Flashcards
ECG course notes
Cards in this deck (70)
- 1The right coronary artery supplies blood tothe right atrium, the
right ventricle, and part of the inferior and posterior surfaces of the
left ventricle.In about 50% of the population, the artery also supplies
blood to the sinoatrial (SA) node. The bundle of His and the AV
node also receive their blood supply from the right coronary artery. - 2What are the 2 branches of the left coronary?The left coronary artery runs along the surface of the left atrium,
where it splits into two major branches, the left anterior descending
and the left circumflex arteries. - 3The left anterior descending supplies blood toThe left anterior descending
artery runs down the surface of the left ventricle toward the apex
and supplies blood to the anterior wall of the left ventricle, the
interventricular septum, the right bundle branch, and the left
anterior fasciculus of the left bundle branch. The branches of
the left anterior descending artery—the septal perforators and
the diagonal arteries—help supply blood to the walls of both
ventricles. - 4The circumflex artery suppliesoxygenated blood to the lateral
walls of the left ventricle, the left atrium and, in about half of
the population, the SA node. In addition, the circumflex artery
supplies blood to the left posterior fasciculus of the left bundle
branch. This artery circles the left ventricle and provides blood to
the ventricle’s posterior portion. - 5Impulses travel out from the SA node and then....through the internodal
tracts and Bachmann’s bundle to the AV node. From there,
they travel through the bundle of His, the bundle branches, and
lastly to the Purkinje fibers. - 6The SA node is located inthe upper right corner of the right
atrium, where the superior vena cava joins the atrial tissue mass. - 7What is the heart's main pacemaker?The SA node
- 8How many impulses does the SA generate per minute?60 - 100 per minute
- 9Can impulses flow backward in the heart?No. When initiated, the impulses follow a specific
path through the heart. They usually can’t flow backward
because the cells can’t respond to a stimulus immediately after
depolarization. - 10What is the function of the AV node?is responsible for delaying the impulses that
reach it. Although the nodal tissue itself has no pacemaker cells,
the tissue surrounding it (called junctional tissue) contains pacemaker
cells that can fire at a rate of 40 to 60 times per minute. The AV node’s main function is to delay impulses by 0.04 seconds
to keep the ventricles from contracting too quickly. This delay
allows the ventricles to complete their filling phase as the atria
contract. It also allows the cardiac muscle to stretch to its fullest
for peak cardiac output. - 11Which ventricle has thicker walls?The left ventricle
- 12Can the Purkinje cells serve as a pacmaker?Purkinje fibers can also serve as a pacemaker and are able
to discharge impulses at a rate of 20 to 40 times per minute,
some times even more slowly. - 13The coronary arteries fill with blood duringThe coronary arteries fill with blood when the ventricles
are in diastole and filling with blood. The aortic valve is
closed at that time, so it no longer blocks blood flow through the
coronary ostium into the coronary arteries. - 14The two valves called the semilunar valves are theThe pulmonic and aortic valves are semilunar.
- 15What does an ECG show?The sequence of cardiac events.An ECG shows the precise sequence of electrical events occurring
in the cardiac cells throughout that process. It allows the
nurse to monitor phases of myocardial contraction and to identify
rhythm and conduction disturbances. A series of ECGs can be
used as a baseline comparison to assess cardiac function - 16Electrodes placed on the skin measurethe direction
of electrical current discharged by the heart. That current is then
transformed into waveforms. - 17What are leads and planes?Electrodes placed on the skin measure the direction
of electrical current discharged by the heart. That current is then
transformed into waveforms.
An ECG records information about those waveforms from different
views or perspectives. Those perspectives are called leads
and planes. - 18A lead provides a view of the heart’s electrical activity betweenone positive pole and one negative pole.
