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Basic Electrocardiography
Basic ECG Fundamentals
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Medical
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09/29/2014

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Term
Normal PR interval
Definition
0.12-0.20sec or 3-5ss
Term
Normal qrs interval
Definition
<0.12 sec or <3ss
Term
How would a prolonged QT interval compare to the RR interval?
Definition
Prolonged QT interval would be >1/2 of the RR interval.
Term
What does the q wave represent in left lateral & inferior leads?
Definition
Septal depolarization
Term
Name the precordial leads
Definition
V1 - V6
Term
Name the Frontal leads
Definition
aVR, aVL, aVF, I, II, & III
Term
EKG needle speed
Definition
25mm/sec
Term
Calculate Heart Rate
Definition
# of large squares (5mm) between R waves divided by 300.
Term
Calculate irregular Heart Rate
Definition
# of R waves in 30 Large squares (5mm) multiplied by 10
Term
What are normal QT intervals for males and females?
Definition
Males <0.45 sec Female <0.46 sec
Term

Name the ECG Leads & Vectors:

 

 [image]

Definition
[image]
Term

Name the waves:

[image]

Definition
[image]
Term
What is the significance of a prolonged QT interval?
Definition
Increased probability of ventricular arrhythmia. Such as Torsades de pointes or Vent Fib.
Term
How many degrees does normal cardiac axis run in relation to lead I?
Definition

+60 degrees

[image]

Term
In relation to Lead I, what is the degree range of normal cardiac axis and what Leads does it correspond to?
Definition

-30 to +90 degrees. Leads aVL thru aVF.

[image]

Term
In left axis deviation, the axis deviation lies where?
Definition

Beyond -30 degrees or beyond aVL.

[image]

Term
In left axis deviation, what types of qrs deflections will be seen in Leads I-III?
Definition
I = positive to Isoelectric (Iso) II = negative III = negative
Term
In right axis deviation, what types of qrs deflections will be seen in Leads I-III?
Definition
I = negative to isoelectric (Iso) II = positive to Iso III = strongly positive
Term
What is the major cause and contributing pathologies of left axis deviation?
Definition
Left Anterior Fascicular Block, which in turn is caused by LAD artery infarction/ischemia; LVH; and cardiomyopathy.
Term
What are the causes of right axis deviation (qrs <0.12sec)?
Definition
Left Post. Fascicular Block due to infarction/ischemia or cardiomyopathy; left lateral infarction; LVH (rare)
Term
In LVH, what can be expected to be seen in Lead V1 & V6?
Definition
Increased wave amplitude (deflection).
Term
What is the Sokolow-Lyon criteria?
Definition

ECG voltage criteria for determining LVH whereby S wave of V1 + R wave of V5 or V6 = >35mm = 90% probability of LVH.

[image]

 

Term
Define LV Strain
Definition
  1. T wave inversion & ST segment depression in V5 & V6
  2. May also present as ST segment elevation in leadsV1 & V2
  3. Chronic condition seen sometimes in LVH.

 [image]

Term
What lead V6 changes are seen in Left Ventricular Hypertrophy (LVH)?
Definition
  1. High amplitude R waves
  2. Prolonged Ventricular Activation Time (prolonged first segment of the r wave)
  3. Loss of qrs and ST wave concordance
  4. ST segment depression
Term
What lead V1 changes are seen in Right Ventricular Hypertrophy?
Definition
  1. R wave greater than 7mm and/or
  2. Wave amplitude R>S
  3. RV Strain Pattern - ST segment depression with deep T wave inversion.
Term
What EKG changes are seen in Right Atrial Enlargement?
Definition
  1. P waves >2.5mm in inferior leads
  2. Cardiac axis towards aVF
  3. P waves are of normal duration <2mm

[image] 

Term
When can you expect to see ST elevations in a suspected ACS patient?
Definition
20-30 minutes post onset.
Term
In an inferior surface MI, what would be the suspected occluded artrey?
Definition
Right Coronary Artery
Term
What leads would an inferior MI involve?
Definition
II, III and aVF
Term
What artery would be suspected in a septal or anterior surface MI?
Definition
Left anterior descending artery
Term
What leads would you examine in an anterior surface MI?
Definition
V1 - V4
Term
What artery would you suspect in a left lateral wall MI?
Definition
Left circumflex artery.
Term
What leads would you examine in a left lateral wall MI?
Definition
I, aVL, V5 & V6
Term
What are the classical STEMI changes seen on a EKG in order of progression?
Definition
  1. Hyperacute T waves
  2. ST elevation
  3. Terminal qrs alterations
  4. T wave inversion
  5. Patholigical Q waves
Term
When is the approximate range of onset and resolution of ST elevation in a STEMI?
Definition

Onset: 20-30 minutes

Resolution: days to weeks

Term

What are the 2 clasical changes seen on an EKG in NSTEMI and Unstable Angina?

