Comparative quantitative electrophysiologic effects of adenosine triphosphate on the sinus node and atrioventricular...

Area of Science:

• Cardiac Electrophysiology
• Pharmacology

Background:

• Adenosine triphosphate (ATP) is an endogenous nucleoside with known effects on cardiac function.
• Understanding the differential effects of ATP on the sinus node (SN) and atrioventricular (AV) node is crucial for interpreting electrophysiologic testing results.

Purpose of the Study:

• To pharmacologically characterize the dose-dependent responses of the SN and AV node to intravenous ATP.
• To compare the electrophysiologic effects and dose-response characteristics of ATP on SN automaticity and AV nodal conduction.

Main Methods:

• Intravenous adenosine triphosphate (ATP) was administered during electrophysiologic testing in 21 patients.
• Dose-dependent effects on sinus cycle length, AV nodal conduction (AH interval), and AV block were assessed.
• Median effect plots were used to derive EC50 values for SN and AV node responses.

Main Results:

• ATP produced dose-dependent prolongation of sinus cycle length with a maximal increase of 294 ms (EC50 = 0.39 mg).
• ATP induced AV block at a higher mean dose (4.4 mg) with an EC50 of 2.98 mg.
• ATP effectively terminated paroxysmal reentrant supraventricular tachycardia at the AV node in 8 of 9 patients.

Conclusions:

• Significant differences exist in the electrophysiologic correlates and EC50 values for SN and AV node responses to ATP.
• Findings suggest potentially distinct mechanisms of action for ATP on SN automaticity versus AV nodal conduction, warranting further investigation.