Week 3 Heart Axis And Cardiac Flow

Question 1

What is one lead

Answer 1

A set of TWO electrodes

Question 2

What does a lead measure

Answer 2

Records a voltage shift
As waves spread over the heart

Question 3

How are direction and strength of a signal related in a lead

Answer 3

When a wave is parallel (same direction) it sis stronger

Perpendicular - no signal

Question 4

Why is einthovens triangle formation used

Answer 4

A wave travelling in any direction will be parallel to at least one of the three leads

Question 5

Ground electrode - purpose

Answer 5

Acts as a baseline

Looks at the natural voltage of the ground

Question 6

By convention - what are the ECG directions for depol and repol

Answer 6

Depol - positive (up)

Repol - negative (down)

Waves travelling away from the positive electrode - opposite ^

Question 7

Why is lead 2 normally used in a single lead trace

Answer 7

Lead 2 has the strongest response to a healthy heart

Several issues can be detected on lead 2 - other leads can then be assessed

Question 8

Q of QRS

Answer 8

Depolarisation in the direction of the negative electrode - downward slope

small magnitude

Question 9

Upwards slope R of QRS

Answer 9

Ventricle is being depolarised

Happens in the direction of lead 2

Huge wave in the positive direction

Question 10

Downward slope R of QRS

Answer 10

Ventricle is still depol
But wave points less at the positive electrode
So is seen returning to 0

Question 11

S of QRS

Answer 11

Opposite direction to positive electrode
Wave travels toward atria
Small magnitude
Trace is negatice

Question 12

What is the heart axis

Answer 12

The mean vector
Describing direction of voltage in the heart

Question 13

Heart axis calculation

Answer 13

Calculates mean of each mean electrical wave
Normal is 0-90 degrees

Question 14

what causes ventricular fibrillation

Answer 14

• AP keeps circling back on itself
• or cardiomyocytes are repeatedly contracting
• or contracting irregularly so ventricle is out of synch

Question 15

when to use a defibrillator

Answer 15

• not for a flatline
• is used for ending FIBrillation

Question 16

how does a defib work

Answer 16

depolarises all cardiac cells at once

to create a fresh signal from myogenic pacemaker cells

to bring back synchrony in beating

Question 17

what are the two valves

Answer 17

mitral/bicuspid - 2 cusps
tricuspid - 3 cusps

Question 18

what is the wiggers diagram

Answer 18

a method to visualise several aspects of the heart at once

Question 19

systole

Answer 19

period of contraction of the ventricles

Question 20

diastole

Answer 20

relaxation of heart muscle + then chamber fills with blood

Question 21

phases of systole

Answer 21

1. isovolumetric contraction
2. rapid ejection phase
3. slow ejection phase

Question 22

phases of diastole

Answer 22

1. isovolumetric relaxation
2. rapid filling phase
3. slow filling phase
4. atrial contraction

Question 23

what phase of diastole is the P wave

Answer 23

atrial contraction / depol

Question 24

what phase of systole is QRS

Answer 24

ventricular contraction

Question 25

what phase of systole is the T wave

Answer 25

ventricular relaxation / repol

Question 26

aortic pressures in 1) diastole 2) ejection phase 3) isovolumetric phase

Answer 26

1) diastole - 80mmHg 2) ejection phase - 120 3) isovolumetric relaxation - aortic valve closes, causes dicrotic notch

Question 27

ventricular pressure 1) isovolumetric contraction 2) ejection phase 3) isovolumetric relaxation

Answer 27

1) ventricle contracts, closed chamber so pressure increases when ventricular pressure crosses (is higher) the aortic pressure, the aortic valve opens 2) ejection phase is the top peak ◠ curve when VP decreases and drops below the aortic pressure, the aortic valve closes 3) isovolumetric relaxation starts - pressure decreases - slope downwards when VP falls below atrial pressure (1-7 mmHg) - mitral valve opens - rapid and slow filling ventricle phase starts

Question 28

Atrial pressure

Answer 28

starts high than VP mitral valve closes when ven pressure raises -> raises atrial pressure ejection phase - atrium is filled + pressure rises when pressure is higher than VP - mitral valve opens and filling phase of ventricle starts

Question 29

ESPVR

Answer 29

end systolic pressure volume relationship the max pressure of left ventricle at any volume a measure of cardiac contractility

Question 30

EDPVR. passive filling curve of the left ventricle during diastole and is a measure of passive chamber stiffness

Answer 30

end diastolic pressure volume relationship passive filling curve of the left ventricle during diastole measure of passive chamber stiffness

Question 31

factors affecting cardiac output:

Answer 31

1. preload 2. frank starling mechanism 3. afterload 4. compliance 5. inotropy

Question 32

what is cardiac output

Answer 32

amount of blood that the heart pumps in a minute

Question 33

what is preload

Answer 33

how much blood is in the chamber at the end of diastole more blood entering heart = more preload so heart increases stroke volume

Question 34

stroke volume

Answer 34

The volume of blood pumped out of the left ventricle of the heart during each systolic cardiac contraction

Question 35

factors that increase preload

Answer 35

these factors increase ventricular filling time 1. increased atrial contractility 2. increased central venous pressure 3. decreased heart rate

Question 36

frank starling mechanism

Answer 36

when the heart is stretched the heart contracts more so end systolic volume is maintained more contracting = more preload = increased stroke volume

Question 37

afterload

Answer 37

the pressure the heart has to pump to push blood out during ventricular contraction (systole)

Question 38

aortic pressure

Answer 38

the pressure at the root of the aorta caused by blood pushed from the LV to the aorta

Question 39

how does afterload determine end systolic volume

Answer 39

increased aortic pressure - increased afterload 1. higher aortic pressure = aortic valve closes earlier 2. less ventricular emptying 3. volume is at the end of systole

Question 40

what is compliance

Answer 40

the inverse of stiffness ie. MORE stiff, LESS compliant

Question 41

how does compliance contribute to preload

Answer 41

it alters EDVPR hypertrophy: preload is reduced by having a stiffer heart ventricle walls do not stretch as far in response to more blood volume

Question 42

what is inotropy

Answer 42

increases the speed of contractility lowers end systolic volume (ESV) affects ESPVR

Question 43

inotropes

Answer 43

make the heart beat with more or less power

Question 44

between which phases does ejection occur

Answer 44

spans from the end of isovolumic contraction to the beginning of isovolumic relaxation