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CARDIOLOGY > Normal Ecg > Flashcards

Normal Ecg Flashcards

1
Q

The electrocardiogram (ECG) is

A

graphical record of potential differences generated during cardiac electrical activity.

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2
Q

The electrical potentials are produced in the heart as the sum of

A

of the potentials generated by the heart muscle cells during depolarization and repolarization.

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3
Q

Depolarisation =

A

change of the transmembrane potential determinated by the movement of electrical charges (electrons or ions)

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4
Q

Repolarisation=

A

restoration of the resting transmembrane potential, induced by the movement of the electric charges in the opposite direction, which compensates for depolarization

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5
Q

Where are the V1, V2 electrodes placed?

A

4th intercostal space

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6
Q

What is the most common error in performing an ECG?

A

L to R reversal

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7
Q

V1 and V2 are often misplaced. Such misplacement usually involves placing these leads too high on the chest. The resulting ECG may generate erroneous ECG patterns:

A

incomplete right bundle branch block, anterior T wave inversion, septal Q waves, ST-segment elevation. These features may falsely suggest acute or old cardiac ischemia, pulmonary embolism, or a type-2 Brugada pattern. On rare occasion, conversely, high placement of V1 and V2 may reveal a true type-1 Brugada pattern. The emergency clinician needs to be aware of the possibility of lead misplacement, and should know how to suspect it based on unusual P wave morphology in V1 and V2.

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8
Q

What physiological / pathological situation mimics the L to R reversal?

A

Dextrocardia

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9
Q

The 6 chest electrodes

A

V1- 4th intercostal space ,right sternal border
V2 - 4th intercostal space , left sternal border
V3 - Midway b/w V2 + V4 , left anterior axillary line
V4 - 5th intercostal space , Left midclavicular line
V5 - level with V4 , left anterior axillary line
V6 - level with V4 , left mid axillary line

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10
Q

ECG lead =

A

the spatial ratio between two points where the electrodes are placed in the electric field of the heart.

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11
Q

Bipolar (standard) limb leads (I, II and III)

A

They form an equilateral triangle, with the heart located in the center
were introduced by Einthoven.

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12
Q

Unipolar (augmented) limb leads (aVR, aVL, aVF)

A

were introduced by Wilson. „

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13
Q

Precordial leads (V1-V6)

A

are unipolar leads, in which the (positive) exploratory electrode is placed on the chest, near the heart

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14
Q

Limb leads – Eithoven’s triangle

The heart walls “seen” from the different ecg limb leads :

A

Lateral wall of the LV : DI, aVL
Inferior wall : DII,DIII, aVF
Endocavitary wall/layer of the heart: aVR

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15
Q

Precordial leads

The heart walls “seen” from the precordial leads:

A

Anterior wall of the heart : V1,V2
Interventricular septum: V3
Apex : V4
Lateral wall of the LV : V5,V6

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16
Q 
Ecg graph paper: 
- Small boxes of 
- Large boxes of 
Paper speed :
Voltage calibration:
A

1) 1mm
2) 5mm
3) 25 mm/sec
4) 10 mm /mV

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17
Q

ECG Recommended steps

A 
Heart rate 
Axis 
Morphology of the waves
Segments and intervals analysis 
Chamber enlargements
Specific changes
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18
Q

The cardiac cycle normally begins with initiation of the impulse at the

A

sinoatrial, or SA node.

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19
Q

After the SA node fires, the resulting depolarization wave passes through

A

the right and left atria, stimulating atrial contraction and producing the P-wave on the surface ECG.

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20
Q

Following activation of the atria, the impulse proceeds to the

A

trioventricular (AV) node, which is the only normal conduction pathway between the atria and the ventricles.

The AV node slows impulse conduction, allowing time for the atria to contract and blood to be pumped from the atria to the ventricles prior to ventricular contraction. Conduction time through the AV node accounts for most of the duration of the PR interval.

Just below the AV node, the impulse passes through the bundle of His.

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21
Q

After the impulse passes through the bundle of His

A

it proceeds through the left and right bundle branches.

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22
Q

After leaving the left and right bundle branches,

A

the impulse passes through the Purkinje fibers, which are interlacing fibers of modified cardiac muscle. On the ECG this is represented as the Q wave.

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23
Q

The impulse passes quickly through the bundle of His, the left and right bundle branches, and the Purkinje fibers, leading to

A

depolarization and contraction of the ventricles.

