Is This a STEMI?
Chesapeake Fire Department
Anthony E. Judkins, NR-P
ALS Tech/FF
Fire Station #12
Objectives
Review 12-lead group patterns
Review coronary anatomy
Identify bundle branch blocks
Determine left ventricular hypertrophic
(LVH) patterns
4-step algorithm for STEMI recognition
Sick or Not sick?
12-Lead Layout
“I See All Leads”
Inferior: II, III, AVF
Septal: V1, V2
Anterior: V3, V4
Lateral: V5, V6 (low lateral leads) & I, AVL
(high lateral leads)
**AVR use in STEMI recognition will be
discussed at later time**
Coronary Arteries
Inferior: Right coronary artery (RCA)
Septal: Left anterior descending (LAD)
artery
Anterior: Left anterior descending artery
(LAD)
Lateral: Left circumflex artery (LCx)
Posterior: Right coronary artery (RCA)
Coronary Arteries in
relation to the 12-lead
LAD$Pre(Stent$
$
$
$
$
LAD$Post(Stent$
$
$
$
$
$
Cardiac Conduction System
Normal electrical
conduction starts at the
SA Node
Moves across the atria
Continues to the AV node
and down the bundle
branches
Terminates in the
Purkinje fibers
Components of the heart
beat
P wave: Atrial depolarization
(electrical firing) and contraction
QRS complex: Ventricular
depolarization and contraction;
simultaneous atrial repolarization
(recharging)
T wave: Ventricular repolarization
ECG Time Intervals
PR interval (0.12-0.20s): represents time it
takes an electrical impulse to travel from
atria to the ventricles
QRS interval (0.08-0.12s): ventricular
depolarization
ST segment: usually an isoelectric line.
Can be elevated or depressed in diseased
states such as ischemia
ST Segment Morphologies
Left Bundle Branch Block
(LBBB)
Anatomy - 10 mm in
length, 4-10 mm wide
Divides into two fascicles
Left Anterior Fascicle and
Left Posterior Fascicle
LBBB Conduction & Changes
Left bundle is blocked
Electrical conduction continues down the right bundle
Delayed conduction down the left bundle
Right ventricle depolarizes before the left
Widened QRS complex ≥ 0.12 s, with a negative
deflection in V1 & V2 and a positive deflection in V6
LBBB Patterns
Q waves are absent in V6
R waves are usually small in
V1 & V2, tall & notched in
V6
Deep & wide S waves in V1 &
V2
ST elevation in V1-V3
T wave elevation in V1-V3
Leads I & AVL may look like
V6
NSR with LBBB
Wide QRS
With negative deflection
Right Bundle Branch Block
(RBBB)
Anatomy - long
and slender
Normal conduction
travels along the
right side of the
ventricular septum
Blood supply from
LAD
RBBB Conduction & Changes
Right bundle is blocked
Electrical conduction continues down the left bundle
Delayed conduction down the right bundle
Left ventricle depolarizes before the right ventricle. This
is the reason for the M-shape or rabbit ear morphology of
the QRS. r = left ventricle depolarization, R’ (R-prime) =
right ventricular depolarization
Widened QRS complex ≥ 0.12 s, with a positive deflection
in V1 & V2 and a wide S wave in I, AVL, & V6
RBBB Patterns
QRS morphology - rSR’ or
classic rabbit ears
configuration in V1 & V2
ST segment depression
T wave inversion may be
noted
Wide S wave in V6
Leads I & AVL may look
like V6
NSR with RBBB
Rabbit Ear Morphology
Wide S
Wave
LBBB vs RBBB
Take home message
Vs
Both bundle branch blocks have QRS complexes ≥ 0.12s
To differentiate between the two, simply: Look at V1, if
the QRS complex is wide and points down, it’s a LBBB.
If the QRS complex is wide and points up with rabbit
ears morphology, then it’s a RBBB.
Ventricular Hypertrophy
Hypertrophy is the
thickening of the
walls of the
ventricles
Can affect left and
right ventricles
Likely associated with
HTN, aortic stenosis,
or dilated
cardiomyopathy
Left Ventricular Hypertrophy (LVH)
Criteria
There are many ways to determine LVH, but there is no one way that is better than
another
We will use the easiest and most accurate way using the Sokolow-Lyon criteria by
looking at the precordial leads (chest). **V1 or V2 and V5 or V6***
Deep S waves in V1/V2 (Pick the lead with the deeper S wave, start at isoelectric line
and count little boxes downward)
Tall R waves in V5/V6 (Pick the lead with the taller R wave, start at the isoelectric
line and count little boxes upward)
T wave deflection opposite the QRS complex (strain pattern)
ST segment will be elevated and opposite QRS complex in V1-V3. This is known as
discordance and is a normal feature of LVH
S wave + R wave ≥ 35 mm = LVH
LVH Patterns
Taller R wave
Deep S wave
Strain Pattern
V1 has the deeper S wave (24 mm)
V5 has the taller R wave (23 mm)
S wave + R wave = 47 mm = LVH
Strain pattern present is normal variant with LVH finding
Tying it all
together
American Journal of Emergency Medicine (2012) 30, 1282–1295
www.elsevier.com/locate/ajem
Diagnostics
The use of a 4-step algorithm in the electrocardiographic
diagnosis of ST-segment elevation myocardial infarction by
novice interpreters
Stephanie M. Hartman, Andrew J. Barros, William J. Brady MD ⁎
Department of Emergency Medicine, University of Virginia School of Medicine, Charlottesville, VA 22908, USA
Charlottesville-Albemarle Rescue Squad, Charlottesville, VA 22901, USA
Received 1 October 2011; revised 14 November 2011; accepted 15 November 2011
Abstract The electrocardiographic (ECG) diagnosis of ST-segment elevation myocardial infarction
(STEMI) represents a challenge to all health care providers, particularly so for the novice ECG
interpreter. We have developed—and present in this article—a 4-step algorithm that will detect STEMI
in most instances in the prehospital and other nonemergency department (ED) settings. The algorithm
should be used in adult patients with chest pain or equivalent presentation who are suspected of STEMI.
