ECG changes in myocardial ischaemia and injury.

1. Ischemia and injury
Dr. Sarah Sreekanth
Assistant professor,
Dept of General Medicine, CHRI
22.03.2015

2. Important to remember!
• ECG is not sufficiently specific or sensitive to
be used without a patient's clinical history

4. Myocardial ischemia and injury
• Mismatch between perfusion and demand
• Ischemic myocardium goes for anaerobic
metabolism to sustain itself
• Can survive but cannot function
• Remains in resting state and does not
participate in contraction
• Reversible if blood supply is restored or
demand is lowered

5. • If blood flow is restored before glycogen gets
depleted, cells resume contraction promptly
(ischemia)
• If severe depletion of glycogen has occurred, it
becomes stunned and recovery is delayed
(injury)
• If complete depletion of glycogen occurs,
necrosis of the cells results, leading to
infarction

6. Why is it clinically important?
• When ECG changes occur in association with
chest pain but without frank infarction, they
confer prognostic significance.
• About 20% of patients with ST segment
depression and 15% with T wave inversion will
experience severe angina, myocardial
infarction, or death within 12 months of their
initial presentation.

7. ECG CHANGES IN ISCHEMIA

8. ECG effects of myocardial ischemia
• Manifest by changes in T waves

9. • T waves may become
– Flattened
– Inverted
– Tall or
– Biphasic
ECG effects of myocardial ischemia

10. • T waves that are deep and symmetrically
inverted (arrowhead) strongly suggest
myocardial ischaemia.
• At least 1 mm deep
• Present in ≥ 2 continuous leads that have
dominant R waves (R/S ratio > 1)
• Dynamic — not present on old ECG or
changing over time
T wave inversion

11. Widespread T wave inversion due to myocardial ischaemia

12. Point to note
• Inverted T waves are normal in leads III, aVR,
and V1
• Associated with a predominantly negative QRS
complex.

13. A – T wave in coronary insufficiency
B – T wave in LVH with strain
C – T wave in digitalis effect
Other causes of T inversion

14. ECG CHANGES IN MYOCARDIAL
INJURY

15. ECG effects of myocardial injury
• Deviation of the ST segment
• ST segment deviated towards the surface of
the injured tissue
• Patterns of deviation
– ST depression
– St elevation

17. Forms of ST depression
• Horizontality
• Upward sloping ST depression
• Downward sloping ST depression

18. ST depression
• Horizontal or downsloping ST depression ≥ 0.5
mm at the J-point in ≥ 2 contiguous
leads indicates myocardial ischaemia.
• ST depression ≥ 1 mm is more specific and
conveys a worse prognosis.
• ST depression ≥ 2 mm in ≥ 3 leads is associated
with a high probability of NSTEMI and predicts
significant mortality (35% mortality at 30 days).
• Upsloping ST depression is non-specific for
myocardial ischaemia.

19. Normal ST segment
Horizontality of ST segment
Plane ST segment Upwards sloping ST Downsloping ST segment

20. Horizontal ST segment depression

21. Upwards sloping ST depression in V2 – V5

22. Downsloping ST depression with T inversion in I, aVL, V5, V6

23. Other causes for ST depression
DEPRESSED ST --->
• D - Drooping valve (MV Prolapse)
• E - Enlargement of the left ventricle
• P - Potassium low
• R - Reciprocal ST Depression (eg. Inferior MI)
• E - Encephalon (Intracerebral) Haemorrhage
• S - Subendocardial Infarct
• S - Subendocardial Ischaemia
• E - Embolism (Pulmonary)
• D - Dilated Cardiomyopathy
• S - Shock
• T - Toxicity (Digitalis/Quinidine

24. ST

25. ST elevation
• Epicardial injury – ST deviated towards
epicardial surface
• Leads oriented towards the epicardial surface
eg Lead V6 will have a raised ST segment
• Leads oriented away will have a depressed ST
segment eg aVR

26. Take home messages
• Ischaemia , injury and infarct are constituents
of a contiguous spectrum caused due to
decrease in perfusion to a given myocardial
region
• Deep symmetrical arrow head T wave denotes
ischaemia
• ST segment deviations (depression and
elevation) reflect injury