In a second‑trimester pregnant woman with new‑onset orthostatic dizziness and an ordered electrocardiogram, what further evaluation and management should be pursued?

Evaluation of New-Onset Orthostatic Dizziness in Second-Trimester Pregnancy

Beyond the EKG, immediately obtain orthostatic vital signs (blood pressure and heart rate supine and after 1–3 minutes standing), order a Holter monitor to capture any paroxysmal arrhythmias, check a complete blood count to exclude anemia, assess thyroid function, and perform an echocardiogram if any arrhythmia is documented or if symptoms persist. 1, 2

Immediate Bedside Assessment

• Measure orthostatic vital signs by recording blood pressure and heart rate with the patient supine, then again after standing for 1–3 minutes. A drop in systolic blood pressure ≥20 mmHg or diastolic ≥10 mmHg, or a heart rate increase ≥30 bpm, confirms orthostatic hypotension. 1

• Position the patient in left lateral decubitus if she remains symptomatic, as this relieves inferior vena cava compression (supine hypotensive syndrome) that commonly causes dizziness and reflex bradycardia in pregnancy. 3, 1

• Assess hemodynamic stability by checking mental status, presence of chest pain, dyspnea, or signs of shock. If the patient is unstable with documented tachycardia, prepare for immediate electrical cardioversion. 2, 4

Essential Diagnostic Workup

Cardiac Monitoring

• Order a 24–48 hour Holter monitor to detect paroxysmal arrhythmias, as supraventricular tachycardia occurs in 20–44% of pregnancies and may be intermittent. 1, 2

• Obtain a 12-lead ECG (in addition to the one already ordered) during any symptomatic episode to identify the arrhythmia type, look for pre-excitation patterns (delta waves suggesting Wolff-Parkinson-White syndrome), or detect conduction abnormalities such as first-degree or second-degree AV block. 1, 4

• Perform an echocardiogram if arrhythmias are documented on Holter monitoring or if symptoms persist, to exclude structural heart disease, peripartum cardiomyopathy, or valvular abnormalities. 1, 2

Laboratory Studies

• Check a complete blood count to rule out anemia, which is common in pregnancy and exacerbates orthostatic symptoms due to reduced oxygen-carrying capacity. 1

• Measure thyroid-stimulating hormone (TSH) and free T4 to exclude hyperthyroidism, as thyroid storm can precipitate atrial fibrillation or flutter with associated tachycardia and dizziness. 4

• Assess blood pressure to screen for preeclampsia (≥140/90 mmHg after 20 weeks gestation), which can present with dizziness, visual disturbances, or severe headache. 1

Critical Differential Diagnoses

Arrhythmias

• Supraventricular tachycardia (SVT) is the most common arrhythmia in pregnancy and can cause serious hemodynamic consequences for both mother and fetus if sustained. 3, 1

• Postural heart block is a rare but important cause of orthostatic dizziness; ambulatory monitoring is essential when conduction abnormalities are present on the baseline ECG. 5

• First-degree AV block is benign and common in pregnancy without structural heart disease, but second-degree or complete heart block warrants closer monitoring. 1

Pregnancy-Specific Conditions

• Supine hypotensive syndrome results from uterine compression of the inferior vena cava, causing decreased venous return and paradoxical sinus slowing; it resolves with left lateral positioning. 3, 1

• Peripartum cardiomyopathy should be ruled out in any pregnant woman with new-onset arrhythmias, particularly ventricular tachycardia, during the last 6 weeks of pregnancy or postpartum. 4

• Physiologic cardiovascular changes in pregnancy include a 40–50% increase in cardiac output, increased heart rate, and decreased vascular resistance, which can unmask underlying cardiac conditions. 6, 7

Management Based on Findings

If Arrhythmia is Documented

• For acute SVT termination, attempt vagal maneuvers (Valsalva, carotid massage) first, followed by intravenous adenosine 6 mg rapid push if vagal maneuvers fail, then intravenous metoprolol if adenosine is ineffective. 1, 2, 8

• For recurrent or symptomatic SVT, initiate prophylactic therapy with cardioselective beta-blockers (metoprolol 50–100 mg twice daily or propranolol 80–160 mg daily in long-acting form) after the first trimester. Avoid atenolol due to its association with fetal growth restriction. 1, 2

• Never use AV nodal blocking agents (adenosine, beta-blockers, calcium channel blockers, digoxin) if pre-excitation is present on the resting ECG, as this can precipitate ventricular fibrillation. 1, 4

If Orthostatic Hypotension is Confirmed

• Recommend non-pharmacologic measures including increased fluid intake (2–3 liters daily), increased salt intake (unless contraindicated by hypertension), compression stockings, and avoidance of prolonged standing. 1

• Consider midodrine (an alpha-1 agonist) for symptomatic orthostatic hypotension that is considerably impairing daily activities despite non-pharmacologic measures. Midodrine increases standing systolic blood pressure by 15–30 mmHg at 1 hour after a 10 mg dose. However, it can cause marked supine hypertension (>200 mmHg systolic), so use cautiously and monitor supine blood pressure. 9

When to Escalate Care

• Send to the emergency department immediately if the patient experiences recurrent episodes of dizziness with tachycardia, syncope or near-syncope, chest pain, dyspnea, or any signs of hemodynamic instability. 1, 2

• Refer to cardiology if Holter monitoring reveals sustained arrhythmias, if structural heart disease is found on echocardiography, or if symptoms persist despite initial management. 1

• Arrange continuous fetal monitoring during any arrhythmia episode, as maternal arrhythmias can cause fetal hypoperfusion. 4

Common Pitfalls to Avoid

• Do not dismiss orthostatic dizziness as "normal pregnancy changes" without proper evaluation, as it may represent serious arrhythmias or structural heart disease. 2

• Do not delay cardioversion in hemodynamically unstable patients due to pregnancy concerns; maternal stability is essential for fetal survival, and cardioversion is not contraindicated in pregnancy. 2, 8

• Do not use amiodarone except as a last resort due to fetal toxicity, including thyroid dysfunction and growth restriction. 2, 4