Determination of preload-recruitable stroke work and elastance by the relationship of arterial blood flow velocity to left ventricular area

Abstract

Objective: The authors investigated the feasibility of an online sampling and display of LV flow-area loops for the determination of LV elastance and preload-recruitable stroke work (PRSW). Automated LV area measurements by echocardiography may be combined with flow velocity measurements in the internal carotid artery to construct LV flow-area loops as estimates of the systolic pressure-volume relationship. Setting: University hospital. Design: Open chest model. Participants: Eight anesthetized minipigs. Interventions: Inferior vena cava occlusion was performed to simultaneously obtain parameters of the LV flow-area relationship and the LV pressure-area relationship. Measurements and Main Results: Parameters were obtained at baseline and during sequential administration of dobutamine (5 μg/kg/min) and halothane (0.8 vol%). Linear regression analysis and analysis of variance were performed to investigate an underlying linear relationship between the corresponding variables. Highly linear elastance and PRSW curves were derived from the flow-area and pressure-area loops (n = 24, R ≥ 0.85). Changes of the curve slopes indicated inotropic changes as well as model independent dP/dt max. Elastance from the pressure-area relationship was expressed by elastance from the flow-area relationship by the term y = 0.52 + 0.04 · x ( R 2 = 0.84; p < 0.0001). Linear regression of PRSW as derived from the flow-area relationship with PRSW as derived from the pressure-area relationship was expressed by y = 0.43 + 0.02 · x ( R 2 = 0.77; p < 0.0001). Conclusion: Indices of the LV pressure-area relationship can be derived from real-time loops constructed from arterial flow velocity and LV area.