Definition
  1. ST segment depression
  2. T wave inversion in leads w/ dominant R wave

Note: Both changes can manifest on the same lead.  See below for each example:

[image][image][image]

Term

True or False

EKG changes seen in unstable angine and NSTEMI are identical.

Definition
True
Term

True or False:

T waves in Leads V1 & V2 can have positive or negative deflections in normal adults.

Definition

True

 

Term
What are causes of  T wave inversion other than Cardiac related?
Definition
  1. Intracranial Pathology
  2. Persistent Juvenile Pattern
  3. Digitalis Tx
  4. Metabolic
    1. Hypokalemia
    2. Hypocalemia
    3. Hypomagnesemia
Term
What is the characteristic EKG morphology of a therapeutic patient on Digoxin?
Definition

Downsloping "reverse tick sign" ST segment.

[image]

 

Term
What is the heart rate treshold for tachycardia?
Definition
HR of ≥ 100bpm
Term
What are the EKG hallmarks of Sinus Tachycardia?
Definition
  1. Normal P waves seen in inferior leads
  2. Normal PR interval
  3. Normal narrow qrs complex (supraventricular origin)
  4. HR ≥100bpm
Term
What are the EKG hallmarks of Junctional Tachycardia?
Definition
  1. HR 100-140bpm
  2. Regular, narrow complex
  3. Negative  P waves in inferior leads
  4. Shortened PR interval (<0.12sec)
  5. P waves which may occur before, after or coincident (hidden) the qrs complex
Term
What are the EKG hallmarks of Ectopic Atrial Tachycardia?
Definition
  1. HR >100bpm
  2. Abnormal P wave morphology (variable P wave axis)
  3. Prolonged PR interval
Term
What are the EKG hallmarks of Atrial Fibrillation?
Definition
  1. Irregularly irregular rhythm (irregular p waves with irregular qrs rhythm)
  2. No identifiable P waves
  3. f waves - atrial depolarization from multiple foci occuring at 400-700bpm
Term
What are the EKG hallmarks of Atrial Flutter?
Definition
  1. Saw-tooth pattern - represents a continuous anti-clockwise re-entry loop of current within the right atria discharging into the left atrium at approx 300pbm
  2. qrs complexs occur at a fixed atrial conduction ratio (atrial flutter w/ 2:1 conduction = 1 qrs/2 flutter waves)
Term
What are the EKG hallmarks of AVNRT (AV Nodal Re-entrant Tachycardia)?
Definition
  1. HR >140pbm (may also also occur 130-140)
  2. Psuedo s waves in inferior leads- represent atrial depolizaation post vent depolarization
  3. Psuedo r waves in aVR or V1 - same as above
  4. Normal qrs complexes
  5. Typically paraxysmal attacks with normal resting EKG (young women)
Term
What are the EKG hallmarks of Ventricular Tachycardia?
Definition
  1. Broad complex qrs >0.12sec
  2. HR commonly 140-200bpm (can be as low as 100bpm)
  3. Tends to be monotonously regular with monomorphic appearance and ≥3 consecutive qrs complexes
  4. AV dissociation

[image]

 

Term
What is the definition of sustained ventricular tachycardia?
Definition
An episode of VT lasting 30 seconds or greater.
Term
What is the definition of "non-sustained" or a "salvo" of ventricular tachycardia?
Definition
VT lasting less than 30 seconds.
Term
AV dissociation is seen in approx 50% of ventricular tachycardias (VT). Describe it's 3 EKG manifestations.
Definition
  1. capture beats
  2. fusion qrs complex
  3. dissociated p waves 
Term

The EKG below is of a patient in VT. What is the type of AV dissociation in this EKG?

 [image]

Definition
Capture beat
Term

The EKG below is of a patient in VT. What is the type of AV dissociation in this EKG?

[image]

Definition
fusion qrs complex
Term

The EKG below is of a patient in VT. What is the type of AV dissociation in this EKG?

[image]

Definition
dissociated p waves
Term

True or False

Ectopic beats occur before the expected Sinus beat

Definition
True
Term

True or False

The qrs complex of an atrial ectopic beat is prolonged

Definition
False - the qrs is of normal duration in an atrial ectopic beat.
Term

True or False

The qrs complex is prolonged in a ventricular ectopic beat.

Definition
True
Term

True or False

Only in atrial ecoptic beat is there a pause of the p wave.

