Cardiac Function

standard limb leads setup

electrodes on both arms

left leg

right leg ground

lead 1 connects

RA-LA

lead 2 connects

RA-LL

lead 3 connects

LL-LA

electrodes on RA

(-) and (-)

electrodes on LA

+ and -

electrodes on LL

+ and +

which are the augmented limb leads

aVR

aVL

aVF

augmented limb leads are _

unipolar

augmented limb leads are designed to _

to have larger deflections than the limb leads

where is aVR positive electrode

right arm

where is aVL positive electrode

left arm

where is aVF positive electrode

left leg

what allows ECG to measure electrical activity

1. the body is a good conductor of electricity

2. potential differences are conducted to the body surface

each lead represents a different _

view of the body

bipolar limb leads record _

voltage between electrodes placed on wrists and legs

aVR produces what kind of deflection

strong negative

aVL produces what kind of deflection

small negative

aVF produces what kind of deflection

strong positive

chest leads are _(polarity)

unipolar

which plane do the limb leads view the heart

vertical plane (frontal)

which plane do the chest leads view the heart

horizontal plane

what creates a positive deflection

depolarization toward +

repolarization away from +

what creates a negative deflection

depolarization away from +

repolarization toward +

P wave corresponds to

atrial contraction

QRS wave corresponds to

ventricular contraction

T wave contributes

ventricular repolarization

PR interval reflects

conduction of depolarization from SA to AV node

QRS interval reflects

time required for ventricular depolarization

QT interval reflects

time starting to contract to the end of repolarization

normal PR interval length (s)

0.12-0.20 s

electrical signals _ mechanical events

precede

T wave starts during which ventricular phase

slow ejection phase

P wave starts during which ventricular phase

before the ventricular filling

QRS interval starts during which ventricular phase

during ventricular filling

R-R interval reflects

represent heart beats

which cardiac conditions have sinus origin

sinus tachycardia

sinus bradycardia

sinus arrhythmia

what signals sinus arrhythmia

P-P or R-R interval varies

most commonly, the change in sinus rate is related to _

respiration

different types of premature beats

atrial

AV nodal

ventricular

ectopic focus

a region of spontaneous firing OTHER than the SA node

what causes atrial premature beats

ectopic focus in the atria

what is affected by AV nodal premature beats

ventricular contraction

what causes ventricular premature beats

ectopic focus in ventricle

supraventricular tachycardia

increase in HR that is occurring above the ventricles

atrial flutter involves what

tachycardia originating in the atria

atrial fibrillation

rapid, random, ineffective contractions of the atrium

what is lost during ventricular fibrillation

pumping capacity

AV node blockage is viewed where on ECG

PR interval

first degree heart block results in

prolongation of PR interval

how does first degree heart block affect HR

slightly decreases HR

how does 2nd degree heart block look on ECG

P waves that are not followed by QRS complexes

how does 3rd degree heart block look on ECG

P waves and QRS complex independent

how does 3rd degree heart block affect ventricular rate

decreases it

when does S1 occur

when AV valves close as the ventricles contract

when does S2 occur

When the semilunar valves close during diastole

when does S3 occur

at the end of rapid ventricular filling

When does S4 occur?

during atrial contraction

what causes the mitral valve to close

contraction of papillary muscles - pulls on chordae tendinae

who might you hear S3 in

a young person or endurance athlete

older person with eccentric hypertrophy

what valves are open during S3

AV valves

what mechanical actions contribute to S1

abrupt tensing of the mitral valve, the chordae tendineae, and the walls of the ventricle

rapid ejection of blood from the ventricle

eccentric hypertrophy

hypertrophic growth of the walls of a hollow organ,especially the heart, in which the overall size and volume are enlarged.

eccentric hypertrophy causes _

chronic volume overload

concentric hypertrophy

hypertrophic growth of the walls of a hollow organ without overall enlargement, in which the walls of the organ are thickened and its capacity or volume is diminished.

what directly contributes to S4

vibrations caused by ventricular filling during atrial systole

components of S2

The first component is aortic valve closure, and the second component is pulmonic valve closure

what produces the sound of heart murmurs

turbulent blood flow through the heart of great vessels

types of murmurs

systolic

diastolic

continuous

when would you hear systolic murmurs

between S1 and S2

valve offers obstruction to the flow of blood

stenosis

causes of heart murmurs

stenosis

regurgitation

diastolic murmurs include what defects

mitral stenosis

aortic regurgitation/insufficiency

when do diastolic murmurs occur in relation to heart sounds

between S2 and S1

defects associated with systolic murmurs

mitral insufficiency

aortic stenosis

pansystolic murmur is caused by

mitral insufficiency (systolic murmur)

diamond shaped murmur is caused by

aortic stenosis (systolic murmur)

mitral stenosis causes what sound

opening 'snap' and a loud late diastolic component

how does aortic insufficiency sound

decrescendo sound starting just after the second heart sound.