Walk test at increased levels of heart rate in patients with dual-chamber pacemaker and with normal or depressed left...

Area of Science:

• Cardiology
• Biomedical Engineering
• Physiology

Background:

• Dual-chamber pacemakers are crucial for managing bradyarrhythmias.
• Left ventricular (LV) function assessment is vital in pacemaker patients.
• The impact of pacing rate on cardiac hemodynamics requires further investigation.

Purpose of the Study:

• To investigate the role of heart rate on cardiac output (CO) in patients with dual-chamber pacemakers.
• To assess hemodynamic responses at rest and during a walk test in patients with depressed or normal LV function.

Main Methods:

• Nine patients with ejection fraction (EF) <50% (Group A) and seven with EF ≥50% (Group B) were studied.
• Hemodynamics were assessed at rest and during three randomized 6-minute walk tests at fixed pacing rates (70, 90, 110 bpm).
• LV function was monitored using radionuclide assessment.

Main Results:

• In Group A (depressed EF), increasing pacing rate did not change CO but decreased stroke volume (SV) and increased end-systolic volume (ESV).
• In Group B (normal EF), increasing pacing rate significantly increased CO, with no changes in ESV or SV.
• Ventricular asynchrony induced by pacing affected cardiac contractility.

Conclusions:

• Elevated pacing heart rates can negatively affect cardiac contractility in patients with dual-chamber pacing and depressed LV function.
• Increased pacing rates do not improve CO at rest or during activity in patients with depressed LV function.
• Dual-chamber pacing at higher rates may not be beneficial for cardiac output in patients with impaired LV function.