Chapter 8-EKG Cycle, Waveforms, Paper
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Depolarization & Repolarization are
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Electrical events
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Contraction and relaxation are
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Mechanical events
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Depolarization should result in a muscle
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Contraction
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Repolarization should result in muscle
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Relaxation
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A heartbeat is an electrical event? T or F
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False-mechanical
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What type of events are depolization and repolarization of the atria and ventricles?
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Electrical
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What are the depolarization and repolarization of the atria and ventricles seen as on the EKG paper?
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Seen as a waveforms
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There can be no heartbeat without depolarization occurring first? T or F
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True
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Baseline (Isoelectric line)
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A flat, horizontal line •Between waves along the baseline •Where no electrical activity is occurring •Flat lines indicate electrical silence •The baseline is the line from which EKG waves and complexes take off
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Deflection
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Movement up or down •Off of the baseline •That tells us something electrical is happening
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A positive deflection indicates movement---the baseline
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Above
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A negative deflection indicates movement---the baseline
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Below
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What does each waveform on the EKG tracing represent?
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Represents the path of an electrical impulse as it is conducted through the heart
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A typical EKG creates a waveform? T or F
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True
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An EKG waveform contains "only positive" deflections off the baseline? T or F
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False- an EKG waveform contains "both positive and negative deflections" off the baseline
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Each waveform represents 1 heartbeat? T or F
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True
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The heart's electrical and mechanical systems are two separate systems? T or F
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True
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The waveforms are repeated on the EKG tracing as the heart continues to be stimulated? T or False
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True
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Only one of the hearts systems can malfunction? T or F
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False-either one or both can malfunction
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P-wave represents
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Represents atrial depolarization •Atrial contraction
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"Electrical" malfunctions show up on an EKG? T- or F
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True
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What does the "shape" of the QRS complex represent
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The shape indicates only the path the electrical signal took through the ventricles
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QRS complex represents
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Ventricular depolarization, ventricular contraction
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Mechanical functions show up clinically? T or F
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True
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T-wave represents
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Ventricular repolarization, Recovery of the ventricles
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U-wave represents
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Represents the slow repolarization (recovery) of the Purkinje fibers
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How does a normal P-wave appear?
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Normal P wave is small, rounded, and upright •Inverted (upside down) in aVR
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What does the raising slope of the P-wave represent and what type of event is it?
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Represents Atrial depolarization, which is an electrical activity
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What does the falling slope of the P-wave represent and what type of activity is it?
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Represents contraction, mechanical activity.
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What does the "rising edge" of the QRS complex represent and what type of activity is it?
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Depolarization, electrical activity
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What does the "falling edge" of the QRS complex represent and what type of activity is it?
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Contraction, mechanical activity
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Why is the QRS complex taller than the P-wave?
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-ventricles are larger than atria -required a stronger electrical stimulus to depolarize
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Do all the complex have distinct Q, R, and S waves?
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No
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What does the "shape" of the QRS complex represent?
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The shape indicates only what path the electrical signal took through the ventricles
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During the T-wave, what are the cardiac muscle cells doing?
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-recovery of the ventricles -Muscle cells are recovering -preparing for another electrical impulse
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How does a normal T-wave appear?
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Upright, broad, and rounded -can be "inverted" (upside down) many things can alter the shape of the T-wave
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Will there always be a T-wave after a QRS complex?
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Yes, a T-wave "always" comes after the QRS complex -if there is a QRS complex there must be "one" and only "one" T-wave
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The rounded curve of the T-wave shows---- which is a/an -----event?
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Ventricular Repolarization (recovery), electrical event
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The return to baseline (flatline) after a T-wave shows----- which is a/an------event?
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Ventricular relaxation, mechanical event
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Why don't we see repolarization of the atria on an EKG?
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-electrical recovery of atria occurs following the P-wave -at the same time as ventricular depolarization -activity of the ventricles is so significant that it dominates -causes atrial repolarization to be hidden by QRS complex -does not appear as a separate wave on the EKG cycle
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Is a U-wave typically seen on a EKG?
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Usually not present
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If a U-wave appears on an EKG where is it found and what does it look like?
