Chronic Heart Failure with Preserved Ejection Fraction (HFpEF): Given the patient's age, LVEF >55%, and presence of moderate to severe mitral regurgitation, moderate aortic regurgitation, and moderate tricuspid regurgitation, HFpEF is a likely diagnosis. The mild left atrial enlargement also supports this diagnosis.

Degenerative Mitral Valve Disease: The presence of moderate to severe mitral regurgitation suggests degenerative mitral valve disease, which is common in elderly patients.
Aortic Valve Disease: Moderate aortic regurgitation indicates aortic valve disease, which could be due to degenerative changes, endocarditis, or other causes.
Tricuspid Valve Disease: Moderate tricuspid regurgitation may indicate tricuspid valve disease, which can be primary or secondary to other conditions such as pulmonary hypertension.

Pulmonary Embolism: Although the RVSP is elevated (50-55mmHg), it is essential to rule out pulmonary embolism, as it can be life-threatening and may not always present with typical symptoms.
Cardiac Amyloidosis: Given the patient's age and presence of heart failure symptoms, cardiac amyloidosis should be considered, as it can present with preserved ejection fraction and valvular regurgitation.
Constrictive Pericarditis: Although less likely, constrictive pericarditis can present with similar echocardiogram findings and should be considered to avoid missing this potentially treatable condition.

Loeffler's Endocarditis: A rare condition characterized by eosinophilic infiltration of the heart, which can cause valvular regurgitation and heart failure.
Carcinoid Heart Disease: A rare condition caused by metastatic carcinoid tumors, which can lead to tricuspid and pulmonary valve disease, as well as heart failure.
Pulmonary Arterial Hypertension (PAH) due to Rare Causes: Such as congenital heart disease, HIV, or schistosomiasis, which can present with elevated RVSP and right heart dysfunction.