47-year-old male smoker with non-diabetic, non-hypertensive c/o bluish discoloration of 4th and 5th fingers of right hand since 3daya associated with pain. O/E BP - 170/90, 76/min. Bluish discoloration of 4th and 5th fingers with decreased capillary filling.

Color Doppler shows decreased blood flow to respective fingers. Echo normal. What is the probable diagnosis and treatment?