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Physio > Electrical Activity of the Heart and the ECG > Flashcards

Electrical Activity of the Heart and the ECG Flashcards

1
Q

Pathway for cardiac conduction

A

SA Node
internodal tract or bachman’s bundle
AV node
right or left bundle branch
conduction pathways to ventricles

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2
Q

why is there a specific pathway for conduction?

A
  • you don’t want all chambers to contract at the same time
  • allows for sequential contraction for directional flow
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3
Q

why are there smaller branches of conduction pathways?

A

there is a lot of muscle mass to stimulate so it helps cover the distance and improve synchronization

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4
Q

why do conduction velocities vary depending on the location in the heart? where does it vary?

A
  • because certain locations have higher resistance to reduce the signals from being sent to places they shouldn’t be yet
  • allows for synchronized contraction, no delay
  • the atria, AV node, and ventricles have 0.5m/s slow velocity whereas everywhere else is ~2-4m/s
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5
Q

what is the sequence of cardiac muscle contraction?

A
  • atria (SA node > internodal > bachmann’s bundle)
  • septum (L to R), bundle of His
  • anteroseptal (bundle of His, initial activation of purkinje fibers)
  • ventricular (branches of the rest of purkinje fibers
  • total length = 250-300ms
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6
Q

what do the peaks represent on an EKG?

A
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6
Q

What does an EKG do?

A

measures the electrical activity of the heart

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6
Q

how does an action potential compare to an ECG?

A

AP = electrical activity in on cell
ECG = multiple AP in the heart within a period of time

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6
Q

what kind of information can you get from an ECG?

A

information on heart rate, rhythm, conduction velocity, and condition of the heart tissue

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7
Q

what is a wave on an ECG?

A

an upward or downward deflection from the isoelectric line

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8
Q

what is the isoelectric line on an ECG?

A

the baseline

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9
Q

what is a segment on an ECG?

A

a section on the isoelectric line only

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10
Q

what are the waves on an ECG? and what do they signify?

A
  • P wave: atrial depolarization
  • QRS wave: ventricular depolarizaiton (and hidden atrial repolarization)
  • T wave: ventricular repolarization
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11
Q

what are the segments on an ECG? and what do they signify?

A
  • PR segment: goes from end of P wave to beginning of QRS wave
  • ST segment: goes from end of QRS complex to the beginning of the T wave
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12
Q

What is lone QT syndrome?

A

when there is only a QT segment on the ECG which signifies the ventricular activity is out of whack

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13
Q

what does it mean when the ST segment is elevated?

A

the patient had a myocardial infarction –> death of cardiac tissue was replaced with fibrous tissue and cannot contract or pass electrical conduction

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14
Q

what are intervals on an ECG?

A

combination of both waves and segments

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15
Q

what are the intervals on an ECG?

A
  • PR interval
  • QRS interval
  • QT interval
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16
Q

What is a PR interval? Duration? what does it represent?

A
  • goes from beginning of P wave to beginning of QRS complex
  • 0.12-0.2 seconds
  • represents the time it takes for action potentials to travel form the SA node through the AV node
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17
Q

What is a QRS interval? Duration? what does it represent?

A
  • goes from the beginning to the end of the QRS complex
  • 0.006-0.1 seconds
  • represents the time it takes for ventricular depolarization
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18
Q

What is a QT interval? Duration? what does it represent?

A
  • goes from the beginning of the QRS complex to the end of the T wave
  • less than 0.42 seconds
  • represents the time between initiation of the QRS complex and the end of the T wave
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19
Q

What is the importance of ECG paper calibration?

A
  • the events that occur are fast
  • the paper is calibrated in the same way in order to have consistent readings
20
Q

ECG paper calibration measurements

A
21
Q

what are ECG leads?

