1. Reentrant SVT (OAVRT, narrow QRS complex) in the WPW syndrome can be treated like other cases of reentrant SVT. Since the AV node is involved in the reentry circuit, any maneuver or drug that slows conduction through the AV node is usually effective. Verapamil in the patient who is not hypotensive or in CHF is by some accounts the optimal drug. Adenosine is very successful at terminating this dysrhythmia in patients with WPW; however, there is some proclivity to increase atrial vulnerability to AF and to ectopic atrial activity, which may reinitiate the dysrhythmia.
2. Antidromic tachycardia (AAVRT, wide QRS complex) is usually associated with a short refractory period in the bypass tract, and such patients are at risk for rapid ventricular rates and degeneration into ventricular fibrillation. Stable patients should be treated with intravenous procainamide and unstable patients should be cardioverted. b-adrenergic agents, adenosine, and calcium channel blockers should be avoided.
3. Atrial flutter or fibrillation with a rapid ventricular response is best treated with cardioversion. As an alternative, agents that prolong the refractory period of the accessory tract—such as intravenous procainamide—can be used. Lidocaine may have some utility, and experimental studies with intravenous flecainide have shown promise. In general, phenytoin, esmolol, propranolol, or verapamil should not be used because of their variable effect on accessory conduction. Digoxin is contraindicated, as it may shorten the refractory period and enhance conduction over the bypass tract.
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