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72 Cards in this Set
- Front
- Back
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with a bundle branch block where does the blockage occur
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in the right or left bundle branch
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how are the ventricles depolarized with a bundle branch block
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*in a series rather than simultaneously
*depolarization is prolonged |
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what is the sequence for NORMAL venticular activation
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1-left to right through the septum
2-right and left ventricular walls |
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NORMAL ventricular activation creates what kind of pattern
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rs pattern in V1 and Rs pattern in V6
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EKG evidence of bundle branch blocks is present in which leads
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*right V1 and V2
*left V5 and V6 (precordial leads) |
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what is the ORS like with a BBB
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> 0.12 sec
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what is an EKG characteristic that will only be seen with a BBB
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triphasic (rSR') pattern
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what will the intrinsicoid deflection be with a BBB
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PROLONGED
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where will changes be seen with a RIGHT bundle branch block
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V1 and V2
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where will changes be seen with a LEFT bundle branch block
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V5 and V6
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why would possible axis deviation occur with a bundle branch block
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d/t change in activation
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with a COMPLETE left BBB what is blocked
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both anterior and posterior fascicles of the left bundle branch are blockede
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what is ventricular depolarization dependent on with LEFT bundle branch block
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depends on the RIGHT bundle branch
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how is the ventricular impulse conducted in a LEFT bundle branch block
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it passes normally down the RBB ad then must spread from the R ventricle to the L ventricle taking longer than usual to depolarize the ventricles
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how does septal deplorization occur in a LEFT bundle branch block
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it is altered to activate from right to left
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what EKG changes occur in V1 with a LEFT bundle branch block
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*loss of R wave
*last half of QRS is neg *ST elevation |
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what EKG changes occur in V6 with a LEFT bundle branch block
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*triphasic (rSR') pattern
*late intrinsicoid deflection *last half of QRS is positive *ST depression |
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what EKG changes occur in V5 with a LEFT bundle branch block
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*triphasic (rSR') pattern
*late intrinsicoid pattern |
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what is the QRS duration with a LEFT bundle branch block
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> 0.12 sec
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what are the possible causes of LEFT bundle branch block
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*acute MI *CAD
*dilated cardiomyopathy *conduction system dz *systemic HTN *LVH *post-cardiac sx *drug toxicity |
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what are the EKG changes seen in leads V1 and V2 with a RIGHT bundle branch block
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*triphasic pattern
*late intrinsicoid deflection |
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why is a late intrinsicoid deflection seen in the leads V1 and V2 with a RIGHT bundle branch block
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impulse is late in reaching epicardial suface of R ventricle
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what are the EKG changes seen in V6 with a RIGHT bundle branch block
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widened S wave
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what type of QRS is seen on EKG with a RIGHT bundle branch block
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> 0.12 sec
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what are the causes of RIGHT bundle branch block
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*systemic and pulm HTN
*cor pulmonale *tetralogy of fallot *congential heart defects (atrial septal defect) *cardiomyopathy *volume overload *drug toxcity *lenegres dz (fibrosis of perkinje fibers) |
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what are the characteristics of an INCOMPLETE bundle branch block
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*has the morphological changes in the QRS associated w/ complete BBB
*QRS duration is NOT prolonged 0.12 sec |
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how is the RIGHT bundle branch divided
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it does NOT divide
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how is the LEFT bundle branch divided
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divides into 3 fasicles
*anterior *posterior *septal |
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what is a hemiblock
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refers to blockage of either the anterior or posterior fascicle of the LEFT bundle branch
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what is the MOST distinctive feature of a hemiblock
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axis deviation
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with a hemiblock and axis deviation what must be ruled out
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other causes of axis deviation
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what are the features of hemiblocks
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*axis deviation
*NORMAL qrs duration *no ST segment or T wave changes present |
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what is the criteria for a left ANTERIOR hemiblock
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*LEFT axis devation
*Q wave in lead I *S wave in lead III *strengthened by presence of Q wave in other lateral leads or S wave in other inf leads |
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what is the criteria for a left POSTERIOR hemiblock
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*RIGHT axis deviation
*Q wave in lead III *S wave in lead I |
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what makes a left axis deviation pathological
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a negative complex in lead II when doing axis deviation
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left anterior fasicle lies how to left posterior fasicle
