Electrophysiology Lecture Flashcards
cardiac output
volume of blood ejected in one minute
stroke volume
mL of blood ejected with each beat
CO equation
CO= HR x SV
Normal CO
4-6 L/ min at rest
Cardiac index
individualized CO based on body size
Cardiac index equation
CI= CO/BSA
Preload
volume of blood in left ventricle at end of diastole
Preload: what is the term for the pressure created
Left ventricular End Diastolic Pressure (LVEDP)
What measures LVEDP
PA catheter: wedge pressure
Afterload
ventricular tension during systolic ejection
another term for afterload
SVR-systemic vascular resistance
how does an increased afterload affect the heart
increases the workload of the heart
what factors increase afterload?
factors that oppose ejection
Contractility and Inotropy
the heart’s contractile force
-strength of the contraction
what is the only artery that carries deoxygenated blood?
PULMONARY ARTERY
Sinoatrial Node (SA)
normal (intrinsic) pacemaker of the heart
SA node rate
60-100 bpm
Atrioventricular (AV) node
1st backup pacemaker “gatekeeper”
AV node rate
40-60 bpm
AV node:
-why is there a slight delay in conduction
allows time for both atria to contract and ventricles to fill
perkinje fibers
2nd backup pacemaker
perkinje fibers rate
15-40 bpm
Perkinje fibers: what does the e-impulse cause?
the left and right ventricles to conrtact simultaneously
Buchman’s bundle:
- location
- function
located in the intra-atrial septum
-cause atria to contract
Layers of the heart:
Endocardium
inner lining
Layers of the heart:
Myocardium
heart muscle
Layers of the heart:
Epicardium
outer surface
Depolarization: contract or relax?
contraction
Repolarization: contract or relax?
Relaxation
What part of a heart muscle is unique?
Intercalated discs
6 properties of cardiac cell:
1) rhythmicity
atomicity generated at a regular rate
6 properties of cardiac cell:
2) excitability
ability of a cell to depolarize in response to a given stimulus
6 properties of cardiac cell:
3) conductivity
ability of a cell to transmit a stimulus from cell to cell
6 properties of cardiac cell:
4) Automaticity
ability of a cell to spontaneously depolarize
“pacemaker” ability
6 properties of cardiac cell:
5) contractility
ability of cardiac myofibrils to shorten in length in response to a electrical signal (help from intercalated discs)
6 properties of cardiac cell:
6) refactoriness
degree to which the heart’s cells are able to respond to electrical stimulus
Absolute refactory period
after a cell depolarizes, it CANNOT respond to a stimulus
Relative refractory period
occurs after cells have had time to repolarize. CAN respond to a stimuli
Action potential
depiction of depolarization and repolarization
Action potential:
PHASE 0
DEPOLARIZATION
- FAST Na+ channels OPEN
- Na+ rushes in cell
- charge +20-+30
Action potential:
PHASE 1
Fast Na+ channels CLOSE
-charge = 0
Action potential:
PHASE 2
PLATEAU
- SLOW Na+ and Ca+ channels OPEN
- K+ flows out
- Ca+ causes CONTRACTION
Action potential:
PHASE 3
REPOLARIZATION
- Slow Na+ and Ca+ channels CLOSE
- K+ continues to move out
- re-establishes the RESTING MEMBRANE POTENTIAL
Action potential:
PHASE 4
AP returns to resting membrane potential
- Na/K+ pump re-established
- charge -80 to -90
Atrial Systole
- passive filling of atria and ventricles ends
- DEPOLARIZATION contracts atria
Atrial Systole:
“atrial kick”
-completes ventricular filling
Isovolumic Contraction
Depolarization travels to the ventricles
- muscles tense but volume doesn’t change
- Rapid rise in Ventricular pressure
Ventricular Systole
Ventricular ejection
- pulmonary and aortic valves open
- STROKE VOLUME
Isovolumic Relaxation
Semilunar valves CLOSE
- Pressure falls
- volume doesnt change
Ventricular Diastole
AV valves OPEN
passive ventricular filling
*Cycle ready to begin again
Heart Rate:
what system determines the rate
Autonomic Nervous System (ANS)
Parasympathetic NS:
- what nerve
- location
- how does it affect the heart
- Vagus nerve
- SA/AV nodes
- SLOWS HR
Sympathetic NS:
- location
- how does it affect the heart
- coronary arteries
- INCREASES HR and CONTRACTILITY
Other regulations of HR: FEEDBACKS
1) Baroreceptors
- location
- stimulus
- what does it send stimuli to
- aortic arch and carotid sinus
- sense change in stretching
- stimulate the ANS
Example of Baroreceptor med
Milurone
Other regulations of HR: FEEDBACKS
2) Chemoreceptors
- location
- stimulus
- carotid arteries and aortic arch
- sense changes in O2 and CO2 pressures
Other regulations of HR: FEEDBACKS
3) Right Atrial Receptors
- stimulis
reflex tachycardia
Other regulations of HR: FEEDBACKS
4) Naturetic Peptides
- stimulus
- reaction
- secretion results from myocardial stretch
- Vasodilation and inhibits the SNS and RAAS
Naturetic Peptides Types
1) Atrial myocardium
2) Ventricular myocardium
1) ANP
2) BNP
what naturetic peptide would you measure for CHF & what value would you want?
