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EKG Guidelines Flashcards

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USMLE® Step 1 flashcards
1
Q

Define anterolateral MI, age recent or probably acute?

A
  • Pathological Q waves (must be greater than or equal to 30 ms wide and 0.1mV deep in amplitude or QS complex) in anterolateral leads V3-V6
  • Evidence of acute or evolving myocardial injury (i.e. ST-elevation in two contiguous leads greater than or equal to 2mm in men or 1.5mm in women in V3 and/or 1mm in V4-V6)

***Only use this diagnosis when both are present:

  • pathological Q waves
  • ST-elevation are present
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2
Q

What EKG finding can demonstrate “pseudo” anterior MI (q-waves)?

A

LAFB

  • low anterior forces or “pseudo” anterior MI
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3
Q

EKG DDx:

  • Lead I - Inverted P-wave
A
  • PAC’s
  • Atrial Rhythm
    • AT
    • MAT
    • SVT
  • PJC’s
  • PVC’s with retrograde activation
  • Dextrocardia
    • (inverted P-QRS-T in leads I and aVL)
    • (reverse R wave progression in the precordial leads)
  • Reversal of right and left arm leads
    • (inverted P-QRS-T in leads I and aVL)
    • (normal R wave progression in the precordial leads)
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4
Q

Define Inferior MI

A
  • Pathological Q waves in at least in at least 2 inferior leads
  • Evidence of acute or evolving myocardial injury
    • ST elevation greater than or equal to 1 mm in two contingous inferior leads
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5
Q

Define LAFB

A
  • LAD ( -45 to -90)
  • qR complexes in I and aVL
  • rS complexes in III
  • Prolonged R wave peak time in aVL ( > 45 ms)
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6
Q

What are EKG conditions/changes that interfere with the EKG diagnosis of posterior MI?

A
  • RVH
  • WPW
  • RBBB
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7
Q

Define ST and/or T wave abnormalities suggesting myocardial ischemia?

A
  • Greater than 1mm of horizontal or downsloping ST-T segment depression

and/or

  • T wave inversion greater than or equal to 2mm
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8
Q

How to differentiate the direction of macro re-entry in atrial flutter?

A
  • Flutter wave amplitude in leads aVF and I
    • aVF / lead I > 2.5 = counter-clockwise
    • aVF / lead I < 2.5 = clockwise
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9
Q

Aberrantly conducted PAC’s are most often this pattern

A

RBBB

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10
Q

What is the differential for irregularly, irregular SVTs?

A
  • Differential Dx:
    • MAT
    • ST with PAC’s (frequent)
    • A-fib (coarse)
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11
Q

What is required to code for RAE?

A

NSR

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12
Q

What are additional pitfalls to avoid in presence of LAFB?

A
  • May result in a false-positive diagnosis of LVH based on voltage criteria in lead I or aVL
  • Can mask presence of inferior wall MI
  • Rarely seen in normal hearts
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13
Q

True/False:

Posterior MI is usually seen in the setting of acute inferior or inferolateral MI, but may also occur in isolate lateral MI

A

True

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14
Q

Define 2nd degree AV block - Mobitz II?

What are the associated features?

A
  • Regular sinus or atrial rhythm with intermittent non-conducted P waves and no evidence of PAC’s
  • Constant P-R interval exists with all conducted beats
  • The R-R interval of non-conducted beat is equal to two P-P intervals
  • Site of block: more commonly (80%) distal to the AV node (intra- or infra-Hisian) –> wide QRS ( > 120ms)
  • Often show signs of conduction system disease (BBB or fascicular block)
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15
Q

Define left anterior fascicular block (LAFB) on EKG

A
  • Left axis deviation (usually more negative than -45)
  • Slight widening of the QRS complex
  • Prominent S wave in V5 and V6
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16
Q

Define Anterior or anteroseptal, age recent or probably acute?

A
  • Pathological Q waves (must be greater than 30ms wide and 0.1mV deep in amplitude or QS complex) in anterior (V3-V4) or anteroseptal (V1-V3) leads; Q wave width may only be 20ms wide in V2-V3
  • Evidence of acute or evolving myocardial injury (i.e. ST-elevation in two contiguous leads greater than or equal to 2mm in men or 1.5mm in women in V2-V3 and/or 1mm in other anterior or atneroseptal leads)

***Only use this diagnosis when both are present:

  • pathological Q waves
  • ST-elevation are present
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17
Q

What is the diagnosis that should be considered?

  • Atrial flutter
  • 3rd degree heart block
  • Junctional tachycardia
A

Digoxin toxicity

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18
Q

What is the EKG criteria for LPFB?

