What is the best course of treatment for a pregnant woman experiencing dizziness, bradycardia, and a mild heart problem, specifically regarding oxygen supplementation?

Management of Oxygen Supplementation in a Pregnant Woman with Dizziness, Bradycardia, and Mild Heart Problem

Oxygen supplementation should only be administered if documented hypoxemia is present (SpO2 <94%), as routine oxygen use during pregnancy without hypoxemia has no proven benefit and may cause fetal harm. 1

Initial Assessment and Positioning

First, immediately position the patient in full left lateral position or use left lateral tilt to relieve potential aortocaval compression, which can cause symptomatic bradycardia and dizziness in pregnant women, particularly if beyond 20 weeks gestation 1. This simple maneuver addresses the supine hypotensive syndrome of pregnancy, where uterine compression of the inferior vena cava causes paradoxical sinus slowing and reduced cardiac output 1.

• Measure oxygen saturation immediately with pulse oximetry to determine if hypoxemia is actually present 1
• Assess hemodynamic stability by checking blood pressure and level of consciousness 2
• Obtain a 12-lead ECG to characterize the bradyarrhythmia 1

Oxygen Supplementation Decision Algorithm

If SpO2 ≥94%:

Do NOT administer supplemental oxygen. 1

• The BTS guidelines explicitly state that oxygen during pregnancy is only required when there is evidence of maternal hypoxemia (oxygen saturation <94%) 1
• There is weak evidence of harm to the fetus if supplemental oxygen is given for long periods during uncomplicated situations without documented hypoxemia 1
• The widespread past practice of routine oxygen supplementation during pregnancy has been abandoned due to lack of benefit 1

If SpO2 <94%:

Administer supplemental oxygen to achieve target saturation of 94-98%. 1

• Women with underlying hypoxemic conditions (such as heart failure) should receive supplemental oxygen to achieve 94-98% saturation 1
• Use the lowest flow rate necessary to achieve target saturation 1
• If the patient has risk factors for hypercapnic respiratory failure (such as severe COPD), adjust target to 88-92% instead 1

Management of Bradycardia

Bradyarrhythmias in pregnancy usually have a favorable outcome in the absence of underlying structural heart disease. 1

Immediate Management:

• If symptomatic bradycardia persists after left lateral positioning, consider temporary pacing rather than pharmacologic intervention 1
• Asymptomatic bradyarrhythmias may become symptomatic due to increased cardiac output demands in patients with structural heart disease, but typically do not require intervention 1

When to Consider Pacing:

• Temporary pacing during delivery is recommended in selected women with complete heart block and symptoms due to risk of bradycardia and syncope 1
• For persistent symptomatic bradycardia unresponsive to positioning, temporary pacemaker placement may be necessary 1

Critical Pitfalls to Avoid

Do not routinely administer oxygen without documented hypoxemia, as this delays recognition of respiratory problems and may harm the fetus 1. The key error is assuming oxygen is beneficial when it is not indicated.

Do not keep the patient supine if beyond 20 weeks gestation, as this can worsen both bradycardia and hypotension through aortocaval compression 1. Positioning is often therapeutic by itself.

Do not assume bradycardia requires immediate pharmacologic treatment—most bradyarrhythmias in pregnancy without structural heart disease have favorable outcomes and resolve with conservative management 1.

Monitoring and Follow-up

• If oxygen is administered, measure arterial blood gases if prolonged administration is required to assess for hypercapnia 1
• Continuous fetal monitoring is essential if maternal hypoxemia or hemodynamic instability is present 2
• Evaluate for underlying structural heart disease with echocardiography if bradyarrhythmia is documented 2
• Consider Holter monitoring if symptoms persist to characterize the arrhythmia 2