A patient presents in the emergency room with a history of chronic high Wood pressure...

The combination of chronic elevated Wood units (indicative of pulmonary hypertension), severe back pain, and a new diastolic murmur strongly suggests an acute aortic dissection involving the ascending aorta or aortic valve.

Aortic dissection can cause tearing of the intima and compromise the aortic valve, leading to acute aortic regurgitation manifesting as a new diastolic murmur. Back pain is a classic symptom due to the dissection extending along the aorta.

Aortic aneurysm may cause symptoms but usually not acute severe pain and murmur. Left ventricular rupture and ruptured papillary muscle are typically complications of myocardial infarction and present differently.

This clinical presentation and echocardiographic assessment are described in the "Textbook of Clinical Echocardiography, 6e", Chapter on Aortic Pathology and Emergencies【20:380-385†Textbook of Clinical Echocardiography】.