Continuous Estimation of Acute Changes in Preload Using Epicardially Attached Accelerometers

Area of Science:

• Biomedical Engineering
• Cardiovascular Physiology
• Surgical Monitoring

Background:

• Hemodynamic instability is a critical concern in surgical patients.
• Accurate assessment of volume status is essential for managing unstable patients.
• Current methods for monitoring volume status can be invasive or intermittent.

Purpose of the Study:

• To evaluate the feasibility of using a miniaturized accelerometer in temporary pacemaker leads for continuous monitoring of cardiac motion.
• To determine if epicardial accelerometer data can accurately assess volume status and guide fluid resuscitation in hemodynamically unstable patients.

Main Methods:

• A miniaturized accelerometer was attached to the epicardium of 9 pigs.
• Recordings were taken during baseline, fluid loading, and phlebotomy.
• The frequency of myocardial acceleration associated with the first heart sound (fS1) was analyzed.
• Sonomicrometry-measured end-diastolic volume (EDV) was used as a reference.
• Standard clinical estimates (GEDV, PAOP) and other indices (SVV, PPV) were compared.

Main Results:

• Changes in fS1 showed a strong correlation with changes in EDV (r²=0.81).
• The diagnostic accuracy of fS1 in identifying fluid responsiveness was 0.79, outperforming PAOP (0.63) and comparable to SVV (0.72).
• Epicardial accelerometer measurements correlated well with preload changes.

Conclusions:

• An epicardially placed accelerometer can reliably assess real-time changes in cardiac preload.
• This technology offers a novel method for continuous volemic status monitoring in open-heart surgery.
• It has the potential to aid in guiding fluid resuscitation strategies.