ECG REVIEW: THE BASICS

Megan Chan, PGY-1

UHCMC 2015

http://thepracticalpsychosomaticist.com/2013/04/01/qtc-interval-prolongation-and-antipsychotics-by-elysha-elson-pharm-d-mph/

THE BASICS

http://flylib.com/books/en/2.569.1.27/1/

THE ECG UNIT

http://cal.vet.upenn.edu/projects/lgcardiac/ecg_tutorial/printerval.htm

THE SYSTEMATIC PROCESS Rate

300/(# large boxes between R—R interval) 300-150-100-75-60-50

Rhythm Regular vs irregular Sinus rhythm?

P before every QRS (easiest to see in leads II and V1) Positive p wave in I & II; negative p in aVR

Axis Normal axis?

Positive QRS sum in I and II (or aVF ) Left deviation?

Up in I, down in II Right deviation?

Down in I, up/down in II

THE SYSTEMATIC PROCESS CONT.

Intervals PR interval: normal 120-200ms (3-5 small

boxes) Short PR interval = WPW Long PR interval = heart block

QRS complex: normal <120ms (≤ 3 small boxes) Long QRS: conduction delays, hyperkalemia,

ventricular rhythm QT interval: normal ≤ 430 in men, ≤ 450 in

females (less than R—R/2) Long QT: MI, myocarditis, hypocalcemia,

hypothyroidism, subarachnoid hemorrhage, drugs—sotolol, amiodarone, hereditary

THE SYSTEMATIC PROCESS CONT.

Conduction Abnormalities AV blocks RBBB LBBB IVCD (interventricular conduction delay) Left Anterior Fascicular Block Left Posterior Fascicular Block

http://healthybeatinghearts.blogspot.com/2011/01/first-week-with-new-pacemaker.html

http://www.zuniv.net/physiology/book/images/11-13.jpg

http://dualibra.com/wp-content/uploads/2012/04/037800~1/Part%209.%20Disorders%20of%20the%20Cardiovascular%20System/Section%202.%20Diagnosis%20of%20Cardiovascular%20Disorders/221.htm

http://www.emedu.org/ecg/crapsanyallans.php

HEMI BLOCKS = LEFT FASCICULAR BLOCKS

http://www.usfca.edu/fac-staff/ritter/Image74.gif

http://aliem.com/wp-content/uploads/2013/08/LAFB.png

http://aliem.com/wp-content/uploads/2013/08/LPFB.png

http://cdn.lifeinthefastlane.com/wp-content/uploads/2011/02/avhisbb.jpg

LAFB

LPFB

HYPERTROPHY

http://dualibra.com/wp-content/uploads/2012/04/037800~1/Part%209.%20Disorders%20of%20the%20Cardiovascular%20System/Section%202.%20Diagnosis%20of%20Cardiovascular%20Disorders/221.htm

THE SYSTEMATIC PROCESS CONT.

Chamber size

RAE LAE RVH LVH

• Tall P > 2.5 mm in lead II

• Large diphasic P with large initial phase in V1

• P> 120ms• Diphasic p

with downward terminal phase > 1mm wide and 1mm deep in V1

• M-shaped P in I, II, or aVL

• R in aVR > 5mm (or R>Q)

• R in V1 > 7mm

• qR in V1• R in V1 + S in

V5/V6 > 10mm

• Deep S in V5/V6 > 7mm

• R in aVL > 11mm

• R in V5/V6 + S in V1/V2 > 35mm

• R in I + S in III > 25 mm

• R in aVF > 20mm

• S in aVR > 14mm

THE SYSTEMATIC PROCESS CONT. Ischemia

What ECG changes do you expect to see? Hyperacute T waves Inverted T waves ST segment

elevation Q waves ST depressions = ???

Subendocardial ischemia ST elevations = ???

Transmural ischemia What are Pathologic Q waves?

1 small box wide and/or >5mm or 1/3 of R wave deep Other changes:

Old septal infarct: No R waves in V1-V3 Old lateral infarct: No R wave progression in V4-V6 RV infarct: ST elevation in V4 & V5 with right sided EKG

THE SYSTEMATIC PROCESS CONT.