A

surface electrodes that are placed on the body on the limbs and the chest
- 10 leads
- 12 electrical vectors recorded (9 direct and 3 augmented)

22
Q

Know locations of leads: see slides 35-38 and KNOW THEM

A
23
Q

how to measure heart rate:

A

normal ECG paper can be used.
each paper measures 25mm/sec so just math: see slide 39
- need to know how to do this

24
Q

what is an arrythmia?

A

any abnormality in the origin (initiation) and/or conduction (propagation) of the cardiac impulse

25
Q

What are the 5 basic types of arrhythmias?

A

1) normotopic
2) ectoptic
3) re-entrant
4) conduction blocks
5) pre-excitation syndromes

26
Q

what are normotopic arrhythmias?

A

when the electrical impulse originates at the SA node, but is too fast, too slow, or irregular

27
Q

what are ectopic arrhythmias?

A

the impulse originate from an area (focus) other than the SA node

28
Q

what are re-entrant arrhythmias?

A

when the electrical impulse moves in a continuous pattern determined by changes in anatomical arrangement

29
Q

what are conduction blocks?

A

when electrical activity originates at the SA node and follows the usual conduction pathways but has unexpected blocks or delays

30
Q

what are pre-excitation syndromes?

A

when electrical activity move through an accessory pathway that bypasses the normal ones, providing an electrical shortcut

31
Q

what are the types of normotopic arrythmias?

A

1) sinus bradycardia
2) sinus tachycardia
3) sinus arrythmia

32
Q

what is sinus bradycardia ?

A

an abnormally slow sinus rate

33
Q

what is sinus tachycardia?

A

an abnormally high sinus rate

34
Q

what is sinus arrhythmia?

A

an irregular sinus rate

35
Q

what are AV junctional blocks?

A

block in the impulse conduction at the level of the AV node

36
Q

what is a first degree heart block?

A

all APs are conducted through the AV junction but the speed of conduction is slower resulting in longer PR interval

37
Q

what is a second degree heart block?

A

not all APs are conducted through the AV junction. some APs do not reach the ventricles, in which some P waves are followed by a QRS complex and some not
- results in P:QRS ratios to vary

38
Q

what is a third degree heart block?

A

APs are completely blocked at the AV junction. the latent ventricular pacemaker fires to maintain ventricular function. the atria are activated by the SA node and the ventricles are activated by Purkinje fibers at a slow rate resulting in no connection between the P wave and the QRS complex, making it impossible to define a PR interval

39
Q

what is fibrillation?

A

the chaotic activation of the muscle with multiple foci being activated at different times
- ectopic initiations of AP
- higher P wave
- can still have normal function until under stress

40
Q

what is atrial fibrillation?

A

chaotic activation of the atrial muscle
- atrial rate is very high
- no recognizable P waves, only f waves
- compatible with life

41
Q

what is ventricular fibrillation?

A

the chaotic activation of the ventricles with multiple foci activated at different times
- causes a twitching of the ventricle
- not contracting as a unit
- no recognizable QRS complex
- ventricular arrest
- unable to pump blood

42
Q

why are defibrillators important for ventricular fibrillation?

A

the electrical current put into the body attempts to correct the irregularity and force them to contract in unison

43
Q

what is a myocardial infarction?

A

reduction in blood flow (ischemia) to cardiac muscle
- can lead to muscle damage

44
Q

what are the infarct zones?

A
  • ischemia
  • injury
  • necrosis (infarction)
  • fibrosis
45
Q

when is ischemia of the heart?

A

occurs when there is an insufficient blood supply to the heart muscle

46
Q

what is injury of the heart?

A

occurs when there is a prolonged period of ischemia

47
Q

what is necrosis of the heart?

A

the death of myocardial cells from lack of oxygen for too long

48
Q

what is fibrosis of the heart?

A

when the myocardial cells die and are replaced with collagen deposition

49
Q

why is fibrosis not good?

A

the connective tissue is not excitable, cannot contract, and will not regain function

50
Q

What are the changes to the ECG with a myocardial infarction

A

Physio (15 decks)

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