Despite the recent advent of and the successful results from
catheter ablation, pharmacological
therapy is still used by most clinicians as the first line
therapy in patients with regular
supraventricular tachycardias. Before prescribing an antiarrhythmic agent, documentation of the
arrhythmia using a 12-lead electrocardiogram (ECG) is necessary to identify the type of
tachycardia. The ECG diagnosis is based on the presence and polarity of the P wave, the P to QRS relationship, the presence of QRS alternation and the effect of
bundle branch block on
tachycardia rate. Most regular
supraventricular tachycardias use the atrioventricular node either passively, as in atrial
tachycardias or flutter, or actively, as paroxysmal junctional
tachycardias. The Sicilian Gambit approach attempted to introduce some rationale in the choice of an antiarrhythmic agent, taking into account
tachycardia mechanism, by defining the critical components of the
tachycardia and the vulnerable parameter, i.e. the component that may readily be affected by an appropriate antiarrhythmic agent. For this approach, an electrophysiological study is particularly useful. The most common regular
paroxysmal supraventricular tachycardias include atrioventricular nodal re-entrant
tachycardias and atrioventricular re-entrant
tachycardias which use an overt or concealed accessory atrioventricular connection (
Kent bundle) or atriofascicular connection (Mahaim). For acute termination of paroxysmal junctional
tachycardia, intravenous
adenosine is the
drug of choice. For the prevention of the
tachycardia attacks in
atrioventricular nodal re-entrant tachycardia, the agents with a depressive effect on the antegrade slow pathway, such as
calcium channel blockers or beta-blockers, are likely to be effective. If they fail,
sodium channel blockers (
propafenone or
flecainide) may be indicated. In
tachycardias involving accessory connections, agents that affect fast channel dependent tissue (
propafenone,
flecainide,
cibenzoline,
disopyramide or
hydroquinidine) are effective.
Potassium current blockers, such as
sotalol or
amiodarone, represent an alternative
therapy. In atrial
tachycardias, the use of
propafenone,
flecainide or
sotalol constitute a logical choice. In
drug-resistant cases,
amiodarone is the most potent agent.
Radiofrequency ablation of the slow atrioventricular nodal pathway, of an accessory connection or of an atrial focus, is indicated in
drug-resistant or
drug-intolerant patients and is increasingly offered as an alternative
therapy.