What condition characterizes a hyperdynamic heart on VV ECMO?

A hyperdynamic heart on venovenous (VV) ECMO typically refers to a situation where there is a significant native cardiac output in the presence of ECMO support. The scenario in which the ECMO cannot effectively capture a substantial portion of the native cardiac output is indicative of a hyperdynamic state. This means that despite the presence of ECMO support, the heart is still generating a considerable output on its own.

When the native cardiac output is elevated, the VV ECMO's role is often to provide additional support while the heart is still functioning well. In this context, if the ECMO is unable to capture two-thirds of the native cardiac output, it highlights the hyperdynamic aspect because it shows that the heart is working effectively and producing more volume than what the ECMO can manage to assist with. Thus, the correct answer underscores this relationship between the native heart function and the competing ECMO support.

The other options do not appropriately define the characteristics associated with a hyperdynamic heart on VV ECMO. For instance, an increased native cardiac output alone does not characterize hyperdynamics without detailing the relationship to ECMO's role. Elevated peripheral vascular resistance does not necessarily connect to hyperdynamic heart states, and excess blood volume in the circuit would confuse