827 Patients with constrictive pericarditis (CP) exhibit a characteristic respiratory variation of their mitral valve (MV) and pulmonary venous (PV) flow velocities when assessed by Doppler echocardiography.Previous studies recognized the usefulness of this variation in differentiating CP from restrictive cardiomyopathy. 1-3 Although the extent of this variation (ie, percent change) is significantly higher in CP patients than in healthy persons, it follows the same pattern: a decrease in MV inflow and PV inflow velocities with inspiration and an increase with expiration.This pat- tern is determined by the direction of change in the intrathoracic pressure (ITP) during a particular phase of spontaneous breathing, that is, a decrement in ITP with inspiration and an increment with expiration. 3 The ITP changes associated with positive pressure ventilation (PPV) are in the opposite direction of those seen with spontaneous breathing. 4-8 Accordingly, PPV may have a different effect on the MV and PV flow velocities. This is important to recognize because noninvasive differentiation of CP from restrictive cardiomyopathy depends mainly on the pattern and magnitude of this variation. Making this distinction is crucial since CP can be cured surgically whereas restrictive cardiomyopathy cannot. The effect of PPV on the pattern and magnitude of respiratory variation of the mitral inflow and PV flow velocities in CP has not been described. Reversal of the Pattern of Respiratory Variation of Doppler Inflow Velocities in Constrictive Pericarditis During Mechanical Ventilation Ibrahim A. Abdalla, MD, R. Daniel Murray, PhD, Hamdy E. Awad, MD, William J. Stewart, MD, FACC, James D. Thomas, MD, FACC, and Allan L. Klein, MD, FACC, Cleveland, Ohio From the Section of Cardiovascular Imaging, Department of Cardiology, The Cleveland Clinic Foundation. Reprint requests: Allan L. Klein, MD, The Cleveland Clinic Foundation, Cardiology, Desk F-15, 9500 Euclid Avenue, Cleveland, OH 44195 (E-mail: kleina@ccf.org). Copyright © 2000 by the American Society of Echocardiography. 0894-7317/2000 $12.00 + 0 27/1/105336 doi:10.1067/mje.2000.105336 Background: Spontaneous inspiration causes a characteristic decrease of the mitral valve (MV) and pulmonary venous (PV) flow velocities obtained by Doppler echocardiography in patients with constrictive pericarditis (CP). This has been explained by the decrement it causes in the intra- thoracic pressure. Positive pressure ventilation (PPV) causes an increment of intrathoracic pressure with mechanical inspiration. Therefore the pattern of respiratory variation produced during PPV may differ from that seen during spontaneous breathing. Objective: Our goal was to describe the effect of PPV on the pattern and magnitude of respiratory variation of MV and PV flow velocities in CP. Methods: We performed intraoperative pulsed Doppler transesophageal echocardiography on 15 patients (13 men, mean age 52 ± 15 years) with CP after general anesthesia and before sternotomy and pericardial stripping. The peak velocity and time- velocity integral (TVI) of the mitral inflow E and A waves and the PV systolic and diastolic waves were measured at onset of inspiration and expiration for 3 to 6 respiratory cycles. Respiratory phase was monitored with a heat-sensitive nasal thermistor. The percent change in Doppler flow velocities from mechanical inspiration (INS) to mechanical expiration (EXP) was calculated with the formula %change = INS – EXP / INS × 100. Results: The peak velocity of the mitral inflow E wave was significantly higher during mechanical inspiration than expiration (57 ± 14.5 versus 47 ± 13.9 cm/s, P < .001). This represented a percent change of 18% ± 7.9% from expiration to inspiration. The mean TVI of the mitral inflow E was also higher during mechanical inspiration than expiration (P = .02). The peak velocity of the PV D wave was higher during mechanical inspiration than expiration (39 ± 17.8 versus 28 ± 14.7 cm/s, P < .001). This represented a mean percent change of 28% ± 13.8%. The mean value of the TVI for the PV D wave was also significantly greater during mechanical inspiration than expiration (P < .05). Conclusions: Positive pressure ventilation reverses the pattern of respiratory variation of the MV and PV flow velocities in CP. The percent change in the peak velocities of the MV and PV flows produced by PPV is the same range reported in CP during spontaneous breathing. (J Am Soc Echocardiogr 2000;13:827-31.)