25. Pollack GH: Cardiac pacemaking: an obligatory role of catecholamines? A possible mechanism underlying spontaneous pacemaking can be deduced from several recent clues. Science 196: 731, 1977 26. Reiffel JA, Bigger JT, Giardina EGV: "Paradoxical" prolongation of sinus node recovery time after atropine in the sick sinus syndrome. Am J Cardiol 36: 98, 1975 27. Strauss HC, Wallace AG: Direct and...

A 58-year-old man with hypertensive cardiovascular disease and atrial flutter underwent electrophysiologic studies, including multiple intra-atrial recordings and atrial stimulation. Although the surface ECG suggested the presence of atrial flutter, intra-atrial recordings demonstrated the presence of (1) sinus-like rhythm localized to an area of approximately 5 mm in and around the region of t...

To assess the role of autonomic regulatory mechanisms on sinoatrial conduction and automaticity in patients with clinical evidence of sick sinus syndrome, electrophysiologic studies were conducted in 12 male patients, mean age 64 4 7 years. Heart rate, sinus node recovery time (SNRT) and sinoatrial conduction time (SACT) were determined before and after autonomic blockade with atropine (0.04 mg...