Modelflow: a new method for noninvasive assessment of cardiac output in pregnant women.

OBJECTIVE: Estimation of cardiac output by continuous finger arterial pressure waveform analysis with Modelflow is a noninvasive technique for beat-to-beat hemodynamic assessment. The purpose of this study was to compare this method in pregnant women with the more commonly used Doppler echocardiography. STUDY DESIGN: In 16 primigravid women, stroke volume was measured serially in first, second, and third trimester and after pregnancy by the Modelflow method and by Doppler echocardiography. Aortic diameter and compliance were assessed serially by echocardiography and pulse wave velocity measurements. RESULTS: Aortic compliance was increased significantly in pregnancy compared with nonpregnant values, but aortic diameter did not change. After adjustment for pregnancy-related changes in pulse wave velocity, blood pressure, and heart rate, Modelflow stroke volume measurements gave comparable results to Doppler echocardiography during and after pregnancy. The observed variation was similar to reported comparisons of Doppler echocardiography with thermodilution. CONCLUSION: After adjustment for pregnancy the Modelflow method is a useful research tool for assessment of stroke volume in pregnant women and offers the advantage of continuous measurement and convenience of application.

Non-invasive assessment of autonomic cardiovascular control in normal human pregnancy and pregnancy- associated hypertensive disorders: a review.

PURPOSE: Pre-eclampsia is a major complication of pregnancy. Although the disorder usually becomes apparent only in the third trimester of pregnancy, evidence is available that underlying pathophysiological abnormalities are already present early in pregnancy. The association between alterations in autonomic cardiovascular control and the development of hypertension in pregnancy has been investigated for some time. Non-invasive methods are especially of interest, since they have the advantage of minimal risk for the mother and the conceptus and enable repeated measurements during pregnancy. If non-invasive tests for autonomic cardiovascular control could demonstrate the increased sympathetic activity, as observed by microneurography than this method is a candidate for early identification of pre-eclampsia. Therefore, the literature on non-invasive testing of autonomic cardiovascular control in normal pregnancies and pre-eclampsia was summarized. DATA IDENTIFICATION AND SELECTION: Medline was searched and 36 articles on autonomic cardiovascular control in human pregnancy by non-invasive test methods were reviewed. For each test method, data of different studies were summarized to evaluate if the method could discriminate between healthy pregnancy and pre-eclampsia. CONCLUSION: Although small differences have been observed between normal pregnancy and pre-eclampsia in individual studies using non-invasive methods, the consistency in the available data is insufficient to discriminate between normal pregnancy and pre-eclampsia. The failure to demonstrate the increased sympathetic activity, as observed by direct microneurography, might be due to methodological factors of the non-invasive studies. Alternatively, sympathetic activity to resistance vessels in skeletal muscle may not be a proper reflection of autonomic cardiovascular control in pregnancy. Well-designed longitudinal research could be useful to test these suppositions.