A
  • RAD ( > +90 degrees)
  • Small R waves with deep S waves (rS complexes) in leads I and aVL
  • Small Q waves with tall R waves (qR complexes) in leads II, III, aVF
  • QRS normal or slightly prolonged
  • Prolonged R wave peak time in aVF
  • Increased QRS voltage in limb leads
  • No evidence of RVH or any other cause of RAD
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19
Q

Define posterior MI

A
  • V2-V3
    • dominant R waves (R wave > S wave with and R wave duration ≥ 40 msec)
    • ST-depression ≥ 1 mm with upright T-waves
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20
Q

What are the EKG criteria for LAFB?

A
  • LAD (usually between -45 and -90 degrees)
  • Small Q waves with tall R waves (qR complexes) in leads I and aVL
  • Small R waves with deep S waves (rS complexes) in leads II, III, aVF
  • QRS duration normal or slightly prolonged (80-110ms)
  • Prolonged R wave peak time in aVL > 45ms
  • Increased QRS voltage in the limb leads
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21
Q

Define 1st degree AV block?

When is this seen (acquired)?

A
  • P-R interval greater than or equal to 200msec
  • Each P-wave is followed appropriated by a QRS
  • High vagal tone (during sleep)
  • Treatment with BB or CCB’s
22
Q

What are causes of LBBB?

A
  • CAD
  • HTN
  • Aortic stenosis
  • Anterior MI
  • Dilated Cardiomyopathy
  • Primary degenerative disease of the conducting system (Lenegre disease)
  • Hyperkalemia
  • Digoxin toxicity
23
Q

Why does SVT typically occur with aberrant conduction in RBBB morphology?

A
  • Right bundle has a longer refractory period than the left bundle
  • Aberrant conduction usually travels down the left bundle
  • Resulting in QRS morphology with RBBB pattern
24
Q

What are the EKG diagnostic criteria of LBBB?

A
  • QRS duration > 120ms
  • Dominant S wave in V1
  • Broad monophasic R wave in lateral leas (I, aVL, V5-V6)
  • Prolonged R wave peak time > 60ms in left precordial leads (V5-V6)
  • Associated features
    • Appropriate discordance
      • ST segments and T waves always go in the opposite direction to the main vector of the QRS complex
    • Poor R wave progression the precordial leads
    • Left axis deviation
25
Q

Define EKG criteria for WPW?

A
  • short PR interval ( < 120ms in adults and < 90ms in children during sinus rhythm)
  • Slurring of QRS complex (delta wave), resulting in the QRS being > 120 ms in adults and > 90 ms in children
    • widened QRS results from fusion of two electrical impulses, one through the normal AV node and the other through the bypass tract
  • Secondary ST-T wave changes
    • ST-T segment deviation opposite in direction of main QRS deflection
  • Pseudo-infarction pattern can be seen in up to 70% of patients
    • due to negatively deflected delta waves in the inferior/anterior leads (“pseudo-Q waves”), or as a prominent R wave in V1-V3 (mimicking posterior infarction)
26
Q

Differentiate MAT from:

  • ST with PAC’s
  • A-fib
A
  • MAT (from ST with PAC’s)
    • will not demonstrate a single, dominant, atrial pacemaker
  • MAT (from A-fib)
    • isoelectric baseline between P-waves
27
Q

Define 3rd degree (complete) AV block?

When can this be seen?

adenosine

A
  • Complete failure of atrial impulses to pass through the AV node and stimulate ventricular activity
  • Results in constant P-P intervals, but the atrial and ventricular rhythms are independent of each other
  • Atrial rate is typically faster than the ventricular rate, as the ventricular rate is driven by either a junctional rhythm, ventricular escape complex, or a ventricular pacemaker
  • MI, degnerative diseases (Lev’s, Lenegre’s), infiltrative diseases (sarcoidosis, amyloidosis), digitalis toxicity, endocarditis, marked hyperkalemia, Lyme disease, myocardial contusion, acute rheumatic fever, severe valvular disease.
28
Q

EKG DDx:

  • Lead II - Multiple P wave morphologies
A
  • Wandering atrial pacemaker (rate < 100 bpm)
  • MAT (rate > 100 bpm)
  • Sinus or atrial rhythm with multifocal PAC’s
29
Q

Define 2nd degree AV block - 2:1?

When can this be seen?

A
  • Regular sinus or atrial rhythm with two P waves for every QRS complex (only every other P wave is conducted)
  • Can be secondary to Mobitz type I or Mobitz Type II AV block
30
Q

Define 2nd degree AV block - Mobitz 1 (Wenckebach)?

When can this be seen?

A
  • Progressive prolongation of the PR interval until a P wave is blocked
  • R-R interval of non-conducted beat must be less than 2 times the P-P interval (otherwise, high degree of AV block exists)
  • Will give the appearance of group beating
  • Site of block: usually in the AV node
  • High vagal tone, AV nodal blocking agents (BB, CCB’s)
31
Q

Define Inferior MI, age recent or probably acute?

