Ionic remodeling of sinoatrial node cells by heart failure

Area of Science:

• Cardiology
• Electrophysiology
• Molecular Biology

Background:

• Heart failure (HF) is associated with decreased heart rate.
• This phenomenon is linked to increased intrinsic cycle length of the sinoatrial node (SAN).
• HF-induced remodeling of SAN cells' electrical properties requires investigation.

Purpose of the Study:

• To evaluate the remodeling of membrane potentials and currents in SAN cells during HF.
• To identify the specific ionic mechanisms underlying HF-induced bradycardia.

Main Methods:

• SAN cells were isolated from control and HF rabbits.
• Electrophysiological properties were measured using patch-clamp technique.
• Key ionic currents, including If and IKs, were quantified.

Main Results:

• HF did not cause SAN cell hypertrophy.
• Intrinsic cycle length increased by 15% due to a 30% decrease in diastolic depolarization rate.
• The hyperpolarization-activated "pacemaker" current (If) was reduced by 40% in HF.

Conclusions:

• HF increases SAN cell intrinsic cycle length by reducing diastolic depolarization rate.
• HF-induced bradycardia is primarily attributable to the remodeling and reduction of the If current.
• IKs current density was also reduced, but plays a minor role in HF-induced heart rate changes.