- 19What is the lead's axis?A lead provides a view of the heart’s electrical activity between
one positive pole and one negative pole. Between the two poles
lies an imaginary line representing the lead’s axis, a term that
refers to the direction of the current moving through the heart. - 20an isoelectric waveform.When no electrical activity occurs or the activity is too
weak to measure, the waveform looks like a straight line, called
an isoelectric waveform. - 21As current travels toward the negative pole, the waveform deflectsAs current travels
toward the negative pole,
the waveform deflects
mostly downward. - 22When current flows perpendicular to the lead, the waveformWhen current
flows perpendicular to
the lead, the waveform
may be small or go in
both directions
(biphasic). - 23As current travels toward the positive pole, the waveform deflectsAs current
travels toward the
positive pole, the
waveform deflects
mostly upward. - 24The term plane refers toThe term plane refers to a cross-sectional perspective of the
heart’s electrical activity. - 25The frontal plane, a vertical cut through the middle of the heart, providesThe frontal plane, a vertical cut through
the middle of the heart, provides an anterior-to-posterior view of
electrical activity. - 26The horizontal plane, a transverse cut through the middle of the heart, providesThe horizontal plane, a transverse cut through
the middle of the heart, provides either a superior or an inferior
view. - 27The two types of ECG recordings are the12-lead ECG and a
rhythm strip. Both types give valuable information about heart
function. - 28Which leads provide information about the heart’s frontal (vertical) plane?The six limb
leads—I, II, III, augmented vector right (aVR), augmented vector
left (aVL), and augmented vector foot (aVF)—provide information
about the heart’s frontal (vertical) plane. - 29Which leads are bipolar and why?Leads I, II, and III require
a negative and positive electrode for monitoring, which makes
those leads bipolar. - 30What are unipolar leads?The augmented leads record information from
one lead and are called unipolar. Like the
augmented leads, the precordial leads are also unipolar, requiring
only a single electrode. - 31Which leads provide information about the heart’s horizontal plane?The six precordial or V leads—V1, V2, V3, V4, V5, and V6—provide
information about the heart’s horizontal plane. - 32Which is the opposing pole of the precordial leads?The opposing pole of those leads is the
center of the heart as calculated by the ECG. - 33Which leads are among the most commonly used leads for monitoring?leads II, V1, and V6 are among the most commonly
used leads for monitoring - 34you should adjust the leads according toAlthough leads II, V1, and V6 are among the most commonly
used leads for monitoring, you should adjust the leads according
to the patient’s condition. - 35All bipolar leads have a third electrode, known asAll bipolar leads have a third electrode, known as the ground,
which is placed on the chest to prevent electrical interference
from appearing on the ECG recording. - 36Lead I provides a view of the heart that shows current moving fromLead I provides a view of the heart that shows current moving
from right to left. - 37The positive electrode for lead I is placed on the........ and the negative electrode is placed on the...........Because current flows from negative to positive,
the positive electrode for this lead is placed on the left arm or on
the left side of the chest; the negative electrode is placed on the
right arm. - 38Lead I produces a............ deflection on ECG tracings and is helpful in monitoring.................Lead I produces a positive deflection on ECG tracings
and is helpful in monitoring atrial rhythms and hemiblocks. - 39Lead II produces aLead II produces a positive deflection.
- 40Connections for lead IIPlace the positive electrode
on the patient’s left leg and the negative electrode on the
right arm. The current travels down and
to the left in this lead. - 41Lead II is useful for detectingLead II tends to produce a positive, highvoltage
deflection, resulting in tall P, R, and T waves. This lead is
commonly used for routine monitoring and is useful for detecting
sinus node and atrial arrhythmias. - 42Lead III produces a ........... deflection.positive
- 43Lead III connectionsThe positive electrode
is placed on the left leg; the negative electrode, on the left arm. - 44Lead III is useful for detecting...Along with lead II, this lead is useful for detecting changes associated
with an inferior wall myocardial infarction. - 45What are augmented leads and why are they called so?Leads aVR, aVL, and aVF are called augmented leads because the
small waveforms that normally would appear from these unipolar
leads are enhanced by the ECG. (See Augmented leads.) The “a”
stands for “augmented,” and “R, L, and F” stand for the positive
electrode position of the lead. - 46In lead aVR, the positive electrode is placed onIn lead aVR, the positive electrode is placed on the right arm
(hence, the R) and produces a negative deflection because the
heart’s electrical activity moves away from the lead. Lead aVR
provides no specific view of
the heart. - 47In lead aVL, the positive electrode is on theIn lead aVL, the
positive electrode is on the left arm and produces a positive deflection
on the ECG. Lead aVL shows
electrical activity coming
from the heart’s lateral wall. - 48In lead aVF, the positive electrode is on theIn lead aVF, the positive electrode is on the left leg
(despite the name aVF) and produces a positive deflection. Lead aVF shows electrical
activity coming from the
heart’s inferior wall - 49How does Lead V1 help?shows the
P wave, QRS complex, and ST segment particularly well. It helps
to distinguish between right and left ventricular ectopic beats
that result from myocardial irritation or other cardiac stimulation
outside the normal conduction system. Lead V1 is also useful
in monitoring ventricular arrhythmias, ST-segment changes, and
bundle-branch blocks. - 50Smallest square on ECG paper1mm,
0.04secs,
0.1mV - 511 second is represented by how many unit squares?25 unit squares
- 52Each large horizontal block equals......secs0.2 secs
- 535 large horizontal blocks equal to1 second
- 54What is an ECG complex?An ECG complex represents the electrical events occurring in one
cardiac cycle. A complex consists of five waveforms labeled with
the letters P, Q, R, S, and T. The middle three letters —Q, R, and
S—are referred to as a unit, the QRS complex. ECG tracings represent
the conduction of electrical impulses from the atria to the
ventricles. - 55What does the P wave represent?The P wave is the first component of a normal ECG waveform.
