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Obstructive sleep apnea is highly prevalent in patients with cardiovascular disease and has detrimental effects on systolic and diastolic function of the ventricles. In this research, the changes in strain (S) and strain rate (SR) during the performance of the Mueller maneuver (MM) in an effort to better understand how negative intrathoracic pressures affect ventricular mechanics.The MM was performed to maintain a target intrathoracic pressure of −40 mm Hg. Echocardiography was used to measure various parameters of cardiac structure and function. Myocardial deformation measurements were performed using tissue speckle tracking. Twenty-four healthy subjects (9 women; mean age, 30±6 years) were studied. Global left ventricular longitudinal S in systole and SR in early filling were significantly decreased during the MM (S: baseline, −17.0±1.6%; MM, −14.5±2.2%; P<0.0001, SR: baseline, 1.09±0.20 s−1; MM, 0.92±0.21 s−1; P=0.01). Global right ventricular longitudinal S was also significantly decreased during the MM (baseline, −22.0±3.1%; MM, −17.2±2.5%; P<0.0001), as was global right ventricular longitudinal systolic SR (baseline, −1.34±0.35 s−1; MM, −1.02±0.21 s−1; P=0.0006).Left ventricular and right ventricular longitudinal deformation are significantly reduced during the MM. These results suggest that negative intrathoracic pressure during apnea may contribute to changes in myocardial mechanics. These results could help explain the observed changes in left ventricular and right ventricular mechanics in patients with obstructive sleep apnea.