ekg basics
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Basic EKG informationTRANSCRIPT
EKG Basics
Dr. Joshi
Objectives History Review of conduction system How EKG is done Normal EKGs Abnormal EKGs
History Einthoven assigned the letters P, Q, R, S
and T to the various deflections, and described the electrocardiographic features of a number of cardiovascular disorders.
In 1924, he was awarded the Nobel Prize in Medicine for his discover
What is an EKG?The electrocardiogram (EKG) is a representation of the electrical events of the cardiac cycle.
Each event has a distinctive waveform, the study of which can lead to greater insight into a patient’s cardiac pathophysiology.
The Normal Conduction System
What types of pathology can we identify and study from EKGs?
Arrhythmias Heart Blocks Myocardial ischemia and infarction Pericarditis Chamber hypertrophy Electrolyte disturbances (i.e.
hyperkalemia, hypokalemia) Drug toxicity (i.e. digoxin and drugs which
prolong the QT interval)
EKG Leads : Eyes Looking at the Heart
Leads are electrodes which measure the difference in electrical potential between either:
1. Two different points on the body (bipolar leads)1. Two different points on the body (bipolar leads)
2. One point on the body and a virtual reference point 2. One point on the body and a virtual reference point with zero electrical potential, located in the center of with zero electrical potential, located in the center of the heart (unipolar leads)the heart (unipolar leads)
EKG Leads
The standard EKG has 12 leads: 3 Standard Limb Leads
3 Augmented Limb Leads
6 Precordial Leads
The axis of a particular lead represents the viewpoint from The axis of a particular lead represents the viewpoint from which it looks at the heart.which it looks at the heart.
Standard Limb Leads
Standard Limb Leads
Augmented Limb Leads
Augmented Limb leads30
90
-150
All Limb Leads
Precordial Leads
Adapted from: www.numed.co.uk/electrodepl.html
Precordial Leads
Summary of Leads
Limb Leads Precordial Leads
Bipolar I, II, III(standard limb leads)
-
Unipolar aVR, aVL, aVF (augmented limb leads)
V1-V6
Anatomic Groups(Septum)
Anatomic Groups(Anterior Wall)
Anatomic Groups(Lateral Wall)
Anatomic Groups(Inferior Wall)
Anatomic Groups(Summary)
Normal EKG
How to read EKG? Rate Rhythm Axis P wave PR interval QRS complexes ST segment T waves QT intervals
Rate 300 / big Square
1500/ small square
Rule of 10 seconds
What is the heart rate?
www.uptodate.com
300/6 = 50 bpm
What is the heart rate?
(300 / ~ 4) = ~ 75 bpm
www.uptodate.com
What is the heart rate?
(300 / 1.5) = 200 bpm
10 Second RuleAs most EKGs record 10 seconds of rhythm per page, one can simply count the number of beats present on the EKG and multiply by 6 to get the number of beats per 60
seconds.
This method works well for irregular rhythms.
What is the heart rate?
The Alan E. Lindsay ECG Learning Center ; http://medstat.med.utah.edu/kw/ecg/
33 x 6 = 198 bpm
The QRS Axis
The QRS axis represents the net overall direction of the heart’s electrical activity.
Abnormalities of axis can hint at:Ventricular enlargementConduction blocks (i.e. hemiblocks)
The QRS AxisBy near-consensus, the normal QRS axis is defined as ranging from -30° to +90°.
-30° to -90° is referred to as a left axis deviation (LAD)
+90° to +180° is referred to as a right axis deviation (RAD)
Determining the Axis
Predominantly Positive
Predominantly Negative
Equiphasic
Quadrant Approach
What is the normal axis?A. 0 degrees to 180 degrees B. 0 degrees to +90 degrees C. -30 degrees to +90 degrees D. -90 degrees to +90 degrees E. -90 degrees to +30 degrees
Answer: c , minus 30 degrees to + 90 degrees
Quadrant Approach: Example 1
The Alan E. Lindsay ECG Learning Center http://medstat.med.utah.edu/kw/ecg/
What is the Axis? Right Axis Deviation Left Axis Deviation Indeterminate Axis Normal AxisAnswer: Right Axis Deviation Why?
Lead I is predominantly negative Lead aVF is positive “ Reaching”
Quadrant Approach Example 2
What is the axis? A. -100 degrees B. -30 degrees C. +15 degrees D. +90 degrees E. Indeterminate
Answer: D, Lead 1 Isoelectric and Lead aVF is positive, and therefore 90 degrees
Quadrant Approach: Example 3
What is the diagnosis? Left Axis Right Axis Indeterminate Axis Normal Axis
Answer: Indeterminate axis, Reason being lead 1, aVL and aVF are isoelectric.