Definition
False - atrial and ventricular ectopic beats are followed by a pause of the next p wave.
Term
A compensatory pause follows a ventricular ectopic beat.  What is a compensatory pause?
Definition
A pause in the next predictable p wave, followed by a p wave occuring at the predictable point as determined by the previous underlining atrial rhythm.
Term
An atrial ectopic beat is usually followed by a non-compensatory pause.  What is a non-compensatory pause?
Definition
A pause in the next p wave following the atrial ectopic beat whereby the next p wave does not occur at a predictable point.  Essentially the SA node resets.
Term

True or False

An escape beat occurs before the next expected sinus beat.

Definition

False

Escape beats occur after an expected sinus beat and represent an automatistic foci in the atrium which fires off when the SA node fails to fire within th expected time frame. See below:

[image]

Term

Choose one:

First degree AV block

  1. Prolonged PR interval
  2. Intermittent failure of p wave conduction
  3. Complete failure of p wave transmission
Definition
Answer: 1 (PR>0.2sec or >5ss)
Term

Choose one:

2nd degree AV block

  1. Prolonged PR interval
  2. Intermittent failure of p wave conduction
  3. Complete failure of p wave transmission
Definition

2 - 

Intermittent failure of p wave conduction

Term

Mobitz types I & II below to what category of AV Block?

  1. 1st dregee
  2. 2nd degree
  3. 3rd degree
Definition
2nd degree AV Block
Term
When would the greatest change in PR interval occur in Mobitz Type I?
Definition
Within the first two beats following the missed qrs complex.
Term

True or False:

In 2° AV Block, Mobitz Type II, there is a progressive prolongation of PR intervals prior to failure of p wave transmission.

Definition
False - this is the criteria for 2° AV Block, Mobitz Type I (also referred to the Wenckeback Phenomena).
Term

True or False:

In 2° AV Block, Mobitz Type II there are prolonged but constant PR intervals prior to p wave transmission failure.

Definition
True
Term
How are Mobitz Type II 2° AV Blocks classified?
Definition
By their p wave to qrs conduction ratios.  For example, the p wave transmits successfully 3 consecutive times but false on the 4th.  The classification would be a Mobitz Type 2 with a 4:3 conduction ratio.
Term
Which type of AV Block would you expect to see wide qrs complexes?
Definition

3rd degree AV Block

Note: There is complete AV dissociation and thus ventricular foci will take over.

Term
The describe the EKG criteria for RBBB
Definition
  1. qrs ≥0.12sec
  2. Slurred s wave in V6
  3. Possible rSR pattern in V1
  4. Positive qrs in V1

[image]


 

Term
Classic "rabbit ears" in V1 is seen in.....
Definition

RBBB

However, do not rely on this diagnostic tool alone.  Many times the notch is much less pronounced or may be fused. RBBB EKG criteria should be:

  1. Positive V1
  2. Prolonged qrs complex >0.12sec
  3. Slurred s wave following r wave in V6
Term

Name the top 3 causes of RBBB?

Definition
  1. Diseases causing chronic R Ventricular pressure such as 1° Pulmonary HTN; Cor Pulmonale and Acute Pulm Embolism. Etiology; - compression of the RBB proximal to the endocardium
  2. LAD infarction. (LAD supplies the RBB)
  3. Myocarditis
Term
EKG Lead morphology changes in LBBB result from...
Definition
  1. Current flow reversal of septal depolarization
  2. Delayed depolarization of the L Vent.
Term
What are the EKG criteria for LBBB?
Definition
  1. qrs ≥0.12sec
  2. Broad R waves in I and V6 (may be notched).
  3. Broad deep S waves in V1-V3
Term
What are some causes of LBBB?
Definition
  1. LAD Infarction
  2. HTN
  3. Myocarditis
  4. Cardiomyopathy
  5. Aortic Valve diseases
Term
The AV node is supplied by which coronary artery?
Definition
Posterior Descending Artery (which is a branch of the RCA)
Term

True or False:

The left anterior descending (LAD) artery supplies the Left and Right bundle branches.

Definition
True
Term

True or False:

An Anterior MI can result in either LBBB or RBBB.

Definition
True
Term
Depolarization wave conducted through cardiac tissue outside normal established pathways is called...
Definition
Aberrancy
Term

True or False:

The RBB has a longer refactory period than the LBB.

Definition
True
Term
What is the main distinguishing factor between a PVC and PJC?
Definition
Opposite wave deflection direction.  PVC wave will deflect in the opposite direction of the normal sinus or junctional wave.  PVC will flow opposite of Lead II.
Term
Describe the EKG criteria and clinical manifestations of Wolf Parkinson White Syndrone.
Definition
  1. A delta wave between p and r waves
  2. Short PR interval
  3. Broad qrs complex
  4. Paroxysmal attacks of tachycardia in young healthy females
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