EKG fundamentals II

Question 1

What is the PR segment?

Answer 1

time for conduction to travel across AV node to bundle of His- end of P wave to beginning of Q wave

Question 2

What is a normal QRS interval?

Answer 2

less than 3 squares, 0.12s

Question 3

What does a longer QRS interval suggest?

Answer 3

ventricular escape rhythm, in which the conduction begins in the ventricles

Question 4

What is the ST segment?

Answer 4

measured from end of S wave to beginning of T wave

Question 5

Elevated ST segment meaning? Depressed?

Answer 5

STEMI; ischemia as angina

Question 6

What is the PR interval?

Answer 6

time for conduction to travel from SA to AV node. Should be 0.12-0.2 sec

A PR interval is measured from the start of the P-wave to the beginning of the QRS complex.

Question 7

Elevated PR interval meaning? Depressed?

Answer 7

elevated- heart block

depressed- WPW

Question 8

What is the QT interval?

Answer 8

measured from beginning of Q wave to end of T wave

Question 9

How is QT interval corrected?

Answer 9

QTc= QT/square root (RR), normal 0.38-0.42s

Question 10

Elevated QT interval meaning?

Answer 10

increased risk of ventricular arrhythmia such as vent tachycardia, vent fibrillation, and tornadoes de pointes

Question 11

How can validity of an ECG be determined?

Answer 11

A. The ECG is labeled with the patient’s name and date.

B. Limb Lead I is almost a mirror image of AVR.

C. The presence of a voltage standardization mark that is two big boxes tall (ten millimeters) in response to a 1millivolt (mv) stimulus, and is five small boxes wide—implying a rate of 25 mm/sec.

D. R-wave progression in the chest leads reveals a more prominent R-wave by Lead V4. The rV4 in mm should be > the sV4.

Exceptions exits. For example, R-wave progression is lost in an anterior wall infarction. The ECG is still valid. An alternative explanation exits for the loss of R-wave progression; the anterior myocardium has been damaged.

Question 12

How do you calculate RR?

Answer 12

Rate = 300/# of large boxes between R-waves

Question 13

What questions must be answered to determine rhythm?

Answer 13

1. Is the QRS rate regular?
2. Is a P-wave present and is it associated in a regular fashion
   with the QRS wave?
3. Is the QRS narrow (120 msec).
4. Is the rate normal, fast or slow?

Question 14

What does a sinus rhythm look like?

Answer 14

• narrow QRS

- uniform P waves

Question 15

Examples of sinus rhythms.

Answer 15

a) NSR: normal sinus rhythm. Upright P-wave in Lead II and rate of 60 to 100.
b) Sinus bradycardia. Upright P-wave in Lead II and rate 100.
ad) Sinus arrhythmia (also know as sinus dysrhythmia). Upright P-wave in Lead II and variable rate normally between 60 and 100. In this normal variant, the rate varies +/- 10% over an average of one minute. For example, if the average pulse is 76 bpm, in sinus arrhythmia, the rate may range from 68-84 (76 +/- 7.6) bpm.

Question 16

What does atrial fibrillation look like?

Answer 16

No P-waves are discernible. The ventricular response is irregularly irregular. Rate is variable and usually between 60 to 120.

Question 17

What does atrial flutter look like?

Answer 17

An organized atrial depolarization at the rate of 300 with a sawtooth pattern. Ventricular response can be 300, 150, 100 in a 1:1, 2:1, 3:1 pattern. This may present as a regular or an irregularly irregular pattern. Ventricular response may also vary with a variable AV block.

Question 18

What does PSVT (paroxysmal supreventrivcular tachycardia) look like?

Answer 18

A regular supraventricular tachycardia with rates between 150 and 220. If a P-wave is discernible, the form should be constant.

Question 19

What does WAP (wandering atrial pacemaker) look like?

Answer 19

A normal rate (60-100) but multifocal P-waves; i.e., at least three P-waves with different shapes and variable PR intervals in the same leads.