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anteriorly and laterally
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with left ANTERIOR hemiblock how does depolarization occur
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depolarization of the left posterior fasicle occurs and then is directed upward and leftward
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what results from depolarization of left ANTERIOR hemiblock
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LEFT axis deviation, tall R waves laterally and deep S waves inferiorly
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how does depolarization occur left POSTERIOR hemiblock
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it is directed down the unblocked anterior fasicle it then moves downward and rightward
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what results from depolarization of left POSTERIOR hemiblock
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RIGHT axis deviation, tall R waves inferiorly and deep S waves laterally
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what other type of block is left ANTERIOR hemiblock commonly seen with
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RIGHT bundle branch block
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which hemiblock is rare to see
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left POSTERIOR hemiblock
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which hemiblock is usually serious b/c it takes a lot of damage to occur
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left POSTERIOR
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what is hypertrophy
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an increase in muscle mass which is caused by a PRESSURE overload
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what is enlargement
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DILATION of a cardiac chamber which is usually caused by a VOLUME overload
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what are the EKG changes indicative of hypertrophy/enlargement
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1-increased duration
2-increased volatage 3-axis shifts |
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increased duration on EKG r/t hypertrophy/enlargement indicates what
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more time needed for depolarization/repolarization
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increased volatage on EKG r/t hypertrophy/enlargement indicates what
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more current is generated by hypertrophied chamber
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axis shifts on EKG r/t hypertrophy/enlargement indicate what
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increased current may shift axis in the direction of hypertrophied chamber
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how are P and T wave axis determined
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similarly to QRS axis
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what is normal P wave axis for adults
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0 to + 75 degrees
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what is normal P wave axis for children
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0 to + 90 degrees
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what is normal T wave axis
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is it variable but shouls be within 60 degrees of QRS axis
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what leads are used to dx atrial enlargement
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II and V1
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1st part of P wave represents left or right atrial depolarization
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RIGHT
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2nd part of P wave represents left or right atrial depolarization
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LEFT
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normal P wave is how long in duration
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less than 0.12 sec
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the largest P wave should be less than ____ mm whether neg or positive
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2.5
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what is the criteria for RIGHT atrial enlargement
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*increased amplitude of the FIRST part of the P wave (> 3mm)
*NO change in duration of the P wave *P wave axis may shift rightward 90 degrees |
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right atrial enlargement is termed what?
why? |
P pulmonale
-b/c lung dz is often the cause |
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what is the criteria for LEFT atrial enlargement
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*increased amplitude of SECOND portion of p wave (occassionally)
*increased P wave duration *NO sig axis deviation |
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what is LEFT atrial enlargment called
why? |
P mitrale
-b/c mitral valve dz is commonly the cause |
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what are the general causes of right and left ventricular hypertrophy
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pressure and volume overload
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PRESSURE overload causes of RIGHT ventricular hypertrophy
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*pulmonary stenosis
*pulmonary HTN *tetralogy of fallot |
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VOLUME overload causes of RIGHT ventricular overload
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*tricuspid or pulmonic insufficiency
*atrial or ventricular septal defects (blood shifting L to R) |
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what is the EKG criteria for RIGHT ventricular hypertrophy
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*right axis deviation that exceeds +100 degrees
*reversal of precordial pattern in V1 and V6 (R wave larger than S wave in V1) (S wave larger than R wave in V6) |
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PRESSURE overload causes of LEFT ventricular hypertrophy
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*systemic HTN
*aortic stenosis *coarctation of the aorta |
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VOLUME overload causes of LEFT ventricular hypertrophy
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*mitral reguritation
*aortic insufficiency *dilated cardiomyopathy *patent ductus arteriosus |
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EKG criteria for LEFT ventricular hypertrophy
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*varied but usually increasing R wave amplitude in leads overlying the LV and increased S wave amplitude in leads overlying the RV
*R wave in V5 or V6 plus S wave in V1 or V2 exceeds 35 mm(if > 40 y/o) |
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venticular strain EKG characteristics
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*asymmetric ST segment depresssion
*T wave inversion |
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when is ventricular strain seen
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look for ventricular strain in the presence of hypertrophy
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what does ventricular strain indicate
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clinically significant hypertrophy and may herald dilation and failure
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