Figure 1. Left atrium and myocardial sleeves of the distal pulmonary veins. Schematic illustrates how the myocardium (white outline) of the left atrium (LA) extends into the distal pulmonary veins. Note that the sleeves of the left-sided veins are longer than those of the right-sided veins and that the left superior pulmonary vein (LSPV) has the longest myocardial sleeve. LIPV = left inferior pulmonary vein, RIPV = right inferior pulmonary vein, RSPV = right superior pulmonary vein.