Table 1.

Definition of Pulmonary Arterial and Right Ventricular Elastance, Coupling Measurements, and Pulmonary Artery Stiffness Metrics

Key Metrics	Measurement Description	Equation
Ea, mm Hg/ml/m2	Arterial elastance	(mPAP − PAWP)/stroke volume index
Ees, mm Hg/ml/m2	RV elastance	mPAP/RV end-systolic volume index
Ees/Ea, ratio	PA–RV coupling metric	(mPAP/RV end-systolic volume)/[(mPAP − PAWP)/stroke volume]
MRI Ees/Ea, ratio	Noninvasive PA–RV coupling metric	Stroke volume/RV end-systolic volume
PA relative area change, %	Noninvasive measurement of PA stiffness	(Maximal pulmonary arterial area − minimal pulmonary arterial area)/minimal pulmonary arterial area
Distensibility, %/PP	Measurement of PA stiffness	PA relative area change/pulse pressure

Definition of abbreviations: Ea = arterial load; Ees = RV elastance; mPAP = mean pulmonary artery pressure; MRI = magnetic resonance imaging; PA = pulmonary artery; PAWP = pulmonary arterial wedge pressure; PP = pulse pressure; RV = right ventricular.