BY / DR. MOHAMED RAMZY YOUSEF ER RESIDENT, QUALITY COORDINATOR QPSD MEEQAT GENERAL HOSPITAL

1. ECG Findings
in
Life-Threatening Conditions
BY / DR. MOHAMED RAMZY YOUSEF
ER RESIDENT, QUALITY COORDINATOR QPSD
MEEQAT GENERAL HOSPITAL

4.  ECG
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Graph Paper
Runs at a paper speed of 25 mm/sec
Each small block of ECG paper is 1 mm2
At a paper speed of 25 mm/s, one small
block equals 0.04 s
Five small blocks make up 1 large block
which translates into 0.20 s (200 msec)
Hence, there are 5 large blocks per
second
Voltage: 1 mm = 0.1 mV between each
individual block vertically

6. 
Elements of the ECG:
•
P wave: Depolarization of both atria;
• Relationship between P and QRS helps distinguish
various cardiac
arrhythmias
• Shape and duration of P may indicate atrial enlargement
•
PR interval: from onset of P wave to onset of QRS
• Normal duration = 0.12-2.0 sec (120-200 ms) (3-4
horizontal boxes)
• Represents atria to ventricular conduction time (through
His bundle)
• Prolonged PR interval may indicate a 1st degree heart
block
•

7. •
QRS complex: Ventricular depolarization
• Larger than P wave because of greater muscle
mass of ventricles
• Normal duration = 0.08-0.12 seconds
• Its duration, amplitude, and morphology are
useful in diagnosing cardiac
arrhythmias, ventricular
hypertrophy, MI, electrolyte derangement, etc.
• Q wave greater than 1/3 the height of the R
wave, greater than 0.04 sec are abnormal and
may represent MI

8. 
ST segment:
• Connects the QRS complex and T wave
• Duration of 0.08-0.12 sec (80-120 msec

T wave:
• Represents repolarization or recovery of
ventricles
• Interval from beginning of QRS to apex of T is
referred to as the absolute refractory period

QT Interval
• Measured from beginning of QRS to the end of
the T wave
• Normal QT is usually about 0.40 sec
• QT interval varies based on heart rate

9. R
P
Q
S

12. 
A 65-year-old woman presents to the ED
with generalized fatigue and palpitations.
She was started on an angiotensinconverting enzyme (ACE) inhibitor 2
months ago but has missed her follow-up
appointments. What metabolic
abnormality could be responsible for the
life-threatening condition shown in her
ECG tracing?

15. 
Life-Threatening Condition (I):
Hyperkalemia. The tracing shows a
regular rhythm at 75 bpm. A P wave is
present in front of each QRS
complex, indicating that the rhythm is
sinus. A flattened P wave (black
arrow), prolonged PR interval (blue
bar), borderline widened QRS complexes
(green bar), and -- more pathognomonic - pointed, narrow, and tented tall T waves
(red arrow) are all features of
hyperkalemia. The patient's serum
potassium when the tracing was recorded
was 7.2 mEq/L.

17. 
An 83-year-old man with known ischemic
cardiomyopathy has an out-of-hospital
cardiac arrest. He is rushed to the ED by
paramedics. What life-threatening
condition is shown in his ECG tracing and
what rhythm is he at risk of developing?

19. 
Life-Threatening Condition (II): Long
QT Interval and T-Wave Alternans.
The tracing shows a sinus rhythm at 60
bpm. The QT interval (black bar) is
prolonged to 680 msec (normal: 300-440
msec), with a QTc also of 680 msec
(normal: < 460 msec). The T-wave
heights alternate (blue arrows), which is
often a precursor to the more severe
rhythm of torsade de pointes.

21. 
A 74-year-old man with mild dementia
presents to the ED with worsening
confusion. His medications include
omeprazole, aspirin, simvastatin, and
digitalis. He lives alone at his home and
his daughter comes to visit once a week to
lay out his weekly medications. What
could be responsible for the lifethreatening condition shown on his ECG
tracing?

23. 
Life-Threatening Condition (III):
Digitalis Toxicity. The tracing shows no P
waves, with a baseline of irregular, fine
undulations, reflecting atrial fibrillation. The
QRS complex is narrow and occurs regularly
sometimes (in the latter part of the middle
strip) and in groups at other times. This
tracing is an example of junctional
tachycardia with variable conduction to the
ventricle. Conducted and skipped QRS
complexes are present in patterns of 2:1
(black asterisk), 3:2 (blue asterisk), or 4:3
(red asterisk). The tracing is highly
suggestive of digitalis toxicity, especially in
this clinical context.

25. 
A 25-year-old man arrives at the ED with
a heavy cough after getting caught
outside in a snowstorm while hiking. A
routine ECG is performed. The concerned
intern takes one look at it and rushes over
to show you what he believes to be a
serious problem. Do you agree with the
intern's assessment of a life-threatening
condition on the tracing?

27. 
Life-Threatening Condition (IV):
Artifact Simulating a Run of
Ventricular Tachycardia. At first glance,
this ECG suggests a run of ventricular
tachycardia. However, sharp deflections
occur regularly at the same rate as the
sinus rhythm seen at the beginning and at
the end of the tracing (black bar). These
deflections are undoubtedly QRS
complexes of the sinus rhythm and
provide an example of an artifact
simulating ventricular tachycardia.

29. 
A 32-year-old woman comes to the ED
complaining of light-headedness and
sweating. She is 5'6" tall and weighs less
than 100 lbs. An ECG is immediately
obtained, which evolves while you are
watching. What life-threatening condition
is seen on the ECG tracing?

31. 
Life-Threatening Condition (V):
Torsade de Pointes. Sinus rhythm is
present at the beginning (blue box), but
the QT interval of the sinus beats is long
(black bar). This is followed by a wide
QRS tachycardia at a rate of
approximately 200 bpm (red box). The
QRS morphology and axis continuously
change, indicating torsade de pointes,
which is life-threatening.