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Flashcards in Intro to EKG Deck (28):
1

P wave

atrial depolarization

2

QRS

ventricular depolarization

3

T wave

ventricular repolarization

4

U waves

inconsistent

5

PR interval

From onset of P wave to onset of QRS is measure of AV node conduction time. Normal is 0.12-0.20 seconds

6

QT interval

From onset of Q to end of T, represents total duration of depolarization and repolarization

7

How to calculate HR from EKG

HR= 300/ # heavy lines btw QRS's OR HR= 1500/ #mm btw QRS's

8

What are EKG leads

Electrodes that measure the difference in electrical potential btw: two different points (bipolary leads) on the body or one point on th body and a virtual reference point with zero electrical potential located in center of heart (unipolar leads)

9

Describe polarity on EKG. Which direction will QRS be in left, lateral and right sided leads?

Depolarization moving toward a positive electrode produces a positive deflection. QRS is + in left and lateral, and - in right leads

10

Describe placement of bipolar limb leads

lead I (+ on one handt, - on other hand), lead II (- on hand, + on foot), lead III (+ on foot and - on hand)

11

Describe placement of augmented limb leads

Unipolar leads. aVL (+ on left wrist), aVR (+ on right wrist), aVF (+ on ankle)

12

What are lateral leads

lead I and aVL : reflect lateral wall changes

13

What are inferior leads:

lead II, III and aVF: reflect inferior wall changes

14

What do the right chest and left chest leads measure

Right chest leads (V1 and V2) moniter RV. Left chest leads (V5 and V6) monitor LV

15

EKG of ventricular hypertrophy

more muscle= more volts= greater amplitude. Left ventricle hypertrophy shows big R waves in left sided leads (I, aVL, V5, V6). Right ventricle hypertrophy shows big R waves in right sided leads (V1, V2)

16

EKG of ischemic changes in heart

ischemia alters ventricular repolarization. Ischemia due to sudden high oxygen demand in the presence of fixed coronary obstruction causes depression of the ST segment. Ischemia due to acute coronary artery obstruction during low oxygen demand causes T wave inversion

ischemia alters ventricular repolarization. Ischemia due to sudden high oxygen demand in the presence of fixed coronary obstruction causes depression of the ST segment. Ischemia due to acute coronary artery obstruction during low oxygen demand causes T wave inversion

17

EKG in transmural injury

Transmural injury in acute coronary syndrome, usually with clot due to platelet aggregation in coronary artery, results in ST elevation

18

EKG in transmural infarct/necrosis

Sizeable Q wave. Infarcts usually only develop in left ventricle. Q waves in inferior leads (II, III, aVF) are due to inferior infarcts. Q waves in V1-V4 are due to anterior wall infarcts. Lead I, aVL and V5,V6 are due to lateral wall infarcts

19

What criteria are required for a 'sizeable' Q wave

> 1/4 the amplitude of R wave, > one small box wide, present in at least 2 leads reflecting same region of left ventricle

20

Describe EKG changes that occur over time in an evolving transmural MI

Hyperactute T waves, T-wave inversion (ischemia), ST elevation (current of injury), Q waves +/- T wave inversion and ST elevation

21

Compare Transmural to subendocardial MI

Transmural: ST elevation with Q waves. Subendochondral: ST depression no Q wave

22

Leads and associated infarct locations

V1-V2: anteroseptal wall. V3-V4: anterior wall. V5-V6: anterolateral wall. II, III, aVF: inferior wall. I, aVL: high lateral wall

23

Prolonged QT definition

QT interval is more than half the RR interval

24

Causes of prolonged QT interval

hypcalcemia, hypokalemia, hypomagnesemia, Class1A or 3 anti-arrhythmic drugs, hypothermia, long QT syndrome

25

Hypercalcemia vs hypocalcemia on EKG

Hyper: shortened QT. Hypo: prolonged QT. Both can predispose to arrhythmia

26

Hypokalemia EKG

Prolonged QT, prominent U waves, inverted T waves

27

Hyperkalemia EKG

mild: Tall T waves makes peaked and symmetrical EKG. Moderate: P + R waves flatten, QRS + T broaden, big S waves. Severe: P+ R waves gone, S and T waves broaden, sine wave pattern

28

How do drugs, electrolytes, etc lead to arrhythmias?

abnormal QT interval and T wave are altered due to alterations in repolarization