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Where is the heart located?
Middle of the thoracic cavity, attached to the thorax via great vessels
Which heart layer is responsible for contraction and pumping?
Atria vs. Ventricles
- Atria: receive blood from the body
- Ventricles: pump blood to lungs and body
Where do the Tricuspid and Mitral (Bicuspid) valves lie?
- Tricuspid: between R atrium and R ventricle
- Mitral: between L atrium and L ventricle
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
What supplies the heart with oxygen?
Cardiac Output Formula is...
CO= SV (stroke volume) x HR (heart rate)
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
ability to spontaneously initiate an electrical impulse
Major ions in cardiac function
Potassium (K), Sodium, (Na), Calcium (Ca)
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
Describe the Depolarized cell state.
Inside of cell is positive, outside of cell is negative.
Absolute Refractory Period
From the onset of QRS to approximately the peak of T wave. Cells are depolarized and cannot be stimulated.
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.
EKG provides information about...
conduction disturbances, electrical effects of meds and electrolytes, and ischemic damage and injury.
When depolarization moves toward a positive or toward a negative the waveform deflection appears as...
- Toward positive electrode= upward
- Toward negative electrode= inverted (downward)
When electrical activity is not detected on an EKG, what appears?
A straight line is recorded, called the "baseline" or "isoelectric" line
In the bipolar leads, which is always positive? negative?
- Positive = L leg electrode
- Negative = R arm electrode
Lead axis I is?
RA (-) ----> LA (+)
Lead axis II is?
RA (-) -----> LL (+)
Lead axis III is?
LA (-) ----> LL (+)
EKG paper: Small squares?
Small square: 1mm x 1mm, 0.04 sec
EKG paper: Large squares?
Large square: 5mm x 5mm, 0.2 sec
P wave represents...
atrial depolarization and spread of impulse across the L & R atria
End of P wave, beginning of QRS complex. Usually represented by an isoelectric line
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
QRS Complex. Normal range?
- Represents the depolarization of the ventricles and HR.
- Normal range= 0.06- 0.12
a negative deflection following the P wave. Always appears as a negative waveform.
First positive deflection following the P Wave or Q wave (if present). Always appears as a positive waveform.
Negative waveform that follows the R wave.
R & S waves represent?
R & S waves represent the depolarization of the L & R ventricles.
End of the S wave, beginning of the T wave
ST elevation/ depression occurs on EKG if...
above or below by 1mm of the PR segment
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)
represents ventricular repolarization
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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