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-sometimes found after the T-wave -small, "upward", rounded curve -(fyi) found in patients with "hypokalemia" low blood potassium level
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What time interval does the P-R interval represent?
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Time it takes for the electrical impulse to travel from the SA node to the AV node •Time from the beginning of atrial depolarization to the beginning of ventricular depolarization
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What time interval does the S-T segment represent?
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Represents the time between: •Contraction of the ventricles •And the beginning of recovery of the ventricles •Time from end of ventricular depolarization (contraction) to the beginning of ventricular repolarization (recovery
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Segment- (S = silence)
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Flat line connecting two waves along the baseline, where no electrical activity is occurring
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Interval
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Represents the time between events occurring in the heart
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Where is the P-R segment found?
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Between the end of the P wave and the beginning of the QRS complex
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The P-R segment represents the time from the end of----to the beginning of ------
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of "atrial depolarization (contraction)" to the beginning of "ventricular depolarization"
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Where is the S-T segment found?
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Between the end of the QRS complex and the beginning of the T wave
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The S-T segment represents the time from the end of -----to the beginning of-------
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Time from end of "ventricular depolarization (contraction) "to the beginning of "ventricular repolarization (recovery)"
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The P-R interval represents the time it takes for the electrical impulse to travel from the ----to the ----
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SA Node to the AV node
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P-R interval is the time from the beginning of ----to the beginning of-----
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of "atrial depolarization" to the beginning of "ventricular depolarization"
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Q-T interval represents the time it takes for the ventricles to ----and ------
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to contract and recover
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There may be more than one P-wave on a waveform, or none at all? T or F
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True
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The Q-T interval is the time the beginning of ---to the end of ----
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beginning of ventricular depolarization to the end of ventricular repolarization
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If there is a QRS complex, there must be a T wave after it? T or F
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True
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The shape of a QRS complex on an EKG tracing can vary? T or F
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True
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All of the QRS complexes have a distinct Q, R, and S wave? T or F
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False-not all QRS complexes have distinct Q, R, S's, may not have all 3 waves, or can have more than one
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The shape of a P-wave is always consistent and the same on the EKG tracing? T or F
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False-Many things can alter the P wave shape •Electrode misplacement, dextrocardia •May be more than one P wave or no P wave at all
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What does the EKG paper look like and how does it produce a tracing?
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Standardized graph paper (8x11 inch) •Designed for EKG machines •Contains a thermo-sensitive coating •Allows the heated stylus to produce tracing
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EKG paper is divided into small and large----?
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Blocks
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The horizontal line on the EKG paper records?
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Horizontal line = Records "time" •Black marks at the top indicate 3-second intervals
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The vertical line on the EKG paper records?
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"Vertical" line = Records "voltage" (amplitude)
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Each small block measures?
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Small block measures •1mm high x 1mm wide
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Each large block measures?
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Large block measures •5mm high x 5 mm wide
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EKG paper rolls out of the electrocardiograph at a pre-set speed at?
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25mm per second (1 inch)
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----large blocks equal 1 second
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5
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----small blocks equal 1 second
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25
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Why must the EKG unit be standardized?
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To ensure an accurate and reliable recording •Allows results of an EKG run on one machine to be accurately compared with results run on another machine
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What needs to be checked on the EKG tracing to ensure the EKG unit is properly calibrated?
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the standardization mark on the EKG tracing to ensure the EKG unit is properly calibrated
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The height of a normal standardized mark on an EKG tracing is--mm high, or ---large blocks
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10 mm high (2 large blocks)
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The width of a normal standardized mark on an EKG tracing is --mm high, or ---small blocks
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2 mm wide (2 small blocks)
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Where does a 3-channel EKG machine automatically record the standardized marks?
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One mark is recorded at the beginning and end of each EKG strip
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What should be done if the standardized mark is more or less than 10 mm high?
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-Machine must be adjusted •Consult operating instructions
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What is the most easily identified structure on an EKG
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QRS complex
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What does the QRS complex consist of?
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Q,R, S waves
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How does a normal QRS complex appear?
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Normal QRS complex is "spiked" •Shape can vary
