This document discusses the ST segment of the electrocardiogram (ECG) and abnormalities that can occur. It begins by defining the ST segment and explaining that abnormalities in elevation or depression are often caused by myocardial ischemia or infarction. Several potential causes of ST segment elevation or depression are then listed and described in more detail. Specific ECG patterns that can indicate different types of myocardial infarction or other conditions are also analyzed.

1. ST SEGMENT
Dr.G.VENKATA RAMANA
MBBS DNB FAMILY MEDICINE

2. • ST Segment
• Flat, isoelectric section of the ECG between the
end of the S wave (the J point) and the
beginning of the T wave
• Represents the interval between ventricular
depolarization and repolarization
• The most important cause of ST segment
abnormality (elevation or depression)
is myocardial ischaemia or infarction

3. • Causes of ST Segment Elevation
• ST segment elevation myocardial infarction
• Coronary vasospasm (Printzmetal’s angina)
• Pericarditis
• Benign early repolarization
• Brugada syndrome
• Left bundle branch block
• Left ventricular hypertrophy
• Ventricular aneurysm
• Ventricular paced rhythm
• Raised intracranial pressure
• Takotsubo Cardiomyopathy

4. Morphology of the Elevated ST segment
Acute STEMI may produce ST elevation with either concave, convex or
obliquely straight morphology

5. ST Segment Morphology in Other Conditions

6. ST Segment Morphology in Other Conditions

7. • Patterns of ST Elevation
• Acute ST elevation myocardial infarction
(STEMI)
• ST segment elevation and Q-wave formation in
contiguous leads
• Septal (V1-2)
• Anterior (V3-4)
• Lateral (I + aVL, V5-6)
• Inferior (II, III, aVF)
• Right ventricular (V1, V4R)
• Posterior (V7-9)

8. • Coronary Vasospasm (Prinzmetal’s angina)
• This causes a pattern of ST elevation that is very
similar to acute STEMI — i.e. localised ST
elevation with reciprocal ST depression
occurring during episodes of chest pain
• However, unlike acute STEMI the ECG changes
are transient, reversible with vasodilators and
not usually associated with myocardial necrosis
• It may be impossible to differentiate these two
conditions based on the ECG alone

11. EVOLUTION OF STEMI

12. Diagnostic ECG criteria for STEMI
In right-sided leads (V3R and V4R), the threshold for abnormal ST elevation
at the J point is 0.5 mm, except in males <30 years in whom it is 1 mm
In posterior leads (V7, V8, and V9), the threshold for abnormal ST elevation at
the J point is 0.5 mm

13. Location of MI by ECG leads

14. ECG localisation of coronary artery territories

15. High Lateral STEMI
•ST elevation is present in the high lateral leads (I and aVL)
•There is reciprocal ST depression in the inferior leads (III and aVF)
•QS waves in the anteroseptal leads (V1-4) with poor R wave progression
indicate prior anteroseptal infarction
•This pattern suggests proximal LAD disease with an acute occlusion of the first
diagonal branch (D1)

17. Inferolateral STEMI Posterior extension
Inferolateral STEMI. Posterior extension is suggested by:
•Horizontal ST depression in V1-3
•Tall, broad R waves (> 30ms) in V2-3
•Dominant R wave (R/S ratio > 1) in V2
•Upright T waves in V2-3

18. Inferolateral STEMI Posterior extension
Marked ST elevation in V7-9 with Q-wave formation confirms involvement of
the posterior wall, making this an inferior-lateral-posterior STEMI (= big territory
infarct!)

