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Supermarket Trolleys That Can Screen for Atrial Fibrillation

A new method of opportunistic screening for atrial fibrillation in supermarkets could provide mass detection without disrupting people's lives, according to a study reported at the annual conference of the Association of Cardiovascular Nursing and Allied Professions of the European Society of Cardiology in Edinburgh today.

Electrocardiogram (ECG) sensors embedded into the handles of supermarket trolleys could effectively identify shoppers with atrial fibrillation (AF), delegates heard. Building on a previous feasibility study, a team from Liverpool John Moores University reported their research using 10 trolleys, each with a sensor placed in the handle, tested across four supermarkets with pharmacies in Liverpool. 

Over the 2-month study period, 2155 (58.1%) of 3709 adults approached agreed to use one of the modified shopping trolleys with a MyDiagnostick single lead ECG sensor embedded in the handle. Participants were asked to hold the handlebar for at least 60 seconds, long enough to enable the sensor to detect the typical AF pattern of irregular RR intervals with an absence of discernible P waves lasting more than 30 seconds.

The sensor either lit up with a green tick, when it did not detect an irregular heartbeat, or a red cross, when it did. Green-lit participants were given a manual pulse check by a researcher to confirm no AF. Those who were given a red light had a manual pulse check from the in-store pharmacist, who then did a second sensor reading using a standalone bar not attached to a trolley, with the participant standing still. 

Of the total cohort, ECG data were available for 220 participants who had either a red light on the sensor and/or an irregular pulse. These recordings were reviewed by the study cardiologist and participants were informed of the results, which were:

  • No evidence of AF in 115 participants, who were contacted and reassured
  • Unclear ECG recording and an invitation to repeat the measurement in 46 people
  • AF confirmed and a cardiologist appointment offered within 2 weeks in 59 participants

Undiagnosed People With AF Identified and Offered Treatment

The average age of the 59 participants with AF was 74 years and 43% were women. Of those, 20 already knew they had atrial fibrillation and 39 were previously undiagnosed – a yield of 1.8% of the total sample.

Study author Ian Jones, emeritus professor of mathematics at Liverpool John Moores University, said: "This study shows the potential of taking health checks to the masses without disrupting daily routines. Over the course of 2 months, we identified 39 patients who were unaware that they had atrial fibrillation. That's 39 people at greater risk of stroke who received a cardiologist appointment."

Further analysis of the Supermarket/Hypermarket Opportunistic Screening for AF (SHOPS-AF) study using different assessments of the 46 unclear ECGs (excluding them all, deeming them all AF, or assuming they were not AF) showed that the sensor’s sensitivity ranged from 0.70 to 0.93, with specificity from 0.15 to 0.97. 

This resulted in a positive predictive value of 0.24 to 0.56, meaning that only one-quarter to one-half of those found to have AF according to the sensor and/or manual pulse check actually had the condition (i.e., a high number of false positives). The negative predictive value was 0.55 to 1.00, meaning that around half of actual AF cases would have been missed (i.e., a high false-negative rate).

High Risk of Adverse Outcomes if AF Remains Undiagnosed

Nevertheless, the team noted that AF is the most common heart rhythm disorder, is increasing in prevalence, and is associated with a high risk of adverse outcomes, including stroke (5-fold relative risk), heart failure, cognitive decline, reduced health-related quality of life, and premature death. AF also contributes to rising healthcare costs. Opportunistic screening could enable earlier diagnosis and treatment to avert these complications – "it could be the shopping trip that saves your life", they said.

The researchers noted that 20% of the ECGs were non-diagnostic, and most of these were complicated with movement artefact. In future they aim to test 30-second ECG sensors with single grip handle locations aiming to reduce artefact and increase specificity. Artificial intelligence models could be incorporated into the analyses to 'clean' the ECG data as well, they said.

"Nearly two-thirds of the shoppers we approached were happy to use a trolley," Professor Jones said, "and the vast majority of those who declined were in a rush rather than wary of being monitored".

He added: "Checking for atrial fibrillation while people do their regular shopping holds promise for preventing strokes and saving lives. A crucial aspect is providing immediate access to a health professional who can explain the findings and refer patients on for confirmatory tests and medication if needed."

Funding for the study was provided by Bristol Myers Squibb. The authors declared no conflicts of interest.