Sinus nodal response to adenosine relates to the severity of sinus node dysfunction.

ABSTRACT

AIMS: It is unknown as to whether the result of adenosine testing for the diagnosis of sinus node dysfunction (SND) depends on the clinical presentation. We investigated whether syncope or presyncope are associated with a more pronounced sinus nodal inhibition by adenosine in SND. METHODS AND RESULTS: We studied 46 patients with SND, 33 with syncope or presyncope and 13 without such history. Controls were 30 subjects undergoing electrophysiological studies for supraventricular tachycardia or unexplained syncope. We calculated the corrected sinus node recovery time after intravenous adenosine 0.15 mg/kg (ADSNRT) as well as after atrial pacing (CSNRT). Corrected sinus node recovery time values >525 ms were considered abnormal. Corrected sinus node recovery time after adenosine injection was more prolonged in SND patients with syncope or presyncope as compared with those without such history [median 4900 inter-quartile range (IQR) 920-8560 ms vs. median 280 IQR 5-908 ms; P< 0.005]. In SND patients with syncope or presyncope ADSNRT was more prolonged than CSNRT (median 4900 IQR 920-8560 ms vs. median 680 IQR 359-1650 ms, P< 0.01). In SND patients without syncope or presyncope no statistical difference was noted between ADSNRT and CSNRT (median 280 IQR 5-908 ms vs. median 396 IQR 270-600 ms, P = 0.80). The sensitivity of CSNRT for SND diagnosis was 57% and the specificity was 100%. A cut-off of 1029 ms for ADSRNT yields the same sensitivity with a specificity of 96.6%. CONCLUSION: In patients with SND syncope or presyncope relate to an exaggerated sinus nodal suppression by adenosine. Prolonged ADSNRT can diagnose cases with severe underlying SND where a more aggressive management strategy is probably warranted.