19. Right ventricular infarction
• In patients with inferior STEMI, right ventricular
infarction is suggested by:
• ST elevation in V1
• ST elevation in V1 and ST depression in V2
(highly specific for RV infarction)
• Isoelectric ST segment in V1 with marked ST
depression in V2
• ST elevation in III > II
• Diagnosis is confirmed by the presence of
ST elevation in the right-sided leads (V3R-
V6R)

21. Inferior STEMI Right ventricular infarction
Inferior STEMI Right ventricular infarction is suggested by:
•ST elevation in V1
•ST elevation in lead III > lead II

22. Repeat ECG of the same patient with V4R
electrode position
•There is ST elevation in V4R consistent with RV infarction

23. Hyperacute Anteroseptal STEMI
Hyperacute Anteroseptal STEMI:
•ST elevation and hyperacute T waves in V2-4
•ST elevation in I and aVL with reciprocal ST depression in lead III
•Q waves are present in the septal leads V1-2
•These features indicate a hyperacute anteroseptal STEMI

24. Extensive anterior MI
Extensive anterior MI (“tombstoning” pattern)
•Massive ST elevation with “tombstone” morphology is present throughout
the precordial (V1-6) and high lateral leads (I, aVL)
•This pattern is seen in proximal LAD occlusion and indicates a large
territory infarction with a poor LV ejection fraction and high likelihood of
cardiogenic shock and death

26. Criteria for ST-segment Elevation for
Prior LBBB or RV-paced Rhythm
• ST-segment elevation greater than 1 mm in the
presence of a positive QRS complex (concordant
with the QRS)
• ST-segment elevation greater than 5 mm in the
presence of a negative QRS complex
(disconcordant with the QRS)
• ST-segment depression greater than 1 mm in V1–
V3

29. A score of 3 points or more has a 90% specificity (but a poor sensitivity) for the
diagnosis of STEMI

31. • Benign Early Repolarization (BER) causes mild ST elevation with tall T-
waves mainly in the precordial leads
• BER is a normal variant commonly seen in young, healthy patients. There is
often notching of the J-point — the “fish-hook” pattern
• The ST changes may be more prominent at slower heart rates and
disappear in the presence of tachycardia
There is slight concave ST elevation in the precordial and inferior
leads with notching of the J-point (the “fish-hook” pattern)

33. Brugada Syndrome
• Inherited channelopathy (a disease of
myocardial sodium channels) that leads to
paroxysmal ventricular arrhythmias and sudden
cardiac death in young patients
• The tell-tale sign on the resting ECG is the
“Brugada sign” — ST elevation and partial RBBB
in V1-2 with a “coved” morphology

34. There is ST elevation and partial RBBB in V1-2 with a coved morphology —
the “Brugada sign”

36. Left Bundle Branch Block
• In Left bundle branch block (LBBB), the ST
segments and T waves show “appropriate
discordance” — i.e. they are directed opposite to
the main vector of the QRS complex
• This produces ST elevation and upright T waves
in leads with a negative QRS complex (dominant
S wave), while producing ST depression and T
wave inversion in leads with a positive QRS
complex (dominant R wave)

38. Left Ventricular Hypertrophy (LVH)
•Left axis deviation
•Deep S waves with ST elevation in V1-3
•ST depression and T-wave inversion in the lateral leads V5-6

40. Ventricular Paced Rhythm
• Ventricular pacing (with a pacing wire in the right ventricle) causes ST
segment abnormalities identical to that seen in LBBB
• There is appropriate discordance, with the ST segment and T wave directed
opposite to the main vector of the QRS complex

41. Raised Intracranial Pressure
• Raised Intracranial Pressure (ICP) (e.g. due to intracranial haemorrhage,
traumatic brain injury) may cause ST elevation or depression that simulates
myocardial ischemia or pericarditis
Widespread ST elevation with concave (pericarditis-like) morphology in a patient
with severe traumatic brain injury

42. Takotsubo Cardiomyopathy
• A STEMI mimic producing ischemic chest pain,
ECG changes +/- elevated cardiac enzymes with
characteristic regional wall motion abnormalities
on echocardiography
• Typically occurs in the context of severe
emotional distress (“broken heart syndrome“)
• Commonly associated with new ECG changes
(ST elevation or T wave inversion) or moderate
troponin rise

