Taking a full-blooded approach to heart monitoring

A portable, non-invasive device using ultrasound to monitor blood flow within the heart will provide doctors with an early warning if patients are at risk of a heart attack, its developers claim.

The system – for both children and adults – will provide hospital staff with a fast and accurate image of any heart problems when an emergency patient is admitted. It is also suitable for continuous cardiac monitoring of aircraft pilots or athletes.

The ultrasonic cardiac output monitor (USCOM) system, developed by Rob Phillips, head of the cardiac faculty at the Australian Institute of Ultrasound, uses continuous wave spectral Doppler ultrasound to measure blood flow across the cardiac valves.This involves sending a constant signal into the body, which has not been done before as it is hard to separate echoes produced by different parts of the body.

Hospitals currently use pulsed Doppler ultrasound instead, but this requires placing a probe within the patient and becomes inaccurate at certain frequencies, creating an incomplete picture.

The USCOM system sends a signal towards the heart using a 1p-size transmitter, which is placed on the skin. The continuous ultrasound bounces off the red blood cells and is altered by their movement, producing a unique echo. This allows the number of red cells flowing across each of the cardiac valves to be counted.

During continuous monitoring, flow changes can indicate that a heart attack is imminent. The digital output of the USCOM machine is displayed on an adjustable LCD, and the system keeps a record of patients’ treatment.

As echo data is suitable for sending over the internet and via wireless, signals from a device worn by a patient could be transmitted to a computer programmed to dial a remote signal analysis centre.

This is useful for monitoring those at risk of a heart attack, such as the elderly, as well as patients who have recently been discharged from hospital. Certain changes would sound an alarm, allowing doctors to intervene before a heart attack occurred.