ST-Segment Depression

Abstract

Usually depression of the ST-segment is considered as a marker of myocardial ischemia. However, there are several non-ischemic conditions that can produce depression of the ST-segment. Differentiating electrocardiographic features are discussed with representative electrocardiograms. The significance of the shape of the ST-segment depression and leads showing this change is discussed in the context of coronary artery disease with the help diagrams and representative electrocardiograms. The importance of reciprocal ST-segment depressions is explained with representative electrocardiograms. Summary and MCQs at the end of the chapter help in quick revision and self-assessment.

Appendices

Summary

ST-segment depression is frequently seen in the following situations:

• Normal variations

Sympathetic overdrive, neurocirculatory asthenia, hyperventilation, ortho static, post meals.

• Subendocardial ischemia

ST-segment depression of >1 mm at the J point is considered significant. It may be horizontal with sharp angle between the ST-segment and the T wave. It is considered the earliest sign of coronary insufficiency.

• Upsloping ST-segment can be seen in the absence of ischemia due to depressing effect of the Ta wave (atrial repolarization). In this situation, the P wave, PR segment, the J point, the ST-segment, and upstroke of the T wave from a smooth unbroken parabola. If parabola is broken and step like, it is considered suggestive of ischemia.

• Down sloping ST-segment suggests severe ischemia.

• Digitalis overdose produces down sloping (inverted correction mark) ST-segment depression with short QT interval.

• Hypokalemia produces ST-segment depression, flattening of the T wave, increased prominence of the U wave with long QT (U) interval.

• Some patients of mitral valve prolapse can have ST-segment depression in inferior and/or lateral chest leads.

• ST-segment depression may persist for hours to days following termination of any tachyarrhythmia.

• ST-segment depression can be secondary to changes in depolarization, for example, right ventricular hypertrophy, left ventricular hypertrophy, right bundle branch block, left bundle branch block, preexcitation, and aberrant intraventricular conduction. ST-segment depression of more than 1 mm in two or more of leads V₁ to V₃ in the presence of LBBB or LVH is considered suggestive of ischemia.

• Hypothyroidism usually does not produce ST-segment deviation.

MCQs

Q1. During angina, ST-segment depression is considered significant if it is:

• (a) ≥0.5 mm

• (b) ≥1.0 mm

• (c) ≥2.0 mm

• (d) ≥2.5 mm

Q2. Subendocardial injury mostly produces ST-segment depression in leads:

• (a) V₁ to V₃

• (b) V₅ and V₆

• (c) V₇ to V₉

• (d) V₃R to V₆R

Q3. Severity of impairment of coronary flow is maximum when ST-segment depression is:

• (a) Horizontal

• (b) Rapid upsloping

• (c) Slow upsloping

• (d) Down sloping

Q4. In normal persons, upsloping ST-segment depression touches the baseline in:

• (a) 0.08 s

• (b) 0.10 s

• (c) 0.14 s

• (d) 0.16 s

Q5. Normally Ta wave falls in:

• (a) The P wave

• (b) The QRS complex

• (c) The ST-segment

• (d) The T wave

Q6. ST-segment depression in leads V₁ to V₄ can be seen in:

• (a) Anteroseptal subendocardial infarction

• (b) Posterior infarction

• (c) Right ventricular subendocardial ischemia

• (d) All

Q7. ST-segment depression in leads V₄ to V₆ is seen in:

• (a) Subendocardial ischemia

• (b) Left ventricular hypertrophy

• (c) Left bundle branch block

• (d) All

Q8. ST-segment depression in leads V₄ to V₆ is seen in:

• (a) Cardiomyopathy

• (b) Myocarditis

• (c) Inferior infarction

• (d) All

Q9. ST-segment depression in seven or more leads with ST-segment elevation in lead aVR more than that in lead V₁ suggests:

• (a) Left main stem disease

• (b) Proximal LCX occlusion

• (c) Proximal RCA occlusion

• (d) All

Q10. Upsloping ST-segment depression with tall positive T waves in anterolateral leads can occur in:

• (a) Subtotal occlusion of LAD

• (b) Subtotal occlusion of LCX

• (c) Occlusion of mid RCA

• (d) All

Q11. ST-segment depression in leads I and aVL can occur in:

• (a) High lateral transmural myocardial infarction

• (b) Inferior infarction

• (c) Posterior infarction

• (d) None

Q12. ST-segment depression in leads III and aVF can occur in:

• (a) Inferior subendocardial infarction

• (b) High lateral transmural myocardial infarction

• (c) Right ventricular infarction

• (d) All

Q13. Upsloping ST-segment depression can be seen in:

• (a) Sympathetic overdrive

• (b) Neurocirculatory asthenia

• (c) Hyperventilation

• (d) All

Q14. ST-segment depression alone in a patient receiving digitalis suggests:

• (a) Inadequate dose of digitalis

• (b) Digitalis effect

• (c) Digitalis toxicity

• (d) Hyperkalemia

Q15. Which of the following should suggest digitalis overdose?

