What is the appropriate emergency department workup for a 24‑week pregnant woman presenting with a near‑syncope episode?

Emergency Department Workup for Near-Syncope in a 24-Week Pregnant Woman

The ED workup for a 24-week pregnant woman with near-syncope should prioritize immediate positioning in left lateral decubitus, followed by a mandatory 12-lead ECG, orthostatic vital signs, and at least 4 hours of continuous fetal heart rate monitoring, with disposition determined by the presence or absence of high-risk cardiac features. 1, 2, 3

Immediate Management Upon Arrival

• Position the patient in left lateral decubitus immediately to relieve aortocaval compression from the gravid uterus, which is a pregnancy-specific cause of presyncope at 24 weeks gestation 1
• If left lateral positioning is not feasible, assist the patient to sit or lie down in any safe position within 1-2 minutes of arrival 1
• Administer supplemental oxygen to maintain maternal oxygen saturation >95% to ensure adequate fetal oxygenation 3
• Establish two large-bore (14-16 gauge) intravenous lines above the level of the diaphragm 3, 4

Risk Stratification and Activation Criteria

Activate emergency cardiology consultation immediately if any of the following high-risk features are present: 1, 2

• No improvement within 1-2 minutes of positioning or symptoms worsen 1
• Near-syncope occurred during exertion (suggests cardiac etiology) 2
• Palpitations preceding the episode 1
• History of structural heart disease or heart failure 1, 2
• Family history of sudden cardiac death 1, 2
• Symptoms suggesting myocardial infarction or stroke 1

Mandatory Diagnostic Testing

12-Lead ECG (Required for All Patients)

• Obtain a 12-lead ECG immediately as it is noninvasive, inexpensive, and can identify life-threatening conditions despite a low 5% overall yield 1, 2
• Specifically evaluate for: myocardial infarction or ischemia, arrhythmias or conduction abnormalities, prolonged QT interval, ventricular hypertrophy, and pre-excitation patterns 2

Orthostatic Vital Signs

• Measure blood pressure and heart rate in supine position, then after standing 1, 2
• Abnormal results are defined as: systolic BP drop >20 mmHg or heart rate increase >20 bpm 1, 2

Laboratory Testing

• Obtain routine blood work including a coagulation panel with fibrinogen level 3
• Serum fibrinogen <200 mg/dL is an adverse factor requiring extended monitoring 3

Fetal Assessment (Mandatory at 24 Weeks)

• Initiate continuous electronic fetal heart rate monitoring for at least 4 hours minimum 3, 4
• Perform fetal heart rate auscultation as soon as maternal stabilization is achieved 3
• Obtain urgent obstetrical ultrasound if gestational age is uncertain or if delivery may be anticipated 3

Disposition Algorithm

Safe for Discharge Criteria (All Must Be Present)

• No structural heart disease 1, 2
• Normal 12-lead ECG 1, 2
• Clinical features clearly suggesting vasovagal or orthostatic syncope 1, 2
• No high-risk features present 1
• Normal fetal heart rate monitoring for 4 hours 3
• No uterine tenderness, significant abdominal pain, or vaginal bleeding 3

Admission Criteria (Any One Present)

Admit for 24-hour observation if any of the following are present: 1, 2, 3

• Age >45 years 2
• History of congestive heart failure or ventricular arrhythmias 2
• Abnormal ECG 2
• Physical exam findings of heart failure 2
• Cardiac murmur suggesting outflow obstruction 2
• Uterine tenderness or significant abdominal pain 3
• Vaginal bleeding 3
• Sustained contractions (>1 per 10 minutes) 3
• Rupture of membranes 3
• Atypical or abnormal fetal heart rate pattern 3
• Serum fibrinogen <200 mg/dL 3

Additional Considerations

Pregnancy-Specific Etiologies to Consider

• Supine hypotensive syndrome (managed by left lateral positioning) 1
• Physiologic changes including increased cardiac output, decreased systemic vascular resistance, and aortocaval compression 2
• Common benign causes: vasovagal syncope and orthostatic hypotension 2
• Life-threatening causes to exclude: pulmonary embolism, cardiac arrhythmias, amniotic fluid embolism 2

Imaging Studies

• Do not defer or delay radiographic studies (including abdominal CT) if indicated for maternal evaluation due to concerns about fetal radiation exposure 3
• Focused abdominal sonography for trauma (FAST) should be considered if intraperitoneal bleeding is suspected 3

Rh Status Management

• Administer anti-D immunoglobulin to all Rh-negative pregnant trauma patients 3
• Perform Kleihauer-Betke testing in Rh-negative patients to quantify maternal-fetal hemorrhage and determine need for additional anti-D doses 3

Critical Pitfalls to Avoid

• Do not assume benign vasovagal syncope without obtaining a 12-lead ECG 1, 2
• Do not discharge patients with any high-risk features, even if symptoms have resolved 1, 2
• Do not delay fetal monitoring in viable pregnancies (≥23 weeks) 3
• Patients with 3-4 risk factors have a 57.6-80.4% risk of 1-year mortality or significant arrhythmia, while those with zero risk factors have 0% 72-hour cardiac mortality 2

Continuous Monitoring

• Continuous cardiac monitoring is appropriate for the first 24 hours if arrhythmia is suspected 2
• Arrange outpatient cardiology follow-up if any concerning features are present 2