Sinus slowing caused by adenosine-5'-triphosphate in patients with and without sick sinus syndrome under various autonomic states.
Adenosine infusion can potentially be used as a diagnostic test for sick sinus syndrome (SSS) based on its negative chronotropic effects. Whether autonomic tone underlies adenosine's negative chronotropic effects remains unknown. This study was to investigate the bradycardiac response of sinus node to ATP in patients with and without clinical SSS by measuring atrial cycle length (ACL) before and after bolus of ATP in different states of autonomic tone. The negative chronotropic effect of ATP was assessed by comparing the mean ACL before ATP administration with the longest ACL after a bolus of ATP infusion (Delta ACL). Our results showed that Delta ACL in patients with SSS were significantly greater than that without SSS (P<.001) in all 4 states, and IHR in patients with SSS were significantly lower than calculated IHR (P<.0001). Moreover, there was no significant difference in Delta ACL between the 4 states in patients with SSS (P = .99). However, Delta ACL was significantly greater during isoproterenol infusion and after propranolol administration in patients without sinus node dysfunction, comparing with baseline state (P<.01), but not after combination of atropine (P = .33). Our results indicate that the negative chronotropic effect of ATP on sinus node is much more dramatic in patients with SSS, in which the intrinsic disease of sinus node is responsible for the abnormal adenosine-mediated sinus arrest, and this effect is influenced by autonomic tone in patients without sinus node dysfunction but not in patients with SSS.
Cardiovascular Division, Department of Internal Medicine, Hyogo College of Medicine, Nishinomiya, Japan. tanbihua@hotmail.com
Bi-Hua
BH
Tan
Hiroki
H
Shimizu
Yoshio
Y
Furukawa
Tetsuzou
T
Kanemori
Mitsumasa
M
Ohyanagi
D000255:Adenosine Triphosphate; D000368:Aged; D016275:Atrial Function / Q000187:drug effects; D001285:Atropine; D006328:Cardiac Catheterization; D003864:Depression, Chemical; D004562:Electrocardiography; D005260:Female; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D007545:Isoproterenol; D008297:Male; D008875:Middle Aged; D011433:Propranolol; D012804:Sick Sinus Syndrome / Q000175:diagnosis*; D012849:Sinoatrial Node / Q000187:drug effects*
D001285:Atropine; D000255:Adenosine Triphosphate; D011433:Propranolol; D007545:Isoproterenol