• (a) New onset of otherwise unexplained ventricular ectopics

• (b) Atrial fibrillation with otherwise unexplained slow ventricular rate

• (c) Bidirectional ventricular tachycardia

• (d) None

Q16. Which of the following does not cause ST-segment depression?

• (a) Hyperkalemia

• (b) Viral myocarditis

• (c) Atrioventricular nodal reentrant tachycardia

• (d) Hyperventilation

Q17. ST-segment depression can be seen in:

• (a) Sympathetic overdrive

• (b) Vagal overtone

• (c) Neurocirculatory asthenia

• (d) All

Q18. ST-segment can depress:

• (a) During hyperventilation

• (b) Following a meal

• (c) On standing from supine position

• (d) None

Q19. ST-segment depression suggests:

• (a) Subendocardial ischemia

• (b) Subepicardial ischemia

• (c) Transmural infarction

• (d) Transmural ischemia

Q20. Which is the earliest ST-segment change suggestive of myocardial ischemia?

• (a) Horizontality

• (b) Rapid upsloping ST-segment depression

• (c) Horizontal ST-segment depression

• (d) Down sloping ST-segment depression

Q21. Down sloping ST-segment depression with short QT interval suggests:

• (a) Digitalis effect

• (b) Hypercalcemia

• (c) Digitalis toxicity

• (d) Hypokalemia

Q22. ST-segment depression with flattening of the T wave, prominent U wave, and prolonged QT (U) interval suggests:

• (a) Hypokalemia

• (b) Hypomagnesemia

• (c) Hypocalcemia

• (d) Hyponatremia

Q23. Mitral valve prolapse can produce ST-segment depression in leads:

• (a) II, III, aVF

• (b) I, aVL

• (c) V₁, V₂

• (d) V₃, V₄

Q24. How long can post tachycardia ST-segment depression persist?

• (a) Seconds

• (b) Minutes

• (c) Hours

• (d) Days

Q25. Post tachycardia ST-segment depression suggests:

• (a) Mild ischemia

• (b) Severe ischemia

• (c) Left ventricular dysfunction

• (d) None

Q26. ST-segment depression in leads V₁ to V₆ can occur in:

• (a) Right ventricular hypertrophy

• (b) Left ventricular hypertrophy

• (c) Left lateral accessory pathway

• (d) Biventricular hypertrophy

Q27. ST-segment depression in leads I, aVL, V₅, V₆ suggests:

• (a) Left ventricular pressure overload

• (b) Left bundle branch block

• (c) Preexcitation

• (d) All

Q28. What is not seen in uncomplicated left bundle branch block?

• (a) Down sloping ST-segment depression in leads I and aVL

• (b) ST-segment elevation in leads V₅, V₆

• (c) ST-segment depression more than 1 mm in leads V₁, V₂

• (d) ST-segment elevation in leads V₁, V₂

Q29. What is not seen in uncomplicated RBBB?

• (a) Down sloping ST-segment depression in leads V₁, V₂

• (b) Down sloping ST-segment depression in leads V₅, V₆

• (c) Horizontal ST-segment in leads V₅, V₆

• (d) ST-segment depression in leads I and aVL

Q30. In aberrant ventricular conduction ST-segment is:

• (a) Isoelectric

• (b) Concordant to terminal QRS

• (c) Discordant to terminal QRS

• (d) Any of the above

1.1 Answers

(1) a (2) b (3) d (4) a (5) b (6) d (7) d (8) d (9) a (10) a (11) b (12) a, b (13) d (14) b (15) a, b, c (16) a (17) a, c (18) a, b, c (19) a (20) a (21) a (22) a (23) a (24) d (25) d (26) c (27) a, b (28) b, c (29) b, d (30) c