Kathleen Tomsin

Role of dysfunctional maternal venous hemodynamics in the pathophysiology of pre-eclampsia: a review

The venous compartment has an important function in regulation and control of cardiac output. Abnormalities of cardiac output have been found in early gestational stages of both early‐ and late‐onset pre‐eclampsia. The venous compartment also maintains the balance between circulating and non‐circulating blood volumes and regulates the amount of reserve blood stored in the splanchnic venous bed. It is well known that adaptive regulation of maternal blood volume is disturbed in pre‐eclampsia. Abnormal venous hemodynamics and venous congestion are responsible for secondary dysfunction of several organs, such as the kidneys in cardiorenal syndrome and the liver in cardiac cirrhosis. Renal and liver dysfunctions are among the most relevant clinical features of pre‐eclampsia.

Impedance cardiography in uncomplicated pregnancy and pre-eclampsia: A reliability study

It has been reported that cardiac contractility is altered in pre-eclampsia compared with normal pregnancy. Because of the non-invasive nature of impedance cardiography (ICG), this method is gaining popularity in the obstetric field. We assessed the reliability of ICG measurements in uncomplicated 3rd trimester pregnancies (UP) and pre-eclamptic pregnancies (PE). ICG measurements were recorded before and after three position changes, and this examination was done twice (session 1 and 2) per subject. For each of the 22 haemodynamic parameters, inter- and intrasession Pearsons correlation coefficients (PCC) were calculated for mean values of 30 measurements per position per subject. PCC was consistently ≥ 0.80 for contractility parameters ‘acceleration-’, ‘velocity-’ and ‘heather-index’ in both UP and PE. These data illustrate that correlation between repeated ICG measurements of cardiac contractility is high under standardised conditions, and that ICG may be useful to study changes of cardiac contractility in pregnancy.

Maternal renal interlobar vein impedance index is higher in early- than in late-onset pre-eclampsia

To test the hypothesis that Doppler characteristics of maternal renal interlobar veins (RIV) are different between pregnancies affected by early‐onset pre‐eclampsia (EP) and those affected by late‐onset pre‐eclampsia (LP).

Diurnal and position-induced variability of impedance cardiography measurements in healthy subjects

Cardiovascular (CV) parameters and their measurements are subject to variation. In this study, we evaluated the reproducibility of impedance cardiography (ICG) measurements following orthostatic and diurnal challenges for a set of 22 CV parameters in ten randomly selected healthy nonpregnant women. A standard protocol was used to record a consecutive series of measurements for each parameter before and after three position changes. This series of measurements was performed twice (AM and PM sessions). For each parameter, measurement‐shift following position change was evaluated at 5% cutoff and compared between sessions. Intra‐ and intersession intraclass correlation (ICC) was calculated for individual measurements per position using repeated‐measures analysis of variance. Intra‐ and intersession Pearson’s correlation coefficient (PCC) was calculated for mean values per position. Intersession correlation for measurement‐shift following position change was 0·42 (5/12) for pressure parameters, whereas this was 0·96 (52/54) for other parameters. Inter‐ and intrasession ICC for individual measurements varied between 0·02 and 1 for all parameters, however inter‐ and intrasession PCC for mean values was consistently >0·80 for stroke volume (SV), stroke index (SI), cardiac output (CO), acceleration and velocity index (ACI and VI), thoracic fluid content (TFC), TFC index (TFCI) and heart period duration (HPD). We conclude that in healthy subjects under standardised conditions, reproducibility of means of multiple ICG measurements is high for SV, SI, CO, ACI, VI, TFC, TFCI and HPD. From our data, we cannot draw conclusions on trends in diseased subjects.

Venous Pulse Transit Time in Normal Pregnancy and Preeclampsia

Uncomplicated pregnancies (n = 16) were evaluated longitudinally and compared to early- (n = 12) and late-onset (n = 14) preeclampsia patients, assessed once at diagnosis. Pulse transit time (PTT), equivalent to pulse wave velocity, was measured as the time interval between corresponding characteristics of electrocardiography and Doppler waves, corrected for heart rate, at the level of renal interlobar veins, hepatic veins, and arcuate branches of uterine arteries. Impedance cardiography was used to measure PTT at the level of the thoracic aorta. In normal pregnancy, all PTT increased gradually (P ≤ .01). Pulse transit time was shorter in late-onset preeclampsia (P < .05) and also in early-onset preeclampsia, with exception for hepatic veins and thoracic aorta (P > .05). Our results indicate that PTT is an easy and highly accessible measure for vascular reactivity at both arterial and venous sites of the circulation. Our observations correlate well with known gestational cardiovascular adaptation mechanisms. This suggests that PTT could be used as a new parameter in the evaluation and prediction of preeclampsia.

