What is the differential diagnosis for chest tightness and tachycardia in a 39-week pregnant patient?

Differential Diagnosis: Chest Tightness and Tachycardia at 39 Weeks Gestation

The differential diagnosis for chest tightness and tachycardia in a 39-week pregnant patient must prioritize life-threatening cardiovascular and obstetric emergencies, with supraventricular tachycardia being the most common arrhythmic cause (occurring in 20-44% of pregnancies), followed by peripartum cardiomyopathy, pulmonary embolism, acute coronary syndrome, and aortic dissection. 1, 2

Cardiac Arrhythmias

Supraventricular Tachycardia (SVT)

• Most common pathologic arrhythmia in pregnancy, affecting 20-44% of pregnant patients, often presenting with sudden-onset palpitations, chest tightness, dizziness, and documented tachycardia (as in this case with pulse 119) 1, 3
• Pregnancy-related hormonal changes, increased catecholamines, and hemodynamic alterations directly promote arrhythmogenesis 4, 5
• Can cause hemodynamic compromise affecting both maternal and fetal perfusion if sustained 1, 6

Ventricular Tachycardia (VT)

• New-onset VT may present during pregnancy, particularly in the last 6 weeks, related to elevated catecholamines and underlying structural disease 4, 6
• Higher risk in patients with previous VT or structural heart disease 4
• Requires immediate differentiation from SVT as management differs significantly 4, 6

Atrial Fibrillation/Flutter

• Rare during pregnancy unless structural heart disease or hyperthyroidism present 6
• Poorly tolerated in pregnancy, particularly with congenital heart disease, causing potential fetal hypoperfusion 6

Structural Cardiac Conditions

Peripartum Cardiomyopathy

• Critical diagnosis to exclude: presents with new-onset heart failure during the last 6 weeks of pregnancy or postpartum, often manifesting with chest tightness, dyspnea, and arrhythmias including VT 4, 6, 7
• Associated with significantly increased mortality if tachycardia is present 7
• Can be misdiagnosed as simple tachycardia or anxiety 8

Tachycardia-Induced Cardiomyopathy

• Heart failure developing solely due to sustained tachycardia, potentially reversible with rate control 8
• Incidence unknown in pregnancy but represents a treatable cause of heart failure 8
• Requires rate control to prevent progression to irreversible cardiomyopathy 6

Acute Coronary Syndrome

• One of the most important causes of nonobstetric mortality in pregnancy 2
• Risk factors include advanced maternal age, hypertension, diabetes, smoking 2
• Presents with chest pain/tightness, often with associated tachycardia 2

Aortic Dissection

• Catastrophic cardiovascular event with poor maternal-fetal outcomes if not diagnosed promptly 2
• Presents with sudden-onset severe chest pain, often tearing quality, with tachycardia as compensatory response 2

Thromboembolic Disease

Pulmonary Embolism

• Leading cause of maternal mortality in developed countries 2
• Presents with chest tightness, dyspnea, tachycardia, and potential hemodynamic instability 7, 2
• Pregnancy is a hypercoagulable state with 5-fold increased VTE risk 2

Obstetric Complications

Obstetric Hemorrhage

• Can present with tachycardia as compensatory response to hypovolemia 7
• At 39 weeks, consider placental abruption, which may present with chest/abdominal pain and tachycardia 7

Preterm Labor

• Abdominal cramping at 39 weeks may represent early labor, with tachycardia from pain or anxiety 1

Metabolic/Endocrine Causes

Thyroid Storm

• Can precipitate atrial fibrillation or flutter with associated tachycardia, diaphoresis, and chest discomfort 6
• Hyperthyroidism exacerbates or causes arrhythmias in pregnancy 3, 5

Infectious Causes

Sepsis

• Presents with tachycardia, fever, and potential chest symptoms if pneumonia present 7
• Requires urgent identification and treatment 7

Benign Causes

Physiologic Sinus Tachycardia

• Most palpitations during pregnancy are benign, caused by normal physiologic changes including increased blood volume, cardiac output, and heart rate 4, 1
• Exacerbated by anxiety, dehydration, caffeine, or physical exertion 4, 5

Premature Atrial/Ventricular Contractions

• Common and usually benign in pregnancy 4, 5
• No treatment typically needed beyond reassurance and avoidance of stimulants 4, 5

Critical Pitfalls to Avoid

• Do not dismiss tachycardia as "normal pregnancy changes" without proper evaluation, as serious arrhythmias and structural disease can present similarly 1, 3
• Do not delay cardioversion in hemodynamically unstable patients due to pregnancy concerns; maternal stability is essential for fetal survival 6
• Do not use AV nodal blockers if pre-excitation present on ECG, as this can precipitate ventricular fibrillation 6
• Do not assume normal fetal heart rate excludes maternal cardiac pathology; independent maternal evaluation is mandatory 3