Differential Diagnosis for 18yo Male with Syncopal Episode and Low Exercise Tolerance

The patient's presentation of a syncopal episode during physical exertion, long-standing low exercise tolerance, occasional ankle swelling, orthopnea, and mild cardiomegaly on chest X-ray suggests a cardiac etiology. The following differential diagnoses are categorized based on their likelihood and potential impact:

• Single Most Likely Diagnosis

  • Hypertrophic Cardiomyopathy (HCM): This condition is a leading cause of sudden cardiac death in young athletes. The patient's symptoms of low exercise tolerance, syncopal episode during exertion, and the presence of mild cardiomegaly are consistent with HCM. The normal blood pressure and elevated heart rate at rest also support this diagnosis, as patients with HCM may have a resting tachycardia.

• Other Likely Diagnoses

  • Dilated Cardiomyopathy: This condition could explain the patient's symptoms of low exercise tolerance, orthopnea, and mild cardiomegaly. However, it is less likely to cause a syncopal episode during exertion compared to HCM.
  • Arrhythmogenic Right Ventricular Cardiomyopathy (ARVC): This rare condition could also lead to syncopal episodes during exertion and has been associated with sudden cardiac death in young athletes. The patient's symptoms and family history (if available) would help in assessing the likelihood of this diagnosis.

• Do Not Miss Diagnoses

  • Aortic Stenosis: Although less common in young individuals, severe aortic stenosis can cause syncope during exertion due to the fixed cardiac output. It is crucial to assess for signs of aortic stenosis, such as a systolic ejection murmur.
  • Long QT Syndrome: This condition can cause syncope and sudden cardiac death, especially during physical exertion or emotional stress. An ECG would be essential to diagnose this condition.
  • Pulmonary Embolism: Although less likely given the chronic nature of the patient's symptoms, a pulmonary embolism could cause syncope, orthopnea, and tachycardia. It is essential to consider this diagnosis, especially if there are risk factors for thromboembolism.

• Rare Diagnoses

  • Restrictive Cardiomyopathy: This condition could explain the patient's symptoms of low exercise tolerance and orthopnea but is less common and would require further evaluation, including echocardiography and potentially cardiac MRI.
  • Congenital Heart Disease: Certain types of congenital heart disease, such as uncorrected or partially corrected defects, could lead to the patient's symptoms. However, these would typically be diagnosed earlier in life unless they are mild or asymptomatic until later.