Last update: May 2020



  ST segment depression is the most common ECG sign of ischemia.

  ST segment depression may be upsloping, horizontal or downsloping.

  ST segment depression developing during ischemic chest pain disappears in a few minutes after resolution of the ischemia.

  A flat ST segment without ST segment depression may be normal. It does not necessarily imply cardiac ischemia. ST segment flattening with less than 1mm ST depresion may be normal.



How is ST segment depression measured?

  ST segment displacement is measured at the junction of the ST segment with the end of the QRS complex (the J point).

  During treadmil exercise test, displacement of ST segment is measured 80 miliseconds after the J point.



Causes of ST segment depression:

  Myocardial ischemia

  Hypokalemia

  Digoxin

  Cocaine

  Left ventricular hypertrophy (with concurrent T wave changes)

  Bundle branch blocks (with concurrent T wave changes)

  During supraventricular tachycardia episodes (in patients with narrow QRS complex, paroxysmal, re-entrant supraventricular tachycardias, the appearance of ST segment depression or T wave negativity during tachycardia does not signify the presence of coronary artery disease).



ST segment depression during treadmil exercise test:

  In patients with uncontrolled systemic arterial hypertension, exercise-induced ST depression may be seen in the absence coronary artery stenosis.

  In the past, the use of ST/HR index was proposed to increase the diagnostic accuracy of the exercise testing. The ST/HR index, divides the difference between ST depression at peak exercise by the exercise-induced increase in heart rate. Later It was reported that the ST segment/heart rate index did not improve the diagnostic accuracy of the exercise test for identifying the presence or severity of coronary artery disease relative to standard visual criteria. Later, another study (QUEXTA Study) including 814 patients also did not find an advantage of the ST/HR index.



References

  J Am Coll Cardiol 2009;53:982-991. (free full-text)

  Ann Intern Med 1998;128(12 Pt 1):965-974.

  Eur Heart J 1993;14:1622-8.

  Circulation 1990;82:44-50. (free full-text)

  J Am Coll Cardiol 1986;8:836-847. (free full-text)




ECG 1. The ECG above belongs to a patient with stable angina pectoris. The patient complained of effort angina in the last 2
weeks. Coronary angiography was performed and then the patient was referred to coronary artery bypass graft operation
because of 3 vessel disease. ST segment flattening is one of the first signs of coronary ischemia and generally preceedes ST
segment depression.

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ECG 2. ST segment depression.




ECG 3a. This ECG is from a different patient. The first stage of treadmill exercise test shows no ST segment depression.

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ECG 3b. In the peak exercise, ST segment depression developes in leads II, III, aVF, V3-V6.

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ECG 3c. Persistence of ST segment depression in the recovery period (after treadmill has been stopped) suggests severe
coronary ischemia. Lateron, coronary angiography was performed and 3 vessel disease (extensive coronary artery disease)
was diagnosed.

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ECG 4. This 67 years old man complains of chest pain even during resting. He had undergone coronary artery bypass graft
operation. The ECG during the chest pain shows ST segment depression in leads V2-V6.

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ECG 5. The ECG above belongs to a hypertensive patient with normal coronary arteries. His blood pressure was not under
control for a long time. ST segment depression is present in lateral leads. The deep S wave in lead C2 and the high R waves
in leads C4 and C5 suggest the presence of left ventricular hypertrophy. In patients with chronic hypertension, observation of
ST depression in lateral leads does not necessarily suggest coronay artery disease.

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ECG 6a. This ECG belongs to a 70 years old patient who complained of chest pain for the last 2 months. Coronary angiography
revealed 99% stenosis in the bifurcation of left main coronary artery, and 70% stenosis in the right coronary artery. The distinct
ST segment depression in leads C3-C6 with mild ST sedpression in inferior leads suggest extensive coronary artery disease.
The presence of ST segment elevation in lead aVR also raises the suspicion of left main coronary artery disease.

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ECG 6b. This ECG was recorded 6 hours later. Because of the effective medical therapy, ST depression is now confined only
to C5 .

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ECG 6c. This ECG was recorded 12 hours later, just before the coronary bypass surgery. There is distinct ST depression in leads
C5 and C6. Diagnosis of left main coronary artery disease necessitates immediate coronary bypass operation.

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Figure 1a. Coronary angiography of the same patient shows 99% stenosis at the
bifurcation of left main coronary artery LAD, Cx and
proximal part of left main coronary artery are normal.



Figure 1b. Coronary angiography of the same patient shows significant stenosis
of the proximal right coronary artery .



ECG 7. ST segment depression is observed in a patient hospitalized for unstable angina pectoris. Coronary angiography
performed on the same day showed significant stenosis of the LAD and Cx coronary arteries. The patient was referred
to coronary artery bypass graft operation.

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ECG 8a. In this patient with coronary artery disease, ST segment depression and U waves with increased amplitude (higher
than that of the T wave) is observed during ischemic chest pain.

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ECG 8b. After the disapperance of chest pain, the ECG shows no more ST depression and increased U wave.

