Hypertrophic Cardiomyopathy (HCM): This condition is characterized by left ventricular hypertrophy, which can lead to chest pain due to increased oxygen demand and potential outflow tract obstruction. The combination of left hypertrophy and chest pain makes HCM a strong candidate for the single most likely diagnosis.

Coronary Artery Disease (CAD): Although CAD typically presents with symptoms related to ischemia, left ventricular hypertrophy can be a response to long-standing hypertension, a common risk factor for CAD. Chest pain in this context could be angina.
Aortic Stenosis: This valvular heart disease can cause left ventricular hypertrophy as the ventricle works harder to pump blood through the narrowed valve. Chest pain (angina) is a common symptom, along with syncope and heart failure symptoms.
Hypertension: Uncontrolled hypertension can lead to left ventricular hypertrophy. Chest pain could be related to hypertension itself or to associated conditions like coronary artery disease.

Aortic Dissection: Although less common, aortic dissection is a life-threatening condition that can cause chest pain and, if it involves the aortic root, could potentially lead to left ventricular hypertrophy due to associated aortic regurgitation or hypertension. Missing this diagnosis could be fatal.
Pulmonary Embolism: While not directly causing left hypertrophy, a large pulmonary embolism can lead to right heart strain and, in some cases, chest pain. The presence of left hypertrophy might be incidental, but the combination with chest pain warrants consideration of this potentially deadly condition.
Myocardial Infarction: Acute myocardial infarction can cause chest pain and, depending on the area of the heart affected, could potentially lead to changes in ventricular function or structure, including hypertrophy in the long term.

Fabry Disease: A genetic disorder that can lead to left ventricular hypertrophy due to the accumulation of globotriaosylceramide in the heart. Chest pain can occur due to ischemia or other cardiac involvement.
Amyloidosis: Involvement of the heart by amyloid deposits can lead to restrictive cardiomyopathy, which might present with left ventricular hypertrophy and chest pain due to ischemia or other mechanisms.
Left Ventricular Non-Compaction: A rare cardiomyopathy characterized by a spongy appearance of the left ventricle, which can lead to hypertrophy and symptoms including chest pain.