Doppler echocardiography . resistance to oxygen assessed by pulsed Responsiveness of raised pulmonary vascular

Objective-To assess whether changes in Doppler echocardiographic indices in the pulmonary artery correlated with changes in pulmonary vascular resistance. Design-Acceleration time, ejection time, maximal flow velocity, and velocity time integrals were measured at the same time as pressure and oxygen saturationt measurements in room air and during 10 minutes of oxygen breathing in the catheterisation laboratory. Pulmonary vascular resistance and pulmonary blood flow (Qp) were calculated from catheterisation data by use of the Fick principle. Patients-14 consecutive patients with a congenital heart defect and a left to right shunt associated with raised pulmonary artery pressure who underwent routine diagnostic cardiac catheterisation to assess their pulmonary vascular resistance. Results-Though pulmonary vascular resistance and systolic pulmonary artery pressure fell significantly during oxygen administration, there was no significant change in the acceleration time or ejection time. Peak velocity increased significantly during oxygen administration. During oxygen breathing Doppler derived measurements of pulmonary flow showed a significant increase in Qp similar to the increase in Qp measured by the Fick principle. There was io significant correlation between the fall in pulmonary vascular resistance and the increase in acceleration time or ejection time, increase in peak velocity, increase in pulmonary artery diameter, or increase in Doppler derived pulmonary blood flow. Conclusions-Measurements of acceleration and ejection time by Doppler echocardiography did not predict the response of pulmonary artery pressure and resistance to oxygen. Though changes in maximal flow velocity across the pulmonary artery and in Doppler derived pulmonary blood flow measurements became significant during oxygen breathing, the correlation of these changes with fall in pulmonary vascular resistance was poor. A prolonged increase in pulmonary artery flow and pressure can lead to the development of irreversible pulmonary vascular disease especially in children with large interventricular communications.' To judge soperability the standard technique is to measure pulmonary artery pressure and calculate pulmonary vascular resistance by the Fick method 'in the catheterisation laboratory."2 Recently several studies have indicated that analysis of the pulmonary artery flow velocity profile by Doppler echocardiography may be a valuable non-invasive means of evaluating pulmonary artery pressure.5 We evaluated the usefulness of Doppler echocardiography in assessing changes in pulmonary artery pressure and resistance after oxygen administration by comparing Doppler derived indices with simultaneous measurement of pulmonary artery pressure and calculation of pulmonary vascular resistance by the Fick principle during cardiac catheterisation. Patients and methods STUDY GROUP AND PATIENT SELECTION We studied 14 children. All had raised pulmonary artery pressure as part of their congenital heart defect. Table 1 lists the diagnoses. Six children (patients 3, 5, 6, 7, 10 and 13) had Down's syndrome. Because sedated patients, especially those with Down's syndrome, can have altered pulmonary vascular resistance because of hypercapnia or acidosis,2 we included only patients with a Pco2 of < 50 and a pH of > 7 34. Because pulmonary vascular resistance varies spontaneously by up to 36% from day to day,6 we only analysed data from patients whose change in pulmonary vascular resistance exceeded 40%. Table 1 Clinical data on 14 patients with pulmonary artery hypertension Age at time Patient Diagnosis of study (yr) 1 VSD, coarctation of the aorta 3-3 2 AVSD 05 3 AVSD 84 4 VSD 0-4 5 VSD 1-5 6 AVSD 05 7 AVSD 0-5 8 Mitral stenosis, subaortic stenosis, 0-8 coarctation of the aorta 9 VSD 09 10 AVSD 11 11 VSD 0-2 12 VSD, coarctation of the aorta 06 13 AVSD 02