Assessing maternal cardiac function by obstetricians: technique and reference ranges.

BACKGROUND: A strong body of evidence has now coalesced indicating that some obstetrical syndromes may result from maladaptive responses of the maternal cardiovascular system. Longitudinal studies have shown that these changes are complex and present before the clinical recognition of preeclampsia and fetal growth restriction, suggesting that hemodynamic maladaptation may play an etiologic role in obstetrical complications. Chronic hypertension is one of the most frequent complications of pregnancy, and recent evidence suggests that control of mild hypertension in early pregnancy improves outcome. The management of chronic hypertension can be improved by understanding specific cardiovascular hemodynamic abnormalities such as increased cardiac output or increased systemic vascular resistance, which can respond to either beta or calcium channel blockers, depending on the hemodynamic findings. Evaluation of maternal cardiac function has not been previously available to obstetrical healthcare providers using diagnostic ultrasound equipment used for fetal evaluation. OBJECTIVE: Obstetrical ultrasound machines may be configured for various probes (endovaginal, abdominal, 3D/4D, and cardiac). This study used a cardiac probe placed in the suprasternal notch to image and measure the descending aorta diameter and the velocity time integral using pulsed and continuous wave Doppler ultrasound in normal pregnant women between 11 and 39 weeks of gestation. These measurements were followed by computation of maternal left ventricular preload, afterload, contractility, and blood flow. STUDY DESIGN: This was a prospective cross-sectional study. A total of 400 pregnant women were recruited between 11 and 39 weeks of gestation. Imaging of the maternal aortic arch was performed by placing a cardiac probe in the suprasternal notch to identify the aortic arch using 2D and color Doppler ultrasound. The end-systolic diameter of the aorta was measured at the junction of the left subclavian artery with the descending aorta, which was followed by insonation of the descending aorta to obtain the Doppler waveform. Following insonation of the descending aorta, measurements of the aortic diameter, velocity time integral, ejection time, mean pressure gradient, heart rate, maternal weight and height, and systolic and diastolic blood pressures were entered into an Excel spreadsheet to compute the following: (1) preload measurements of stroke volume, stroke volume index, and stroke work index; (2) afterload measurements of systemic vascular resistance and the potential-to-kinetic energy ratio; (3) contractility measurements of inotropy and the Smith-Madigan inotropy index; and (4) blood flow measurements of cardiac output and the cardiac output index. Fractional polynomial regression analysis was performed for each of the above measurements using gestational age as the independent variable. RESULTS: The diastolic and mean arterial blood pressure decreased from 11 to 18 weeks of gestation and then increased until term. The afterload measurements demonstrated similar characteristics, as all values decreased from 11 weeks until the mid and late second trimester, after which all values increased until term. Changes in contractility demonstrated an increase from 11 weeks to 25 to 28 weeks, followed by a decline until term. Changes in blood flow demonstrated an increase from 11 to 27 weeks and then declined until term. The continuous wave Doppler values were greater than the pulsed Doppler values except for the contractility measurements. Examples of abnormal cardiac measurements were identified in pregnant patients with hypertension and fetal growth restriction. An Excel calculator was created to provide quick computation of z-score measurements and their corresponding centiles described in this study. CONCLUSION: The technique for evaluation of maternal cardiac function described in this study would allow screening of maternal left ventricular preload, afterload, contractility, and blood flow in the obstetrical clinical milieu once a cardiac probe is acquired for obstetrical ultrasound machines used for fetal evaluation. The above measurements would allow the clinician to select appropriate hypertensive medication on the basis of the results of the evaluation of the maternal left ventricle.

Effect of Cardiac Phase on Cardiac Output Index Derived from Dynamic CT Myocardial Perfusion Imaging.

