Test 4 Flashcards
(62 cards)
1
Q
5 phases of the cardiac Cycle
A
1) Isovolumetric Ventricular Contraction
2) Ventricular Ejection
3) Isovolumetric Relaxation
4) Ventricular Filling
5) Atrial Systole
2
Q
Isovolumetric (putting out effort but not moving) Ventricular Contraction
A
- wall tension of the ventricles increases
- intraventricular pressures increase
- mitral and tricuspid vavles close
- pulmonic and aortic vavles remain closed (R of the QRS complex) until there is a certain amount of pressure in the ventricles
- volume stays the same
3
Q
Mitral valve closes when
A
LV pressure exceeds LA pressure
4
Q
Ventricular ejection
A
- Pressure = flow x resistance
- intraventricular pressure has risen and eventually the pressure exceeds the pressure in the pulmonary artery and aorta which results in the valves opening.
- LV achieved maximum volume
5
Q
Ventricular ejection fraction
A
- about 40-60% of blood in the ventricles is ejected
- EF=SV/EDV
6
Q
T wave created by
A
Ventricular repolarization toward the end of ventricular systole
7
Q
Isovolumetric relaxation
A
- Toward the end of ventricular systole, the pressure inside the ventricles fall below that of aorta and pulmonary artery
- AV and PV valves slam closed and the MV and TV already closed
- blood continues to fill the atria
8
Q
Dicrotic notch
A
- Reflective pressure wave as the aortic valve slams closed after ventricular systole
- important for intra-aortic balloon pump (IABP)
9
Q
Rapid Ventricular Filling
A
- Atrial pressure greater than ventricular pressure
- MV and TV open
- Blood flows passively from the pressurized atria into the ventricles
- 70% of the ventricular filling takes place by PASSIVE PROCESS
10
Q
Atrial Systole (Atrial Kick)
A
- Coincides with late ventricular diastole
- ventricles receive a 30% boost from the atrial kick for more effective diastolic filling
11
Q
P wave
A
atrial depolarization
12
Q
Cardiac Output
A
CO= Heart rate x stroke volume
13
Q
Factors affecting stroke volume
A
- Preload
- afterload
- contractility (inotropy)
14
Q
Preload
A
- Passive stretching of the ventricular walls
- caused by the blood volume in the ventricles at the end of diastole (EDV)
- Valvular insufficiency may allow backflow altering the EDV
15
Q
Afterload
A
- Resistance
- pressure the the LV must overcome to eject blood
16
Q
Contractility (inotropy)
A
- Capability of the heart walls to contract after depolarization
- ability to contract depends on how much fiber gets stretched at EDV and health of the fibers
17
Q
Doplarization
A
- electrical change of cell membrane potential making it less negative
- Na+ coming in
18
Q
Repolarization
A
- electrical change of cell membrane potential making it more negative to its resting state after depolarization
- K+ leaving
19
Q
Nernst equation
A
EMF= (+or-61.5/valence)(log([inside]/[outside])
-Na, K, Ca, Cl
20
Q
SA node as the pacemaker
A
- it does not require a stimulus to fire like most nerve cells
- self-firing
21
Q
SA node ion potentials
A
- SA node slowly leaks K+ out of the cell and slowly leaks Na+ into the cells (funny current)
- when the leaks reduce the membrane potential to -40mV it hits the excitation threshold
- once excitation occurs, you just can’t stop it
22
Q
Cardiac conduction
A
Heart cannot contract and pump unless and until there’s electrical stimuli
23
Q
automaticity
A
cell’s ability to spontaneously initiate an impulse
24
Q
excitability
A
cell’s responsiveness to an electrical stimuli
25
conductivity
cell's ability to transmit electrical stimulus to another cell
26
contractility
how well a cell contracts after exposure to a stimulus
27
conduction
-electrical stimuli created by pacemakers cells usually travels through the heart via the CONDUCTION SYSTEM
28
Conduction system pathway
SA node-> internodal tracts-> AV node-> Bundle of His-> right and left bundle branches-> purkinje fibers
29
Conduction rate of SA node (affected by sympathetic or parasympathetic inervation)
SA node: 100 bpm
| -not from an upstream source with a faster inherent rate
30
Conduction rate of AV node (affected by sympathetic or parasympathetic inervation)
AV node: 40-60 bpm
| -not from an upstream source with a faster inherent rate
31
Conduction rate of purkinje fibers (affected by sympathetic or parasympathetic inervation)
