Effects of sensor selection on exercise stroke volume in pacemaker dependent patients

Area of Science:

• Cardiology
• Biomedical Engineering
• Exercise Physiology

Background:

• Pacemakers are crucial for managing bradycardia.
• Rate-adaptive pacemakers adjust heart rate based on physiological demand.
• Sensor technology, including activity (ACT) and QT interval sensing, aims to optimize pacemaker response during exercise.

Purpose of the Study:

• To evaluate the impact of different sensor settings (activity sensing, QT sensing, and dual sensing) on the cardiovascular response to graded exercise in patients with VVIR pacemakers.
• To compare the mechanisms of cardiac output increase during exercise under various sensor configurations.

Main Methods:

• Ten elderly patients with VVIR pacemakers underwent three graded exercise tests.
• Pacemaker sensor programming was randomized to activity sensing (ACT), QT sensing, or dual sensing (ACT = QT).
• Cardiovascular parameters including oxygen uptake (VO2), heart rate (HR), stroke volume (SV), and cardiac output (Qc) were measured at rest and during exercise.

Main Results:

• Peak oxygen uptake (VO2) did not differ significantly across sensor settings.
• Cardiac output (Qc) increased linearly with VO2 regardless of sensor setting.
• Activity sensing (ACT) alone resulted in a higher HR response but failed to increase SV during exercise.
• QT sensing and dual (ACT = QT) sensing led to increased Qc mediated by both HR and SV, with longer diastolic filling times.

Conclusions:

• The cardiovascular response to graded exercise differs based on pacemaker sensor selection.
• Activity sensing alone may not adequately support stroke volume augmentation during exercise.
• Dual or QT sensing strategies appear more effective in optimizing cardiac output during exercise by enhancing both heart rate and stroke volume.