Purpose: The aortic time-enhancement curve obtained from dynamic CT myocardial perfusion imaging can be used to derive the cardiac output (CO) index based on the indicator dilution principle. The objective of this study was to investigate the effect of cardiac phase at which CT myocardial perfusion imaging is triggered on the CO index measurement with this approach. Methods: Electrocardiogram (ECG) gated myocardial perfusion imaging was performed on farm pigs with consecutive cardiac axial scans using a large-coverage CT scanner (Revolution, GE Healthcare) after intravenous contrast administration. Multiple sets of dynamic contrast-enhanced (DCE) cardiac images were reconstructed retrospectively from 30% to 80% R-R intervals with a 5% phase increment. The time-enhancement curve sampled from above the aortic orifice in each DCE image set was fitted with a modified gamma variate function (MGVF). The fitted curve was then normalized to the baseline data point unaffected by the streak artifact emanating from the contrast solution in the right heart chamber. The Stewart−Hamilton equation was used to calculate the CO index based on the integral of the fitted normalized aortic curve, and the results were compared among different cardiac phases. Results: The aortic time-enhancement curves sampled at different cardiac phases were different from each other, especially in the baseline portion of the curve where the effect of streak artifact was prominent. After properly normalizing and denoising with a MGVF, the integrals of the aortic curve were minimally different among cardiac phases (0.228 ± 0.001 Hounsfield Unit × second). The corresponding mean CO index was 4.031 ± 0.028 L/min. There were no statistical differences in either the integral of the aortic curve or CO index among different cardiac phases (p > 0.05 for all phases).

Assessing Patent Ductus Arteriosus (PDA) Significance on Cardiac Output by Whole-Body Bio-impedance.

We evaluated the effectiveness of a whole-body bioimpedance device (NICaS®, NI Medical, Petach Tikva, Israel) to predict the presence of a hemodynamically significant patent ductus arteriosus (PDA) in premature infants. A total of 36 infants less than 35 week's gestation age and birth weights of less than 1750 g were included in the study. Using the NICaS® device, we obtained whole-body bioimpedance measurements of stroke volume index (SI), cardiac output index (CI) and total peripheral resistance index. A total of 61 measurements were taken together with echocardiograph imaging. The study population was divided into three groups according to the echocardiograph results: group 1-small PDA, group 2-moderate PDA, and group 3-large PDA. Both SI and CI significantly increased from a median value of 22.6 ml/m2 and 3.4 l/min/m2 to 23.8 and 3.7, to 39.8 and 5.4 between groups 1, 2 and 3 respectively. The difference was statistically significant between groups 1 and 3 (P = 0.005 for SI and P = 0.002 for CI) and between groups 2 and 3 (P = 0.037 for SI and P = 0.05 for CI). We found statistically significant differences in SI and CI between infants with large PDAs and infants with no or small and medium PDAs. We suggest that these differences can be used in real time, in addition to echocardiography, in assessing the presence of significant PDAs.

[Effects of application of pulse contour cardiac output monitoring technology in early treatment of patients with large area burns].