Question 20

What does MAT (multifocal atrial tachycardia) look like?

Answer 20

(multifocal atrial tachycardia). Similar to WAP but a tachycardia with rate 100-200.

Question 21

What does junctional rhythm look like?

Answer 21

No P-wave is present or related to the QRS complex. Rate is 40-60. If rate 60-100, it is called an accelarted junctional rhythm. If >100, it is called a junctional tachycardia.

Question 22

What does PAC (premature atrial contraction) look like?

Answer 22

These are isolated complexes which occur before the normal sinus beat. The P-wave has a different form. A compensatory pause with a normally spaced sinus beat follows a PAC.

Question 23

What does PJC (premature junctional beat) look like?

Answer 23

Like a PAC, compensatory pause follows a PJC, but no P-wave precedes the QRS complex.
WARNING: Compensatory pauses are tricky and exceptions to this rule exist.

Question 24

How can axis be determined?

Answer 24

Axis can be easily determined by using three limb leads: I, AVF, and II. If the QRS is more positive in Lead I, the axis must be between –90 and +90. If the QRS is also positive in AVF, the axis must be between 1 and +180. The intersection of these two leads is 1 to +90. Thus, if the QRs is positive in both Leads I and AVF, the axis is “normal” and somewhere between 0 and 90.

If the QRS is positive in Lead I and negative in AVF, the intersection is between 0 and –90. Then, Lead II becomes helpful in determining the axis. If the QRS is positive in Lead II, the axis is between –30 and 0. If the QRS in Lead II is negative, the axis will be –30 or less.

Question 25

What is a ‘normal’ axis?

Answer 25

is defined as –29 to +89.

Question 26

What is Left axis deviation (LAD)? RAD?

Answer 26

is or = +90.

Question 27

What is left anterior hemlock (LAHB)?

Answer 27

diagnosed when the axis is less than –30 (i.e., -31) and no other reason for an axis shift is present. By definition, LAHB is LAD. Other synonyms include left anterior superior hemiblock (LASH) and (LAFB).

Question 28

Second degree AV block is divided into two classes:

Answer 28

Mobitz Type I or Wenckebach and Mobitz Type II or non Wenckebach.

In Mobitz Type I, the PR interval gradually increases until a QRS is dropped.

In Mobitz II, the PR interval is constant, but the QRS complex is still dropped.

Question 29

What is third degree AV block?

Answer 29

complete disassociation of the atria with the ventricles; i.e., the P-wave with the QRS.

Here, no signal is transmitted via the AV node and the His-Purkinje system. The rate would depend on the escape rhythm. This produces independent atrial and ventricular rhythms.

Question 30

QRS longer than 0.12s represents what?

Answer 30

A QRS > or = 120 msec defines bundle branch block, an abnormal ventricular beat such as a PVC, or a ventricular rhythm.

Question 31

Three leads are helpful in the delineation of bundle branch block etiology:

Answer 31

I, V1, and V6. Leads I and V6 measure forces toward the left side of the heart.

Lead V1 is over the right side of the heart. The QRS changes from a right bundle block (RBBB) would be more obvious here.

Examining the “late” QRS forces will help determine whether a RBBB or LBBB exists. Late peaking R waves in the lateral leads would suggest a LBBB; late peaking R waves in the anterior leads (the R’ or Rabbit ears) would suggest a RBBB. Leads that show abnormal depolarization will also show abnormal repolarization; look for T wave inversion or ST depression in these leads.

Question 32

What are some causes of prolonged QT intervals?

Answer 32

Type 1A antiarrhythmics, tricyclic antidepressants, phenothiazines,
hypokalemia hypocalcemia, hypomagnesemia, and CNS depression.

Question 33

Shortened QT intervals can be seen in the setting of what?

Answer 33

hypercalcemia.

Question 34

What is Right Atrial Abnormality (RAA)?

