Differential Diagnosis for Substernal Chest Pain

Single Most Likely Diagnosis

• Acute Coronary Syndrome (ACS): The patient's symptoms of substernal chest pain radiating to the jaw, diaphoresis, nausea, and significant relief with nitroglycerin are classic for ACS. The elevated serum cardiac troponin I (0.20 ng/mL) and EKG changes (T-wave inversions in multiple leads) further support this diagnosis. The patient's history of type 2 diabetes mellitus and hyperlipidemia increases his risk for coronary artery disease.

Other Likely Diagnoses

• Hypertensive Emergency: The patient's blood pressure is significantly elevated (160/100 mm Hg), which could be contributing to his chest pain. Hypertensive emergencies can cause chest pain due to acute coronary syndrome, aortic dissection, or hypertensive cardiomyopathy.
• Gastroesophageal Reflux Disease (GERD): Although less likely given the response to nitroglycerin and EKG changes, GERD can cause substernal chest pain that radiates to the jaw and is exacerbated by lying down or eating certain foods.

Do Not Miss Diagnoses

• Aortic Dissection: Although the patient's symptoms and initial response to nitroglycerin suggest ACS, aortic dissection is a life-threatening condition that must be considered, especially given the patient's significantly elevated blood pressure. Aortic dissection can cause severe, tearing chest pain that radiates to the back or jaw.
• Pulmonary Embolism (PE): The patient's symptoms of chest pain and diaphoresis, along with a slightly elevated plasma D-dimer (0.15), necessitate consideration of PE, especially if there are other risk factors present (e.g., recent immobilization, family history of thrombophilia). However, the normal oxygen saturation and lack of other typical PE symptoms (e.g., dyspnea, tachypnea) make this less likely.
• Myocarditis or Pericarditis: These conditions can cause chest pain and EKG changes. Myocarditis might present with elevated troponins, while pericarditis typically has characteristic EKG findings (e.g., widespread ST elevation) and might not respond to nitroglycerin.

Rare Diagnoses

• Spontaneous Coronary Artery Dissection (SCAD): A rare cause of ACS, more common in younger women but can occur in anyone. It presents similarly to traditional ACS but is due to a tear in the coronary artery wall.
• Takotsubo Cardiomyopathy: Also known as "stress cardiomyopathy," this condition can mimic ACS with chest pain, EKG changes, and elevated troponins but is caused by extreme emotional or physical stress leading to transient left ventricular dysfunction.