Cardiac Physiology Flashcards
Normal electrical activation
1 SA node
- AV node
- Bundle of His
- Bundle branches (left and right)
- Purkinje fibers
Which is the fastest intrinsic rate
SA node
Primary pacemaker
SA node
What is the absolute refractory state
That period when a muscle cell is not excitable. From phase 1 until info phase 3.
What is the relative refractory period
During phase 3 and the muscle cell contract is the stimulus is strong
Electrocardiograph normal complex
- P wave
- P-R interval
- QRS complex
- T wave
What does the P wave represent
Atrial systole
What does P-R interval represent
From atrial to ventricular depolarization
What does the QRS complex represent
Ventricular systole (depolarization)
What does the T wave represent
Ventricular diastole (repolarization)
What is the normal duration for the QRS complex
.10sec
1 small box on the electrocardiograph is equal to
.04 seconds
1 big box on the echocardiogram is equal to
.2 seconds
5 big boxes on the electrocardiograph is equal to
1 second
Normal values for R-R interval
Between 3 to 5 big boxes (60-100 beats per min)
Normal values for QRS complex
Less than 3little boxes (less than .12 seconds)
Normal values for PR interval
Less than 1 big box (less than .2 seconds )
Frank starling law
Length tension relationship
-the more blood that enters the ventricle during diastole (preload) the greater the force of the contraction (systole) required to eject the blood. In other words, increased myocardial fiber length means increased tension
Increased volume preload =
Increased contractility
Increased myocardial fiber length =
Increased tension (river band theory)
Acute AI is _________ because we shift up the starling curve.
Hypercontractile
Chronic AI is ________ when we drop off the end
Failure
Preload definition
Load (volume) exerted on the ventricle at end diastole
Preload determines
Force of contraction
The greater the load
The greater the force of contraction (frank starling law)
Increased preload is increased by
- MR
- TR
- PI
- AI
- Ventricular and atrial septal defects
- Fluid overload
Afterload definition
Resistance against which the ventricle must pump
Afterload determines
The tension the myocardium must generate
Echo finishings for preload
Dilation
Echo findings for afterload
Hypertrophy
After load is increased by?
Any state of pressure overload such as
- Hypertension
- Aortic stenosis
- Pulmonic stenosis
LV function indicators
- Stroke volume
- Ejection fraction
- Cardiac output
Stroke volume equation
SV= end diastolic volume (EDV) - end systolic volume (ESV)
Stroke volume varies with
End diastolic volume
Heart rate
Size
Ejection fraction
EF= stroke volume divided by end diastolic volume (100)
Normal is > 55%
Cardiac output definition
The volume of blood pumped from the LV each min
Cardiac output equation and norm
CO= stroke volume X heart rate
Normal is 4-6 L/min
Which study does not allow for the calculation of ejection fraction A) 2D echo B) cardiac angio C) chest x Ray D) cardiac nuclear study
Cheat x Ray
Bernoulli equation
4v squared
Aliasing
- Occurs when the dipper shift excess the nyquist limit
- Nyquist limit = half the PRf (pulse repetition frequency
- A problem with higher velocities in pulsed Doppler (spectral and color flow)
- Occurs sooner with higher frequency transducers
How do you eliminate aliasing on PW spectral Doppler
Switch to continuous wave Doppler
Doppler stroke volume
SV = VTI(FVI) times CSA
Doppler stroke volume
VTI
Is the velocity time integral as calculated by tracing the Doppler spectral display (sometimes called the flow velocity integral FVI) it represents how far the blood travels in centimeters with each ejection. Normally 12cm for the mitral and 20cm for aorta
Doppler stroke volume
CSA
Is the Ross sectional area calculated one of two ways
1. CSA (cm sq)= 3.14 times (D divided by 2) sq
2CSA (cm sq)= 0.785 tines Dsq
D= the diameter of any office
Maneuvers altering cardiac physiology
- Breathing2. Standing
- Squatting
- Hand grip
- Valsalva
- Sit ups
- Amyl nitrite inhalation
Maneuvers altering cardiac physiology
- breathing
Inspiration: increases venous return
Expiration : decreases venous return
Maneuvers altering cardiac physiology
- standing
Decreases venous return and stroke volume
Maneuvers altering cardiac physiology
- squatting
Increased: venous return,SV,CO
(Increases AR)
(Decreases IHSS)
Maneuvers altering cardiac physiology
- handgrip
Increased: HR, CO , arterial pressure
Decreases: AS. Increased:MR
Maneuvers altering cardiac physiology
- valsalva
2 main phases-strain and release
1. During strain: decreases venous return,SV,CO
(Most murmurs decreases during straining,IHSS increases)
2. During release: increases venous return, CO, BP
Maneuvers altering cardiac physiology
- sit ups
Increases HR,CO,and SV
Maneuvers altering cardiac physiology
- amyl nitrite inhalation
Vasodilator
Decreases peripheral resistance
Increases HR
(Increases forward flow murmurs, decreases AR/MR)
Does venous return increase or decrease with inspiration
Increases
Inhalation of amyl nitrite causes
Decreases afterload
Mitral vavlve velocity during inspiration
Decreases
Between which heart sound will the murmur of aortic stenosis be heard?
S1-S2
know isovolumetric timing with ECG
after R wave=
After T wave=
after r wavw= isovolumic contraction
after T wave= isovolumic relaxation
on the wiggers diagram when is the mitral valve open
4-1
whats the duration of IVRT and IVCT
70msec
the duration of isovolumic relaxation time will increase with
bradycardia (slow heart rate)
during the cardiac cycle this event never happens
aortic valve is open and mv is open
correct order for cardiac cycle
- mechanical diastole
- electrical diastole
- electrical systole
- mechanical systole
normal arterial pressure is approx. _____. thus the aortic pressure lives ____
120/80
lives high
normal left atrial pressure is approx. ____. thus the atrial pressure lives___
10mmHg
low
the left ventricular pressure bounces between ___ and ___.
aortic and atrial–> high and low
the valve that lies between the left ventricle and the aorta is the ____ it lives___
Aortic valve and it lives high
the valve that lives between the atrium and the left ventricle is the ___ and it lives____
MV lives low
when a normal valve is open, there is very little ____________ between the chambers on either side of the valve
pressure differences
when aortic valve is open , the LV and aortic pressures are?
nearly identical
when the mitral valve is open, the atrial and LV pressures are
nearly identical