Passing strange: flow in the failing ventricle.

Heart failure is diverse in its manifestations and pathophysiology with changes in chamber size and volume, wall motion, valvular competence, intracardiac pressures, and electrical events. These are routinely measured with well-established methods. However, it is common to observe different degrees of compensation despite echocardiographically similar degrees of cardiac dysfunction. How can we explain this phenomenon? One persistent gap in our understanding of the failing heart is the global behavior of the intracardiac blood flow and its potential impact on pump efficiency and disease progression. The concepts that ventricular filling and ejection are separate events distinct in timing and location and that acceleration and ejection of the stroke volume are only events due to systolic myocardial contraction are familiar but likely oversimplified. It seems reasonable that rather than coming to a halt at end diastole, flowing blood would keep moving as filling transitions to ejection and that it would be efficient for blood in the end-diastolic left ventricle (LV) to already be moving toward the aortic valve for ejection. Until recently, there was a lack of measurement tools able to accurately resolve the complex in vivo 3D flow fields to investigate these and other flow-based questions. New tools that can measure 3D flow throughout the cardiac cycle noninvasively are becoming increasingly mature, and a more detailed perspective is emerging on the organization of intracardiac blood flow. It is now possible to investigate the routes, behaviors, and interactions of the blood transiting the ventricles in normal and failing hearts1–3 and to consider the possible impact of flow characteristics on the efficiency of ventricular function. A focus on the flow aspects of cardiac function allows us to address a new and complementary set of questions. How does the efficiency of flow through the heart change with chamber dimensions, shape, and wall properties, …