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


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%.


CONCLUSIONS
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.
3rd Cardiology Department, Hippokration Hospital, Aristotle University Medical School, 49 Konstantinoupoleos Street, 54642 Thessaloniki, Greece. fragakis.nikos@googlemail.com
Nikolaos
N
Fragakis
Antonios P
AP
Antoniadis
Panagiotis
P
Korantzopoulos
Panagiota
P
Kyriakou
Konstantinos C
KC
Koskinas
Paraschos
P
Geleris
D000241:Adenosine / Q000008:administration & dosage; D000368:Aged; D000369:Aged, 80 and over; D000889:Anti-Arrhythmia Agents / Q000008:administration & dosage; D002304:Cardiac Pacing, Artificial / Q000379:methods; D005260:Female; D006801:Humans; D007275:Injections, Intravenous; D008297:Male; D008875:Middle Aged; D012372:ROC Curve; D011930:Reaction Time / Q000187:drug effects; D012680:Sensitivity and Specificity; D012720:Severity of Illness Index; D012804:Sick Sinus Syndrome / Q000175:diagnosis*; D012849:Sinoatrial Node / Q000187:drug effects* / Q000503:physiopathology; D013575:Syncope / Q000175:diagnosis*
D000889:Anti-Arrhythmia Agents; D000241:Adenosine