Unit 4: EKG and Cardiology Basics

• Topic 01

  Cardiac Anatomy — Chambers, Valves, and Conduction System

  45 questions
• Topic 02

  Electrical Conduction — SA Node, AV Node, Bundle of His, Purkinje Fibres

  48 questions
• Topic 03

  ECG Paper, Speed, and Standardisation

  79 questions
• Topic 04

  12-Lead Electrode Placement — Limb and Precordial Leads

  45 questions
• Topic 05

  Normal Sinus Rhythm — Rate, Regularity, and Waveform Components (P, QRS, T)

  45 questions
• Topic 06

  Sinus Arrhythmias — Tachycardia, Bradycardia, and Dysrhythmia

  45 questions
• Topic 07

  Common Arrhythmias — PAC, PVC, Atrial Fibrillation, Heart Blocks

  39 questions
• Topic 08

  Artefact Recognition and Troubleshooting

  42 questions
• Topic 09

  Holter Monitor and Event Monitor Setup

  45 questions

A few questions from this unit, with the answer and a full explanation. The complete bank is available when you start practising.

1. How can the medical assistant distinguish somatic tremor artifact from atrial fibrillation on an ECG strip?

   • A
     In somatic tremor, the R-R intervals remain regular despite the chaotic baseline; in atrial fibrillation, the R-R intervals are truly irregularly irregular with no consistent pattern
     Correct answer
   • B
     Atrial fibrillation and somatic tremor are indistinguishable on a standard ECG; clinical correlation is always required
   • C
     Somatic tremor artifact causes the QRS complexes to widen to more than 0.12 seconds; atrial fibrillation preserves normal QRS width
   • D
     Somatic tremor produces fine, uniform 60-Hz spikes; atrial fibrillation produces slow, wandering baseline drift
   Explanation

   The critical distinction is R-R interval regularity. Somatic tremor adds an irregular oscillating signal to the tracing, but the underlying heart rhythm continues normally with consistent R-R intervals visible on careful measurement. Atrial fibrillation produces true irregularly irregular ventricular responses — no two consecutive R-R intervals are the same. If the R-R intervals are regular despite the chaotic baseline, somatic tremor artifact is the most likely explanation. When uncertain, a repeat ECG with the patient better relaxed and warmed will typically resolve somatic tremor but not true AF.

2. In respiratory sinus arrhythmia, what happens to the heart rate during inspiration?

   • A
     Heart rate is unaffected by breathing — only expiration influences heart rate in sinus arrhythmia
   • B
     Heart rate increases (R-R interval shortens) because vagal tone decreases during inspiration
     Correct answer
   • C
     Heart rate does not change during inspiration; the change occurs only during the pause between breaths
   • D
     Heart rate decreases because sympathetic tone decreases during inspiration
   Explanation

   During inspiration, pulmonary stretch receptors signal the brainstem to transiently reduce parasympathetic (vagal) outflow to the SA node. With less vagal inhibition, the SA node fires more frequently — the R-R intervals shorten and the heart rate increases. This is the classic pattern of respiratory sinus arrhythmia: rate up on inspiration, rate down on expiration. The opposite — expiratory deceleration — completes the cycle.

3. An ECG shows a slow, rhythmic undulation of the baseline that appears synchronised with the patient's breathing rate. The waveforms are otherwise well-formed. Which of the following is the most appropriate sequence of corrective actions?

   • A
     Increase the paper speed to 50 mm/sec to compress the baseline oscillations and make them less visible
   • B
     Ask the patient to breathe normally and more shallowly; check and reapply any electrodes with poor adhesion; re-prep the skin if electrode contact is suspect; if artifact persists, repeat the ECG
     Correct answer
   • C
     Activate the AC interference filter to suppress the slow baseline oscillations
   • D
     Replace all electrodes with a fresh set, re-prep all sites, and repeat the ECG immediately regardless of current quality
   Explanation

   Wandering baseline linked to respiration is caused by the chest wall moving with each breath, physically tugging on electrodes or altering the skin-electrode contact. The correct approach is sequential: first instruct the patient to breathe normally and shallowly; then check electrode adhesion and re-prep the skin if needed. The AC filter is designed for 60-Hz electrical interference, not slow respiratory baseline drift. Asking the patient to hold their breath entirely is impractical for a full 10-second recording and may induce movement. Disconnecting the RL ground electrode would worsen artifact, not reduce it.