Validation of a noninvasive cardiac output monitor in maternal cardiac disease: comparison of NICOM and transthoracic echocardiogram

BACKGROUND

The physiological changes to the cardiovascular system during pregnancy are considerable and are more pronounced in those with cardiac disease. In the general population, noninvasive hemodynamic monitoring is a valid alternative to pulmonary artery catheterization, which poses risk in the pregnant population. There is limited data on noninvasive cardiac output monitoring in pregnancy as an alternative to pulmonary artery catheterization.

OBJECTIVE

We sought to compare transthoracic echocardiography with a noninvasive cardiac output monitor (NICOM, Cheetah Medical) in pregnant patients with and without cardiac disease.

STUDY DESIGN

This was a prospective, open-label validation study that compared 2-dimensional transthoracic echocardiography with NICOM estimations of cardiac output in each trimester of pregnancy and the postpartum period. Participants with and without cardiac disease with a singleton gestation were included. NICOM estimations of cardiac output were derived from thoracic bioreactance and compared with 2-dimensional transthoracic echocardiography for both precision and accuracy. A mean percentage difference of ±30% between the 2 devices was considered acceptable agreement between the 2 measurement techniques.

RESULTS

A total of 58 subjects were enrolled; 36 did not have cardiac disease and 22 had cardiac disease. Heart rate measurements between the 2 devices were strongly correlated in both groups, whereas stroke volume and cardiac output measurements showed weak correlation. When comparing the techniques, the NICOM device overestimated cardiac output in the control group in all trimesters and the postpartum period (mean percentage differences were 50.3%, 52.7%, 48.1%, and 51.0% in the first, second, and third trimesters and the postpartum period, respectively). In the group with cardiac disease, the mean percentage differences were 31.9%, 29.7%, 19.6%, and 35.2% for the respective timepoints.

CONCLUSION

The NICOM device consistently overestimated cardiac output when compared with 2-dimensional transthoracic echocardiography at all timepoints in the control group and in the first trimester and postpartum period for the cardiovascular disease group. The physiological changes of pregnancy, specifically the mean chest circumference and total body water, may alter the accuracy of the cardiac output measurement by the NICOM device as they are currently estimated. Although NICOM has been validated for use in the critical care setting, there is insufficient data to support its use in pregnancy.

Nontraumatic Fat Embolism Found Following Maternal Death after Cesarean Delivery

Introduction Fat embolism is a rare form of nonthrombotic embolization. Limited literature exists regarding the diagnosis of fat embolism during the perinatal period. We present the first case of maternal death that resulted from nontraumatic fat embolization following Cesarean delivery. Case Description A 29-year-old gravida 1 with a complex medical and surgical history underwent a primary Cesarean delivery at term. On postoperative day 2 the patient was found to be unresponsive. Despite resuscitative efforts, the patient succumbed. Autopsy findings were remarkable for diffuse pulmonary fat emboli. Furthermore, there was no histological evidence of either amniotic fluid embolism or thromboembolism. The primary cause of death was attributed to nontraumatic fat embolization. Discussion Multiple risk factors may have contributed to the development of nontraumatic fat embolization in our patient. Obstetricians should maintain a high level of suspicion for nontraumatic fat embolization in cases of maternal respiratory decompression and sudden maternal mortality.