Differential Diagnosis for Palpitations during Exercise

The patient presents with palpitations during exercise that lasted for 30 minutes, prompting an ER visit. Despite normal EKG, bloodwork, and chest X-ray, several potential diagnoses should be considered.

• Single Most Likely Diagnosis
  • Anxiety or Stress-Related Palpitations: Given the normal diagnostic tests, anxiety or stress-induced palpitations are a common cause, especially if the patient has a history of anxiety or if the palpitations are triggered by physical exertion or emotional stress.
• Other Likely Diagnoses
  • Dehydration or Electrolyte Imbalance: Although bloodwork was normal, mild dehydration or electrolyte imbalances not severe enough to be detected on initial bloodwork could cause palpitations, especially during and after exercise.
  • Mitral Valve Prolapse: A condition where the two valve flaps of the mitral valve do not close smoothly or evenly but instead bulge (prolapse) upward into the left atrium when the heart contracts. It can cause palpitations and is often benign but can be a source of concern during exercise.
  • Supraventricular Tachycardia (SVT): A condition characterized by fast heart rhythms that originate above the ventricles. It can be triggered by exercise and may not always be caught on a single EKG if the patient is not experiencing the arrhythmia at the time of the test.
• Do Not Miss Diagnoses
  • Hypertrophic Cardiomyopathy (HCM): A condition where the heart muscle becomes thick, which can lead to obstruction of blood flow and increase the risk of sudden cardiac death, especially during intense physical activity. It's crucial to diagnose HCM due to its potential for severe outcomes.
  • Arrhythmogenic Right Ventricular Cardiomyopathy (ARVC): A rare heart condition where the muscle in the right ventricle is replaced by fat and scar tissue, potentially leading to life-threatening arrhythmias, particularly during exercise.
  • Long QT Syndrome: A disorder of the heart's electrical activity that can cause sudden, uncontrollable, dangerous arrhythmias. Exercise can trigger these arrhythmias, and a normal EKG at rest does not rule out the condition.
• Rare Diagnoses
  • Pheochromocytoma: A rare tumor of the adrenal gland that can cause episodes of palpitations, hypertension, and other symptoms due to excessive catecholamine release. It's rare but should be considered in the differential diagnosis due to its potential severity.
  • Thyroid Storm: A life-threatening condition that represents an extreme exacerbation of thyrotoxicosis, which can cause palpitations among other severe symptoms. Although rare, it's a critical diagnosis not to miss.

Each of these diagnoses requires careful consideration of the patient's history, physical examination, and potentially additional diagnostic testing to determine the underlying cause of the palpitations.