AAIR Versus DDDR Pacing in Patients with Impaired Sinus Node Chronotropy: An Echocardiographic and Cardiopulmonary Study. - Vardas, P.E.; Simantirakis, E. N.; Parthenakis, F. I.; Chrysostomakis, S. I.; Skalidis, E.I.; Zuridakis, E.G. (Pacing & Clinical Electrophysiology, 1997)