Intravenous injection of adenosine triphosphate for assessing sinus node dysfunction in patients with sick sinus syndrome

The clinical value of rapid intravenous injection of adenosine triphosphate (ATP, Adephos Kowa # L3, CAS 56-65-5) for assessing sinus node function was examined in 5 patients with sick sinus syndrome (SSS) and 6 normal controls. All patients with SSS showed cardiac pauses longer than 3 s on a 24-h Holter ECG monitoring. First, after prophylactic insertion of a temporary pacemaker in the right ventricle, overdrive suppression test was conducted using the standard technique, and sinus node recovery time (SNRT) was observed to evaluate the sinus node function. Then, 10 min later, 10 mg of ATP was rapidly injected intravenously, and body surface and intracavitary ECG were continuously recorded until the basal state was regained. The rapid injection of ATP resulted in a slight inhibition of sinus node automaticity in normal subjects, but marked inhibition was in patients with SSS associated with suppression of AV conduction. The longest post ATP atrial cycle (AA) interval in the intracavitary ECG showed a close inverse relationship with SNRT corrected for basal sinus length (CSNRT), according to the following formula: longest AA interval (ms) = 3.32 x CSRT (ms) +254.4 (r = 0.91, p < 0.001). The results suggest that rapid intravenous injection is a useful tool for the diagnosis of SSS.