Control of vascular contractility by the cardiac pacemaker

Area of Science:

• Cardiovascular Physiology
• Autonomic Nervous System Regulation

Background:

• Vascular tissues exhibit rhythmic contractile activity.
• The relationship between cardiac and vascular contractility is not fully understood.
• Pulsatile pressure changes in arteries are a known phenomenon.

Purpose of the Study:

• To investigate the synchronization between cardiac and aortic contractile activity in vivo.
• To determine the origin of the pacemaker controlling vascular contractions.

Main Methods:

• Recording of rhythmic contractile activity from rabbit aorta in vivo.
• Electrical pacing of the heart to various rates.
• Selective excision of atrial tissues.

Main Results:

• Aortic contractions were synchronized with cardiac pulsatile activity across a range of heart rates.
• Aortic contractions ceased upon termination of cardiac contractility.
• Pulse-synchronized contractions were locked to the atrial rate when atria and ventricles contracted asynchronously.
• Excision of the right atrium abolished pulse-synchronized contractions.

Conclusions:

• A common pacemaker controls both cardiac and vascular contractility.
• The right atrium plays a crucial role in coordinating cardiac and vascular events.
• This coordination ensures synchronized physiological function between the heart and aorta.