Cardiac anatomy: what the electrophysiologist needs to know

The rapid development of interventional procedures for the treatment of arrhythmias in humans, especially the use of catheter ablation techniques, has renewed interest in cardiac anatomy. Effective and safer catheter based procedures have come from an improved understanding of not only the gross anatomic details of the heart, but also some architectural and histological features of various cardiac regions and their neighbouring landmarks. This article aims to provide the basic anatomic information needed to understand mapping and ablative procedures for the cardiac interventional electrophysiologist. The correct attitudinal position and spatial relationships of the different cardiac structures should be understood. Viewed from the frontal aspect of the chest, the right ventricle (RV) is the most anteriorly situated cardiac chamber because it is located immediately behind the sternum. The cavity of the right atrium (RA) is anterior, while the left atrium (LA) is the most posteriorly situated chamber. Owing to the obliquity of the interatrial septum (IS) plane (which is at an angle of about 65° from the sagittal plane), and to the different levels of the mitral and tricuspid valve (TV) orifices, the LA is situated more posteriorly and superiorly than the RA. The introduction of non-fluoroscopic electroanatomic mapping technologies has enabled electrophysiologists to interpret correctly the gross morphology and attitudinal position of the cardiac chambers during the course of a mapping procedure.1 Intracardiac echocardiography has also been used to visualise some endocardial structures such as the oval fossa (OF) or terminal crest (TC) and to monitor the effects of ablation. In spite of these recent developments, conventional fluoroscopy remains the essential guide during an electrophysiological study and ablation procedure. Fluoroscopic examination is performed using the frontal and oblique projections. Two or more fluoroscopic views are usually needed to define the anatomic position in the heart and to estimate more …