Non-Invasive Pressure-Volume Analysis by Three-Dimensional Echocardiography: A Novel Powerful Method for Evaluating Left Ventricular Function

Pressure-volume (PV) analysis is the gold standard for evaluating left ventricular (LV) function but is rarely used clinically due to its invasiveness. We validated a non-invasive method for PV analysis by 3D echocardiography against invasive reference measurements and a novel index of LV efficiency against LV efficiency derived from metabolism by positron emission tomography-computed tomography (PET/CT). In 22 canines, LV volume was measured invasively using piezoelectric crystals and LV pressure by micromanometer. Echocardiography and peak pressure were used to obtain 3D LV volume traces and LV pressure trace estimates. Stroke work, single-beat contractility indices, arterial elastance and an index of LV efficiency were derived from echocardiography and compared with their invasively measured counterparts at baseline and different interventions. In 12 sheep, the LV efficiency index was compared with efficiency calculated as stroke work divided by total LV glucose metabolism from PET/CT. The sheep underwent 8 weeks of rapid dyssynchronous pacing to induce heart failure (HF). Recordings were performed during synchronous and dyssynchronous electrical activation, at baseline, and after 8 weeks pacing-induced HF. In canines, there was a very good correlation and agreement between non-invasive and invasive measurements of LV stroke work (r=0.98, P<0.0001; difference 237±212 mmHg×ml, mean±SD). The non-invasive and invasive efficiency indices also showed very good agreement (r=0.95, P<0.0001; difference 0.4±3.4%). The changes in LV function by the different interventions resulted in similar changes in the non-invasive and invasive PV indices (both P<0.005). In sheep, the efficiency index showed similar decline compared to efficiency by PET/CT after induction of HF and after switching from synchronous to dyssynchronous electrical activation (r=0.67, P<0.001 for all interventions). Non-invasive PV analysis by 3D echocardiography is feasible and accurate, making PV-loop parameters for evaluating LV function accessible for clinical use. Further studies should explore the clinical utility of this method.