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ECG 9a. The ECG above belongs to a 56 years-old man complaining of palpitation and left shoulder pain.
The horizontal ST segment depression in leads V4 to V6 shows myocardial ischemia.
The patient was sent to coronary angiography laboratory immediately after this ECG.

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ECG 9b. Coronary angiography showed critical stenosis in the Obtus marginale branch of the circumflex artery which was
successfully stented. The ECG above was recorded immediately after the stenting.
Both tachycardia and ST segment depression disappeared.

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ECG 10. The ECG above belongs to a 55 years-old man complaining of chest pain. Coronary angiography showed significant
stenosis of the diagonal branch of the LAD artery. The ST segment depression in leads V3 to V6 show ischemia.

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ECG 11. The ECG above belongs to a 42 years-old anxious man who was complaining of atypical chest pain.
There is sinus tachycardia with widespread ST segment depression of UPSLOPING type.
Upsloping type ST segment depression is NOT typical for ischemia. Coronary angiography showed normal coronary arteries.

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ECG 12a. The ECG tracings above are from the Holter recording of a 63 years-old man with chest pain.
Treadmil exercise test also showed ST segment depression and the patient underwent coronary angiography.
The 70% stenosis in his LAD coronary artery was stented. His RCA and Cx coronary arteries were normal.

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ECG 12b. The ECG above belongs to the same man. It was recorded just before the treadmil exercise test.
ST segment depression is not seen.

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ECG 12c. The ECG above belongs to the same man.
It was recorded 3 minutes and 46 seconds after the onset of treadmil exercise test.
This is his peak exercise ECG. The test was stopped due to the emergence of ST segment depression.

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ECG 12d. The ECG above belongs to the same man.
It was recorded 2 minutes after termination of his test (recovery phase)
ST segment depression persists at this stage.

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ECG 13. The above ECG is from a 55 years-old hypertensive woman with typical chest pain.
Coronary angiography showed significant stenoses of the three coronary arteries.
Leads V4 to V6 show 1 mm horizontal ST segment depression.

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ECG 14a. The ECG above is from a 46 years-old man with moderate mitral stenosis.
He is totally asymptomatic: no dyspnea, no chest pain.
PR interval shortening with Delta waves are clearly seen: WPW syndrome.
The heart rate is 97/minute. At this rate, leads V2 to V6, I and aVL show ST segment depression.
Leads III and aVR show ST segment elevation.

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ECG 14b. Above ECG belongs to the same man. It was recorded one day after ECG 14a.
The patient ingested 40mg Propanolol 90 minutes before recording of the above ECG.
Slowing of the heart rate by Propranolol was attempted to make reliable Doppler evaluation of the mitral valve.
Now the rhythm is sinus bradycardia with a rate of 42/minute.
At this heart rate, ST segment elevations and depressions are not seen anymore.
The ST segment deviations seen in ECG 14a were rate-dependent.
Be careful when evaluating ST segment deviations in patients with WPW syndrome.
It is well-known that treadmill exercise test is not a reliable diagnostic tool in patients with WPW syndrome.

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ECG 15a. The ECG above belongs to a 62 years-old asymptomatic man.
It was recorded while he was being prepared for a possible kidney donation to his daughter.
Horizontal ST depression is most prominent in inferior leads. Leads V4 to V6 also show mild ST depression.
He did not complain of chest pain.
However, coronary angiography was performed solely because of the horizontal ST depression.
A significant stenosis (70%) with dissection was noted in his dominant Circumflex (Cx) coronary artery.
Horizontal ST segment depression should increase the suspicion for myocardial ischemia (coronary artery disease).

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ECG 15b. The ECG above belongs to the same man.
It was recorded after successful stenting of his Cx artery. ST depression is not seen any more.

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ECG 16. Above ECG is from an asymptomatic 74 years-old man with hypertension and Diabetes Mellitus.
Coronary angiography showed significant stenoses in Circumflex (obtus branch) and LAD coronary arteries.
His right coronary artery (RCA) was normal.
Leads V5 and V6 show horizontal ST depression.

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ECG 17. Short-lasting baseline drift may result in the appearance of ST segment depression limited to a single beat.
Actually there is no ST depression and no ischemia. This is just an artifact.
Myocardial ischemia resulting in ST depression is not expected to resolve in a second.
Baseline drift is also seen in the left part of the above ECG.

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ECG 18. Above is an ECG from a 49 years-old hypertensive man with retrosternal chest pain, not related to effort.
ECHOcardiography showed septal hypertrophy of the left ventricle.
Inferior leads (II, III, aVF) show horizontal ST segment depression.
After the above ECG, he underwent coronary angiography which showed 90% stenosis in his Circumflex (cx) coronary artery.

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ECGs 19a. Above is an ECG from a 33 years-old man with chest pain.
They were recorded in the ambulance.
Do you think they show typical ischemic changes?



ECG 19b. The ECG above also belongs to the same patient.
It was recorded 4 hours before the ECGs 19a, in the emergency room of a hospital.
After two days, this patient underwent coronary angiography which showed slow coronary flow.

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