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FHB Exam 1 - Cardiovascular Physiology > EKG Conference > Flashcards

Flashcards in EKG Conference Deck (28)
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1
Q

The action potential duration is represented by what part of the EKG?

A

Q-T interval

  • usually 230-450 msec
2
Q

What occurs during the P-R interval?

A

Depolarization of Atria, Bundle Branches, Purkinje & Bundle of His

3
Q

What is the term for the following:

  1. Area of EKG that includes a waveform
  2. No waveform
A

Interval

Segment

4
Q

When does the SA node depolarize on the EKG?

A

Before the P wave

5
Q

When is the plateau of the action potential, as reflected on the EKG?

A

S-T Segment (no waveform)

6
Q

If all the QRS complexes were tall, how would this be seen clinically?

A

HYPERTROPHY of the ventricles (in football players for example)

  • seen via XRAY –> hypertrophy of the ventricles
7
Q

Everyone has the same Q-T interval. True or False?

A

False!

NO FIXED QT INTERVAL SINCE EVRYONE HAS A DIFFERENT BASE HR

8
Q

When does depolarization of the ventricles occur?

A

QRS complex

9
Q

How is the speed of the Action Potential reflected on an EKG?

A

the timing of QRS –> narrow QRS = fast AP

slurred QRS = slow AP

10
Q

What are the slow activating AP of the heart? When are these cells depolarized on the EKG?

A

1.Sa and AV node

  1. Before the Pwave
  2. During the middle of the p wave = AV Nodal (activated before atrial depolarization)
11
Q

How does the His Bundle enter the left and right bundle branches?

A

through the SEPTUM

  • first place depolarization of the heart is spread (depolarization starts here as well)
12
Q

The EKG provides info on contractile ability and strength of the heart. True or False

A

FALSE!

  • but we can infer from the EKG various changes
13
Q

What si the value in seconds of one small box? A large box?

A

Small - 0.04 seconds

Large - 0.2 seconds

14
Q

How do you calculate HR on EKG?

A

300/ # of boxes between each QRS

15
Q

What is the main change during a tachycardia?

A

HR

  • diastole is decreased, so with length-interval relationship the systole is shortened so that diastole can be prolonged a little to allow increases filling
16
Q

What are the values for the following

  1. P-R Interval
  2. QRS
  3. Q-T interval
  4. Tachycardia
  5. Bradycardia
A
  1. 120-200 (.12 -0.2)
  2. 70-100msec (0.07-0.1)
  3. 230-450 (0.23-0.45)
  4. cycle length less than 0.6 seconds (600 msec) & greater than 100 beats/min
  5. cycle length greater than 1 second (1000 msec) & les than 60 beats/min
17
Q

Of the precordial leads, which is strongest and why?

A

V6

  • closest to left ventricle so positive deflection is largest
18
Q
Describe the location of the precordial leads.
V1
V2
V3
V4
V5
V6
A

V1 - 4th intercostal space at the right sternal border
V2 - 4th intercostal space at the LEFT sternal border
V3 - is placed halfway between V2 and V4
V4 - 5th intercostal space at the left midclavicular line
V5 - same level as V4 at the left ANTERIOR axillary line
V6 - same level as V4 at the left midaxillary line

V1 and V2 = septal leads. Electrical activity of the inter-ventricular septum is best measured in these leads.

V3 and V4 = anterior leads. Electrical activity of the anterior (front) wall of the left ventricle is best measured in these leads.

V5 and V6 = left precordial or lateral precordial leads.

19
Q

A notched QRS is often the sign of what?

A

Bundle Branch block

ex: RBBB
- As conduction through the myocardium is slower than conduction through the Bundle of His-Purkinje fibres,
- since NOT conducting through His-Prukinje system (and through muscle) - the action potential is slower and QRS is widened!!
- The QRS complex often shows an extra deflection which reflects the rapid depolarisation of the left ventricle followed by the slower depolarisation of the right ventricle.

20
Q

Can an EAD or DAD be seen on an EKG?

A

NO!!!

  • no membrane potentials seen directly on EKG
21
Q

What is the mnemonic to distinguish Left & Right bundle branch block?

A

A mnemonic to distinguish between ECG signatures of Left bundle branch block (LBBB) and right, is WiLLiaM MaRRoW; i.e., with LBBB, there is a W in lead V1 and an M in lead V6, whereas, with RBBB, there is an M in V1 and a W in V6.

22
Q

What are the:

  1. Inferior Leads
  2. Lateral Leads
  3. Antero septal
A
  1. Leads II, III, avF
  2. V5, V6, avL, I
  3. V1-V2 = septal
    V3-V4 = anterior
23
Q

In PVC, what has changed due to changes in AP?

A

Contractility

  • Ca handling
24
Q

After a PVC, will arterial pressure be higher or lower? Why does a PAUSE occur?

A

HIGHER than normal

= increased after load

  • SA blocked in AV node since ventricle is still in refractory period –> recovers after this pause
  • increase contractility due to PESP
25
Q

What is the last part of the heart to be activated? The first?

A
  1. Epicardial Surface (endo to epi)

2. Septum

26
Q

Why does repolarization cause a positive waveform? Where does repolarization start?

A
  1. Vector of depolarization is in the same direction as the vector of depolarization

(even though it is an opposite electrical event)

2, EPICARDIAL SURFACE

27
Q

What Repolarizes first, epicardium or endocardium?

A

EPICARDIUM

  • shorter AP & quicker depolarization because there is a K+ current
  • epicardial cells have more iTo
    = shorter AP as a result
28
Q

What are two possible causes of Left and right axis deviation?

A
  1. Hypertrophy of respective ventricle (L for LAD or R for RAD)
  2. Bundle Brnach block
  • right block = RAD
  • left block = LAD

more negative than -30 = LAD

more positive than 90 = RAD