Does Routine Pressure Wire Assessment Influence Management Strategy at Coronary Angiography for Diagnosis of Chest Pain?

The choice of management in an individual patient is determined largely by the presence and distribution of significant coronary narrowings. Usually, this significance is judged by the visual estimation of a narrowing on an angiogram. However, although this is the standard way of assessing coronary narrowings, it is now widely published that pressure wire measurements are more accurate because they assess the true physiological consequences of the narrowing. Interventional cardiologists now frequently use Fractional Flow Reserve (FFR) measurements to help them decide if arteries require stenting.The hypothesis for this study is that routine measurement of FFR in the main coronary arteries could provide diagnostic information above and beyond that obtained by an angiogram alone. This additional information may well then affect the choice of management in a proportion of these patients. For example, a narrowing considered to be significant angiographically may be shown to be insignificant with FFR, or vice versa.

Background

Coronary artery disease (CAD) is a major cause of morbidity and mortality in the United Kingdom. It accounts for approximately half of all cardiovascular related deaths annually and, according to statistics from the British Heart Foundation, CAD related expenditure was £3,500 million in 2003 alone. Much effort has been placed on improving methods that detect and assess the severity of CAD and facilitate more rapid and appropriate management for CAD patients. Once diagnosed, CAD may be treated in 3 ways: (1)tablets alone, (2)tablets plus angioplasty with stents or (3) tablets plus coronary artery bypass graft surgery (CABG). The method of choice depends primarily on the extent and severity of disease at the time of coronary angiography. Coronary angiography is the current conventional method for the diagnosis of CAD and is used in the assessment of disease severity. For the angiographic procedure,vascular access is secured via the femoral artery or radial artery route and a dye is injected into the coronary artery blood vessels. The progress of the dye through the coronary blood vessels provides a visual assessment of where narrowings are present in the coronary arteries.

Where there is thought to be significant flow obstruction, particularly in symptomatic patients, one of the above three treatments will be offered.

While coronary angiography has revolutionised the management of CAD, the procedure is not without limitation. The purely visual assessment of disease severity with coronary angiography is subjective and patient management can depend on the cardiologist reviewing the films. Many such narrowings can be graded 'moderate' severity and deciding whether these are of haemodynamic significance is notoriously difficult by angiography alone. In recent years, the Radi pressure wire has been shown to provide accurate physiological haemodynamic data about coronary narrowings. Furthermore, the FFR measurement derived predicts clinical outcome, hence giving a 'cut-off' measurement for severity of disease that correlates with the requirement for revascularisation with either stents or surgery. Thus FFR is now frequently used in clinical practice by interventional cardiologists to decide if narrowings require treatment. However, the majority of diagnostic angiography in the UK is performed by non-interventional cardiologists who do not currently have access to the pressure wire technology. In this study, we speculate that if we measure the FFR routinely in all the main coronary arteries of patients undergoing coronary angiography the FFR data obtained may affect the angiogram-derived management of some patients in terms of the choice of tablets/stents/CABG. For example, some narrowings that look significant angiographically may not be haemodynamically important by FFR and vice versa. Clearly this could make a difference between revascularising a patient or not.