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Supernormal Conduction in the Anomalous Bundles of the Wolff-Parkinson-White Syndrome: An Overlooked Electrophysiologic Property With Potential Clinical Implications

Cátedra de Cardiología, Facultad de Medicina, Pontificia Universidad Católica Argentina, pablochiale{at}fibertel.com.ar, Centro de Arritmias Cardíacas de la Ciudad Autónoma de Buenos Aires, División Cardiología, Hospital J. M. Ramos Mejía, and Instituto Sacre Coeur Buenos Aires, Argentina

Ernesto Albino, MD

Centro de Arritmias Cardíacas de la Ciudad Autónoma de Buenos Aires, División Cardiología, Hospital J. M. Ramos Mejía

Hugo A. Garro, MD

Centro de Arritmias Cardíacas de la Ciudad Autónoma de Buenos Aires, División Cardiología, Hospital J. M. Ramos Mejía, and Instituto Sacre Coeur Buenos Aires, Argentina

Horacio Selva, MD

Centro de Arritmias Cardíacas de la Ciudad Autónoma de Buenos Aires, División Cardiología, Hospital J. M. Ramos Mejía

Raúl J. Levi, MD

Centro de Arritmias Cardíacas de la Ciudad Autónoma de Buenos Aires, División Cardiología, Hospital J. M. Ramos Mejía

Rubén A. Sánchez, MD

Centro de Arritmias Cardíacas de la Ciudad Autónoma de Buenos Aires, División Cardiología, Hospital J. M. Ramos Mejía, and Instituto Sacre Coeur Buenos Aires, Argentina

Marcelo V. Elizari, MD

Centro de Arritmias Cardíacas de la Ciudad Autónoma de Buenos Aires, División Cardiología, Hospital J. M. Ramos Mejía

Carlos B. Álvarez, MD

Cátedra de Cardiología, Facultad de Medicina, Pontificia Universidad Católica Argentina, and Instituto Sacre Coeur Buenos Aires, Argentina

The anterograde refractory period (RP) of the accessory pathway (AP) is the main determinant factor of ventricular rate during atrial fibrillation in the Wolff-Parkinson-White (WPW) syndrome. We describe 3 examples of anterograde supernormal conduction (SNC) and 1 of retrograde SNC in APs. The paradoxical early recovery of propagation due to SNC, well inside a prolonged anterograde RP in the AP, may play a relevant role to determine the rate of ventricular response during atrial fibrillation, eventually leading to extremely fast ventricular rates, syncope, and even ventricular fibrillation in patients with WPW syndrome supposed a priori to be exposed to a low risk of sudden cardiac death. This may require very precise conditions, including an enhanced adrenergic influence on the heart. Retrograde SNC in APs may also participate in the mechanism of paroxysmal supraventricular tachycardias that are not easily induced by programmed cardiac stimulation.

Key Words: anterograde supernormal conduction • AV accessory pathways • isoproterenol • refractory periods • retrograde supernormal conduction

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