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12 Lead ECG

Terms in this set (62)

12 lead ECG
a standard assessment tool taht uses 10 electrodes. one on each limb and 6 on the chest
anterior leads
leads V3 and V4, which are positioned over the front (anterior) of the left ventricle
aV leads
augmented voltage leads; they use an average rather than a single identifiable negative lead
bipolar limb leads
leads I,II, and III
electrocardiogram (ECG)
graphic representation of the electrical activity of the heart
electrode
an adhesive pad that contains conductive gel and is designed to be attached to the Pts skin
lateral leads
leads V5, V6, I and aVL, which look at the heart from the lower and upper aspect of the left side
leads
electrodes connected to the monitor or ECG machine by wires, which relay the electrical impulse from the generator to the myocardium
modified chest left (MCL)
precordial voltage leads, when acquired with a 3 or 4 lead monitor
precordial lead electrodes
the six precordial or voltage leads, which are designated V1 through V6; second type of electrode and true chest leads
septum
a dividing wall or membrane, especially between bodily spaces or masses of soft tissues. the septum of the heart is examined by leads V1 and V2
unipolar limb leads
leads aVR, aVL and aVF
mm
millimeters
ms
milliseconds
mv
millivolts
P wave
represents depolarization of the left and right atria
QRS complex
represents the conduction of the electrical impulse from the bundle of His throughout the ventricular muscle, or ventricular depolarization
QRS duration
refers to the width of the QRS complex; used to determine wide vs narow complexes. in adults > 120 milliseconds is considered wide
QRS size measurement
determines conditions such as the presence of an enlarged heart, ST segment elevation, or pulmonary conditions stemming from the lack of voltage
QT interval
determines certain drug and electrolyte imbalances and other conditions of delayed repolarization; it is measured from the start of the QRS complex to the end of the T wave
R wave progression
refers to the size of the positively deflected R wave in the precordial V leads as they progressively increase in size from leads V1 to V4
T wave
represents ventricular repolarization and follows the ST segment
transition zone
occurs between leads V3 and V4; it is the point at which the overall R wave should go from predominately negative to positive
axis
the general direction of electrical impulses as they travel through the heart
extreme right axis deviation (ERAD)
a condition in which the direction of the impulse is predominantly backward due to the axis being deviated toward the right shoulder
fascicles
the two main divisions of the left bundle branch
hemiblock
a block of one of the 2 fascicles of the left bundle branch system
hemifascicles
two separate fascicles formed by the division of a right bundle branch and a left bundle branch
hexaxial system
a system that includes limb leads I, II, III and the augmented leads a VL, a VR, and a VF
left anterior hemiblock
occurs when the anterior hemifascicle of the left bundle branch system becomes blocked, causing a pathological left axis deviation (-40 to -90 degrees)
left posterior hemiblock
occurs when the posterior fascicle of the left bundle branch system is blocked, causing a right axis deviation (90 to 180 degrees)
physiological left axis deviation
the rotation of the axis slightly more to the left, showing an upward deflection in lead I and either an upward or an isoelectric deflection in lead II; range is from 0 to -40 degrees
bifascicular block
a right bundle branch block combined with a hemiblock or a left bundle branch block
bundle branch block (BBB)
an electrical phenomenom charecterized by a widened QRS complex of at least 0.12 sec (120 milliseconds) or greater and in most cases,a definitive QRS morphology pattern
ejection fraction
the volume percent of blood ejected in one contraction; one measure of left ventricle effectiveness; the normal range is between 60 and 75 percent
J point
the point in which the QRS complex turns into the ST segment
syncytium
cardiac muscle cell groups that are connected together and function collectively as a unit; the feature of the ventricles or the atrium that produces simultaneous depolarization
turn signal criteria
used to diagnose bundle branch blocks and works only in lead MCL-1 (V1) when the QRS is 0.12 sec
intraventricular heart block
a block within the ventricular conduction system
AV dissociation
a condition in which the atria and ventricles do not activate in a synchronous fashion but beat independent of each other
cannon A waves
pressure waves that shoot up through the jugular veins at irregular intervals
concordance
all the same; that is, precordial leads are up or down, and both conditions suggest VT
RS interval
measures the venticular activation time; begins at the start of the R waveand continues to the tip, or nadir point, of the s wave
atherosclerosis
the continuous buildup of plaque, resulting in the narrowing of the artery lumen
fibrinolytics
medications such as reteplase and tenecteplase, which stimulate the break down of fibrin in blood cells and prevent the polymerization of fibrin into new clots
pathological Q wave
signifies infarction, or death of the tissue; the pathological Q wave is more than 40ms wide, or one third of the R wave height
ST segment depression
when reciprocal to ST segment elevation, confirms the diagnosis of a myocardial injury. in cases without ST elevation, indicates ischemia or subendocardial (single layer thick) injury
ST segment elevation
a significant finding that indicates acute transmural injury across the three layers of the heart
T wave inversion
an early sign of acute coronary syndrome and myocardial ischemia
right ventricular infarction
occurs when there is an occlusion of the right coronary artery proximal to the acute marginal branches
left atrial enlargement (LAE)
a condition caused by hypertension, pulmonary edema, mitral or aortic valve stenosis, left ventricular hypertrophy (LVH), or acute myocardial infarction
right atrial enlargement (RAE)
a condition caused by congenital heart disease, tricuspid or pulmonary valve disease, or pulmonary hypertension (any cause)
left ventricular hypertrophy (LVH)
a condition in which the cardiac muscle responds to increased resistance in the circulation by becoming enlarged
right ventricular hypertrophy (RVH)
caused by increased pressure, or volume, in the right ventricle
hypercalcemia
a condition in which there is an excessive amount of calcium in the blood
hyperkalemia
a condition in which there is an excessive amount of potassium in the blood
hypocalcemia
a condition in which there is abnormally low blood calcium
hypokalemia
a condition in which there is abnormally low concentration of potassium in the blood
QTc
the rate corrected QT interval
isoelectric line
the bottom of the calibration spike (one millivolt or two large squares), found at the start of the 12 lead print out
sec
seconds
interventricular heart block
a block within the ventricular conduction system
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