A
  • Pathological Q waves (must be greater than or equal to 30ms wide and 0.1mV deep in amplitude or QS complex) in at least two inferior (II, III, or aVF) leads
  • Evidence of acute or evolving myocardial injury (i.e. ST-elevation greater than or equal to 1 mm in two congiusou inferior leads)

***Only use this diagnosis when both are present:

  • pathological Q waves
  • ST-elevation are present
32
Q

Describe the different types of WPW

A
  • Type A: positive delta wave in all precordial leads with R/S > 1 in V1
  • Type B: negative delta wave in leads V1 and V2
33
Q

Classic features for a rhythm originating in ventricular myocardium

A
  • Wide QRS ( > 0.28s)
  • R wave in lead aVR (“northwest axis”)
  • capture complexes
  • > 100 ms from onset of R wave to the nadir of the S wave in > 1 chest lead
  • atypical RBBB = R > R’ in V1
    • R wave usually < R’
34
Q

What is the term for rhythm of ventricular origin with HR < 100 bpm?

A

AIVR

35
Q

How do you distinguish between:

  • coarse A-fib
  • MAT
A

MAT → isoelectric baseline between P-waves

36
Q

Describe differences in etiologies of QT prolongation:

A

QT prolongation due to:

  • Hypocalcemia → normal T waves
    • ST lengthening without a change in T wave duration or morphology
  • Medications or Genetic disorders → complex T wave morphology
37
Q

What is “T-wave memory?”

When is it seen?

A
  • TWI’s occurring in ECG of patients in their NSR when they had abnormal ventricular activation transiently due to various causes
  • Causes:
    • RV pacing
    • VT
    • intermittent LBBB
    • intermittent WPW syndrome
38
Q

Differentiate location of conduction delay in 1st degree AV block

A
  • Narrow QRS
    • conduction delay typically occurs in the AV node
    • usually due to:
      • medications that delay AV conduction (BB, CCB, Digoxin)
      • normal physiology / High vagal tone (high fitness levels, nausea, pain, sleep)
  • Wide QRS
    • may represent conduction delay in the His-Purkinje system
      • usually in conjunction with RBBB, LAFB, LPFB, LBBB
39
Q

Posterior MI cannot be diagnosed in the presence of this?

A

RBBB

40
Q

What is one key finding when coding for acute inferior Q wave MI?

A

aVL

  • there will virtually always be reciprocal ST segment depression
  • even if the ST segment elevation in other leads is minimal
41
Q

What is one key finding when coding for acute lateral Q wave MI?

A

aVF

  • there will virtually always be reciprocal ST segment depression
  • even if the ST segment elevation in other leads is minimal
42
Q

What is required for the diagnosis?

  • Acute cor pulmonale including pulmonary embolus
A
  • Symptoms of acute decompensation (sudden onset dyspnea, collapse)
  • EKG findings:
    • RV strain pattern (ST-depression + TWI in R precordial leads)
    • Rhythm change (ST, A-fib)
43
Q

When evaluating for signs of acute or active CAD?

  • ST-T changes suggesting myocardial ischemia
A
  • significant ST depression is observed
  • often with concomitant inverted or biphasic T waves
  • but without abnormal Q waves
44
Q

When evaluating for signs of acute or active CAD?

  • ST-T changes suggesting myocardial injury
A
  • ST elevation
  • with or without abnormal Q waves
45
Q

When evaluating for signs of acute or active CAD?

  • Old or age indeterminate
A
  • abnormal Q waves are observed in 2 or more contiguous leads
  • not associated with ST-elevation
46
Q

What distinguishes acute or recent?

  • Anterior
  • Anteroseptal
A

ST elevation in lead V1

47
Q

What distinguishes age acute or recent?

  • Lateral
  • Anterolateral
A
  • Anterolateral
    • must show > 1 mm ST-elevation in at least two contiguous leads
    • V4-V6
  • Lateral
    • must show > 1 mm ST-elevation in at least two contiguous leads
    • I, aVL
48
Q

Define Juvenile T-waves, normal variant

A
  • TWI - localized to R precordial leads (V1 - V3)
    • shallow in depth
    • seen in younger, healthy individuals
    • typically females
  • Upright T waves in I, II, V5, V6
49
Q

What is a major key to differentiating wide QRS tachycardias?

  • VT
  • SVT with aberrancy
A

Evaluate how tachycardia begins and ends

  • VT
    • starts - PVC
    • ends - gradual slowing of the rate and then termination
  • SVT with aberrancy
    • starts - PAC with long PR interval + narrow QRS complex
    • ends - narrow complexes at a similar rate and retrograde P waves
50
Q

Define:

  • Poor R-wave progression
A
  • R wave in V3 < 3 mm or
  • R/S transition zone in V5 or V6
    • first precordial lead with R/S > 1
51
Q

What is the differential diagnosis:

  • Dominant R wave in V1
A
  • Normal
  • RBBB
  • RVH
  • Dextrocardia
  • Limb lead reversal
  • Pacing
  • WPW
  • Duchenne muscular dystrophy
  • HCM
  • Posterior MI

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