EKG Interpretation Flashcards
Lead Location and View of Heart
- V1: 4th intercostal on right - septum view (anterior wall)
- V2: 4th intercostal on left - septum view (anterior wall)
- V3: directly between V2 and V4 - anterior view
- V4: 5th intercostal midclavicular - anterior view
- V5: level with V4 anterior axillary - lateral view
- V6: level with V5 midaxillary - lateral view
Direction of EKG Spikes
- upward/positive deflection - neg. to pos. direction
- downward/negative defletion - pos. to neg. direction
- equiphasic deflection/pos. AND neg. - between neg. and pos.
EKG Paper Wave Description
- small box:
- 1mm tall x 0.04sec wide
- large box:
- 5mm tall x 0.2sec wide
- paper speed: 25mm/sec
Order and Meaning of Waves
- P (upward)- atrial depolarization
-
QRS complex- ventricular depolarization and contraction
- Q (downward)- depolarization of interventricular septum
- R (larger upward)
- S (downward)
- T (modest upward)- ventricular repolarization
- U (small/nonobserved upward)- recovery of Perkinje fibers
Intervals vs. Segments
invertval - contains a wave
segment - section with no wave
Pathologic Q Wave
>.04sec (1 small block) wide
>25% of height of R wave
J point
level of ST segment compared to PQ segment
EKG Reading Scheme
(what you need to read)
- Rate:
- 300, 150, 100, 75, 60, 50…
- strip is 10sec - count # beats x 6
- Rhythm:
- P-QRS coupling present and constant
- QRS complexes occurring regularly
- Waves: present and normal
- Axis
- Intervals:
- PR interval
- QRS interval
- QT interval
What is the QRS Axis
summation vector of where the heart’s electrical current
is spending most of its time (avg direction of electrical activity)
normal = -30 to +90
On what is the axis charted
Einthoven’s Triangle / Hexaxial System
Causes of Axis Deviation
- left axis deviation (-30 to -90)- left ventricular hypertrophy
- right axis deviation (+90 to 180)- MI (tissue death) in left ventricle
- extreme right axis deviation (-90 to 180)- “no mans land”
- could be extreme right or left
- typically a congenital anomaly
2 Steps to Determining Axis
- QRS complex in I and aVF:
- +/+ = normal
- +/- = POSSIBLE left axis (0 to -30 is normal)
- Look at Lead II:
- (+) = normal
- (-) = left axis
- Look at Lead II:
- -/+ = right axis
- -/- = extreme right axis
- Look for equiphasic lead in 1st 6 leads
- axis will be at right angle to equiphasic lead
- will point to quadrant determined by step 1
Why a bundle branch block (BBB) occurs
block in propogation of AV signal
ventricles normally contract simultaneously, but this interrupted
see split in QRS complex as a result
Right BBB
- “rabbit ears” (RSR’) in V1 and V2
- prominent S wave in 1 and aVL
d/t lungs
Left BBB
- “rabbit ears” (RR’) in V5 and V6
- broad R waves in 1, aVL, V6
d/t ischemic heart failure, HTN
Role of T-wave in BBB
- want T wave to be inverted with BBB (downward)
- elevated T wave may be an infarction
Hemiblocks (Fascicular Block)
- Anterior hemiblock
- left axis deviation > -45’ with no explanation
- small q in 1, aVL
- small r in II, III, aVF
- Posterior hemiblock
- right axis deviation > +120’ with no explanation
- small r in 1, aVL
- small q in II, III, aVF
Bifascicular Blocks
- RBBB + anterior fascicular block
- RBBB + posterior fascicular block
Complete Heart Block (3rd degree)
All 3 Fascicles blocked - no coupling
(atria no longer talking to ventricles - irregular rhythms)
look for P without QRS periodically
Chamber Enlargement - Right Atrium
P-wave large (>3mm) and pointed particularly in inferior leads
Chamber Enlargement - Left Atrium
Wide, notched P wave (>.12sec) particularly in inferior leads
Chamber Enlargement - Right Ventricle
- axis moves to right (spending more time here)
- J point lowered (ST depression)
- inverted T-wave
Chamber Enlargement - Left Ventricle
- amplified S and R waves
- (S-wave in V1) + (greater of R-wave in V5 or V6) > 35mm
- then check lead II to see if it’s negative
First Degree Block
prolonged PR interval
(0.1 - 0.2sec)
Second Degree: Mobitz Type 1 (Wenckebach)
short PR -> longer PR -> even longer PR -> dropped QRS
Second Degree Block: Mobitz Type II
P-wave then dropped QRS (no P-wave lengthening)
DANGEROUS!
Third Degree (Complete) Block
No P to QRS Coupling
(often requires pacemaker)
Potassium
Potassium (K+) “lives under the T-wave”
- Increased potassium - elevated T-wave
- Decreased potassium - lowered T-wave and U-wave created
Calcium
Ca++ determines time of repolarization
- Low Ca++ = prolonged QT interval (longer to repolarize)
- High Ca++ = shortened QT interval
EKG Changes d/t MI
- ischemia- ST depression with or without T-wave inversion
- injury- ST elevation with or without loss of R wave
- infarction- DEEP Q waves
Timing of EKG Changes with Acute Occlusion
- pathologic Q waves: hours to days
- ST segments: minutes to hours
- T-waves:
- Hyperacute T-waves in minutes
- T-wave inversion in hours
Location of Ischemia per EKG
- inferior:
- 2, 3, aVF
- right coronary and circumflex
- lateral
- 1, aVL, V5, V6
- left circumflex
- septal
- V1, V2
- LAD
- anterior
- V3, V4
- LAD
“Fooler” EKG
“Humped” ST elevation (possible ventricular aneurism)
Digoxin Effect
inverted T-wave in lateral leads
“moustache affect”
“knife-like” chest pain eased with bending over
ST elevation in I and II and “all over”
Pericarditis
“Slurring” of QRS - Delta wave
followed by tachycardia in later EKG
Wolff-Parkinson-White Syndrome
IMPORTANT!
Wolff-Parkinson-White
Orthodromic
impulse flows up accessory path to atria - atria overstimulated tachycardia
Wolff-Parkinson-White
Antidromic
impulse flows down accessory path
Accessory Path through AV Node
Lown-Ganong-Levine (LGL) Syndrome
- short PR segment
- no delta wave d/t accessory path
Posterior Wall MI
- ST depression in V1 - V4 (septal and anterior)
- R/S wave ratio greater than 1 in V1 or V2
Right Ventricular MI
- ST elevation in V1 (only lead that looks directly at right ventricle)
- ST elevation in III > II (b/c III is more rightward facing than II)
