Assessing the Efficacy of CARDIOgoniometry (CGM) to Determine Physiologically Significant Stenosis in Patients With Stable Coronary Artery Disease in Comparison to Fractional FLOW Reserve - CARDIOFLOW

Overview

The CARDIOFLOW study compares the standard test, a pressure wire test called fractional flow reserve (FFR), with a new method that is based on taking a detailed "3D" ECG called Cardiogoniometry (CGM). FFR is an angiographic technique which measures the physiological significance of a coronary stenosis and trial data has shown that basing management decisions on this data improves prognosis. However FFR studies are expensive and invasive, whereas CGM is painless and simply involves placing 4 sticky pads to the patient's chest / back and is similar to an ECG (heart tracing). The investigators want to see whether we can use this new method to find out whether treatment with coronary angioplasty would be of benefit. If so, then in the future, clinicians could use this method (CGM) rather than pressure wire assessment (FFR). This would have several advantages; in particular, it can be easily performed in the clinic and avoids the need to use an expensive pressure wire.

This study aims to test the hypothesis that cardiogoniometry (CGM) is helpful to identify physiologically significant coronary artery stenosis in comparison to fractional flow reserve (FFR). Last year in the UK 202 098 patients underwent coronary angiography to determine whether they had significant coronary artery disease. However, it is well recognised that, even with orthogonal views, angiography is limited in terms of its ability to determine the functional importance of coronary lesions. In particular those lesions judged to be 50-70% stenosed may not necessarily cause ischaemia as this depends on factors such as the lesion length and, importantly, the size of the territory supplied by the vessel. There have been several studies that have demonstrated the clinical utility of evaluating such lesions with FFR. The measurement of FFR is an index of the physiological significance of a coronary stenosis and is defined as the ratio of maximal blood flow in a stenotic artery to normal maximal flow. It is calculated by comparing the ratio of the aortic pressure and the pressure distal to the coronary stenosis during maximal hyperaemia. These pressures are measured by introducing a coronary pressure guide wire into the artery and hyperaemia is induced by giving an infusion of adenosine intravenously. An FFR ratio of \<0.80 indicates that the coronary stenosis is causing significant ischaemia and would benefit from PCI. This has since been incorporated into ESC clinical guidelines on myocardial revascularisation. However this is an invasive procedure and the pressure wires are relatively expensive compared to standard angioplasty wires. On the contrary, CGM is a cheap and non-invasive technique that can be easily applied. The aim of the proposed study is to assess whether CGM may be able to aid clinicians in identifying if a coronary stenosis is physiologically significant at inducing myocardial ischaemia in conjunction with standard coronary angiography. CGM is form of 3D vector electrocardiography which can provide quantitative analysis of myocardial depolarisation and repolarisation. It has been shown to be more sensitive and specific than standard 12-lead ECG at diagnosing stable coronary artery disease. Furthermore, other work has showed CGM to be more sensitive than 12-lead ECG at detecting patients with ACS. More recently in 2012, further work found that CGM was more sensitive and specific than the 12 lead ECG at identifying abnormal myocardial perfusion scans (MPS). FFR validity was initially based on a comparison with MPS and therefore we hypothesise that CGM may be comparable to FFR.