It inquires as to the presence of ST-segment elevation as well as the presence of STEMI confounding/
mimicking patterns; the algorithm also makes use of reciprocal ST-segment depression as an adjunct in
the ECG diagnosis of STEMI. If STEMI is detected by this algorithm, then management decisions can
be made based upon this ECG diagnosis. If STEMI is not detected using this algorithm, then we can
only note that STEMI is not “ruled in”; importantly, STEMI is not “ruled out.” In fact, more expert
interpretation of the ECG will be possible once the patient (and/or the ECG) arrive in the ED where
ECG review can be made with the more complex interpretation used by expert physician interpreters.
© 2012 Elsevier Inc. All rights reserved.
1. Introduction
Ischemic heart disease describes an entire spectrum of
illness, ranging from acute to chronic entities related to
and typically occurs when there is an atherosclerotic plaque
rupture and subsequent thrombus formation and accompanying vasospasm [1]. Approximately 935 000 people in the
United States experience an AMI every year with approximately one third of these infarctions being STEMI [2].
“If STEMI is not detected using this algorithm, then we
can only note that STEMI is not “ruled in”; importantly
STEMI is not ruled out.”
–William J. Brady, MD
4-question Algorithm Article
Summary
***Review the 12-lead ECG in this order***
Is there STE in at least 2 contiguous leads? Y or N
Is the QRS complex of normal width? Y or N
Is the QRS complex of normal height? Y or N
Is there ST depression in at least one lead? Y or N
Is there ST elevation in at least two
contiguous leads?
Refer to Mnemonic “I See All Leads” for anatomical
leads
Is there at least 1-2 mm elevation in 2 contiguous
leads? ***At least 1 mm in limb leads & 2 mm in the
chest leads***
If the answer is YES, then move to the next question
If the answer is NO, then
NOT likely a STEMI
STOP
Is the QRS of normal width?
Is the QRS complex less than 0.12 s?
Rule out a LBBB or a ventricular paced rhythm
If the answer is YES, then move to the next question
If the answer is NO, then
NOT likely a STEMI
STOP
Is the QRS complex normal height?
Pick deeper S wave from V1 or V2 and taller R wave
from V5 or V6. (S + R) = sum of little boxes
Is the sum less than 35 mm? Rule out LVH
If the answer is YES, then move to the next question
If the answer is NO, then
NOT likely a STEMI
STOP
Is there ST depression in at least one
lead?
Is there one lead with at least 1 mm ST depression?
If the answer is YES, then consider STEMI activation
If the answer is NO, then
STOP
Not likely a STEMI
Consider Benign Early Repolarization (BER),
Pericarditis, or another cardiomyopathy
Practice
Normal ECG
Is there STE in at least 2 contiguous leads? No
Is the QRS complex of normal width? N/A
Is the QRS complex of normal height? N/A
Is there ST depression in at least one lead? N/A
STOP
Is there STE in at least 2 contiguous leads? Yes
Is the QRS complex of normal width? No
STOP
Is the QRS complex of normal height? N/A
Is there ST depression in at least one lead? N/A
LVH Pattern
Is there STE in at least 2 contiguous leads? Yes
Is the QRS complex of normal width? Yes
Is the QRS complex of normal height? No
STOP
Is there ST depression in at least one lead? N/A
STE
ST Depression
STE
STE
Inferior Wall STEMI
Is there STE in at least 2 contiguous leads? Yes (II, III, AVF)
Is the QRS complex of normal width? Yes (0.10 s)
Is the QRS complex of normal height? Yes (total less than 35 mm)
Is there ST depression in at least one lead? Yes (AVL)
References
Hartman, S. M., Barros, A. J., Brady, W. J. (2012). The Use of a 4-step
algorithm in the electrocardiographic diagnosis of ST-segment elevation
myocardial infarction by novice interpreters.
The American Journal of
Emergency Medicine, 30, 1282-1295.
Brady, W. J., Hudson, K. B., Naples, R., Sudhir, A., Mitchell, S., Ferguson, J.,
Reiser, R. (Eds.). (2013). The ECG in Prehospital Emergency Care.
London: Wiley-Blackwell.
Chan, T. C., Brady, W. J., Harrigan, R., Ornato, J. P., Rosen, P. (Eds.).
(2005). ECG in Emergency Medicine and Acute Care. Philadelphia:
Elsevier Mosby.
Brady, W. J., Truwit, J., (Eds.). (2009). Critical Decisions in Emergency &
Acute Care Electrocardiography. London: Wiley-Blackwell
Questions or need
reference texts?
ajudkins@cityofchesapeake.net