Multisensor Array for the Localisation of Coronary Artery Stenosis (MALCAS)

This project is a trial of a novel device, in the form of a stick-on patch containing miniature accelerometers and microphones, designed to detect sounds produced by disturbed blood flow in stenosed coronary arteries. Initially, acoustic data will be collected from a small group of healthy volunteers to confirm proof of concept. Recordings from the patch will then be made on up to 100 patients who, having presented with chest pain to the Barts Heart Clinic, are undergoing simultaneous CTa investigations to determine the presence or absence of occlusive CAD.

The purpose of the study is to determine if the nature of the signals recorded by the patch makes it possible to distinguish those patients who have identifiable CAD, as detected by CTa (the reference method) from those in whom no occlusive lesions can be seen in the CTa images. The measurements on patients will be preceded by a trial on 20 healthy volunteers to establish base line readings and to ensure the reliability of the patch and the associated data acquisition system, in the field.

Coronary artery disease (CAD) is the leading cause of death worldwide. In Europe alone in 2014 the resulting cost of health care, and lost production was around €100 billion per year. Existing diagnostic methods apart from ECG require skilled operators and expensive equipment.

Recent advances in cCTA make it possible to detect and localise occlusive lesions with high accuracy and precision, whilst minimising the use of contrast media, albeit at the cost of some exposure to ionising radiation. Of equal or greater concern is the fact that approximately 2/3 of symptomatic patients are found, on investigation, to be occlusion-free, representing a great waste of resources and thus a loss of productivity for the healthcare system and the patients themselves, to say nothing of their distress on facing a false positive diagnosis and the risks associated with contrast injection and exposure to unnecessary ionising radiation.

The non-invasive system proposed here would be applied to symptomatic patients with stable chest pain attending a cardiac outpatient clinic with the intention of screening out the 2/3 mentioned above, resulting in large cost and time savings.

More generally, prevention of CAD, facilitated by routine screening in a primary care setting would also have the potential to relieve the economy of a major burden. Thus, there is scope for enormous life and cost saving in the early-days detection and mitigation of CHD. Apart from the immediate cost savings the longer term benefits include, for example, more appropriate allocation of imaging infrastructure, streamlining of patients in intermediate risk categories who require a more refined risk stratification; a novel technology with potential application to other near surface sites (e.g. carotid stenosis) and with potential development for deep sites (e.g. femoral stenosis); a sensing device suited to the localisation software being developed by co-workers arising from our previous EPSRC funding. There is also the potential for a 'take home' diagnostic kit which can collect and report data via domestic WiFi.

Current assessment of patients with symptoms of CAD who are referred to cardiac clinics is in most cases recommendation for a non-invasive imaging test, followed, if positive, by invasive coronary angiography. In 2010-2012 at Barts Health only 25% of coronary CT angiography scans were followed by invasive confirmation of advanced disease or treatment with either coronary angioplasty or bypass graft surgery. This was observed in a population of patients "appropriately referred" to testing, according to current NICE clinical guideline 95.

This percentage is in keeping with a large US multicentre registry where around 65% of the patients were found to be free of occlusive vascular disease following angiographic investigation. This study also showed that, although some demographic and clinical characteristics could be useful in determining the likelihood of obstructive coronary artery disease, the incremental value of non-invasive tests (resting ECG, echocardiography, imaging stress tests and coronary CT angiography) was limited. The implications are two-fold: whilst clinical assessment alone is insufficient to diagnose or exclude the presence of disease, imaging tests have an exceedingly low diagnostic yield. It was estimated that the volume of unnecessary non-invasive tests performed in the US in the decade between 2000 and 2010 cost the US economy more than $500m.

Despite impressive technological advances in medical imaging equipment introduced over the last years, translating into better accuracy and precision, we are witnessing a paradoxical increase in the number of imaging tests performed per year, which also includes multiple testing in the same patient .

Given the financial pressure on the healthcare system, large numbers of unnecessary imaging tests are unsustainable, as are the productivity losses related to hospital visits, the risks of false positive findings, and unnecessary referrals to invasive procedures which expose patients to the risk of complications (e.g. bleeding, contrast induced nephropathy, stroke, repeat radiation exposure).

The investigators propose a non-invasive system to pre-screen symptomatic patients attending a cardiac outpatients' clinic. This approach is aimed at supporting a more appropriate use of imaging resources, refining the identification of patients requiring an imaging test and/or an invasive procedure, reducing the number of unnecessary imaging tests and angiographic investigations, resulting in large cost and time savings.