BNP
Other regulations of HR: FEEDBACKS
5) RAAS System
- stimulus
- where does it work
- what does it cause a release in
- activated by low BP
- kidneys
- Aldosterone
RAAS:
how does aldosterone work in body
-makes kidneys retain Na and H2O to raise BP
Endoplasmic reticulum
Stores Ca+
releases Ca+ after depolarization
Troponin/Tropomyosin
Ca+ binds to tropnin
- Tropomyosin opens myosin binding sites
- measure for MI
Actin and Myosin
actin and myosin attach to pull segments of heart muscle together
EKG’s paper:
- small box
- large box
- five large boxes
- 0.04 sec
- 0.20 sec
- 1 second
P wave
DEPOLARIZATION (contraction) of both ATRIA
-atrial kick
PR interval
- event
- time value
- time it takes for action potential to move from SA node to AV node
- 0.12-0.20
QRS
- event
- time value
- DEPOLARIZATION (contraction) of VENTRICLES
- REPOLARIZATION (relaxation) of ATRIA
- 0.06-0.10
T wave
- event
- what can happen here?
- REPOLARIZATION (relaxation) of VENTRICLES
- Relative Refactory
QT
- event
- time
- total time of depolarization and repolarization of ventricles
- 0.36-0.44
what does a prolonged QT mean?
-med examples
lethal venticular dysrhythmias
ex) Zofran
What does a wide QRS wave mean?
> 3 boxes means conduction delay in 1 or both ventricles
What does a peacked T wave?
electrical instability r/t HYPERKALEMIA
what does an inverted T wave mean?
Old infarction or evolving ischemia
*CHECK BMP
What does a U wave mean?
-when is it noticible
HYPOKALEMIA or VENTRICULAR OVERLOAD
-when HR 95
Why would a QT interval be >0.44?
HYPOKALEMIA or meds
Three laws of deflection:
-electrodes moving towards positive electrode
-UPRIGHT DEFLECTION
Three laws of deflection:
-electrodes moving away from + electrode
-DOWNWARD DEFLECTION
Three laws of deflection:
-moving PAST + to -
biphasic
EKG lead placement:
-V1
4th R ICS
EKG lead placement:
-V2
4th L ICS
EKG lead placement:
V3
between v2-v4
EKG lead placement:
V4
5th ICS MCL
EKG lead placement:
V5
between 4 & 6
EKG lead placement:
V6
MAL
einthoven’s triangle
triangle bipolar leads form
Bipolar leads
I, II, III
Unipolar Leads
avR, avL, avF
precordial unipoloar
V1-V6
which way does energy travel
negative to positive, top to bottom,
-bulk of heart muscle at bottom
12 lead EKG
- 1 and aVf
- avR
- want to be posiitve
- want to be negative
Hexaxial System normal value
-30 to +90
Causes of LEFT axis deviation
- inferior wall MI
- LBBB
- L vent. hypertrophy
- Aging
Causes of RIGHT axis deviation
- lateral wall MI
- RBBB
- Emphysema
- R vent hypertrophy
Elevated ST waves meaning
MI
Depressed ST waves meaning
Ischemia
ST segment change
1 mm
2 mm
1= high risk 2= low risk
ATRIAL HYPERTROPHY
-what wave do you see it in
P wave
Atrial hypertrophy -
LEFT SIDE
- “m” shaped p wave
- P mitrale
Atrial hypertrophy
RIGHT SIDE
- “peaked” p wave
- P pulmonale
Ventricular Hypertrohy
-what wave do you see it in
TALL or WIDE QRS d.t lengthened depolarization time
atrial kick is ___ % of C.O
30% and fills ventricles
what wave will change with a BBB
widened QRS
what leads show a BBB
V1-V6 (precordial unipolar)
