The syndrome of heart failure is characterized by symptoms that are relatively insensitive and nonspecific. Physical diagnosis may be unreliable even in the hands of experienced clinicians, despite the presence of significantly elevated filling pressures or a significantly depressed cardiac output. Instrumentation and devices such as the insertion of a pulmonary artery catheter and the implantable hemodynamic monitor have a major role in the diagnosis and management of cardiovascular disease. They provide a means of measuring intracardiac pressures for point-in-time measurements (cardiac catheterization), short term in an acute situation (insertion of a pulmonary arterial catheter), and, more recently, a long-term assessment increasing our understanding of the nuances of the hemodynamic derangements associated with heart failure and other conditions. With improved ability to accurately assess and monitor filling pressures, clinicians can more precisely adjust therapy with the goal of improving patient symptoms and possibly outcomes.