) • This is true for every lead ACUTE MI in LBBB ACUTE MI in LBBB EXCESSIVE DISCONCORDANCE CONCORDANT CONCORDANT ST:S wave = 0.25 or more ST Elevation ST Depression 5
5/23/14 Acute MI in LBBB Acute MI in LBBB Annals of EM, October 2008 • 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 ST segments in AMI/LBBB Annals of EM, August 2012 • Excessive Discordance – ST elevation: S wave >= 1:4 – ST depression: R wave >= 1:4 – Significant improvement in sensitivity and specificity 6
5/23/14 1) 65 y.o. F with fatigue 1) 65 y.o F with fatigue – baseline LBBB NOT STEMI! STEMI! 3 9 22 28 Another pt with LBBB and Chest Pain Yet another pt with LBBB and Chest Pain 4 2 c 4 c 16 7
5/23/14 80 y.o. M with CP and pacer ACUTE MI in Paced Rhythms • Same as with LBBB! Take Home Points Prior ECG Dx of AMI in LBBB 1. Determine if LBBB – LBBB man 2. Do not use New LBBB to predict AMI 8
5/23/14 Take Home Points Take Home Points Dx of AMI in LBBB Dx of AMI in LBBB 3. Determine if AMI is present 3. Determine if AMI is present Expected ST segments Acute MI – Opposite terminal R or S wave • 1 mm Concordant ST segments (in same direction as last wave of QRS) in any lead – or isoelectric – in every lead • Excessive Discordance of ST segments (opposite to terminal R or S wave) – ST:S wave ratio > = 1:4 Treatment of Chest Pain with Widen your knowledge LBBB or a Paced Rhythm and lighten your load! • 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 9
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