Intro to EKG

Question 1

Where does the blood supply of the SA node come from?

Answer 1

right coronary artery (59% of people), left coronary artery (38% of people) or both (3% of people)

Question 2

Where does the blood supply of the AV node come from?

Answer 2

always from the right coronary artery

Question 3

What are the EKG distributions?

Answer 3

Anteroseptal: V1-V4. Anterior: V2–V4. Anterolateral: V4–V6, I, aVL. Lateral: I and aVL, V5, V6. Inferior: II, III, and aVF. Inferolateral: II, III, aVF, and V5 and V6

Question 4

What is the normal range of the PR interval?

Answer 4

0.12 sec - 0.20 sec

Question 5

What does the Q wave represent?

Answer 5

depolarization of the intraventricular septum .**When at least 1/3 as high as the R wave, considered to be indicative of a transmural MI

Question 6

What is the normal range of the QRS interval?

Answer 6

0.04 to 0.12 sec. Anything >0.12 is considered a Bundle Branch Block or Interventricular conduction delay

Question 7

What does the R wave represent?

Answer 7

the point when half of the ventricular myocardium has been depolarized

Question 8

What causes a widened QRS complex?

Answer 8

A block in either the right or left bundle branch that delays depolarization of the ventricles

Question 9

What does the ST segment represent?

Answer 9

Period from the end of ventricular depolarization to the beginning of ventricular repolarization. Elevation or depression is a hallmark sign of ischemia, CAD or impending MI (STEMI)

Question 10

What is the normal range of the ST segment?

Answer 10

Norm 0.08 to 0.12 sec

Question 11

When are prominent U waves observed?

Answer 11

seen in hypokalemia, but may be present in hypercalcemia, thyrotoxicosis, or exposure to digitalis, epinephrine

Question 12

What is the normal range for the QT interval?

Answer 12

0.34 seconds to 0.43 second

Question 13

What does the QT interval represent?

Answer 13

total duration of electrical activity of the ventricles.

Question 14

What are two ways to calculate rhythm?

Answer 14

1) Count the # of R waves in a 6 second rhythm strip, then multiply by 10. 2) Find a R wave that lands on a bold line. Count the # of large boxes to the next R wave (300,150,100,75,60,50)

Question 15

How do you determine regularity?

Answer 15

Look at the R-R distances using markings on a paper. Classify as regular, occasionally irregular, regularly irregular, or irregularly irregular

Question 16

What can cause biphasic P waves?

Answer 16

Bifid = P mitrale (LA hypertrophy). Pointy = P pulmonale (RA hypertrophy)

Question 17

What can cause a prolonged PR interval?

Answer 17

1st-3rd degree AV blocks.

Question 18

Describe R wave progression

Answer 18

QRS complex should start out negative in lead V1 and end up positive by V6. The R wave will be tallest in lead V3 or V4.

Question 19

What does a transition of R wave from negative to positive in V1 or V2 indicate?

Answer 19

is referred to as an early transition and can be indicative of a previous posterior wall MI.

Question 20

What is the QRS axis?

Answer 20

Represents the overall direction of the heart’s activity. Axis of –30 to +90 degrees is normal

Question 21

What EKG findings characterize a right bundle branch block?

Answer 21

wide bunny ears QRS in V1, V2 and sometimes inverted T waves

Question 22

What is the EKG criteria for a LBBB?

Answer 22

QRS > 120 ms, Dominant S wave in V1, Broad R wave in leads I, AVL, V5-V6. Absent Q waves in leads I, V5, V6. ST and T waves normally opposite direction to QRS

Question 23

What is the EKG criteria for a intraventricular conduction delay?

Answer 23

QRS duration >0.10s and criteria for specific bundle branch or fascicular blocks not met

Question 24

What is the EKG criteria for a LVH?

Answer 24

The R wave in V5 plus the S wave in V1 exceeds 35 mm. Baseline ST depression in V5, V6

Question 25

What might cause ST depression?

Answer 25

coronary ischemia, hypokalemia, digitalis toxicity

Question 26

What is the criteria for ST elevation to indicated an MI?

Answer 26

An elevation of >1mm and longer than 80 milliseconds following the J-point

Question 27

What EKG changes are seen with a NSTEMI?

Answer 27

during ischemia and infarction ST depression and T wave inversion. Afterwards ST returns to baseline but T wave inversion persists

Question 28

What EKG changes are seen with a a STEMI?

Answer 28

during ischemia ST depression, peaked T waves then T wave inversion. during infarction ST elevation and appearance of Q waves. Afterwards ST segments and T waves return to normal but Q waves may persist

Question 29

What is a lengthened QT interval a biomarker for?

Answer 29

ventricular tachyarrhythmias like torsades de pointes and sudden death.

Question 30

What is the QT interval dependent on?

Answer 30

the heart rate (the faster the heart rate the shorter the QT interval) and may be adjusted to improve the detection of patients at increased risk of ventricular arrhythmia.

Question 31

What could cause QT prolongation?

Answer 31

Na channel blockers, hypoelectrolytes, hypothermia, AMI, increased ICP