13 weeks' gestation • heart palpitations • chest tightness • Dx?

Physical exam findings are often unremarkable unless the patient is actively experiencing SVT in the office, in which case prominent jugular pulsations may be seen due to simultaneous contraction of the atria and ventricles.

The initial evaluation of a pregnant patient presenting with tachycardia should include a BMP, TSH, 12-lead EKG, and transthoracic echocardiography.^3,5 In most patients with AVNRT, the results of these tests will be normal. A Holter monitor can be used to document an arrhythmia if the episodes are relatively frequent or an event monitor can be used if the episodes are infrequent.⁵

EKG findings. When patients are actively experiencing SVT, EKG findings include a P wave obscured by the QRS complex, sometimes manifesting as a pseudo-R wave in the V1 lead and a pseudo-S wave in leads II, III, and AVF. The QRS complex is narrow and the R-R interval is regular.⁶

Types of treatment

Valsalva maneuvers. Treatment of AVNRT in pregnancy should first involve addressing any precipitating causes, including metabolic and endocrine abnormalities.³ As virtually all antiarrhythmic drugs cross the placenta and are traceable in breast milk,^2,3 patients should be counseled to try to stop episodes using Valsalva maneuvers before moving to pharmacologic treatment.

Antiarrhythmics. First-line pharmacologic treatment for the prevention of AVNRT in pregnancy is metoprolol or verapamil.^2,5 Neither drug has been associated with adverse outcomes in infants, although there is a large body of evidence suggesting that low levels of metoprolol are present in breast milk.⁷

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