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EKG: Chapter 2

Terms in this set (49)

hypertrophy
increase in muscle mass (shown in the QRS Complex
pressure overload
-causes most hypertrophy
-heart is forced to pump blood against an increased resistance
-seen in patients with systemic hypertension or aortic stenosis
enlargement
Dilation of a particular chamber (shown in the p wave)
volume overload
The chamber dilates to accommodate an increased amount of blood
Hypertrophied myocardium
Demands more blood supply for the overgrown heart muscle, but it has a reduced density of capillaries and is therefore more susceptible to ischemia than is normal myocardium
Changes to EKG wave when a chamber hypertrophies
-Increased wave duration due to longer depolarization time
-Increase in amplitude
-Electrical axis (mean electrical vector) shift due to larger percentage of electrical current
Most dramatic EKG wave change is seen in
Amplitude
mean vector
Average vector of all the instantaneous vectors
mean electrical axis
Direction of the mean vector
Direction of the mean QRS vector
Leftward and inferiorly
Normal QRS axis
0-90 degrees
Which leads quickly determine normal QRS axis
Leads 1 and aVF
If the QRS complex is ____ in leads 1 and aVF, then the QRS axis must be normal
Predominantly positive
Lead 1 will record a predominantly positive QRS complex if
The mean QRS vector is directed anywhere between -90° and +90°
The lead aVF will record a predominantly positive QRS complex if
The mean QRS vector is directed anywhere between 0° and 180°
If the QRS complex is predominantly positive in both lead 1 and lead aVF
The QRS axis must lie in the quadrant where both are positive, between 0° and 90°
If the QRS complex in either lead 1 or lead aVF is NOT predominantly positive
The QRS axis does not lie between 0° and 90°, not normal
Biphasic wave
Positive and negative deflections extended equally on both sides of the baseline
Axis
Refers to the direction of the mean electrical vector, representing the average direction of current flow. It is defined in the frontal plane only
To determine the axis of any wave
Find the lead in which the wave is most nearly biphasic. The axis must lie approx. perpendicular to that lead
If the axis lies between 90° and 180°
Right axis deviation
If the axis lies between 0° and -90°
Left axis deviation
If the axis becomes totally disoriented and lies between -90° and 180°
Extreme right axis deviation
Normal axis lead 1:______ Lead aVF:______
Positive; positive
Left axis deviation lead 1:_____ Lead aVF:_____
Positive; negative
Right axis deviation lead 1:_____ lead aVF:_____
Negative; positive
Extreme right axis deviation lead 1:____ lead aVF:_____
Negative; negative
With right atrial enlargement, the ________________ of the first portion of the p wave increases
Amplitude of the first portion
The presence of p waves with an amplitude exceeding 2.5 mm in at least one of the inferior leads II, III, and aVF diagnoses what?
Right atrial enlargement
With left atrial enlargement, the ___________ of the p wave increases
Amplitude of the second portion
The diagnosis of left atrial enlargement requires that
The terminal portion of the p wave should be at least 1 small block(0.04 second) in width.
To diagnose atrial enlargement
Look at leads II and V1
Right atrial enlargement is characterized by
-P waves with an amplitude exceeding 2.5 mm in the inferior leads
-No change in the duration of the p wave
-Possible right axis deviation of the p wave
Left atrial enlargement is characterized by
-The amplitude is the terminal (negative) component of the P wave may be increased and must descend at least 1 mm below the isoelectric line in lead V1
-The duration of the P wave is increased, and the terminal portion of the P wave must be at least 1 small block(0.04 second) in width
-No significant axis deviation is seen because the left atrium is normally electrically dominant
In the limb leads, the most common feature associated with right ventricular hypertrophy is
Right axis deviation
The QRS axis must exceed ____ in order to diagnose right ventricular hypertrophy
100°
Right ventricular hypertrophy precordial lead criteria
-Lead V1: R wave is larger than the S wave
-Lead V6: S wave is larger than the R wave
Most common causes of right ventricular hypertrophy
Pulmonary disease and congenital heart disease
left ventricular hypertrophy
Increased R wave amplitude in leads overlying the left ventricle and increased S wave in leads overlying the right ventricle
Left ventricular hypertrophy precordial lead criteria
-The R wave amplitude in lead V5 or V6 plus the S wave amplitude in lead V1 or V2 exceeds 35mm
-The R wave amplitude in lead V5 exceeds 26mm
-The R wave amplitude in lead V6 exceeds 20mm
-The R wave amplitude in lead V6 exceeds the R wave amplitude in lead V5
Left ventricular hypertrophy limb lead critera
-The R wave amplitude in lead aVL exceeds 11mm
-The R wave amplitude in lead aVF exceeds 20mm
-The R wave amplitude in lead 1 exceeds 13mm
-The R wave amplitude in lead 1 plus the S wave amplitude in lead III exceeds 25mm
Most accurate criteria to diagnose left ventricular hypertrophy
The R wave amplitude in lead aVL plus the S wave amplitude in V3 exceeds 20 in women and 28 in men
Secondary Repolarization Abnormalities Of Ventricular Hypertrophy include
-Downsloping ST-segment depression
-T wave inversion (the T wave changes its axis so that it is no longer closely aligned with the QRS axis)
Right ventricular repolarization abnormalities will be seen in leads
V1 and V2
Left ventricular repolarization abnormalities will be most evident in leads
1, aVL, V5, and V6
Right ventricular hypertrophy is characterized by
-Right axis deviation is present, with the QRS axis exceeding 100°
-The R wave is larger than the S wave in V1, whereas the S wave is larger than the R wave in V6
Characterized by voltage criteria and, not infrequently, secondary repolarization abnormalities
Left ventricular hypertrophy
Most useful criteria for left ventricular hypertrophy
-The R wave in V5 or V6 plus the S wave in V1 or V2 exceeds 35mm
-The R wave in aVL is 11mm
-The R wave in aVL plus the S wave in V3 exceeds 20 in women and 28 in men
-Left axis deviation exceeding -15° is also often present
secondary repolarization abnormalities include
Asymmetric, T-wave inversion and downsloping ST-segment depression
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