Intravenous adenosine: a noninvasive diagnostic test for sick sinus syndrome

Adenosine has a well established negative chronotropic effect on the sinoatrial node. The most widely utilized test of sinus node function remains the sinus node recovery time (SNRT), which generally requires catheterization. We compared the effect of adenosine (150 mcg/kg IV) on the lengthening of sinus cycle length (ADO:SCL) in 12 control patients (group I) and in 11 patients with clinical sick sinus syndrome (SSS) (group II), eight of whom had undergone prior permanent pacemaker implantation. Using 675 msec as an abnormal result indicating sinus node dysfunction (two standard deviations above the mean value established in controls), ADO:SCL had a sensitivity and specificity of 64% and 100%, which were equal to that observed for the corrected sinus node recovery time (CSNRT) (abnormal value > or = 550 msec). There was a significant difference in the CSNRT between group I (304 +/- 149 msec) and group II (1,199 +/- 916 msec, P = 0.003). There was no significant difference in ADO:SCL between groups I (256 +/- 210 msec) and group II (1,213 +/- 1,719 msec, P = 0.069); however, there was substantial overlap between patients exhibiting an abnormal ADO:SCL and CSNRT. As such, a significant difference in ADO:SCL was evident between group II patients (1,784 +/- 1,950 msec, n = 7) exhibiting an abnormal CSNRT and group I patients, P = 0.014. In conclusion, ADO:SCL has the same sensitivity and specificity for sinus node dysfunction as compared to the CSNRT. Intravenous adenosine may prove to be a useful noninvasive test to assess the need for permanent pacemaker implantation.