aka 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
Q1.1 What rhythm is shown?
This is a classic example of sick sinus with the “tachy-brady” syndrome
- 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.
Q 1.2 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
Q 2.1 What rhythm 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.
Q 2.2 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
Q 3.1 What rhythm is shown?
A narrow complex tachycardia is interrupted by a run of polymorphic VT, which rapidly deteriorates into ventricular fibrillation.
Q 3.2 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
Q 4.1 What rhythm 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
Q 4.2 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.
- Consider: Isoprenaline infusion.
Rhythm Strip 5
Q 5.1 What rhythm is shown?
This is a typical ECG recording of a patient receiving a bolus of adenosine for AVNRT.
- 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
Q 5.2 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.
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- Mattu A, Brady W. ECGs for the Emergency Physician 2
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