The Mueller maneuver attenuates left atrial phasic volumes and myocardial strain in healthy younger adults

The left atrium (LA) is a key, but incompletely understood, modulator of left ventricular (LV) filling. Inspiratory negative intrathoracic pressure swings alter cardiac loading conditions, which may impact LA function. We studied acute effects of static inspiratory efforts on LA chamber function, LA myocardial strain, and LV diastolic filling. We included healthy adults (10M/9F, 24±4 years) and used Mueller maneuvers to reduce intrathoracic pressure to -30 cmH2O for 15 seconds. Over 6 repeated trials, we used echocardiography to acquire LA- and LV-focused 2D images, and mitral Doppler inflow and annular tissue velocity spectra. Images were analyzed for LA and LV chamber volumes, tissue relaxation velocities, trans-mitral filling velocities, and speckle-tracking derived LA longitudinal strain. Repeated measures were made at Baseline, Early Mueller, Late Mueller, then Early Release and Late Release. In the Late Mueller compared to Baseline, LV stroke volume decreased by -10±4 mL (P<0.05) then returned to Baseline upon release; this occurred with a -11±9 mL (P<0.05) end-diastolic volume reduction. Early diastolic LV filling was attenuated, reflected by decreased tissue relaxation velocity (-2±2 cm/s, P<0.05), E-wave filling velocity (-13±14 cm/s, P<0.05), and LA passive emptying volume (-5±5 mL, P<0.05), each returning to Baseline with release. LA maximal volume decreased (-5±5 mL, P<0.05) during the Mueller maneuver, but increased relative to Baseline following release (+4±5 mL, P<0.05), while LA peak positive longitudinal strain decreased (-6±6 %, P<0.05) then returned to Baseline. Attenuated LA and in turn LV filling may contribute to acute stroke volume reductions experienced during forceful inspiratory efforts.