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Where is the heart located?
Middle of the thoracic cavity, attached to the thorax via great vessels
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Which heart layer is responsible for contraction and pumping?
Myocardium
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Atria vs. Ventricles
- Atria: receive blood from the body
- Ventricles: pump blood to lungs and body
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Where do the Tricuspid and Mitral (Bicuspid) valves lie?
- Tricuspid: between R atrium and R ventricle
- Mitral: between L atrium and L ventricle
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Where do the Semilunar Pulmonary and Aortic valves lie?
- Pulmonary: from the R ventricle to the pulmonary artery
- Aortic: from the L ventricle to the Aorta
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What supplies the heart with oxygen?
Coronary Arteries
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Cardiac Output Formula is...
CO= SV (stroke volume) x HR (heart rate)
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Define CO. What's the normal adult CO?
- CO: amount of blood ejected (pumped) by the ventricles in 1 minute
- Normal adult CO= 4-8 LPM
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Define automaticity
ability to spontaneously initiate an electrical impulse
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Major ions in cardiac function
Potassium (K), Sodium, (Na), Calcium (Ca)
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Describe the Polarized state of a cell. What does it appears as on an EKG?
- Resting state with no electrical activity. The inside of the cell is negative, outside is positive with uneven distribution of ions across the cell membrane.
- EKG Baseline
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Describe the Depolarized cell state.
Inside of cell is positive, outside of cell is negative.
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Absolute Refractory Period
From the onset of QRS to approximately the peak of T wave. Cells are depolarized and cannot be stimulated.
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Relative Refractory Period
- "Vulnerable Period" because cells are repolarizing and can be stimulated (if stimulus is strong enough) thus possibly resulting in ventricular chaos.
- Downslope of T wave.
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EKG provides information about...
conduction disturbances, electrical effects of meds and electrolytes, and ischemic damage and injury.
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When depolarization moves toward a positive or toward a negative the waveform deflection appears as...
- Toward positive electrode= upward
- Toward negative electrode= inverted (downward)
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When electrical activity is not detected on an EKG, what appears?
A straight line is recorded, called the "baseline" or "isoelectric" line
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In the bipolar leads, which is always positive? negative?
- Positive = L leg electrode
- Negative = R arm electrode
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Lead axis I is?
RA (-) ----> LA (+)
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Lead axis II is?
RA (-) -----> LL (+)
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Lead axis III is?
LA (-) ----> LL (+)
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EKG paper: Small squares?
Small square: 1mm x 1mm, 0.04 sec
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EKG paper: Large squares?
Large square: 5mm x 5mm, 0.2 sec
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P wave represents...
atrial depolarization and spread of impulse across the L & R atria
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PR Segment
End of P wave, beginning of QRS complex. Usually represented by an isoelectric line
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PR Interval. What is the normal range?
- From the beginning of the P wave to the beginning of QRS Complex. Reflects the impulse travel time from the SA node through the AV node, HB, R & L bundles, and into the Purkinje fibers.
- Normal range= 0.12- 0.20
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QRS Complex. Normal range?
- Represents the depolarization of the ventricles and HR.
- Normal range= 0.06- 0.12
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Q Wave...
a negative deflection following the P wave. Always appears as a negative waveform.
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R Wave...
First positive deflection following the P Wave or Q wave (if present). Always appears as a positive waveform.
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S Wave...
Negative waveform that follows the R wave.
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R & S waves represent?
R & S waves represent the depolarization of the L & R ventricles.
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ST segment
End of the S wave, beginning of the T wave
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ST elevation/ depression occurs on EKG if...
above or below by 1mm of the PR segment
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ST depression can indicate? ST elevation?
- Depression: myocardial ischemia, digoxin, or low K
- Elevation: myocardial injury, infarction, or pericarditis, or cardiac tamponade.
3 I's of MI (ischemia, injury, infarction)
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T Wave
represents ventricular repolarization
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QT Interval. Normal range?
- From beginning of Q to the end of the T wave. Represents total ventricular activity.
- Normal range= 0.44 or >
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