43. Takotsubo Cardiomyopathy

44. • Less Common Causes of ST segment Elevation
• Pulmonary embolism and acute cor pulmonale (usually
in lead III)
• Acute aortic dissection (classically causes inferior
STEMI due to RCA dissection)
• Hyperkalemia
• Sodium-channel blocking drugs (secondary to QRS
widening)
• J-waves (hypothermia, hypercalcaemia)
• Following electrical cardioversion
• Others: Cardiac tumour, myocarditis, pancreas or
gallbladder disease

45. • Transient ST elevation after DC
cardioversion from VF

46. J waves in hypothermia simulating ST
elevation

47. • Causes of ST Depression
• Myocardial ischemia / NSTEMI
• Reciprocal change in STEMI,Posterior MI
• Digoxin effect
• Hypokalemia
• Right bundle branch block
• Right ventricular hypertrophy
• Left bundle branch block
• Left ventricular hypertrophy
• Supraventricular tachycardia
• Ventricular paced rhythm

48. Morphology of ST Depression
• ST depression can be either upsloping, downsloping, or
horizontal
• Horizontal or downsloping ST depression ≥ 0.5 mm at
the J-point in ≥ 2 contiguous leads indicates myocardial
ischaemia (according to the 2007 Task Force Criteria)
• Upsloping ST depression in the precordial leads with
prominent De Winter T waves is highly specific for
occlusion of the LAD
• Reciprocal change has a morphology that resembles
“upside down” ST elevation and is seen in leads
electrically opposite to the site of infarction
• Posterior MI manifests as horizontal ST depression in
V1-3 and is associated with upright T waves and tall R
waves

50. ST segment morphology in myocardial
ischemia

51. Reciprocal change

52. ST segment morphology in posterior MI

53. Patterns of ST depression
• Myocardial Ischemia
• Unlike myocardial infarction, ischaemia is
reversible and so the associated ECG
abnormalities are seen only while the patient is
experiencing an episode of pain
• ST segment depression is the commonest
abnormality associated with ischaemia and is
usually ‘horizontal’

55. Reciprocal Change
• ST elevation during acute STEMI is associated
with simultaneous ST depression in the electrically
opposite leads:
• Inferior STEMI produces reciprocal ST depression
in aVL (± lead I)
• Lateral or anterolateral STEMI produces reciprocal
ST depression in III and aVF (± lead II)
• Reciprocal ST depression in V1-3 occurs
with posterior infarction

56. • Inferior STEMI with complete heart block

57. •Reciprocal ST depression in aVL with inferior STEMI

58. •Reciprocal ST depression in III and aVF with high lateral STEMI

59. Posterior Myocardial Infarction
• ST depression in the anterior leads V1-3, along with dominant R waves (“Q-
wave equivalent”) and upright T waves
• ST elevation in the posterior leads V7-9

60. De Winter T Waves
• A pattern of up-sloping ST depression with symmetrically peaked T
waves in the precordial leads is considered to be a STEMI
equivalent, and is highly specific for an acute occlusion of the LAD

61. Digoxin Effect
• Treatment with digoxin causes downsloping ST
depression with a “sagging” morphology, reminiscent of
Salvador Dali’s moustache

63. Hypokalemia
• Causes widespread downsloping ST depression with T-wave
flattening/inversion, prominent U waves and a prolonged QU interval

65. Right ventricular hypertrophy with ‘strain’
• Causes ST depression and T-wave inversion in the right
precordial leads V1-3

66. Right Bundle Branch Block (RBBB)
• Produce a similar pattern of repolarisation abnormalities
to RVH, with ST depression and T wave inversion in V1-3

67. Supraventricular tachycardia (SVT)
• SVT (e.g. AVNRT) typically causes widespread horizontal ST depression,
most prominent in the left precordial leads (V4-6)
• This rate-related ST depression does not necessarily indicate the presence
of myocardial ischaemia, provided that it resolves with treatment