Transcript 2007_02_15-DaSilva-Advanced_ECG

“Advanced” EKG Reading
Stefan Da Silva
With special guest….
Dr. S. Weeks
Outline
• Quick review of EKG basic interpretation
• Dr. Weeks to take over
Basics
• Can’t really do the “advanced” without the
basics.
• Rate, Rhythm, Axis, Intervals, Infarction
Basics
• Rate
– SA node NORMALLY sets rate, usually cannot fire faster then ~
220 bpm.
– Ectopic beats will fire whenever they want and are usually
considered abnormal (PVC, PAC, etc).
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•
•
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Atrial ectopic pacemakers inherently fires ~75 bpm
AV nodal pacemaker enjoys ~60 bpm
Ventricular pacemaker likes 30 – 40 bpm (idoventricular rhythm)
HOWEVER, all the above will fire between 150 – 250 bpm in
pathological and emergency situations and ectopic pacemakers will
take over the rhythm when they are firing faster that SA node.
• When the SA node fails and the “ectopic” site takes over that = escape
beat/rhythm.
• Tachycardia and Bradycardia
• 300, 150, 100 then 75, 60, 50 (measured from R wave to R wave)
Basics
• Rhythm
– Sinus vs non-sinus
– Regular vs Irregular
– Sinus:
• P wave in front of every QRS with P wave positive in II, III,
aVF and neg in aVR.
– Sinus arrhythmia:
• Irregular rhythm but identical p waves
– Non-sinus
• Can be: varying rhythm, extra/skipped beats, rapid rhythm,
heart blocks.
Basics
• Axis
– More than just “thumb up/thumb down” and leads I and
aVF
– Refers to direction of electrical stimulus/depolarization.
– Related to ventricular depolarization
• Mean QRS vector = general direction of ventricular
depolarization
• Usually pointed downward and slightly to left since the
“vectors” representing depolarization of left ventricle are larger
due to thicker wall and septum (septum usually depolarizes
from left to right.)
Basics
Basics
Basics
• Mean QRS vector
Basics
• Remember these
diagrams
Basics
• Axis
– Therefore if heart is displaced to right then
Mean QRS vector will be displaced as well
– A hypertrophied ventricle has greater electrical
activity therefore mean vector will be displaced
to that side
– In infarction, dead myocardium cannot conduct
therefore mean QRS vector tends to point away
from infarcted area.
Basics
• Axis
– Calculation:
Basics
• Axis
– Examine lead I
• If positive QRS then vector located in left half
• If negative QRS then vector located in right half
– Examine lead aVF
• If positive QRS then vector points downward
• If negative QRS then vector points upward
– This will give you the general quadrant
• ie. Why the thumb rule works….
Basic
• Axis
– Then find most isoelectric lead and mean vector will be
at about 90 degrees towards the already specified
quadrant
– Plot it out….it helps.
– Why is axis important….
• It can help with diagnosis
– extreme RAD  Vtach, hyperK….
– RAD  RVH, PE, VSD…
– LAD  inf MI, hyperK, poor LV function, dilated LV, LAFB,
LVH.
Basics
• Intervals/Segments
– PR interval
• Start of P wave to start of QRS
• Normal: 0.12 - 0.2 sec
– Remember each small square is 0.04 sec
– QRS interval
• Start of QRS to end of QRS
• Normal: < 0.12
– QT interval
• Start of Q wave (or R wave if not Q) to termination of T wave.
• Quick and dirty: usually prolonged if greater than half the R-R
interval
• QTc:
Basics
• Bundle Branch Block
– More than the “bunny ears”
– Leads V1 and V6 (chest leads)
– Determine which direction the “last” half of the
QRS is pointing, it will point to the ventricle
that is depolarizing last, which will be the side
of the bundle branch block.
– Dr. Weeks to explain better than me….
Basics
• A little more on P waves
– Ensure going in right direction
– Tall P wave lead II  right atrial abnormality
(look for RAD, RVH)
– Wide P wave lead II +/- negative portion V1 
left atrial abnormality (look for MR, MS, AS,
HCM)
Basics
– Hypertrophy
• Increase in the thickness of the wall of that chamber.
• Right Ventricular Hypertrophy
– R wave of V1 gets progessively smaller
• Left Ventricular Hypertrophy
– S wave in V1 plus R wave in V5 > 35 mm
– T wave inversion can also occur
– Also if > 10mm in I or aVL then LVH
Basics
• Infarction
– Ischemia, injury, infarction
– T wave inversion  ischemia
– ST segment elevation/depression  injury
• Elevation = > 1 mm in 2 or more contigous leads
• Depression = > 0.5 mm in 2 or more contigous leads
Basics
I Lateral
aVR
V1 Septal
II Inferior
aVL Lateral V2 Septal
III Inferior
aVF
Inferior
V4 Anterior
V5 Lateral
V3 Anterior V6 Lateral
Basics
• Lots to remember and lots of variation but
remember the basics and then work from
there….