Risky Rhythyms

ECG Exigency 003

5 risky rhythms. Each tells a story.
Can you work out what is happening before its too late? What can you do to save the day?

Rhythm strip 1

tachy brady syndrome

Q1. What is shown?

  • Runs of tachycardia interspersed with long sinus pauses (up to 6 seconds).
  • The sinus rate is extremely slow, varying from 40 bpm down to around 10 bpm in places.
  • Sinus beats are followed by paroxysms of junctional tachycardia at around 140 bpm.

This is a classic example of sick sinus with the “tachy-brady” syndrome

Q2. What will you do next?

  • This patient needs a pacemaker, stat!
  • Admit to a monitored bed on a coronary care unit.
  • Commence temporary pacing via external pads or pacing wire until a permanent pacemaker can be arranged.

Rhythm strip 2


Q1. What is shown?

  • Six beats of sinus rhythm at 90 bpm.
  • The 7th beat is a premature atrial complex (PAC) with different morphology P, QRS and T waves, which initiates a run of a supraventricular tachycardia at 150bpm.
  • The onset of the SVT is typical of an AV-nodal re-entry tachycardia (AVNRT), although with the rate of 150bpm, atrial flutter with a 2:1 block is also a possibility.

Q2. What will you do next?

  • Scrutinise the 12-lead ECG for flutter waves.
  • Try some adenosine (or vagal stimuli such as a Valsalva manoeuvre or carotid massage); this should unmask any flutter waves and may convert AVNRT to sinus rhythm.
  • Flutter may require DC cardioversion or treatment with anti-arrhythmics (e.g. amiodarone).

Rhythm Strip 3

narrow complex, polymorphic VT, VF

Q1. What is shown?

  • A narrow complex tachycardia is interrupted by a run of polymorphic VT, which rapidly deteriorates into ventricular fibrillation.

Q2. What will you do next?

  • Precordial thump!
  • Start charging the defibrillator!
  • Shock at 200 J (biphasic) or 360 J (monophasic). Three stacked shocks if the arrest is witnessed and monitored.
  • Start CPR!

Rhythm Strip 4

R on T, torsades

Q1. What is shown?

  • Sinus rhythm, or possibly ectopic atrial rhythm (biphasic / inverted P waves in lead II)
  • Rate of 90 bpm
  • Prolonged QTc interval of 540 ms (greater than half the R-R interval)
  • Ventricular ectopics with ‘R-on-T’ phenomenon
  • The second ventricular ectopic initiates a run of torsades de pointes

Q2. What will you do next?

  • DC cardioversion if unstable.
  • Load with magnesium (e.g. 2 g over 1-2 minutes) and start a magnesium infusion.
  • Correct hypokalemia.
  • Consider:
    • Overdrive pacing to achieve a ventricular rate of 90-120 bpm.
    • Isoprenaline infusion.

Rhythm Strip 5

AVNRT and adenosine bolus

Q1. What is shown?

  • AV-nodal re-entry tachycardia (AVNRT) at 140 bpm
  • A pause in the middle of the strip with several ventricular escape complexes
  • Cardioversion to sinus rhythm at 90 bpm at the end of the strip

This is a typical ECG recording of a patient receiving a bolus of adenosine for AVNRT.

Q2. What will you do next?

  • Get a 12-lead ECG to confirm return to sinus rhythm.
  • If the patient is well and remains in sinus rhythm they can be discharged.
  • Consider electrophysiology follow up for recurrent AVNRT.

For more great ECG cases see the ECG library or ECG clinical case library


  • Cameron P, Jelinek G, Kelly AM, Murray L, Brown AFT. Textbook of Adult Emergency Medicine (3rd edition), Churchill Livingstone Elsevier 2009.
  • Mattu A, Brady W. ECGs for the Emergency Physician 1, BMJ Books 2003.
  • Mattu A, Brady W. ECGs for the Emergency Physician 2, BMJ Books 2008.
  • Phibbs, BP. Advanced ECG: Boards and Beyond (2nd edition), Saunders Elsevier 2006.
  • Wagner, GS. Marriott’s Practical Electrocardiography (11th edition), Lippincott Williams & Wilkins 2007.
Print Friendly


  1. David Lindfield says

    Thank you for this. So many cases recently on the web involve the most extreme,advance and complicated ECGs. I feel that I can follow these with 100 percent accuracy.