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29 Cards in this Set
- Front
- Back
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The general ECG theory?
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The whole body is a voltmeter. This machine measures the difference in electrical potential between 2 points.
The positive electrode is always the interrogator. The negative electrode is the reference. |
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What is depolarizatoin of the cell?
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At rest the cell in negative inside and positive outside. Depolarization causes the positives to go inside and the negatives to go outside.
Halfway through the depolarization is the max potential difference. Repolarization causes another potential difference. |
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What are the letter segments in an ECG?(P,PQ,QRS,ST,T,QT)
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P-wave = atrial depolarization
PR segment = conduction through from the SA through the AV nodes QRS = Depolarization of both ventricles. R amplitude is proportional to the heart mass. ST interval = Time after ventricular repolarization but before repolarization T wave = repolarization of the ventricles QT interval = about the time the ventricles are active which is the refractory period |
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What is an isoelectric line?
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The level lines between the waves. Changes between the ST segment could be a myocardial ischemia.
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What are the V-leads?
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6 leads across the heart that are used to locate abnormalities.
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Explain einthovens traingle?
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It represents the body as a circuit.
Lead 1 = R to L(-,+) Lead 2 = R to B(-,+) Lead 3 = L to B(-,+) The R wave amplitude 2 = 1+3 If a wave is flowing towards a positive the lead is positive |
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Why is the bottom of the triangle with the interrogators both there?
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Because this is hte average flow of depolarization from the SA node to the Apex.
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What are the augmented limb leads?
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They are a way to give a better look at the ECG by using two reference points and one interrogator.
AVR = right AVL = Left AVF = foot Anything perpendicular to the interrogator will be neutral. |
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The V-leads where are they located and what do they do?
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They run from R to L V1-6. It treats the thorax as the frontal plane and considers an aggregate of these leads to locate. V1 are RV events, 3 and 4 are LV apical events.
V6 are posterolateral events. |
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What is the perspective of the interrogating electrodes of the V leads?
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V1 on the right ventricle sees a little depolarization but the charge is mostly taken away by a large negative wave. V6 sees a lot of depolarization because it is a large positive wave. V3 sees a perpendicular wave and it there fore gets averaged out.
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Flow signs and charges
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Flow to a + = +
Flow to a - = - Flow to and interrogator = + Flow away from an interrrogator = - Flow perp to an interrogator = 0 |
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What are the mean cardiac vectors?
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The normal range of vectors is -30 through 90 degrees with zero being the left arm. Anything outside this is an abnormal vector.
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What is left vector deviation?
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If the vector goes past -30 degrees then we think of an inferior wall infarction. It could also be a left anterior fasicular block, or left ventricle hypertorphy.
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What is right vector deviation?
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A vector going past 90 degrees. This could be RV hypertrophy, Acute right heart strain or a left posterior fasicular block.
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What is the size principle of muscle?
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It only occurs in SKM and means that smaller units are activated before larger ones. Cardiac muscle doesn't do this.
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How does one alter contraction in cardiac muscle?
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You need a way to increase intercellular calcium in the muscle.
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What are the phases of a cardiac muscle contraction?
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1. Action potential from an adjacent ccell
2. CA enters the T tubule and calcium channels open 3. Ca induces ryandone release(SR) of more Ca 4. Local release causes a Ca spark 5. Sum up all the sparks to get a Ca signal 6. Ca bings to troponin and initiates contraction 7. Relaxation happens after Ca release from muscle 8. Ca goes back to SR 9. Intracellular exchange with Na occurs 10. The Na gradient is made high with the Na/K ATPase |
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What kind of drug is digitalis and what does it do?
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Digitalis is a cardiac glycoside. It blacks the Na/K ATPase.
It increases extracellular K It also increasess ventricular contractility |
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How are performance and preload related?
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Preload is the amount of blood the heart has to work with = EDP, CVP, PCWP
Performance is related to the LVP, CO, and SV THere is a hyperbolic direct relationship between these two. Increased preload = increased performance. |
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How are performance and afterload related?
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Increased after load will decrease performance as long as contractility and HR are fixed.
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Performance and contractility are related how?
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Increased contractility will increase performance as long as afterload is the same.
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How are performance and extracardiac pressure related?
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Increased ECP with fixed contractility and HR will shift the curve left decreasing preload and performance
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How do you reduce afterload?
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Try to vasodialate. Targeting the venous preload wouldn't work so wel
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How is long term BP control accomplished?
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It is done by the influence of the kidney on fluid balance.
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What factors effect the vascular resistance?
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1. Sympathetic Tone
2. Autoregulatory factors |
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Explain the blood flow volume loop?
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1. All valves are closed
2. Isovolumic contraction is an increase in pressure with no volume increase. 3. Aortic vavles open and ejection happens 4. During ejection the pressure peaks as the volume goes down. 5. Then there is isovolumic relaxation 6. The mitral valves open 7. Filling occurs and volum goes up with a slight pressure increase |
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What is stenosis?
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A narrowing of the valves that causes a buildup in pressure.
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What is regurgitation/incompetance of teh valves?
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It's a backflow in the valves that is because they don't close right.
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Heart sounds and what happens when?
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S1 is the AV valves closing
S2 is the aortic and pulmonary valves closing S3 is from turbulence filling the ventricles S4 is from turbulence during atrial ejection |
