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Cardiac Pacing Systems and Their Normal Functioning

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Insights into Electrocardiograms with MCQs

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Abstract

Surface electrocardiogram is the first investigation in the evaluation of a case with permanent pacemaker implantation. Analysis of the pacing spike and its relation with the paced QRS and configuration of the paced QRS gives adequate information about the type of pacemaker implanted. Electrocardiogram also gives important information about functioning of the pacemaker. All these issues are discussed in detail with representative electrocardiograms. Normal variations produced by the pacemaker in the surface electrocardiogram are also discussed with representative electrocardiograms. Knowledge of these variations is necessary to prevent wrong conclusion of pacemaker malfunction. Summary and MCQs at the end of the chapter help in quick revision and self-assessment.

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References

  1. Olshansky B, Chang MK, Pogowizd SM, Goldschlager N. Cardiac pacing and pacemaker rhythms. In: Olshansky B, Chung MK, Pogowizd SM, Goldschlager N, editors. Arrhythmia Essentials. Burlington: Jones Bartlett Learning; 2012. p. 240–60.

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  2. Vijayraman P, Ellenbogen KA. Bradyarrhythmias and pacemakers. In: Fuster V, Walsh RA, Harrington RA, editors. Hurst’s the heart. New York: Mc Graw Hill; 2011. p. 1025–57.

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  3. Haisty WK, Lim TH, Wagner GS. Artificial cardiac pacemakers. In: Wagner GS, editor. Marriot’s practical electrocardiography. Philadelphia: Wolters Kluwer; 2001. p. 423–44.

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  4. Swerdlow CD, Wang PJ, Zipes DP. Pacemakers and implantable cardioverter-defibrillators. In: Mann DP, Zipes DP, Libby P, Bonow RO, editors. Braunwald’s heart disease. Philadelphia: Elsevier; 2015. p. 721–42.

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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

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  1. Sitaram Mittal
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Appendices

Summary

  • Nomenclature of permanent pacemakers has four letters. The first letter indicates the paced chamber (A, atrium; V, ventricle; D, dual). The second letter indicates the sensed chamber. The third letter indicates response to sensing (I, inhibited; T, triggered). The fourth letter indicates the presence or absence of rate adaptive pacing (0, none, R, rate modulation). Modes commonly used are VVI or DDD.

  • In a VVI pacemaker, there is a single lead positioned in the right ventricle. It senses spontaneous ventricular depolarization and gives an impulse if there is no spontaneous ventricular depolarization for the preset interval. Atria and ventricle contract independently. There is no atrioventricular synchronization. On electrocardiogram each pacing spike is followed by a paced QRS. There is no relation between the P waves and the QRS complexes. However, paced QRS complexes may be followed by a retrogradely conducted P wave falling on the ST segment or on the T wave following the paced QRS. If there is a spontaneous QRS, it is sensed by the pacemaker, and the subsequent paced beat is postponed for the preset minimum pacing RR interval.

  • In DDD → (dual chamber) pacing, there are two leads. One is in the right atrium and the other is in the right ventricle. Normally, the right atrial P wave is sensed. It is followed by a prefixed atrioventricular delay, a ventricular pacing spike, and a paced QRS. In case of sinus bradycardia, the sequence of events on the surface ECG is atrial pacing spike →, paced P wave → preset, atrioventricular delay →, ventricular pacing spike →, and paced QRS. Atrioventricular synchrony is maintained. There is also an upper limit for atrial sensing to avoid fast ventricular rate during atrial fibrillation. DDD pacing is preferred in most circumstances as it maintains atrioventricular synchrony. VVI pacing can be useful in the presence of atrial fibrillation to avoid fast ventricular rate.

  • In biventricular pacing one lead is positioned in the right ventricle, and the other is positioned in a tributary of the coronary sinus overlying the left ventricle. This is performed in cases of left bundle branch block with a wide QRS. The aim is to synchronize the contractions of the two ventricles.

  • In unipolar pacing systems, pacing spikes are large. In bipolar pacing systems, pacing spikes are very small and may not be visible in some leads.

  • In a case of pacing from right ventricular apex, QRS shows left bundle branch block configuration with left axis deviation. In a case of pacing from right ventricular outflow tract, QRS shows left bundle branch block configuration with inferior axis.

  • Biventricular pacing in a case of left bundle branch block produces a QRS which is narrower than that before pacing.

MCQs

Q1. Which of the following is correct for the VOO mode of pacing?

  1. (a)

    Ventricular pacing

  2. (b)

    Ventricular sensing

  3. (c)

    Inhibition from ventricular sensing

  4. (d)

    All

Q2. Applying magnet over the pulse generator of a VVI pacemaker changes it to:

  1. (a)

    VOO mode

  2. (b)

    VVO mode

  3. (c)

    VOI mode

  4. (d)

    None

Q3. In VVI pacemaker, which parameter is not programmable?

