Effects of acute intrathoracic pressure changes on left ventricular geometry and filling Acute changes in intrathoracic pressure (ITP) affect left ventricular (LV) function. It has been suggested that this functional impairment could be the result of an alteration in LV filling caused by a reduction in LV compliance induced by the rearrangement of biventricular geometry that occurs under these condttlons. Therefore, to evaluate the effects of an acute increase or decrease in ITP on LV geometry and filling, we used two-dimensional and Doppler echocardiography to study 25 normal volunteers both during the Miller maneuver (acute decrease in ITP induced by a forced inspiration agafnst a closed airway) and during continuous positive airway pressure breathing. During both maneuvers LV geometry was altered as demonstrated by the significant Increase in the normalized curvature radius of the interventricular septum and the unchanged curvature radius of the LV free wall. LV filling was altered during both maneuvers as demonstrated by significant decreases in early peak flow velocity, early-to-late peak flow velocity ratio, and early deceleration rate. Thus, during maneuvers that acutely decrease or increase ITP, alterations in LV geometry occur. These acute distortions of LV geometry may be one of the mechanisms responsible for alterations in LV filling. (AM HEART J 1988;116:455.) Sabino Iliceto, MD, Michele Dambrosio, MD, Margherita Sorino, MD, Gaetano D’Ambrosio, MD, Antonio Amico, MD, Tommaso Fiore, MD, and Paolo Rizzon, MD. Bari, Italy Acute changes in intrathoracic pressure (ITP) affect cardiac performance.1-s Left ventricular (LV) func- tional alterations occurring under these conditions have been attributed to several factors, such as decreased venous return to the left atrium,lO-lz car- diocirculatory reflexes, 13-15 decreased LV contractili- ty,16* l7 changes in LV afterload,‘, *, l8 and impaired LV filling after acute alterations in biventricular geom- etry.” 9.18-21 Although several investigators33 18, ls, 21 have suggested that changes in LV diastolic filling (after distortion of LV geometry induced by right ventricular loading) could be responsible for the impairment of LV function during acute changes in ITP, very little is known about the effects of these sudden changes on LV diastolic filling dynamics in humans, During acute right ventricular loading the alterations in LV geometry occur mainly in the short-axis plane s, 18-23; the interventricular septum (IVS) shifts leftward with a consequent decrease in septal-lateral diameter and an increase or no change in the anterior-posterior diameter. Therefore, when From the Division of Cardiology and Institute of Anaesthesiology. Univer- sity of Bari. Received for publication Nov. 13, 1987; accepted March 7, 1988. Reprint requests: Sabino Iliceto, MD, Divisione di Cardiologia, Universit& di Bari Policlinico, 70124 Bari, Italia. these geometric alterations occur, commonly avail- able imaging techniques are of little value in the assessment of LV diastolic filling characteristics. Doppler two-dimensional echocardiography (2DE) enables the evaluation of flow velocity at any cardiac site. Previous investigators have shown that, in the absence of aortic regurgitation, transmitral blood flow velocity reflects the patterns of LV filling.24-26 Thus, being an expression of overall LV filling, Doppler evaluation of transmitral flow appears to be an ideal tool for the assessment of diastolic filling during maneuvers that acutely affect LV geometry. The purpose of this study was to evaluate the effects on LV geometry and diastolic tilling dynamics of acute right ventricular loading induced by sudden changes in ITP. We studied 25 healthy men by means of 2DE and Doppler tech- niques during the Miiller maneuver (acute decrease in ITP) and during continuous positive airway pres- sure (CPAP) breathing (acute increase in ITP). METHODS Twenty-five healthy male volunteers, aged 22 to 29 years (mean 26 years), entered this study. All subjects had normal clinical, ECG, and 2DE findings. The only criteri- on for admission to this study was the quality of the 2DE and Doppler examinations; all subjects underwent high- quality ultrasound studies at rest. 455