An 18-year-old woman attends the ED with palpitations and dizziness. An ECG shows a broad complex tachycardia with an irregularly irregular rhythm and a ventricular rate of 160 bpm. Her BP is 88/60 mmHg but she has no chest pain or dyspnoea. She had been told several years earlier that she had a ‘Wolff–Parkinson–White ECG’ and offered ‘a procedure’ for this but declined. She has had no previous admissions to hospital and is on no regular medication. What is the best treatment?
This is likely to be pre-excited AF and is potentially life-threatening as AF conducted antegradely down an accessory pathway may degenerate into VF. The patient is haemodynamically compromised as she complains of dizziness and is hypotensive. She should undergo DC cardioversion as soon as possible. AV nodal blocking drugs, such as adenosine, digoxin, verapamil, and beta-blockers, should be avoided as they encourage conduction down the accessory pathway.
Which of the following antiarrhythmic medications would be the best choice for treatment of a patient with atrial fibrillation (AFib) and significant renal insufficiency?
Propafenone. Sotalol and dofetilide are primarily excreted by the renal route and should be used cautiously, if at all, in patients with significant renal insufficiency. Flecainide primarily undergoes hepatic elimination (approximately 70%) but has 25% renal elimination. The route of elimination for propafenone is 99% hepatic.
Which of the following antiarrhythmic medications has active metabolites?
Amiodarone. Sotalol, dofetilide, and flecainide do not have significant active metabolites. Amiodarone is metabolized to the active metabolite desethylamiodarone.
A patient arrives at the emergency department with symptomatic narrow complex tachycardia. The patient is hemodynamically stable. The decision is made to administer intravenous (IV) adenosine.
Under which of the following circumstances should the dosage of adenosine be reduced?
The patient is taking dipyridamole. Dipyridamole potentiates the effect of adenosine by interfering with metabolism; therefore, a reduced dose of adenosine is recommended. Although not a part of this question, it is important to remember that adenosine also needs to be used with extreme caution in heart transplant patients as a markedly exaggerated response to adenosine can be seen in the denervated heart. An increased dose of adenosine is recommended in the presence of methylxanthines such as theophylline, which antagonizes the effect of adenosine (blocks receptors), and other factors such as slow circulation time, valvular regurgitation, and left-to-right shunts that reduce the effectiveness of adenosine.
Which of the following medications is contraindicated for use with dofetilide?
Verapamil. Verapamil may increase serum levels of dofetilide because of interference with renal excretion and hepatic metabolism.
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