Everything Else Pericardial Effusion

Low voltage (R waves < 5mm in limb leads, <10mm in precordial leads)

Pericarditis Diffuse ST elevations and PR depressions

Pulmonary Embolism “S1Q3T3”:S wave in I, Q wave in III, T wave inversion

in III

Location Leads Occluded Vessel

Anterior V2-V4 LAD

Anteroseptal V1-V4 LAD

Anterolateral V1-V6, I, aVL LAD, diagonal

Lateral V5-V6, I, aVL Circumflex, diagonal

Inferior II, III, aVF RCA, circumflex

Posterior Tall R in V1-V3, ST depression in V1-V2

RCA

http://www.edoctoronline.com/media/19/photos_245a975b-66ad-4f7e-86d8-82d3ca7d0120.jpg

http://dotwordpressdotcom.wordpress.com/med-school/clinical-skills/ecgs/

THE DR. ORTIZ METHOD 4 step method to interpreting 80% of ECGs in 1

minute What are the most important ECG leads?

II— best axis, dx inferior wall MI, most studied V1—best p wave, dx anterior wall MI & RBBB V5—dx lateral wall MI, LBBB, & LVH

What 2 leads are best for determining axis? I & II

100% sensitive & specific w/ zero false + Normal axis is -30 to 90 aVF was used > 100 years ago

Special thanks to Dr. Jose Ortiz!

THE DR. ORTIZ METHOD Step 1: Demographics

Verifying pt name and calibration of ECG Step 2: Two second look at lead II

Regularity of the tracing. Any funny beats? P waves

Upright sinus “M” shape LAE Mountain peaks RAE

Axis: QRS positive 50% chance of normal axis Intervals

Normal QRS <3 boxes >3 boxes BBB

Q waves –75% risk for inferior MI

THE DR. ORTIZ METHOD Step 3: Study three things about the

QRS Axis: normal vs L deviation vs R deviation

Confirm suspected axis by looking at lead I Width: normal vs RBBB vs LBBB

> 3 boxes wide = abnormal Look at V1 If RSR’ then RBBB; If large S then LBBB.

Height: normal vs low voltage vs LVH Remember “14-12-35” for LVH

Lead I: R > 14 Lead aVL: R > 12 S in V1 + R in V5/V6 > 35

THE DR. ORTIZ METHOD

Step 4: Rate, ST segments, T waves, Infarcts Anterior/Septal infarct: V1-V4 Inferior infarct: II, III, aVF Lateral infarct: aVL, I, V5, V6

DRAW A NORMAL ECG

http://www.lysosomalstorageresearch.ca/Fabry_eClinic/electrocardiography-ecg.html

I

II

III

aVR

V1 V4

aVL V2 V5

aVF V3 V6

Same as II

Same as II

Same as II Same as II

Inverted II

Same as aVR but T & P waves can be + or –

Biphasic QRS

Similar to V3 but less QRS voltage

Similar to V3 with larger S, smaller R

HOW TO DRAW A NORMAL ECG

Similar to V3 with smaller

S, taller R

Similar to V4 with smaller S,

taller R(R wave

progression)

REFERNCES

Agabegi SS, Agabegi ED. Step up to Medicine, 3rd ed. 2013. Lippincott Williams & Wilkins. Philadelphia, PA.

Gomella LG, Haist SA. Basic EKG reading. In: Clinician’s Pocket Reference. McGraw-Hill; 2007. http://flylib.com/books/en/2.569.1.27/1/. Accessed Nov 18, 2014.

Longo DL, Fauci AS, Kasper DL, et al. Electrocardiography. In: Harrison’s Principles of Internal Medicine, 18th ed. 2012. McGraw Hill. New York, NY.

University of Illinois at Chicago. Online ICU Guidebook. 2013. http://chicago.medicine.uic.edu/UserFiles/Servers/Server_442934/Image/1.1/residentguides/final/icuguidebook.pdf. Accessed December 1, 2014.