Differential Diagnosis for Recurrent SVT

Given the patient's symptoms and normal baseline tests, the differential diagnosis can be organized into the following categories:

• Single Most Likely Diagnosis
  • Vagal nerve stimulation: The patient's symptoms of SVT triggered by activities such as bending, burping, or swallowing suggest vagal nerve stimulation as the most likely cause. The vagus nerve can stimulate the heart, leading to SVT, and these activities can stimulate the vagus nerve.
• Other Likely Diagnoses
  • Esophageal irritation: Esophageal irritation or conditions such as gastroesophageal reflux disease (GERD) can stimulate the vagus nerve, leading to SVT. The proximity of the esophagus to the heart and the shared innervation make this a plausible cause.
  • Right atrial stimulation: Right atrial stimulation, possibly due to anatomic or functional abnormalities, can also lead to SVT. Although the echocardiogram is normal, subtle abnormalities may not be detected.
• Do Not Miss Diagnoses
  • Cardiac sarcoidosis: Although rare, cardiac sarcoidosis can cause SVT and may not be detected on baseline tests. It is essential to consider this diagnosis due to its potential severity and impact on treatment.
  • Hyperthyroidism: Despite a normal TSH, hyperthyroidism can cause SVT, and other thyroid function tests (e.g., free T4, free T3) may be abnormal. It is crucial to rule out hyperthyroidism due to its potential to cause severe cardiac complications.
• Rare Diagnoses
  • Intrinsic cardiac anomalies: Rare congenital or acquired cardiac anomalies, such as an accessory electrical pathway, can cause SVT. These conditions may not be detected on baseline tests and require further evaluation.
  • Autonomic dysfunction: Autonomic dysfunction, such as postural orthostatic tachycardia syndrome (POTS), can cause SVT and may be considered in patients with recurrent episodes.

To further evaluate the patient's condition, the following tests may be indicated:

• Electrophysiology study (EPS) to assess the heart's electrical conduction system and identify potential abnormalities
• Esophageal function tests (e.g., manometry, pH monitoring) to evaluate esophageal irritation or dysfunction
• Ambulatory monitoring (e.g., Holter monitor) to capture and analyze SVT episodes
• Additional thyroid function tests (e.g., free T4, free T3) to rule out hyperthyroidism
• Cardiac MRI or CT to evaluate for cardiac sarcoidosis or other intrinsic cardiac anomalies

These tests can help determine the underlying cause of the patient's SVT and guide treatment decisions.