A 58 year old man presents with pain and blackish discoloration of his right little toe for 1 week, in a background of exertional dyspnea, fatiguability and intermittent headaches for 4 months. No other symptoms are present.

He has no known medical conditions and has never smoked. At a recent checkup, a fasting blood sugar, lipid profile, liver and renal profile, ECG, chest x-ray and echocardiogram were found to be normal.