The heart walls and coronary circulation

The left ventricle is cone shaped. Although the limits are imprecise it can be divided, except at the apex, into four walls, named classically septal, anterior, lateral, and inferoposterior (Figure 2). The basal part of the inferoposterior wall often branches upward and then becomes really posterior and for that reason it was named the posterior wall. For more than 60 years, the terms posterior infarction, injury, and ischemia have been applied when it was considered that the basal part of the inferoposterior wall was affected (Bayés de Luna 1999, Chou Te-Chuan et al. 1977, Goldman 1964, Kennedy et al. 1970, Wagner 2002). Other names have been given to the walls of the heart (Roberts & Gardin 1978), but the consensus of the North American Societies of Imaging (Cerqueira 2002) divided the left ventricle into 17 segments and 4 walls – septal, anterior, lateral, and inferior (Figures 3 and 4). This consensus states that the classical inferoposterior wall should be called inferior “for consistency” and segment 4 inferobasal instead of posterior. Figures 3 and 4 show the 17 segments into which the four cardiac walls are divided (6 basal, 6 medial, 4 inferior, and the apex), and in the right side of Figure 4 the heart walls with their corresponding segments on a polar “bull’s-eye” map are shown. We believe that this terminology is the most appropriate and facilitates interpretation of the ECG. If one considers that the heart is located in the thorax strictly in a posteroanterior position, as is presented in a bull’s-eye polar map or in transverse images by cardiovascular magnetic resonance (CMR) in the case of involvement (injury or necrosis) of the basal part of the inferior wall (classically called posterior wall), the necrosis vector in a sagittal view would be directed strictly posteroanteriorly. This would produce an RS (R) morphology in V1−2 and the injury vector