Non-invasive assessment of gestational hemodynamics: benefits and limitations of impedance cardiography versus other techniques

To obtain data for maternal stroke volume and cardiac output during pregnancy, it is preferable to use a non-invasive, accurate and reproducible method. In this aspect, impedance cardiography is an excellent technique which is also highly accessible and easy to perform. This paper is a comprehensive review on the published literature about impedance cardiography and highlights the strengths and limitations of its applications in obstetrics.

Maternal venous Doppler characteristics are abnormal in pre‐eclampsia but not in gestational hypertension

To compare functional characteristics of maternal thoraco‐abdominal arteries and veins in proteinuric and non‐proteinuric hypertension in pregnancy.

Intra-Abdominal Pressure Measurements in Term Pregnancy and Postpartum: An Observational Study

Objective To determine intra-abdominal pressure (IAP) and to evaluate the reproducibility of IAP-measurements using the Foley Manometer Low Volume (FMLV) in term uncomplicated pregnancies before and after caesarean section (CS), relative to two different reference points and to non-pregnant values. Design Observational cohort study. Setting Secondary level referral center for feto-maternal medicine. Population Term uncomplicated pregnant women as the case-group and non-pregnant patients undergoing a laparoscopic assisted vaginal hysterectomy (LAVH) as control group. Methods IAP was measured in 23 term pregnant patients, before and after CS and in 27 women immediately after and 1 day after LAVH. The midaxillary line was used as zero-reference (IAPMAL) in all patients and in 13 CS and 13 LAVH patients, the symphysis pubis (IAPSP) was evaluated as additional zero-reference. Intraobserver correlation (ICC) was calculated for each zero-reference. Paired students t-tests were performed to compare IAP values and Pearsons correlation was used to assess correlations between IAP and gestational variables. Main outcome measures ICC before and after surgery, IAP before and after CS, IAP after CS and LAVH. Results The ICC for IAPMAL before CS was lower than after (0.71 versus 0.87). Both mean IAPMAL and IAPSP were significantly higher before CS than after: 14.0±2.6 mmHg versus 9.8±3.0 mmHg (p<0.0001) and 8.2±2.5 mmHg versus 3.5±1.9 mmHg (p = 0.010), respectively. After CS, IAP was not different from values measured in the LAVH-group. Conclusion IAP-measurements using FMLV is reproducible in pregnant women. Before CS, IAP is increased in the range of intra-abdominal hypertension for non-pregnant individuals. IAP significantly decreases to normal values after delivery.

Characteristics of heart, arteries, and veins in low and high cardiac output preeclampsia.

OBJECTIVE To assess the feasibility of non-invasive measurements of maternal cardiac output in relation to birth weight percentile and cardiovascular physiology in preeclampsia. STUDY DESIGN In a cohort of 62 women with preeclampsia, impedance cardiography was used to measure cardiac output and to evaluate heart and arteries. Venous characteristics were assessed by combined electrocardiogram-Doppler ultrasonography. Statistical differences were evaluated by Mann-Whitney U-tests. RESULTS Cardiac output correlated with birth weight percentile (P=.002), with more small for gestational age newborns in low cardiac output preeclampsia (<7.5L/min) than in high cardiac output preeclampsia (≥8.9L/min) (12/29 vs. 2/16, P=.044). This was associated with lower aortic flow indices and shorter venous pulse transit times in low than in high cardiac output preeclampsia. CONCLUSION Non-invasive impedance cardiography measurements of maternal cardiac output correlate with birth weight percentile and are associated with different functionality of heart, arteries, and veins in low and high cardiac output preeclampsia.

Non-invasive cardiovascular profiling using combined electrocardiogram–Doppler ultrasonography and impedance cardiography: An experimental approach

In the present study, the feasibility of cardiovascular profiling using both combined electrocardiogram (ECG)–Doppler ultrasonography and impedance cardiography (ICG) was evaluated. Fourteen non‐pregnant healthy women received 500 mL saline solution (NaCl 0.9% at 999 mL/h) intravenously by steady state infusion. Before and after this acute volume loading, we measured orthostatic‐challenged cardiac and arterial characteristics using ICG and assessed venous characteristics by combined ECG–Doppler before and during the Valsalva manoeuvre. Changes are expressed as the mean ± SEM and were evaluated by the one‐sample Wilcoxon signed‐rank test. After volume loading, the observed fall in stroke volume after postural change from supine to standing decreased (–14 ± 3 vs –23 ± 2%; P = 0.011). Hepatic A wave velocity increased 63 ± 28% after volume loading (P = 0.007) and decreased during the Valsalva manoeuvre (–205 ± 21%; P = 0.001). Volume loading raised the thoracic fluid content index in both the supine and standing positions (7 ± 2% and 10 ± 1%, respectively; P ≤ 0.014). Combined ECG–Doppler ultrasonography and ICG enables the non‐invasive identification of concomitant haemodynamic changes at the level of the heart, the arterial bed and the venous compartment. Our data support the view that non‐invasive cardiovascular profiling is feasible, which seems particularly useful for the evaluation of patients who are not critically ill, such as pregnant women.