Objective: To analyze the changes and relationship of early hemodynamic indexes of patients with large area burns monitored by pulse contour cardiac output (PiCCO) monitoring technology, so as to assess the guiding value of this technology in the treatment of patients with large area burns during shock period. Methods: Eighteen patients with large area burns, confirming to the study criteria, were admitted to our unit from May 2016 to May 2017. Pulse contour cardiac output index (PCCI), systemic vascular resistance index (SVRI), global end-diastolic volume index (GEDVI), and extravascular lung water index (EVLWI) of patients were monitored by PiCCO instrument from admission to post injury day (PID) 7, and they were calibrated and recorded once every four hours. The fluid infusion coefficients of patients at the first and second 24 hours post injury were calculated. The blood lactic acid values of patients from PID 1 to 7 were also recorded. The correlations among PCCI, SVRI, and GEDVI as well as the correlation between SVRI and blood lactic acid of these 18 patients were analyzed. Prognosis of patients were recorded. Data were processed with one-way analysis of variance, single sample ttest and Bonferroni correction, Pearson correlation analysis, and Spearman rank correlation analysis. Results: (1) There was statistically significant difference in PCCI value of patients from post injury hour (PIH) 4 to 168 (F=7.428, P<0.01). The PCCI values of patients at PIH 4, 8, 12, 16, 20, and 24 were (2.4±0.9), (2.6±1.2), (2.2±0.6), (2.6±0.7), (2.8±0.6), and (2.7±0.7) L·min(-1)·m(-2,) respectively, and they were significantly lower than the normal value 4 L·min(-1)·m(-2)(t=-3.143, -3.251, -11.511, -8.889, -6.735, -6.976, P<0.05 or P<0.01). At PIH 76, 80, 84, 88, 92, and 96, the PCCI values of patients were (4.9±1.5), (5.7±2.0), (5.9±1.7), (5.5±1.3), (5.3±1.1), and (4.9±1.4) L·min(-1)·m(-2,) respectively, and they were significantly higher than the normal value (t=2.277, 3.142, 4.050, 4.111, 4.128, 2.423, P<0.05 or P<0.01). The PCCI values of patients at other time points were close to normal value (P>0.05). (2) There was statistically significant difference in SVRI value of patients from PIH 4 to 168 (F=7.863, P<0.01). The SVRI values of patients at PIH 12, 16, 20, 24, and 28 were (2 298±747), (2 581±498), (2 705±780), (2 773±669), and (3 109±1 215) dyn·s·cm(-5)·m(2,) respectively, and they were significantly higher than the normal value 2 050 dyn·s·cm(-5)·m(2)(t=0.878, 3.370, 2.519, 3.747, 3.144, P<0.05 or P<0.01). At PIH 4, 8, 72, 76, 80, 84, 88, 92, and 96, the SVRI values of patients were (1 632±129), (2 012±896), (1 381±503), (1 180±378), (1 259±400), (1 376±483), (1 329±385), (1 410±370), and (1 346±346) dyn·s·cm(-5)·m(2,) respectively, and they were significantly lower than the normal value (t=-4.593, -0.112, -5.157, -8.905, -7.914, -5.226, -6.756, -6.233, -7.038, P<0.01). The SVRI values of patients at other time points were close to normal value (P>0.05). (3) There was no statistically significant difference in the GEDVI values of patients from PIH 4 to 168 (F=0.704, P>0.05). The GEDVI values of patients at PIH 8, 12, 16, 20, and 24 were significantly lower than normal value (t=-3.112, -3.554, -2.969, -2.450, -2.476, P<0.05). The GEDVI values of patients at other time points were close to normal value (P>0.05). (4) There was statistically significant difference in EVLWI value of patients from PIH 4 to 168 (F=1.859, P<0.01). The EVLWI values of patients at PIH 16, 20, 24, 28, 32, 36, and 40 were significantly higher than normal value (t=4.386, 3.335, 6.363, 4.391, 7.513, 5.392, 5.642, P<0.01). The EVLWI values of patients at other time points were close to normal value (P>0.05). (5) The fluid infusion coefficients of patients at the first and second 24 hours post injury were 1.90 and 1.39, respectively. The blood lactic acid values of patients from PID 1 to 7 were 7.99, 5.21, 4.57, 4.26, 2.54, 3.13, and 3.20 mmol/L, respectively, showing a declined tendency. (6) There was obvious negative correlation between PCCI and SVRI (r=-0.528, P<0.01). There was obvious positive correlation between GEDVI and PCCI (r=0.577, P<0.01). There was no obvious correlation between GEDVI and SVRI (r=0.081, P>0.05). There was obvious positive correlation between blood lactic acid and SVRI (r=0.878, P<0.01). (7) All patients were cured except the one who abandoned treatment. Conclusions: PiCCO monitoring technology can monitor the changes of early hemodynamic indexes and volume of burn patients dynamically, continuously, and conveniently, and provide valuable reference for early-stage comprehensive treatment like anti-shock of patients with large area burns.