It represents atrial depolarization—conduction of an electrical
impulse through the atria. - 56How do you evaluate a P wave?When evaluating a P wave, look closely
at its characteristics, especially its location, configuration, and deflection. (Understand these better) - 57What are the characteristics of a normal P wave?Location: precedes the QRS complex
amplitude—2 to 3 mm high
duration—0.06 to 0.12 second
configuration—usually rounded and upright
deflection—positive or upright in leads I, II, aVF, and V2 to V6;
usually positive but variable in leads III and aVL; negative or inverted
in lead aVR; biphasic or variable in lead V1. - 58If the deflection and configuration of a P wave are normal— for example, if the P wave is upright in lead II and is rounded and smooth—and if the P wave precedes each QRS complex, you can assume thatthis electrical impulse originated in the sinoatrial
(SA) node - 59The atria start to contract partway through the P wave. Will you see this on the ECG?The atria start to contract partway through the P wave,
but you won’t see this on the ECG. Remember, the ECG records
electrical activity only, not mechanical activity or contraction. - 60Peaked, notched, or enlarged P waves may representAtrial hypertrophy
or enlargement associated with chronic obstructive pulmonary
disease, pulmonary emboli, valvular disease, or heart failure. (Understand these better) - 61Inverted P waves may signifyInverted P waves may signify retrograde or reverse conduction
from the atrioventricular (AV) junction toward the atria. When an
upright sinus P wave becomes inverted, consider retrograde or
reverse conduction as possible conditions. - 62Varying P waves indicate thatthe impulse may be coming from
different sites, as with a wandering pacemaker rhythm, irritable
atrial tissue, or damage near the SA node. - 63Absent P waves may signifyconduction by a route other than the SA node, as with a
junctional or atrial fibrillation rhythm. - 64The PR interval tracksthe atrial impulse from the atria through
the AV node, bundle of His, and right and left bundle branches. - 65When evaluating a PR intervallook especially at its duration.
Changes in the PR interval indicate an altered impulse formation
or a conduction delay, as seen in AV block. - 66A normal PR interval has the following characteristicsA normal PR interval
has the following characteristics (amplitude, configuration, and
deflection aren’t measured):
• location—from the beginning of the P wave to the beginning of
the QRS complex
• duration—0.12 to 0.20 second. - 67Short PR intervals (less than 0.12 second) indicatethat the impulse
originated somewhere other than the SA node. This variation
is associated with junctional arrhythmias and preexcitation
syndromes. - 68Prolonged PR intervals (greater than 0.20 second) may representa conduction delay through the atria or AV junction
due to digoxin toxicity or heart block—slowing related to ischemia
or conduction tissue disease. - 69The QRS complex follows the P wave and representsThe QRS complex follows the P wave and represents depolarization
of the ventricles. Immediately after the ventricles depolarize,
as represented by the QRS complex, they contract. That contraction
ejects blood from the ventricles and pumps it through the
arteries, creating a pulse. - 70Pay special attention to the duration and configuration when evaluating a QRS complex. A normal complex has the following characteristics• location—follows the PR interval
• amplitude—5 to 30 mm high but differs for each lead used
• duration—0.06 to 0.10 second, or half of the PR interval.
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- Professional Clinical Research Topics (Clinical Research) Flashcards on ECG course notes, created by A M on 15/10/2015.
- Created by
- A M · Oct 2015
- Updated
- May 5, 2016
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