Investigating the Fidelity of Classic Cardiovascular Metrics in the Context of a Failing and Mechanically Supported Heart

Abstract

The advent of mechanical circulatory support devices (MCS) has ushered in a new era in the treatment of low cardiac output states. Proper titration of MCS is essential for optimal therapeutic outcomes and relies on monitoring metrics of cardiac state. However, innovation in clinically determining these metrics has lagged compared to treatment options. Consequently, many rely on assumptions about the cardiovascular environment that are invalidated by the use of MCS, raising concerns about their reliability.

This work used thermodilution, the gold standard method for measuring a patient’s cardiac output, as well as a newly developed MCS-based method, to explore under what conditions traditional metrics are impacted by MCS. Data from porcine studies and clinical trials were used to examined how the validity of both measurement methods can be impacted by changes in a patient’s cardiac state as well as commonly used medical interventions like mechanical ventilation and pharmacologic treatment, with and without MCS present. Ultimately, we found that thermodilution remains valid under conditions where beat-to-beat variability in flow is low, a limitation not present in the new MCS-based method.

Translation of this work to the clinic will help better inform physicians on when thermodilution measurements should and should not be used to titrate MCS support due to possible unreliability. What’s more, understanding when and how traditional, “gold standard” metrics, such as thermodilution, fail is essential for validating newer, more reliable metrics like the MCS-based method. Both of these consequences will ultimately improving patient outcomes.