Palpitations in a young man: broad-complex irregular tachycardia
A 26-year-old man attends with sudden-onset palpitations and light-headedness that began 90 minutes ago while watching television. He has had three shorter episodes in the past year, each lasting 10 to 20 minutes, and was told previously that he had panic attacks. He takes no regular medication and has no other medical history. On examination he is anxious but fully alert. Blood pressure 108/70 mmHg, pulse 220 beats/min and irregular, respiratory rate 20, oxygen saturation 98% on air, temperature 36.6 °C. The heart sounds are variable in intensity and there is no murmur. The ECG shows a broad-complex, irregularly irregular tachycardia with varying QRS morphology and no discernible P waves. Chest radiograph is normal; potassium 4.0 mmol/L, magnesium 0.85 mmol/L, troponin normal. He remains haemodynamically stable during the first 30 minutes of assessment.
1. What is the rhythm, what is the mechanism, and which drugs must be avoided?
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Rhythm
This is a broad-complex, irregularly irregular tachycardia with varying QRS width and no visible P waves at rates up to 220–280 beats/min. That is pre-excited atrial fibrillation - atrial fibrillation conducting antegradely down an accessory pathway, with fusion beats producing different QRS morphologies.
Mechanism
The accessory pathway bypasses the AV node and can conduct very rapidly, so the ventricular rate is not limited by AV nodal refractoriness. This is why rates can reach 300 beats/min and why degeneration to ventricular fibrillation is the feared complication.
Drugs to avoid
- Adenosine - may transiently block the AV node and increase accessory pathway conduction.
- Verapamil and diltiazem - can precipitate hypotension, accelerate conduction and cause ventricular fibrillation.
- Digoxin - similarly shortens accessory pathway refractoriness.
- Beta-blockers are also best avoided in the acute pre-excited setting for the same reason.
- Amiodarone is not a first-line agent here and is best avoided unless under electrophysiology guidance.
The previous label of “panic attacks” fits recurrent paroxysmal tachycardias and should be revisited once he is stable.
2. How would you manage him acutely while he remains stable, and what would you do if he deteriorated?
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If stable
- Continuous cardiac monitoring, defibrillator immediately available, IV access, oxygen only if hypoxic.
- Correct potassium and magnesium to high-normal values.
- Procainamide 10–15 mg/kg intravenously over about 20 minutes (maximum 1 g) is a reasonable first-line agent; it slows accessory pathway conduction. Ibutilide is an alternative in some centres.
- A fluid bolus may help if he becomes vasovagal.
- Escalate early to cardiology/electrophysiology and involve the anaesthetist if there is any sign of instability.
If he deteriorates
Evidence of hypotension, ischaemic chest pain, acute heart failure or reduced consciousness mandates synchronised direct-current cardioversion - for example 120–200 J biphasic - with sedation or anaesthesia, and immediate advanced life support backup. Do not attempt chemical conversion with an AV nodal blocker while unstable.
After conversion
Observe on a monitored bed, obtain a 12-lead ECG in sinus rhythm to look for delta waves, and arrange an echocardiogram. Warn him that the arrhythmia can recur before definitive treatment.
3. What is the definitive long-term management, and what advice would you give him before discharge?
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Definitive management
Refer to electrophysiology for risk assessment and catheter ablation of the accessory pathway, which is curative in the great majority and is the treatment of choice in a young symptomatic patient with pre-excitation. Electrophysiology study defines pathway location and refractoriness; asymptomatic pre-excitation is managed differently from symptomatic WPW.
Medication
If ablation is delayed, avoid AV nodal blocking drugs as monotherapy. A beta-blocker may be used in some pathways only after electrophysiology advice; flecainide or propafenone are alternatives in selected patients without structural heart disease.
Advice before discharge
- Explain the diagnosis and correct the previous “panic attack” label.
- Give written advice: if palpitations are associated with blackout, chest pain, breathlessness or near-collapse, call emergency services rather than waiting.
- Advise against strenuous competitive sport and high-risk activities until electrophysiology review, in line with local guidance.
- Discuss driving restrictions according to local licensing rules for arrhythmia with syncope (he has not syncopised here, so restrictions are less likely, but this must be checked).
- Arrange follow-up with the arrhythmia clinic and give a copy of the ECG to the patient.