Which pathological state can cause an expected false low measurement in cardiac output using a pulmonary artery catheter?

A false low measurement in cardiac output when using a pulmonary artery catheter can occur in the presence of tricuspid regurgitation. This condition leads to incomplete and backward flow of blood from the right ventricle back into the right atrium during systole. Because this regurgitant flow can cause a dilution of the stroke volume that is being measured, the overall cardiac output appears lower than it actually is.

In this scenario, the pulmonary artery catheter relies on measuring pressures and flows; if blood is flowing back into the atrium rather than being effectively ejected into the pulmonary artery, the measured cardiac output will not accurately reflect the true hemodynamic state. Instead, it may show diminished cardiac output readings, highlighting the impact of the tricuspid valve’s incompetence on these measurements.

The other conditions listed affect hemodynamics differently and do not typically lead to this specific false low measurement in the context of cardiac output monitoring using a pulmonary artery catheter.