Answer 34

also known as RAE (right atrial enlargement) and RAH (right atrial hypertrophy).

It was previously known as P-pulmonale.

Since atrial depolarization is typically greatest in the direction of Lead II, a peaked P-wave of > or = 2.5 small boxes is diagnostic of RAA. Lead III and AVF are also used with this criteria.

Question 35

What is Left Atrial Abnormality (LAA)?

Answer 35

is also known as LAE and LAH (left atrial enlargement and left atrial hypertrophy). Another name for this abnormality is P mitrale.

Here, the P-wave is Leads II, I or L are prolonged to 0.12 sec. In addition, the terminal negative component of the P-wave in V1 can contain one small box and typically has a sinusoidal wave appearance.

Question 36

What is Right Ventricular Hypertrophy (RVH)?

Answer 36

must be suspected in the presence of a prominent R-wave in Lead V1 or V2, i.e., the R-wave must be greater than the S-wave. In addition, right axis deviation (RAD) and right atrial abnormality (RAA) must be present. Other associated findings include, incomplete RBBB, and right ventricular strain.

Question 37

What is Left Ventricular Hypertrophy (LVH)?

Answer 37

can be diagnosed by using multiple criteria.

1) Chest lead criteria include the addition of the S-wave from V1 or V2 to the R-wave of V5 or V6. A sum of 35 is positive in patients 35 years of age or older.
2) Limb lead criteria include the sum of the R-wave in Lead I and the S-wave in Lead III 25.
3) Also, any R-wave in Lead AVL 12.

The presence of a strain pattern makes the diagnosis more certain. LAD is often seen with LVH. These criteria are not necessarily valid in patients less than 35 years of age.

Question 38

What is ischemia?

Answer 38

Ischemia is cellular hypoxia. Cells are not irreparably damaged. Ischemia is typically manifested by ST-segment depression and/or T-wave inversion.

Question 39

What is injury?

Answer 39

Injury is cellular damage, but some, if not all, of the cells can recover. Injury is manifested by ST-segment elevation and hyper-acute or tombstone-appearing T-waves

Question 40

What is Infarction?

Answer 40

is cellular death. Cells cannot be repaired. Infarction is manifested by loss of R-wave forces and by the development of Q-waves in leads consistent with vascular supply. Examples of this include Leads II, III, and AVF for inferior infarctions. Leads I, AVL, V5-6 will show changes in a lateral infarction. Leads V1-3 will show changes in an anterior infarction. Significant Q waves are a minimum of one small box wide and are ¼ to 1/3 the height of the R wave.

Question 41

Loss of R-wave forces and by the development of Q-waves in the I or AVL leads suggests infarction of what vessel?

Answer 41

high lateral- circumflex

Question 42

Loss of R-wave forces and by the development of Q-waves in the II, III, or AVF leads suggests infarction of what vessel?

Answer 42

inferior-RCA

Question 43

Loss of R-wave forces and by the development of Q-waves in the V1-V2 leads suggests infarction of what vessel?

Answer 43

septal-LAD

Question 44

Loss of R-wave forces and by the development of Q-waves in the V1-V4 leads suggests infarction of what vessel?

Answer 44

Anterior-LAD

Question 45

Loss of R-wave forces and by the development of Q-waves in the V5 or V6 leads suggests infarction of what vessel?

Answer 45

Lateral-circumflex

Question 46

Any injury pattern that encompasses all major vessel distributions should lead to the suspicion of _____.

Answer 46

pericarditis.

Question 47

What would suggest right bundle block?

Answer 47

rabbit ears in V1 or V2 and widened QRS

Question 48

What would suggest left bundle block?

Answer 48

rabbit ears in V5 or V6 and widened QRS

Question 49

A widened QRS with no other abnormality is called what?

Answer 49

intraventricular conduction delay

Question 50

How is infarction seen on an ECG?

Answer 50

Q waves at least 1/3 the size of the overall QRS complex