Procainamide infusion test: Inability to identify patients with Wolff-Parkinson-White syndrome who are potentially at risk of sudden death

Persistence of preexcitation in sinus rhythm with procainamide infusion has been reported to occur in patients with a short anterograde accessory pathway effective refractory period (AERPAP) and this test has been proposed as a reliable noninvasive method to identify patients with the Wolff-Parkinson-White syndrome who are at risk of sudden death. However, sudden death correlates best with a shortest preexcited RR interval during atrial fibrillation (SRRPE) of 260 msec or less. We infused 10 to 12 mg/kg procainamide to 56 patients to determine whether persistence or loss of preexcitation in sinus rhythm identified patients with SRRPEs of 260 or less or greater than 260 msec, respectively. Atrial fibrillation was induced in 53 patients. Of these, 32 patients had persistence of preexcitation with procainamide infusion and SSRPE in this group of patients was shorter than that in patients in whom preexcitation was lost (194 ± 44 vs 235 ± 55 msec, p < .05). However, preexcitation persisted after procainamide infusion in only 31 of 46 (67%) patients with SRRPEs of 260 msec or less. Furthermore, 15 of 21 patients who lost preexcitation had SRRPEs of 260 msec or less and two of these patients had a history of ventricular fibrillation. The correlation between AERPAP and SRRPE was studied in a separate group of 79 patients with single accessory pathways. There was a significant (p < .001) but poor (r = .58) correlation between these two variables. Thus, the procainamide test regarding accessory pathway refractoriness often cannot be extrapolated to SRRPE. We conclude that the procainamide infusion test does not reliably predict SRRPE and is therefore of limited value as a noninvasive method to identify patients with Wolff-Parkinson-White syndrome who are at potential risk of sudden death.