**1. Introduction**

Heart failure is characterized by the inability of the heart to maintain sufficient cardiac output (CO) to meet the metabolic demands of the body. Reduced CO activates compensatory mechanisms directed towards reestablishing CO, thereby initiating a cycle which can lead to cardiomyopathy. Therapeutic strategies for addressing heart failure have been developed primarily based on studies of male populations; however, heart failure in women has a distinct phenotype. In women, heart failure develops later in life, generally presents with preserved systolic function, and is less commonly attributable to ischemic heart disease. In many women, the initiating event in heart failure is extrinsic, specifically, poor venous return resulting from inadequate calf muscle (soleus) pump activity during upright posture. Such "second heart" failure has been identified in approximately half of all adult women, an observation which helps to explain the fact that while women's survival rate with heart failure is better than in men, their quality of life with heart failure is far worse. A determination that inadequate venous return is arising from calf muscle pump failure can permit effective early intervention to slow or reverse cardiomyopathy, while significantly improving quality of life in affected women.
