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Y1 - HPP1 > Cardiovascular System II - ECG > Flashcards

Cardiovascular System II - ECG Flashcards

1
Q

What is an electrocardiogram (ECG

A

Measured by electrodes put on skin pick up electrical fields from signals conducted in heart

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2
Q

Describe an ECG

A

Body fluids are saline, conduct electrical signals well, EKGs recorded from limb leads/chest leads

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3
Q

What do different leads emphasise?

A

Different aspects of electrical signals

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4
Q

What are the different parts of a heartbeat shown on an ECG?

A

P wave, PR interva;, QRS complex, S-T segment, T-wave, QT interval

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5
Q

What is the P wave?

A

Atrial depolarisation

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6
Q

What is the PR interval?

A

Time from onset of atrial activation to onset of ventricular activation

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7
Q

What is the QRS complex?

A

Ventricular depolarisation

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8
Q

What is the S-T segment?

A

Isoelectric, Ventricles before repolarisarion

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9
Q

What is the T-wave?

A

Ventricular repolarisation

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10
Q

What is the OT interval?

A

Duration of ventricular activation and recovery

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11
Q

How is the paper divided on an ECG sheet?

A

Paper divided into small 1mm and large 5mm squares

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12
Q

How many smalls squares in 1 large square?

A

1 large square = 5 small squares

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13
Q

What length per time does the paper at?

A

25mm per second

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14
Q

Describe the time calculated from small and large squares

A

1 small square (1/25) = 0.04sec
1 large square = ⅕ = 0.2 sec
5 large squares = 1 sec
300 large squares = 1 min

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15
Q

What are the steps to calculating heart rate from an ECG sheet?

A

Count no. large squares btw consecutive beats eg R-R interval
Divide 300 by n.o of large squares in R-R interval
Eg large squares btw 2 beats = 4, 300 large squares = 1 min, time for 1 beat = 4 squares, N.o of beats per min = 300/4

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16
Q

What is an arrythmia?

A

Abnormalities in heart rhythm

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17
Q

What are the 2 causes of arrythmias?

A

Malfunction of the conductive system

Abnormal impulse generation (ectopic beats)

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18
Q

Describe malfunction of the conductive system

A

Partial damage to AV node, lead to heart block causing more than one P wave in each QRS-T complex

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19
Q

Describe abnormal impulse generation

A

Originate in atria/ventricle in absence of nodal damage/initiate extra systoles

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20
Q

Describe ectopic beats

A

Loss or addition of a beat
If many ectopic foli form, discharge asynchronously means cardiac tissue is fibrillating - Heart may not pump blood when this occurs

21
Q

Describe the difference between atrial and ventricular fibrillation

A

Atrial fib - QRS complex can form but superimposed on irregular baseline with no clear P waves
Ventricular fib - No QRS-T waves, causing no cardiac output result in death

22
Q

What is tachycardia?

A

Heart rate over 100 beats/min

23
Q

What are the causes and other types of tachycardia?

A 
Benign factors (very dangerous)
Atrial fibrillation, atrial flutter, atrial tachycardia, ventricular tachycardia
24
Q

What is bradycardia?

A

Heart rate under 60 beats/min

25
Q

Describe bradycardia

A

Leads to fatigue, weakness

Atrial bradycardia caused by vagal nerve stimulation, AV node, absence of electrical impulse from sinus node

26
Q

What is a heart block?

A

Blockage of part of the electrical system of heart

27
Q

What is caused (symptoms) and what can a heart block lead to?

A

Lightheadedness, syncope (fainting), palpitations (as opposed to coronary heart disease (CAD) - Blood vessels of heart)
CAD leads to angina/MI

28
Q

What are the 5 types of blood vessels?

A

Arteries, Arterioles, Capillaries, Venules, Veins

29
Q

What are the 3 layers of a muscular arteriole?

A 
Tunica intima (innermost layer)
Tunica media (middle layer)
Tunica adventitia (outer layer)
30
Q

Describe tunica intima

A

Single monolayer of endothelial cells on thin layer of connective tissue
Endothelial cells from main barrier to other circulating blood factors eg plasma proteins
Endothelium secrete vasoactive substances which contribute in regulating vascular tone (nitric oxide, prostacyclin)

31
Q

Describe tunica media

A

Consists of spindle-shaped smooth muscle cells embedded in matrix of elastin/collagen
Provides mechanical strength, contractile power for blood vessel (contraction and dilation)

32
Q

Describe tunica adventitia

A

Connective tissue sheath, no distinct outer border, binds to vessel loosely in place
Consists mostly of fibroblasts and nerve endings

33
Q

Describe elastic arteries

A

Conducting vessels - Diameter 1-2cm in man

34
Q

Name examples of elastic arteries and what are they characterised by?

A

Pulmonary artery, Aorta, Major aortic branches (eg iliac arteries)
Distensible walls - High elastin in medial layer

35
Q

What does elastin allow?

A

Vessels to expand/receive stroke volume during ventricular ejection (and recoil during diastole)

36
Q

Why is collagen within the medial layer?

A

Provides rigid support preventing vessels from over-distending

37
Q

Describe the classification of arterioles (resistance arteries)

A

Diameter (20-100M), relatively thick walls (20-30M)
Provide main resistance to blood flow - High resistance due to narrow lumen
Regulate blood flow locally by inc/dec flow

38
Q

Describe the classification of capillaries (exchange vessels)

A

Diameter (6-10M)
Single layer of endothelial cells
Thickness (0.2-1M) facilitates rapid transfer of metabolites between blood/tissue

39
Q

Describe the classification of capacitance vessels (venules and veins)

A

Thinner walls than arteries
Allows easy distension/collapse - Act as reservoir of blood
Many veins innervated by vasoconstrictor nerve fibres - Allows volume of blood in vessels to be actively controlled

40
Q

Define blood pressure

A

Pressure exerted by circulating blood upon walls of blood vessels

41
Q

Describe blood pressure

A

Systemic arterial pressure measured on upper arm - Measure of pressure in brachial artery

42
Q

How is blood pressure expressed?

A

As systolic pressure over diastolic pressure (mmHg) eg 120/80

43
Q

Describe pressure gradient in blood vessels

A

Mean systemic blood pressure = 93mmHg in arteries to 10mmHg in vena cava
Velocity of flow depends on total cross sectional area
Flow is slowest in caps, fastest in aortic major arteries

44
Q

Why does pressure never reach zero?

A

Arteries aren’t completely empty of blood

45
Q

What is the equation for pulse pressure?

A 
PP = SP - DP
SP = Systolic pressure
DP = Diastolic pressure
46
Q

What is the magnitude of pulse pressure due to?

A

Stroke volume, Speed of ejection from heart, Arterial compliance

47
Q

Describe pulse pressure

A

Average - 30-40mmHg - Incr with exercise due to inc stroke volume, Lowered by low stroke volume (eg trauma, blood loss), Long term inc due to aortic stiffening

48
Q

Define mean arterial blood pressure

A

Average bp over entire body

Average arterial pressure during single cardiac cycle

49
Q

Equation for mean arterial blood pressure: MAP = (CO x SVR) + CVP
What do they mean?

A 
CO = Cardiac output
SVR = Systemic vascular resistance
CVP = Central venous pressure

Y1 - HPP1 (16 decks)

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