The Left Ventricular Ostium

Received June 17, 2008; accepted September 4, 2008. Idiopathic ventricular arrhythmias (VAs) arising from the left ventricle (LV) are often accessible for catheter ablation from the aortic sinuses of Valsalva or adjacent to the mitral annulus (MA).1 The aortic and mitral valves are direct apposition and attach to an elliptical opening at the base of the LV known as the LV ostium.2 The VAs arising from this region are being increasingly recognized as targets for catheter ablation.3–7 This review describes the anatomic features of the LV ostium and the electrocardiographic, electrophysiological, and angiographic characteristics that are relevant to the mapping and ablation of these arrhythmias. The dominant central structure of the heart is the junction of the aorta with the LV. Fundamental for understanding idiopathic VAs arising near the aortic and mitral valves are 2 concepts: first, these arrhythmias arise from the LV ostium (Figure 1); and second, the LV ostium is covered by the aorto-ventricular membrane, a tough fibrous structure which is perforated by the aorta anteriorly and the mitral valve (MV) posteriorly (Figure 2). The anatomic concept of the LV ostium and its covering, the aorto-ventricular membrane, are based on the pioneering work of McAlpine.2 Figure 1. The left ventricular ostium (postero-cranial view). The left panel includes the aortic root with the right coronary sinus (R), left coronary sinus (L), and noncoronary sinus (N). In the right panel, the root of the aorta has been removed to demonstrate the elliptical ostium of the left ventricle (LV) with the junction of the right coronary cusp (RCC), left coronary cusp (LCC), and LV summit demonstrated. APM indicates anterior papillary muscle; LA, left atrium; LAFT, left anterior fibrous trigone; LFT, left fibrous trigone; L-RCC, the junction between the LCC and RCC; PPM, posterior papillary muscle; PSP, postero-superior …