Left atrial conduit function modulates right ventricular afterload, exercise capacity and survival in heart failure patients

AIMS: To assess if left atrial phasic function characteristics modulate functional capacity/survival by impacting on the pulsatile component of right ventricular (RV) afterload, as represented by pulmonary arterial compliance (PAC). MATERIALS AND METHODS: Sixty heart failure patients (67 ± 11 years, ejection fraction 39 ± 11%, range 20--62%) underwent 6 min walk test (6MWT) and 3D transthoracic echocardiography. Left atrial conduit was computed off-line, gathering simultaneous real-time 3D multibeats (six cycles) left atrial and left ventricular (LV) volume curves, with conduit (time) = LV (time) - LV minimum volume - left atrial maximum volume - left atrial (time), expressed as % LV stroke volume. Atrial stiffness (Kla) was computed using noninvasively assessed wedge pressure divided by left atrial reservoir (maximum - minimum) volume. PAC was obtained as ratio between RV stroke volume, obtained as pulsed Doppler RV outflow tract envelope∗cross-sectional area, and pulmonary pulse pressure, obtained by transforming tricuspid regurgitant velocity in millimetres of mercury and considering diastolic pulmonary as a fixed fraction of systolic 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 noninvasively assessed 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.