Nonpulsatile

Nonpulsatile is an adjective used in physiology and medicine to describe flow or pressure that lacks regular rhythmic variation associated with the heartbeat. In healthy humans, arterial blood flow is normally pulsatile due to the rhythmic pumping of the heart. Nonpulsatile flow, by contrast, is continuous and shows minimal systolic–diastolic variation.

The term is commonly used when discussing blood flow produced by clinical or mechanical systems. Devices such as continuous-flow left ventricular assist devices (LVADs) and certain cardiopulmonary bypass (CPB) pumps generate nonpulsatile systemic circulation. Hemodialysis and other extracorporeal circuits can also produce relatively steady, nonpulsatile flow. In these contexts, native cardiac activity may still introduce some pulsatility, but the overall flow waveform is markedly flatter than normal arterial pulsations.

Measurement and interpretation often involve Doppler and pressure waveform analysis. The pulsatility index (PI) quantifies the dynamic component of flow; nonpulsatile flow is characterized by a low or near-zero PI. Clinically, the degree of pulsatility can be relevant to assessing microcirculatory perfusion and endothelial function, though findings about the benefits or drawbacks of nonpulsatile versus pulsatile flow are mixed and device- and context-dependent.

In practice, nonpulsatile flow is typical for many modern mechanical support and extracorporeal systems, where the priority is continuous perfusion and simplicity of control. Ongoing research continues to evaluate the physiological and clinical implications of nonpulsatile flow, particularly regarding organ perfusion, vascular health, and patient outcomes in settings such as CPB and LVAD support.