Quadrant Approach: Example 4
What is the answer? Left Axis Deviation Right Axis Deviation Indeterminate axis Normal Axis
Answer: Left axis deviation Lead I positive, and aVF negative
(leaving)
P wave and PR interval It is important to remember that the P
wave represents the sequentialactivation of the right and left atria, and it is common to see notched or biphasic P waves of right and left atrial activation.
P duration < 0.12 sec P amplitude < 2.5 mm Frontal plane P wave axis: 0o to +75o May see notched P waves in frontal plane PR = less than 20 miliseconds
QRS complexes The QRS represents the simultaneousactivation of
the right and left ventricles, although most of the QRS waveform is derived from the larger left ventricular musculature.
QRS duration < 0.10 sec QRS amplitude is quite variable from lead to lead
and from person to person. Two determinates of QRS voltages are:
Size of the ventricular chambers (i.e., the larger the chamber, the larger the voltage)
Proximity of chest electrodes to ventricular chamber (the closer,the larger the voltage)
EKG in MI is important but …… Poor sensitivity for Myocardial Infarction
(40-50%)
3-10% of MI patients have initial normal EKG
25% of patients with missed MI had misread EKG
EKG Findings you dare not miss !
Acute inferior STEMI
A 55 year old man with 4 hours of "crushing" chest pain
A 63 year old woman with 10 hours of chest pain and sweating
Acute anterior STEMI
A 60 year old man with 5 hours of chest pain and diaphoresis
Anterolateral STEMI
A 60 year old woman with 3 hours of chest pain
Acute posterior MI
A 79 year old man with 5 hours of chest pain
New LBBB, Inferior MI
A 70 year old man with exercise intolerance
Complete heart block
An 82 year old lady with dizzy spells !
AF with complete Heart block
75 y o male with blood pressure 60/40
Ventricular tachycardia
87 yo man with hx of recurrent syncope
Sinus Arrest
64 yo male who missed a session of HD
69 yo male with syncope.
Wenkebach
What is this?
Early Repolarization
Right Bundle Branch Block (RBBB)
"Complete" RBBB has a QRS duration >0.12s Close examination of QRS complex in various
leads reveals that the terminal forces (i.e., 2nd half of QRS) are oriented rightward and anteriorly because the right ventricle is depolarized after the left ventricle. This means the following: Terminal R' wave in lead V1 (usually see rSR' complex)
indicating late anterior forces Terminal S waves in leads I, aVL, V6 indicating late
rightward forces Terminal R wave in lead aVR indicating late rightward
forces The frontal plane QRS axis in RBBB should be in
the normal range (i.e., -30 to +90 degrees
RBBB
Left Bundle Branch Block(LBBB)
Complete" LBBB" has a QRS duration >0.12s. Close examination of QRS complex in various
leads reveals that the terminal forces (i.e., 2nd half of QRS) are oriented leftward and posteriorly because the left ventricle is depolarized after the right ventricle. Terminal S waves in lead V1 indicating late posterior
forces Terminal R waves in lead I, aVL, V6 indicating late
leftward forces; usually broad, monophasic R waves
LBBB
LAFB LAFB is the most common of the
intraventricular conduction defects. It is recognized by
1) left axis deviation; 2) rS complexes in II, III, aVF; and 3) small q in I and/or aVL.
LAFB
Left Posterior Fascicular Block Rare Right axis deviation in the frontal plane
(usually > +100 degrees) rS complex in lead I qR complexes in leads II, III, aVF, with R in
lead III > R in lead II QRS duration usually <0.12s unless
coexisting RBBB
Left Posterior Fascicular Block(LPFB)
Bifascicular Blocks
RBBB plus either LAFB (common) orLPFB (uncommon)
Features of RBBB plus frontal plane features of the fascicular block (axisdeviation, etc.)
Bifascicular Block
Right Atrial Enlargement RAE is recognized by the tall (>2.5mm) P
waves in leads II, III, aVF. RVH is likely because of right axis
deviation (+100 degrees) and the Qr (or rSR') complexes in V1-2.
Right Atrial Enlargement
LVH with "Strain"
Criteria for LVH Sokolow + Lyon (Am Heart J, 1949;37:161)
S V1+ R V5 or V6 > 35 mm
Cornell criteria (Circulation, 1987;3: 565-72) SV3 + R avl > 28 mm in men SV3 + R avl > 20 mm in women
Framingham criteria (Circulation,1990; 81:815-820) R avl > 11mm, R V4-6 > 25mm S V1-3 > 25 mm, S V1 or V2 + R V5 or V6 > 35 mm, R I + S III > 25 mm
REMEMBER: S in V1 plus R in V5 or 6 > 35
RVH
Knowledge is beautiful
References Up to date ECG Library Alan E. Lindsay ECG learning Center Wikipedia