  1. (a)

    Atrioventricular delay

  2. (b)

    Sensing threshold

  3. (c)

    Pulse width

  4. (d)

    Pacing current

Q4. Large pacing spike suggests:

  1. (a)

    Unipolar pacing

  2. (b)

    Bipolar pacing

  3. (c)

    DDD pacing

  4. (d)

    Biventricular pacing

Q5. Normal QRS in a patient with pacemaker suggests:

  1. (a)

    AAI pacing

  2. (b)

    DDD pacing

  3. (c)

    Biventricular pacing

  4. (d)

    VVI pacing

Q6. Right bundle branch block pattern in a patient with pacemaker suggests:

  1. (a)

    Biventricular pacing

  2. (b)

    Pacing from the RVOT

  3. (c)

    Left ventricular epicardial pacing

  4. (d)

    DDD pacing

Q7. AAI pacemaker is useful in:

  1. (a)

    Sinus pause

  2. (b)

    Sick sinus syndrome with complete atrioventricular block

  3. (c)

    Atrial flutter with complete Atrioventricular block

  4. (d)

    Atrial fibrillation

Q8. Pacemaker of choice for a patient of complete atrioventricular block with left ventricular diastolic dysfunction is:

  1. (a)

    AAI

  2. (b)

    VVI

  3. (c)

    DDD

  4. (d)

    Biventricular

Q9. Pacemaker of choice in chronic atrial fibrillation with complete atrioventricular block in:

  1. (a)

    AAI

  2. (b)

    AAI(R)

  3. (c)

    VVI

  4. (d)

    DDD

Q10. Double pacing spikes suggest:

  1. (a)

    Unipolar pacing

  2. (b)

    Bipolar pacing

  3. (c)

    DDD pacing

  4. (d)

    Biventricular pacing

Q11. Left bundle branch block configuration with inferior axis suggests:

  1. (a)

    Pacing from the right ventricular apex

  2. (b)

    Pacing from the right ventricular outflow tract

  3. (c)

    Left ventricular epicardial pacing

  4. (d)

    Biventricular pacing

Q12. Time taken for the normal activation of the heart to reach the right ventricular apex is:

  1. (a)

    0.01 second

  2. (b)

    0.02 second

  3. (c)

    0.03 second

  4. (d)

    0.04 second

Q13. Slightly longer interval after a sensed beat suggests:

  1. (a)

    Sensing failure

  2. (b)

    Pacing failure

  3. (c)

    Hysteresis

  4. (d)

    None

Q14. Fusion beat suggests:

  1. (a)

    Sensing failure

  2. (b)

    Pacing failure

  3. (c)

    Battery depletion

  4. (d)

    Normal function

Q15. In VVI pacing, retrograde activation of the atria can produce:

  1. (a)

    Atrial fibrillation

  2. (b)

    Atrial tachycardia

  3. (c)

    Atrial flutter

  4. (d)

    Echo beat

Q16. Pacing spike is small in:

  1. (a)

    Unipolar pacing

  2. (b)

    Bipolar pacing

  3. (c)

    Dual chamber pacing

  4. (d)

    Biventricular pacing

Q17. DDD pacing means:

  1. (a)

    Atrial as well as ventricular sensing and pacing

  2. (b)

    Ventricular sensing and pacing

  3. (c)

    Atrial sensing and ventricular pacing

  4. (d)

    Ventricular sensing and atrial pacing

Q18. VVI pacing means:

  1. (a)

    Ventricular pacing

  2. (b)

    Ventricular sensing

  3. (c)

    Inhibition by ventricular sensing

  4. (d)

    All

Q19. DDD pacing:

  1. (a)

    Preserves atrioventricular synchrony

  2. (b)

    Causes atrioventricular dissociation

  3. (c)

    Can cause 1:1 ventriculoatrial association

  4. (d)

    All

Q20. In biventricular pacing, one lead is placed in the right ventricular apex and the; the other lead is placed:

  1. (a)

    In the left ventricular apex

  2. (b)

    On the left ventricular epicardium

  3. (c)

    In tributary of the coronary sinus

  4. (d)

    In the right atrium

Q21. Pacing from the right ventricular apex produces:

  1. (a)

    Left bundle branch block configuration of QRS with left axis

  2. (b)

    Left bundle branch block configuration of QRS with inferior axis

  3. (c)

    Left bundle branch block configuration of QRS with right axis

  4. (d)

    Right bundle branch block configuration of QRS with left axis

Q22. Biventricular pacing in a case of left bundle branch block can produce:

  1. (a)

    Widening of QRS

  2. (b)

    Narrowing of QRS

  3. (c)

    Right bundle branch block

  4. (d)

    None

Answers

(1) A, (2) A, (3) A, (4) A, (5) A, (6) C, (7) A, (8) C, (9) C, (10) C, (11) B, (12) D, (13) C, (14) D, (15) D, (16) B, (17) A, (18) D, (19) A, (20) C, (21) A, (22) B

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

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Mittal, S. (2023). Cardiac Pacing Systems and Their Normal Functioning. In: Insights into Electrocardiograms with MCQs. Springer, Singapore. https://doi.org/10.1007/978-981-99-0127-2_14

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  • DOI: https://doi.org/10.1007/978-981-99-0127-2_14

  • 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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