A female of 40 years presenting with intolerance to cold, constipation and hoarseness of voice was found to have cardiomegaly on chest roentgenogram.which of the following investigations is the best to determine the cause of her cardiomegaly ?

• A. Coronary angiography
• B. Left ventricular angiography
• C. Right ventricular angiography
• D. Echocardiography