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24
Q

P wave

A

atrial depolarisation

can be positive , equidiphasic or negative

25
Q

QRS complex

A

ventricular depolarisation
Q wave : the first negative deflection before the R wave
R wave: positive deflection
S wave: the first negative wave after the R wave

26
Q

T wave

A

ventricular repolarization

can be positive , equidiphasic or negative

27
Q

Abnormalities of axis can hint at:

A 
Ventricular enlargement
Conduction blocks (i.e. hemiblocks)
28
Q

By near-consensus, the normal QRS axis is defined as ranging from :
-30° to -90° is referred to as :
+90° to +180° is referred to as :

A

1) -30° to +90
2) left axis deviation (LAD)
3) right axis deviation (RAD)

29
Q

Key Principles

A

If the QRS is POSITIVE in any given lead, the axis points in roughly the same direction as this lead.
If the QRS is NEGATIVE in any given lead, the axis points in roughly the opposite direction to this lead.
If the QRS is ISOELECTRIC (equiphasic) in any given lead (positive deflection = negative deflection), the axis is at 90° to this lead.

30
Q

Common causes of LAD

A 
May be normal in the elderly and very obese
Due to high diaphragm during pregnancy, ascites, or ABD tumors
Inferior wall MI
Left Anterior Hemiblock
Left Bundle Branch Block
WPW Syndrome
Congenital Lesions
RV Pacer or RV ectopic rhythms
Emphysema
31
Q

Common causes of RAD

A 
Normal variant
Right Ventricular Hypertrophy
Anterior MI
Right Bundle Branch Block
Left Posterior Hemiblock
Left Ventricular ectopic rhythms or pacing
WPW Syndrome
32
Q

Normal Sinus Rhythm

A 
Originates in the sinus node
Rate between 60 and 100 beats per min
P wave axis of +45 to +65 degrees, ie. Tallest p waves in Lead II
Monomorphic P waves
Normal PR interval of 120 to 200 msec
Normal relationship between P and QRS
Some sinus arrhythmia is normal
33
Q

p wave upright in leads

A

I and II

34
Q

The P wave

A

< 3 small squares in duration

< 2.5 mm in amplitude

35
Q

Junctional escape

A

Depolarization initiated in AV junction when 1 or more impulses from the sinus node are ineffective or nonexistent.
Rate : 40- 60 bpm
Rhythm : Irregular in single junctional escape complex ; regular in junctional escape rhythm
P waves : depends on the site of the ectopic focus.They will be inverted , and may appear before or after the QRS complex , or they might be absent , hidden by the QRS .
QRS is usually normal

36
Q

Junctional escape

A

Depolarization initiated in AV junction when 1 or more impulses from the sinus node are ineffective or nonexistent.
Rate : 40- 60 bpm
Rhythm : Irregular in single junctional escape complex ; regular in junctional escape rhythm
P waves : depends on the site of the ectopic focus.They will be inverted , and may appear before or after the QRS complex , or they might be absent , hidden by the QRS .
QRS is usually normal

( No relation b/w P wave and QRS complex??)

37
Q

PR interval

A

AV node conduction
From the beginning of P wave to the beginning of q wave
120-200 ms

38
Q

Short PR interval

A 
WPW Syndrome 
delta wave
short PR ( 0.08s)
long QRS 0.12 sec

Accessory pathway ( Bundle of Kent ) allows early activation of the ventricle ( delta wave and short PR interval)

39
Q

Normal QRS complex

A

Completely negative in lead aVR , maximum positivity in lead II
rS in right oriented leads and qR in left oriented leads (septal vector)
Transition zone commonly in V3-V4
RV5 > RV6 normally
Normal duration 50-110 msec, not more than 120 msec
Physiological q wave not > 0.03 sec

40
Q

Amplitude of QRS

A

Depends on the following factors

  1. electrical force generated by the ventricular myocardium
  2. distance of the sensing electrode from the ventricles
  3. Body build;a thin individual has larger complexes when compared to obese individuals
41
Q

Left ventricular hypertrophy
Sokolow & Lyon criteria
Cornel criteria
others

A

S&L : S (V1) + R(V5 or V6)>35mm
Cornel criteria : S(V3) + R(avL)> 28 mm ( men ) or > 20 mm ( women)
others : R (avL) > 13mm

42
Q

Premature ventricular Complexes (PVCs)

A

is a relatively common event where the heartbeat is initiated by the heart ventricles ( arrow ) rather than by the SA node.Rate depends on underlying rhythm and number of PVCs. - Ocassionally ireegular rhythm .

