Left atrial conduit function: a Janus two-faced diastolic, powerful parameter

Heart failure (HF) is a frequent clinical condition in which the heart cannot guarantee an adequate cardiac output, or it can do that at the cost of increasing intra-cardiac pressures, causing symptoms, reduced quality of life and poor prognosis. Left atrial (LA) function has an underappreciated role in HF pathophysiology. Aim: to assess if a larger LA conduit contribution to the left ventricular (LV) filling was associated with a heavier pulmonary haemodynamic burden, and, consequently, with a reduced patients’ functional capacity and worse survival. Methods: 60 HF patients (67 ± 11 years, ejection fraction 39 ± 11%, range 20-62%) underwent 6 minute walk test (6MWT) and 3D transthoracic echocardiography. LA conduit was computed off-line,gathering simultaneous real-time 3D multibeats (six cycles)LA and LV volume curves, with conduit (time) = [LV volume(time) - LV minimum volume] - [LA maximum volume - LA volume(time)], and expressed as % LV stroke volume. Atrial stiffness (Kla) was computed using noninvasively assessed wedge pressure divided by LA reservoir (maximum - minimum) volume. Pulmonary arterial compliance (PAC), representing the pulsatile component of right ventricular (RV) afterload wasobtained as the ratio between RV stroke volume and noninvasively estimated pulmonary pulse pressure. Results: Conduit averaged 34±12%, PAC 3.1±1.1 ml/mmHg, 6MWT 404±154 m. Conduit was independent of LV volumes and ejection fraction, showing a direct dependence on noninvasive Kla (r=0.56; P <0.001). Dividing patients into tertiles according to 6MWT and to PAC, the largest conduit fraction was associated with the lowest functional capacity (P<0.001) and most deranged PAC (P<0.001), respectively, suggesting outmost RV haemodynamic burden. Tertiles of conduit predicted survival (P=0.01). Conclusion: conduit depends on Kla and appears to be increased in heart failure patients with lowest capacity and worst survival, likely as RV pulsatile afterload, as reflected by PAC, is highest in these individuals.