The Future Cardiac Catheterization

Although X-ray angiography has been widely accepted and used as a real-time imaging modality, its traditional format is still limited by its two-dimensional (2D) representation of three- dimensional (3D) structures and the consequent imaging artifacts that impair optimal visualization. More than 50 years after the performance of first coronary angiogram, the basic principle of coro- nary angiography has not changed, even with the introduction of modern X-ray imaging system. Recognition of these limitations has resulted in the development of 3D imaging techniques de- signed to address specifically the weaknesses of traditional angiographic techniques. Recent tech- nical endeavors focus mainly on reduction of the X-ray dose, 3D coronary reconstruction and quan- titative analysis, optimal viewing strategy, and enhancement of stent visualization. The final representation, however, is still limited to the tradi- tional 2D display format, which is inherently flawed for helping the interventionist appreciate the patient's true 3D anatomy and interaction with the implanted device in vivo. Recently, the focus in heart disease research and treatment has been expanded from coronary artery disease (CAD) to structural heart disease (SHD). The categories of SHD include hemody- namic and electrophysiologic abnormalities of any of the four cardiac chambers, any of the four heart valves, and the presence of congenital or acquired defects between heart chambers and the great vessels. SHD affects approximately 5 million people in the United States, and approx- imately 1 million of those cases require surgical intervention each year. The development of novel interventional therapies for SHD has followed the recognition that growing population of patients who have SHD are being suboptimally treated with palliative medication-based therapy; open heart surgery is the major surgical option. There- fore innovative approaches in visualization are more important and urgent in SHD treatment than CAD treatment to facilitate diagnosis, plan therapy, to provide image-guidance of interven- tions, to clarify anatomical and pathophysiological issues, and to quantify device-anatomy interactions. The physicians who perform image-guided interventions in CAD or SHD do not have the advantage of direct observation of the therapeutic target that surgeons often enjoy. These issues are compounded for most cardiologists by their limited training and experience in navigation and visual-spatial skills in the complex 3D spatial rela- tionships of the whole heart and novel device/ anatomy fitting. Preprocedural planning for inter- ventions typically uses the 2D imaging of echocar- diography and angiography. SHD interventions usually are performed with fluoroscopic image guidance with a variable use of 2D ultrasound. During the last 5 years, a quest has begun to modify existing modalities or to develop other imaging modalities to guide interventions in SHD and cardiac electrophysiological procedures. This transition is driven by the frequent inability to visualize the target of the intervention (valves, chamber defects, heart muscle, and cardiac conduction tissue) by fluoroscopy and by the