Pressures do not equal volumes: implications for heart failure management in patients with CardioMEMS

Pulmonary arterial pressures are often used as surrogates for intravascular blood volume. However, the relationship between pressure and volume remains controversial. To contextualize and provide concrete examples and impact on clinical management, we report two cases of heart failure (one in heart failure with reduced ejection fraction and one in heart failure with preserved ejection fraction) where pressure-based measurements did not accurately represent the intravascular status and affected clinical management.