Controlled cryothermal injury to the AV node: feasibility for AV nodal modification

Area of Science:

• Cardiovascular Electrophysiology
• Cryosurgery Applications
• Cardiac Ablation Techniques

Background:

• Supraventricular tachycardia management often requires modulating cardiac conduction.
• Selective injury to the atrioventricular (AV) node-His bundle region can induce a negative dromotropic effect.
• Complete AV block must be avoided when targeting AV nodal tissue.

Purpose of the Study:

• To investigate the efficacy of cryosurgery for controlled injury to the AV node-His bundle region.
• To determine the optimal temperature and duration for cryothermal ablation in this region.
• To assess the potential for achieving a therapeutic negative dromotropic effect without complete heart block.

Main Methods:

• Cryosurgery was applied to the AV node-His bundle region in twelve anesthetized dogs using a 15 mm circular cryoprobe.
• Temperatures ranged from -15°C to -60°C for 15 to 60 seconds.
• Electrophysiological testing, including conduction intervals and pacing, was performed before and after cryoablation.

Main Results:

• Cryoablation at -60°C for 15-60 seconds resulted in complete heart block and fibrosis in 5 out of 6 dogs.
• Lower temperatures or shorter durations allowed for the return of atrioventricular conduction postoperatively.
• Five dogs showed prolonged AH intervals, and three demonstrated prolonged Wenckebach cycle length, indicating a negative dromotropic effect.

Conclusions:

• Controlled cryothermal injury to the AV node-His bundle region can achieve a desirable negative dromotropic response.
• Careful modulation of cryosurgery parameters (temperature, duration) is crucial to prevent complete heart block.
• This technique holds promise for treating supraventricular tachycardia by selectively altering cardiac conduction.