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Mid–Late QRS Changes Suggestive of Myocardial Necrosis

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Insights into Electrocardiograms with MCQs

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Abstract

Conventionally an abnormal Q wave is considered suggestive of myocardial necrosis. However, a large percentage of patients with acute myocardial infarction may not show abnormal Q waves. Electrocardiographic abnormalities may be confined to the upslope, the top, or the downslope of the R wave. Such changes may occur as isolated abnormality or may occur with abnormal Q wave. Various mid–late QRS changes suggestive of myocardial necrosis are discussed with the help of explanatory diagrams and representative electrocardiograms. Summary and MCQs at the end of the chapter help in quick revision and self-assessment.

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References

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Author information

Authors and Affiliations

  1. Ex Senior professor and head of the department of cardiology, Jawaharlal Nehru Medical College, Ajmer, India

    Sitaram Mittal

Authors
  1. Sitaram Mittal
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Appendices

Summary

  • Nontransmural myocardial necrosis may not produce a Q wave. QRS complex may show any of the following changes.

  • Significant loss of the R wave voltage in correctly placed leads. At times, there may be only partial loss of the R wave voltage, which may present as a notch on the top of the R wave or the top of the R wave may look like a spike.

  • Slow (poor) progression of the R wave in the precordial leads. Left ventricular hypertrophy, pulmonary thromboembolism, and emphysema can also produce this finding.

  • Nonprogression of the R wave in the precordial leads. Left bundle branch block, left ventricular hypertrophy, emphysema, left pneumothorax with mediastinal shift, uncomplicated dextrocardia, pectus excavatum, and congenital absence of the pericardium can also produce this finding.

  • Reverse progression of the R wave (sudden reduction of R wave amplitude) in a precordial lead. This finding is specific of myocardial necrosis.

  • Slurring of the ascending limb, top, or the descending limb of the R wave in absence of any QRS widening suggestive of bundle branch block.

  • Fragmentation of the QRS complex in at least two contiguous leads.

  • Localized widening of QRS, which is not typical of any bundle branch block (peri-infarction block).

  • Above findings are nonspecific. They are important only when there is a new appearance in the classical clinical setting of acute coronary syndrome.

MCQs

Q1. Which part of the ventricles is depolarized last?

  1. (a)

    Base of the right ventricle

  2. (b)

    Base of the left ventricle

  3. (c)

    Base of the interventricular septum

  4. (d)

    Apex of the heart

Q2. Loss of R wave voltage is not caused by

  1. (a)

    Multiple infarcts

  2. (b)

    Technical error

  3. (c)

    Obesity

  4. (d)

    Last trimester of pregnancy

Q3. Slow progression of the R wave is not seen in

  1. (a)

    Subendocardial infarction

  2. (b)

    Pulmonary embolism

  3. (c)

    Emphysema

  4. (d)

    Dextroversion

Q4. Nonprogression of the R wave is not seen in

  1. (a)

    Left bundle branch block

  2. (b)

    Nontransmural myocardial infarction

  3. (c)

    Pectus excavatum

  4. (d)

    Technical dextrocardia

Q5. Reverse progression of the R wave is seen in

  1. (a)

    Nontransmural myocardial infarction

  2. (b)

    Emphysema

  3. (c)

    Dextrocardia

  4. (d)

    Left pneumothorax

Q6. Isolated slurring of a narrow QRS is seen in

  1. (a)

    Nontransmural infarction

  2. (b)

    Bundle branch block

  3. (c)

    Peri-infarction block

  4. (d)

    Transmural myocardial infarction

Q7. What is not correct for fragmented QRS?

  1. (a)

    It suggests inhomogeneous depolarization

  2. (b)

    QRS is narrow

  3. (c)

    It is associated with recurrent cardiac events

  4. (d)

    It is specific of myocardial infarction

Q8. Fractioned QRS is not seen in

  1. (a)

    Systemic hypertension

  2. (b)

    Hypertrophic cardiomyopathy

  3. (c)

    Aortic stenosis

  4. (d)

    None

Q9. Fractioned QRS is not seen in

  1. (a)

    Sarcoidosis

  2. (b)

    Brugada syndrome

  3. (c)

    Arrhythmogenic right ventricular dysplasia

  4. (d)

    Large VSD

Q10. Fractioned QRS is not seen in

  1. (a)

    Repaired TOF

  2. (b)

    Large primum ASD

  3. (c)

    Ebstein anomaly

  4. (d)

    Corrected transposition

Answers

(1) c, (2) d, (3) d, (4) d, (5) a, (6) a, (7) d, (8) d, (9) d, (10) b, d.

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© 2023 The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.

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Cite this chapter

Mittal, S. (2023). Mid–Late QRS Changes Suggestive of Myocardial Necrosis. In: Insights into Electrocardiograms with MCQs. Springer, Singapore. https://doi.org/10.1007/978-981-99-0127-2_22

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  • DOI: https://doi.org/10.1007/978-981-99-0127-2_22

  • Published:

  • Publisher Name: Springer, Singapore

  • Print ISBN: 978-981-99-0126-5

  • Online ISBN: 978-981-99-0127-2

  • eBook Packages: MedicineMedicine (R0)

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