The advent of percutaneous therapies has revolutionized our approach to treatment of valvular heart disease. The ability to perform such interventions safely and effectively relies heavily on anatomical details. Fluoroscopic anatomy alone is inadequate to guide valvular interventions due to poor visualization of the complex 3-dimensional valve unit. More advanced imaging technology is thus required to support fluoroscopy in guiding valvular interventions. Understanding valvular anatomy and correlating it real time with presented multimodality imaging is critical for procedural success in the catheterization laboratory.
In this chapter, we describe the anatomy of the 4 cardiac valves, applying it to fluoroscopic and multimodality imaging, to guide percutaneous valvular interventions for the cardiac interventionalist.
GENERAL ORIENTATION OF THE VALVES
The heart is normally situated obliquely in the chest such that the interventricular and interatrial septa are approximately 45° to the anteroposterior projection (Fig. 4-1). Therefore, a 45° left anterior oblique (LAO) projection will allow distinction of the left and right structures, whereas a 45° right anterior oblique (RAO) projection will discriminate anterior and posterior structures. The planes of the mitral and tricuspid valves are virtually at right angles to the septal plane with some inferior tilt with the mitral plane situated slightly posterior to the tricuspid valve plane. In other words, LAO 45° caudal 15° may visualize the mitral and tricuspid valves en face, whereas RAO 45° caudal 15° may provide one of the side views for these valves. The inflow and outflow of the left ventricle are aligned closely with an angle of 15° to 20° in a normal heart, whereas the inflow and outflow of the right ventricle are aligned almost at 90°.
Anatomic structures as visualized under fluoroscopy in the right anterior oblique (A), left anterior oblique (B), anteroposterior (C), and left lateral (D) views.
The aortic valve plane is typically tilted caudally and leftward, with the end on view being either LAO 60° caudal 35° or RAO 30° cranial 45°. Side views can be obtained with either RAO 20° caudal 20° or LAO 40° cranial 30° projections. Pulmonary valve is tilted quite posteriorly and to the right, such that the end on view is RAO 10° caudal 50°, and the pulmonary valve plane ranges from RAO 30° cranial 20° to LAO 30° caudal 20°. The right ventricle wraps around the outflow of the left ventricle, being mostly anterior to the left ventricle with only the inferior margin to the right of the left ventricle; the outflow tract of the right ventricle is superior and to the left of the aortic valve. The left atrium forms most of the posterior aspect of the heart as appreciated on the lateral fluoroscopic views.
FIBROUS SKELETON OF THE HEART
The fibrous skeleton (Fig. 4-2) ...