A flat ST segment with no ST segment depression may be normal. It does not necessarily imply cardiac ischemia.

 
ST segment flattening with less than 1mm ST depresion must be treated in the same way.





ECG 1. The ECG above belongs to a 54 years-old hypertensive woman with Diabetes Mellitus.
Leads V2 to V6 show
ST segment flattening with 0.5 mm ST depression.
Her serum creatinine level was 1.2 mg/dL.
Her ECHOcardiogram is normal: no structural heart disease.
Her coronary angiography (performed 3 months ago) was also normal: normal coronary arteries.
Her treadmill exercise test, on the same day with the above ECG, is also normal: no recent-onset ischemia.
Flat ST segment with ST depression < 1mm does not necessarily imply the diagnosis of coronary artery disease.

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ECG 2. Above is an ECG from a 63 years-old woman with hypertension and coronary artery disease.
Her LAD coronary artery was stented 9 years ago.
Recently, coronary angiography showed extensive narrowing of the Diagonal branch (of LAD coronary artery).
A recent myocardial perfusion scintigraphy showed ischemia in the Diagonal artery territory.
Lead I and leads V4 to V6 show
> 1 mm horizontal ST segment depression.
This ECG finding strongly suggests myocardial ischemia.

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ECG 3. Above is an ECG from a 45 years-old woman with diabetes mellitus and normal coronary arteries.
Leads V3 to V6 show ST segment flattening with < 1mm ST depression.
Flat ST segment with ST depression < 1mm does not necessarily imply the diagnosis of coronary artery disease.

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ECG 4. Above is an ECG from an 82 years-old woman with extensive coronary artery disease.
Coronary artery bypass grafting surgery was recommended for her 3-vessel (extensive) coronary artery disease.
Many leads show
ST segment flattening without ST segment depression. However, this is not typical for cardiac ischemia.
Flattened ST segment does not necessarily imply the diagnosis of coronary artery disease.

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ECG 5. Above ECG is from a 27 years-old man with chronic renal failure and systemic hypertension.
He has no chest pain and no known coronary artery disease.
ECOcardiography showed concentric (diffuse) left ventricular hypertrophy: septum and posterior wall are 1.3 cm in thickness.
Tall QRS complexes in chest leads are compatible with voltage criteria for left ventricular hypertophy.
Leads V5 and V6 show flattened ST segment but
ST segment depression is NOT more than 1 mm.
This pattern is NOT typical for coronary artery disease or myocardial ischemia.

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