Purkinje fibers: 20-40 bpm
| -not from an upstream source with a faster inherent rate
32
how electrical signals captured
- via electrodes
- amplified
- then sent to a monitor producing an ECG
33
ECG
- voltage graph
- 5 large blocks is a second
- one large box is .20 seconds and .5 mV
- each smaller box in the large box is .04 sec and each small box is .1 mV
34
one ECG wave =
one cardiac cycle
35
p wave
- atrial depolarization
| - first wave on ECG
36
Q wave
first negative deflection (below isoelectric line)
37
R wave
-first upward or positive deflection
38
S wave
first negative deflection after the R wave
39
T wave
- ventricular repolarization/ recovery
| - usually rounded upward immediately after QRS complex
40
U wave
- purkinje fiber repolarization (often not seen)
| - usually only seen in slow heart rhythms
41
PR interval
- atrial impulse extending from the SA node through the AV node, bundle of his, and Right and Left branches
- Starts at the beginning of the P wave and ends at the beginning of the QRS complex
- normally .12-.20 seconds
- greater than .20 seconds= conduction delay through the atria or AV junction
- less than .12= the impulse started somewhere other than the SA node
42
QRS interval/ QRS Complex
- Follows P wave
- measured from beginning of Q wave to End of S wave
- REPRESENTS THE INTRAVENTRICULAR CONDUCTION TIME
- Wide QRS may be due to MI or conduction delay (AV block)
- "Notched" may be due to bundle branch block
43
ST Segment (very important)
- Represents the end of ventricular depolarization and the beginning of repolarization
- VERY IMPORTANT in open heart Sx
- Should be isoelectric (flat and at baseline)
- depression may suggest acute MI or ischemia
- elevation may suggest injury to the myocardium
- OBSERVE BOTH PRE-OP AND POST-OP!
44
QT interval
- represents ventricular depolarization and repolarization
- measured from beginning of QRS to end of T wave
- length varies with rate (increased HR= short QT interval)
- Normal: .36-0.44
- prolonged QT= longer relative refractory period
- short QT= hypercalcemia, digoxin toxicity
45
Elusive U wave
- purkinje/ ventricular recovery/ repolarization
- not on every strip
- upright and round
46
8 easy steps to evaluating ECG's
1) Are the atria and ventricles “regular”?
2) What’s the rate?
3) Evaluate the P waves
4) What’s the P-R interval duration?
5) What’s the QRS complex duration?
6) Evaluate the T waves
7) What’s the Q-T interval?
8) “Other” (ectopic beats, abnormal rhythms, unique rate characteristics)
47
Are the Atria and Ventricles regular?
| What to look at
- measure P to P interval (atrial regularity)
| - measure R to R interval (ventricular regularity)
48
Whats the rate?
- the 10x method
- 1500 method (# of small squares between P-P and divide 1500 by that #)
- Bradycardia= 100bpm
49
Evaluate the P waves
- Are they present?
- is there one P wave for every QRS complex
- normal size and shape?
50
What is the P-R interval duration
- Should be .12-.20 seconds
- is the interval constant
- is there QRS complex for every P wave
51
What is the QRS complex duration
- Normal .06-.12
- Prolonged suggests a conduction delay through ventricles (ischemia, electrolyte abnormalities, drugs)
- Is the shape normal for that lead
52
Evaluate T waves
-are they present?
-normal shape?
-if peaked= hyperkalemia
-inversion is normal in peds and yound females
-other causes of T wave inversion = ischemia, pulmonary emboli,
cardiomyopathy, electrolyte abnormalities
53
What is the Q-T interval
- Normal: .36-.44 seconds
- # of small boxes from beginning of the QRS Complex to the end of the T wave and returning to baseline and multiply by .04
54
PR interval >.20 suggests
-Conduction delay through atria or AV junction
55
PR interval
-impulse started somewhere other than SA node
56
QRS interval Wide may be due to
-MI or conduction delay (AV block)
57
QRS interval "notched" may be due to
bundle branch block (RBBB or LBBB)
58
ST segment depression may suggest
-acute MI or ischemia
59
ST segment elevation may suggest
-injury to the myocardium
60
QT interval prolonged
-longer relative refractory period
61
QT interval short
hyercalcemia
62
Elusive U wave seen prominently in
hypercalcemia and hypokalemia
