Quantitative relation between sites of atrial impulse origin and cycle length

Area of Science:

• Cardiovascular Physiology
• Cardiac Electrophysiology

Background:

• The origin of atrial impulses is multicentric, with sites distributed across the right atrium.
• An intrinsic relationship exists between these impulse origin sites and cardiac cycle length (CL).

Purpose of the Study:

• To quantitatively investigate the relationship between atrial impulse origin sites and cardiac cycle length (CL).
• To establish an anatomic-functional model of atrial pacemaker hierarchy.

Main Methods:

• Recorded atrial activation sequence maps from 360 electrodes in 132 dogs.
• Determined impulse origin sites across a range of heart rates (80-240 bpm).
• Utilized cardiac nerve stimulation and pharmacological interventions to alter CL and impulse origin.

Main Results:

• A significant correlation was found between the site of impulse origin and CL.
• Both sinus node (SN) and extranodal sites predictably control impulse initiation.
• These sites function consistently across varying heart rates, with SN predominating at certain rates.

Conclusions:

• The identified relationship allows for the specification of an atrial pacemaker hierarchy model.
• Quantified responses of atrial regions to pharmacological and physiological interventions can be determined.
• This research provides insights into the complex control of cardiac rhythm.