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

Area of Science:

• Electrophysiology
• Cardiology
• Pharmacology

Background:

• Sinus node dysfunction (SND) diagnosis can be challenging.
• The impact of clinical presentation on adenosine testing outcomes in SND is not well understood.

Purpose of the Study:

• To investigate if syncope or presyncope influences the sinus nodal response to adenosine in SND patients.
• To compare adenosine-induced sinus nodal inhibition with that from atrial pacing in SND.

Main Methods:

• Studied 46 SND patients (33 with syncope/presyncope, 13 without) and 30 controls.
• Measured corrected sinus node recovery time after intravenous adenosine (ADSNRT) and atrial pacing (CSNRT).
• Defined abnormal corrected sinus node recovery time as >525 ms.

Main Results:

• ADSNRT was significantly prolonged in SND patients with syncope/presyncope compared to those without (median 4900 ms vs. 280 ms, P<0.005).
• In syncope/presyncope patients, ADSNRT was more prolonged than CSNRT (P<0.01).
• A cutoff of 1029 ms for ADSNRT showed 57% sensitivity and 96.6% specificity for SND diagnosis.

Conclusions:

• Syncope or presyncope in SND patients is associated with exaggerated sinus nodal suppression by adenosine.
• Prolonged ADSNRT can identify severe SND cases requiring potentially more aggressive management.
• Adenosine testing provides valuable diagnostic information in SND, particularly in patients with syncopal symptoms.