Hi, Thanks for posting in HCM. I understand your concern. Toes turning black in an elderly woman with history of heavy smoking is due to thromboangiitis obliterans or Buerger disease . The symptoms are due to recurring and progressive inflammation and clotting of small and medium arteries and veins of the hands and feet causing gangrene like symptoms. Ultrasound and Doppler examination of the legs would tell the status of the blood vessels. Smoking cessation has been shown to slow the progression of the disease and decrease the severity of amputation in most patients, but does not halt the progression. Taking some anti-oxidant medications like Vitamin E and Selenium might help to slow down the progression. Hope the information provided would be helpful. All the best.