Contemporary angiography in the diagnosis and treatment of cardiovascular disease

Abstract

BackgroundCardiovascular disease is the leading cause of death in the developed world. Angiography allows the visualisation of arteries through the use of real time X-ray imaging when injected with iodinated contrast media (ICM). Due to its excellent temporal resolution and real time imaging capability, angiography has been the cornerstone of the diagnosis and percutaneous treatment of cardiovascular disease for many years. The number and diversity of diagnostic and therapeutic procedures that utilise angiography are increasing rapidly but the technology of angiography is not without risk to patients and the staff in attendance. ICM used in angiography is excreted by the kidneys and is toxic. The cohort of patients being treated for cardiovascular disease are often elderly with pre-existing renal disease and more complex angiographic procedures can cause renal failure. There is also risk to the patient and the staff working in the room from the stochastic and deterministic effects of ionising radiation that is used to produce the images. Currently there is no multicentre reference levels for radiation dose to patients undergoing cardiac angiography procedures in Australia and globally there is little data on the factors impacting on staff dose during these procedures and the potential reductions available with newer X-ray systems. As new procedures, such as trans catheter aortic valve impanation (TAVI) emerge, there is a need to investigate the radiation doses associated with these, to investigate the impact of ICM on renal function and to assess new imaging techniques that may be useful for some of these newer procedures.MethodologyRadiation benchmarks will be established for diagnostic and interventional procedures for Queensland public hospitals, with comparisons to the literature. With a single centre focus, radiation dose and procedural data will be collected to investigate the different variables that impact on radiation dose to the patient and the staff during diagnostic cardiac angiography and structural cardiac intervention. Further, the impact of latest generation X-ray equipment on radiation dose will be investigated during electrophysiology procedures, which are traditionally seen as high dose procedures. The impact of ICM usage and the effect on patient’s renal function and mortality will be investigated during trans-catheter aortic valve implantation (TAVI). 3D angiography will be investigated to assess its effectiveness, accuracy, ICM use and radiation dose compared to 2D angiography and computed tomography (CT) for patients undergoing TAVI. Finally, the degree of X-ray beam distortion, inherent in the design of all X-ray systems will be assessed for TAVI devices.Results and conclusionsRadiation dose 75th percentile reference levels of 5864CGycm2 and 12900CGycm2 for diagnostic and interventional angiography procedures across all public hospitals in Queensland were established, which are very comparable to other international benchmarks. Radiation dose during diagnostic procedures is multifactorial but patient obesity was highlighted as the biggest predictor for both a high patient and staff radiation dose. During structural cardiac intervention the trans-oesophagel echocardiography operator had the highest radiation dose when compared to the rest of the team, but additional shielding was shown to reduce radiation dose by 82% and newer X-ray technology can dramatically reduce radiation dose, as demonstrated during electrophysiology procedures by up to 92%. ICM use was relatively high during TAVI procedures when compared to the literature but did not appear to be associated with acute kidney injury (AKI). The severity of AKI is important in determining mortality in these patients, which was linked to chronic kidney disease, respiratory failure, previous stroke, blood transfusion and retrieval or removal of the device, the latter being a new finding in this area. 3D rotational X-ray (DynaCT) can accurately determine the calibre and tortuosity of the ilio-femoral arteries, for patients selected for TAVI, using less ICM than CT but it was inadequate as assessing calcification in this particular study. The TAVI device was demonstrated to be significantly affected by X-ray beam distortion, when imaged toward the periphery of the image which could affect the implant depth.Overall, cardiac angiography is evolving rapidly, with many new procedures utilising this technology. Radiation dose to patients and staff is now better understood, with new equipment and shielding technologies demonstrating dose reduction. The volume of ICM in these new procedures is not associated with AKI but pre-existing conditions are more relevant, as well as procedural complications. ICM volume can be reduced for these procedures through the use of new imaging technology, though it does have some limitations and TAVI devices can be susceptible to the effects of X-ray beam distortion.