Differential Diagnosis for Syncope with Hypotension and Rash

Single Most Likely Diagnosis

• Cardiogenic Shock: Given the history of right ventricular (RV) infarct and the presentation of syncope with significantly low blood pressure (77/65), cardiogenic shock is a highly plausible diagnosis. The development of rashes could be secondary to poor perfusion or a manifestation of an allergic reaction to medications used in the management of the cardiac condition.

Other Likely Diagnoses

• Anaphylaxis: Although less likely than cardiogenic shock given the primary context, anaphylaxis can cause hypotension, syncope, and rash. It's essential to consider, especially if there's any history of allergy or recent exposure to potential allergens.
• Septic Shock: Infection leading to septic shock could present with hypotension, rash (if the cause is a specific infectious agent like meningococcus), and syncope. The history of RV infarct might not directly relate, but sepsis can lead to cardiac dysfunction.
• Vasovagal Syncope with Hypotension: While typically not associated with rash, a severe vasovagal episode could lead to prolonged hypotension and potentially a rash due to decreased perfusion.

Do Not Miss Diagnoses

• Pulmonary Embolism (PE): A history of RV infarct increases the risk of PE, which can cause syncope and hypotension. Although rash is not a typical presentation, it's crucial not to miss PE due to its high mortality rate if untreated.
• Aortic Dissection: Although more commonly associated with severe back or chest pain, an aortic dissection can lead to syncope, hypotension, and potentially a rash if there's involvement of peripheral arteries. Given the catastrophic nature of this condition, it must be considered.
• Cardiac Tamponade: This condition, which can be a complication of RV infarct, leads to impaired cardiac filling, resulting in hypotension and potentially syncope. A rash could be seen in the context of decreased perfusion.

Rare Diagnoses

• Stevens-Johnson Syndrome/Toxic Epidermal Necrolysis (SJS/TEN): These are severe skin conditions usually triggered by medications or infections, leading to rash and potentially life-threatening complications, including hypotension and syncope due to fluid loss and systemic inflammation.
• Neurocardiogenic Syncope with Atypical Presentation: While typically characterized by a prodrome and brief loss of consciousness, atypical presentations could include prolonged hypotension and rash due to autonomic dysfunction.