REVIEW ARTICLE/BRIEF REVIEW • Echocardiography Findings in Amniotic Fluid Embolism: A Systematic Review of the Literature

INTRODUCTION

Amniotic fluid embolism (AFE) – one of the leading causes of maternal death in high-income countries – is a rare clinical syndrome reported to complicate one to eight per 100,000 pregnancies with a mortality rate between 20% and 60%.

Presentation includes profound maternal hypotension (with or without respiratory distress) and severe coagulopathy, often progressing to maternal cardiac arrest.

Point-of-care echocardiography has emerged as a valuable tool in the diagnostic algorithm of patients with hemodynamic instability or cardiac arrest, and several reports have suggested using echocardiography to both help identify and promptly manage AFE.

Therefore, the goal of this systematic review was to describe echocardiographic findings in patients with AFE who fulfilled established diagnostic criteria.

METHODS

Data sources and search strategy

Along with a medical librarian, a search strategy was developed where an electronic search was conducted from database inception to 20 November 2021 in Medical Literature Analysis and Retrieval System (MEDLINE) and Excerpta Medica Database (Embase).

The search strategy was adapted for each database based on its specific nomenclature. The search was restricted to articles written in English. There was no geographic location restriction.

Article selection and eligibility criteria

All case series or case reports of patients suspected of having AFE were screened, and disagreements were first resolved by discussion. If disagreement persisted, a third author was asked to independently review to achieve consensus. Full-text manuscripts were independently reviewed by two independent authors and disagreement was resolved by consensus.

All publications reporting AFE diagnosed by the United Kingdom Obstetrical Surveillance System (UKOSS), Japan, or USA criteria, and reporting echocardiography findings were included for analysis.

RESULTS

From the 2,636 publications were identified from MEDLINE and Embase, eighty-four cases from 80 publications were found to satisfy all inclusion and exclusion criteria.

Quality assessment using the JBI checklist for case series revealed that 15/84 (18%) of cases were considered to have a low risk of bias, whereas 24/84 (29%) and 45/84 (54%) had an intermediate and high risk of bias, respectively.

All patients (100%) met AFE criteria as defined by UKOSS, with 50/84 (60%) patients meeting the Japan criteria, and 36/84 (43%) meeting the USA criteria. Seven (9%) patients died, and 54/84 (64%) patients had a cardiac arrest. Perimortem Cesarean delivery was performed in 14 (17%) patients, and 18/84 (21%) required ECMO.

Most patients (55/82 with data, 67%) showed signs of RV involvement, including 11/82 (13%) patients who had biventricular failure. Left ventricular dysfunction was reported in 24/82 (29%) of patients, while 14/82 (17%) had normal function.

The echocardiography findings were not dependent on meeting one proposed AFE criteria over another.

When comparing patients who did not meet Japan or USA criteria with the patients meeting UKOSS criteria, there was no difference in the presence of RV dysfunction (P = 0.08), LV dysfunction (P = 0.69), or biventricular dysfunction (P = 0.96).

Right ventricular dysfunction was more frequent in patients who had a cardiac arrest and the presence of RV failure on univariate logistic regression was associated with both cardiac arrest and a composite outcome of cardiac arrest, maternal mortality, and the use of ECMO. Normal ventricular function was associated with a lower incidence of cardiac arrest.

Approximately, half (40/84, 48%) of echocardiograms were performed periresuscitation, defined as within one hour of the event; 5/84 (6%) were performed between one and six hours after the event, 11/84 (13%) occurred between six and 24 hr after the event, and 3/84 (4%) occurred at least 24 hr after the event. In nearly one third of cases (25/84, 29%), the timing of the echocardiogram was not specified.

Of the 26 patients who had a follow-up echocardiogram following clinical resolution of acute illness, 23 (88%) had resolution of ventricular dysfunction.

CONCLUSION

The authors concluded that right ventricular dysfunction is the most common finding in acute AFE and is associated with an increased risk of cardiac arrest.

They further commented that these findings further support the contemporary view of acute pulmonary hypertension and RV failure as the cause of cardiorespiratory collapse in AFE.

Finally, they believe that echocardiography may be useful to narrow the differential diagnosis in obstetrical shock, and to triage the highest risk AFE patients who may require more advanced hemodynamic support.