  • no p wave associated with PVCs
  • May produce bizarre looking T wave
43
Q

Artificial pacemaker

A

Sharp , thin spike
Rate depends on pacemaker , p wave may be absent or present
Ventricular paced rhythm show wide ventricular pacemaker spikes

44
Q

localizing MI

A

Look at ST changes

Q wave in all leads

45
Q

Location of MI
Anterior
Septum
Left lateral

A

Lead with ST change : Affected coronary artery :

1) V1,V2,V3,V4 , LAD
2) V1,V2 LAD
3) I ,avL ,V5,V6 Left circumflex artery

46
Q 
Location of MI 
Inferior
Right atrium
Posterior 
Right ventricle
A 
Lead with ST change :
Affected coronary artery :
1)II,III,avF RCA
2) aVR ,V1 RCA
3) Posterior chest leads RCA
4) Right sided leads RCA
47
Q

T wave

A

Reflects ventricular repolarization ( epicard -> endocard)
Aspect : rounded , assymetric, with steeper downward slope
Consostent with QRS complex
positive in most derivatives
negative :avR +/- in LIII,avF,V1
Amplitude < 1/3 QRS ( <6 mm)
Duration : 0.13 - 0.30 s
Modified by factors:
Physiological : SNVP -> T high asymmetric ( precordial)

Humoral factors :
Decreased PO2 ,Ca++,K+

48
Q

U wave

A

corresponds to papillary muscle repolarization or post-depolarization in Purkinje fibers
Aspect : small , rounded
Same direction with T waves from the same derivation

Amplitude < 1/4 from the same derivation :
more obvious decreased FC , [K+]
Better expressed in chest precrodial leads ( V1 ,V2)

49
Q

QT interval

A

Normally corrected for HR
Bazett’s formula
Normal 350 to 430 msec
With a normal HR (60-100), the QT interval should not exceed half of the RR interval roughly

50
Q

Measurement of QT interval

A

The beginning of the QRS complex is best determined in a lead with an initial q wave -> LI,II,avL,V5 or V6
QT interval shortens with tachycardia and lenghthenswith bradycardia

51
Q

QTc

A 
Normal QTc 
Men < 0.43 
- borderline 0.43 - 0.45
- prolonged >0.45
Women <0.43 
- borderline 0.43 - 0.47
- prolonged >0.47
52
Q

Causes of Long QTc

A 
Congenital
- Romano Ward
- Jervell and Lange Nielson
Drugs
- Antiarrhythmics
- Class Ia and III
- Antibacterials
- Erythromycin
Other drugs
- Terfanidine, cisapride, TCA
Electrolyte disturbances
- Low K and Mg
Other causes
- IHD
- SAH
- Bradycardia due to SSS or AV block
- Hypothyroidism
53
Q

Shortened QT

A

Digitalis effect
Hypercalcemia
Hyperthermia
Vagal stimulation

54
Q

Normal variants in ECG

A

Sinus arrhythmia
Persistent juvenile pattern
Early repolarisation syndrome
Non specific T wave changes

55
Q

Features of ERPS

A 
Vagotonia / athletes’ heart
Prominent J point
Concave upwards, minimally elevated ST segments
Tall symmetrical T waves
Prominent q waves in left leads
Tall R waves in left oriented leads
Prominent u waves
Rapid precordial transition
Sinus bradycardia

Early Recognition Prevents Streptokinase infusion !

56
Q

ECG Motion Artifacts Overview

A

Motion artefact due to tremor or shivering can obscure the waveforms of the ECG or stimulate pathology , making ECG interpretation difficult
In certain circumstances ( e.g hypothermia ) the presence of shivering artefact may actually aid diagnosis

57
Q

Causes of Tremor

A 
Benign Essential Tremor (physiological tremor ) 
Parkinsons Disease (resting tremor )
Cerebellar disease (intention tremor)
Alcohol /Benzodiazepine withdrawal
Anxiety
Thyrotoxicosis
Multiple sclerosis
Drugs : Amphetamines , cocaine , β- agonists (adrenaline , salbutamol) theophylline,caffeine , lithium
58
Q

Other types of motion artefacts

A

Fever ( rigors)
Hypothermia (shivering)
Cardiopulmonary resuscitation ( chest compressions)
A non-compliant , mobile ,talkative patient ( = the most common cause)

59
Q

The role of ECG

A

HR determination;
Assessment of cardiac conduction function;
Determination of the electrical axis of the heart;
Determination of: cardiac arrhythmias and conduction disorders;
Determination of ischemic changes
It does NOT provide information about the pump function of the heart.

CARDIOLOGY (19 decks)

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