Wearable device, system and method for monitoring cardiac function/stress during apnoeic episode

A system comprising:

• a wearable device configured to be worn on a chest near a sternum of a user, the wearable device comprising:
• a ballistocardiography (BCG) sensor configured to measure mechanical forces generated by a heart,
• an electrocardiography (ECG) configured to measure electrical activity of the heart, and
• a processor operatively connected to the BCG sensor and the ECG sensor to generate BCG data from the mechanical forces and ECG data from the electrical activity;
• and
• a server arrangement communicably coupled to the wearable device for receiving the BCG data and the ECG data, the server arrangement is configured to:
• filter respiratory signals and heart signals from the BCG data;
• determine that an apnoeic episode has occurred based on a respiratory signal amplitude derived from the filtered BCG data being below a predefined threshold for at least a predetermined duration;
• for the apnoeic episode, determine a compensatory mechanical output of the heart using the ECG data by:
• calculating ultra-short-term heart rate variability (HRV) from an ECG time segment corresponding to an apnoeic period and from an ECG time segment corresponding to a non-apnoeic period;
• identifying a reduction in HRV during the apnoeic period relative to the non-apnoeic period;
• and
• correlating the identified reduction in the ultra-short-term HRV with cardiac stress indicators;
• and
• predict a risk of a cardiac condition based on the determined compensatory mechanical output during the apnoeic episode.

A method comprising:

• measuring mechanical forces generated by a heart using a ballistocardiography (BCG) sensor;
• measuring electrical activity of the heart using an electrocardiography (ECG) sensor;
• generating BCG data from the mechanical forces and ECG data from the electrical activity using a processor;
• filtering respiratory signals and heart signals from the BCG data;
• determining that an apnoeic episode has occurred based on a respiratory signal amplitude derived from the filtered BCG data being below a predefined threshold for at least a predetermined duration;
• for the apnoeic episode, determining a compensatory mechanical output of the heart using the ECG data by:
• calculating ultra-short-term heart rate variability (HRV) from an ECG time segment corresponding to an apnoeic period and from an ECG time segment corresponding to a non-apnoeic period;
• identifying a reduction in the ultra-short-term HRV during the apnoeic period relative to the non-apnoeic period;
• and
• correlating the identified reduction in the ultra-short-term HRV with cardiac stress indicators;
• and
• predicting a risk of a cardiac condition based on the determined compensatory mechanical output during the apnoeic episode.