Acute Coronary Syndrome (ACS): This is the most likely diagnosis given the presentation of chest pain with signs of ischemia. ACS, which includes conditions such as myocardial infarction (MI), is characterized by a reduction in blood flow to the heart muscle, leading to ischemia or necrosis.

Stable Angina: Although less severe than ACS, stable angina can present with chest pain and signs of ischemia, especially during periods of increased demand or decreased supply of oxygen to the heart muscle.
Coronary Artery Spasm: Also known as variant angina, this condition involves sudden spasms of the coronary arteries, which can cause chest pain and ischemia.
Cardiac Syndrome X: Characterized by chest pain with evidence of myocardial ischemia on diagnostic tests but without significant coronary artery disease on angiography.

Aortic Dissection: A life-threatening condition where there is a tear in the inner layer of the aorta, which can cause severe chest pain and can lead to ischemia if branches of the aorta are compromised.
Pulmonary Embolism: Although typically presenting with dyspnea and tachycardia, a large pulmonary embolism can cause chest pain and signs of ischemia due to the strain on the right heart.
Pericarditis: Inflammation of the pericardium can cause chest pain and, in severe cases, signs of ischemia if there is significant impairment of cardiac function.

Coronary Artery Anomalies: Congenital anomalies of the coronary arteries can cause ischemia and chest pain, especially during exertion.
Kawasaki Disease: A rare condition in adults, but can cause coronary artery aneurysms leading to ischemia.
Cardiac Sarcoidosis: A condition where granulomatous inflammation affects the heart, potentially leading to ischemia and arrhythmias.
Cardiac Tumors: Rarely, cardiac tumors can cause ischemia by obstructing coronary blood flow or by invading the myocardium.