Differential Diagnosis for Syncopal Episode

The patient's presentation of recurrent syncope, bradycardia, and abnormal EKG findings suggests a cardiac origin. The following differential diagnoses are considered:

• Single most likely diagnosis
  • Sick Sinus Syndrome (SSS): The patient's EKG shows a prolonged P-R interval and dropped QRS, which, combined with the history of recurrent syncope and self-terminating runs of atrial fibrillation (a-fib), points towards SSS. The patient's age and smoking history also increase the likelihood of this condition.
• Other Likely diagnoses
  • Atrioventricular (AV) Block: The dropped QRS on the EKG suggests an AV block, which could be contributing to the patient's bradycardia and syncope.
  • Cardiac Amyloidosis: The elevated BNP (1870 pg/mL) and troponin (0.4) could indicate cardiac amyloidosis, especially in the context of recurrent syncope and abnormal EKG findings.
• Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
  • Myocardial Infarction (MI): Although the troponin is only slightly elevated (0.4), MI should always be considered in the differential diagnosis, especially given the patient's smoking history and age.
  • Pulmonary Embolism (PE): Although less likely, PE can cause syncope and should be considered, especially if there are other symptoms such as dyspnea or chest pain.
  • Hypothyroidism-related Cardiac Dysfunction: The elevated TSH (12.3) suggests hypothyroidism, which can contribute to cardiac dysfunction and arrhythmias.
• Rare diagnoses
  • Neurocardiogenic Syncope: Although less likely given the patient's age and EKG findings, neurocardiogenic syncope should be considered, especially if other cardiac causes are ruled out.
  • Arrhythmogenic Right Ventricular Cardiomyopathy (ARVC): This rare condition can cause syncope and arrhythmias, but it is less likely given the patient's age and presentation.