ECG: Hypokalemia

1. DR. PRIYA KUBENDIRAN
M-1 UNIT
PROF DR.RUCKMANI’S UNIT

2. BRIEF HISTORY
A 40 year old male was admitted on 10.08.09 with
c/o acute watery diarrhoea – 3 days
No H/O vomiting/fever
No H/O any chest discomfort
H/O recurrent episodes of diarrhoea over the past
4 months.
Not a k/c of DM/SHT/PT/BA/IHD

3. O/E : conscious, oriented
afebrile
pallor +
mild dehydration +

PR – 110/min
BP – 96/70 mm Hg
RS – NVBS +, no added sounds
CVS – S1 S2 +, no murmur
P/A – soft, no organomegaly
CNS- NFND

5. ECG TAKEN ON 10.08.09
HR – 100/min
Normal sinus rhythm
Axis – 70˚
PR interval – 0.16 s
QRS interval – 0.08 s
QU – 0.48 s

6. Lab investigations :
B.urea - 36 mg/dl
S.creatinine – 0.7 mg/dl
S.electrolytes Na – 138 meq/l
Cl - 90 meq/l
Hco3 – 20 meq/l
K - 2.2 meq/l
ELISA for HIV1 - positive

8. Cardiac evaluation
Echocardiogram:
No RWMA
Normal Echo study

9. After adequate hydration, i.v antibiotics and
corrective measures for hypokalemia
oral KCl 15 ml tds
i.v - 20 mEq/day
3 days later repeat s.potassium – 4.2 mEq/L
A repeat ecg was taken

11. REPEAT ECG ON 14.08.09
HR – 43/min
Normal sinus rhythm
QRS axis - 60˚
PR interval – 0.16 s
QRS interval – 0.08 s
QT interval – 0.48
QTc – 0.41 s

12. ECG CHANGES IN HYPOKALEMIA
The ecg changes are due to
DELAYED VENTRICULAR REPOLARIZATION
Diagnosis is therefore based on ST segment, T
wave & U wave abnormalities

13. T wave
-progressive dimunition in amplitude, may
eventually disappear
- a remnant of T maybe visible as a slight
irregularity (minimal upward bump) on ST segment
U wave
progressive increase in amplitude & maintains
its rounded appearance
may get superimposed on T -TU complex
ST segment
ST depression is seen in all leads which may be
horizontal or concave upwards

14. Prominent U waves combined with ST segment
depression & flattened T waves –
ROLLER COASTER EFFECT

15. QT interval
U wave may be mistaken for a T wave leading
to an incorrect diagnosis of prolonged QT interval
QT interval is usually unchanged
P wave
increase in amplitude/ duration
PR interval
1
st
degree AV block is common
Prolongation may lead to superimposition of P
on TU – TUP complex
2
nd
degree AV block of Wenkebach type may be
seen

16. QRS complex
decreased voltage & increased duration
Arrythmias
Atrial & ventricular ectopics
Atrial tachycardia with block with AV
dissociation
Ventricular tachycardia
Ventricular fibrillation
Torsades de pointes

17. 1.ST depression ≥ 0.5 mm
2.U wave amplitude > 1 mm
3.U wave amplitude > T wave amplitude in same
lead
Typical ecg : 3 features in 2 leads
Compatible ecg : 2 features- U wave related
characteristics is present