Measures of cardiac contractility variability during ischemia

Area of Science:

• Cardiology
• Biomedical Engineering
• Physiology

Background:

• Acute myocardial infarction (AMI) is a major cause of mortality.
• Heart rate variability (HRV) is established for ischemia detection, but cardiac contractility variability remains underexplored.
• Autonomic tone changes during ischemia are critical but difficult to quantify non-invasively.

Purpose of the Study:

• To investigate novel variability analysis using linear and non-linear measures during myocardial ischemia.
• To explore the utility of cardiac contractility variability for detecting ischemia.
• To compare changes in HRV and contractility variability before and after acute coronary artery occlusion.

Main Methods:

• Utilized a swine model of acute coronary artery occlusion.
• Analyzed 23 linear and non-linear variability measures of cardiac contractility and HRV.
• Compared physiologic measures before and after induced myocardial ischemia.

Main Results:

• A significant negative correlation (r=-0.92, p<0.05) was found between Poincare plot spread of RR intervals and contractility changes.
• Approximate entropy of S1 heart sound intensity strongly correlated (r=0.96, p<0.05) with ischemia-induced contractility changes.
• Non-linear variability measures effectively detected autonomic tone alterations due to ischemia.

Conclusions:

• Non-linear measures of variability show potential for detecting changes in autonomic tone during myocardial ischemia.
• These parameters could enable early detection of AMI events in patients with implantable devices.
• Further clinical studies are warranted to validate these preliminary findings.