People with CHD who have no symptoms are said to have silent ischemia. Silent ischemia may affect up to 3 to 4 million Americans. Though they have no pain, the arteries leading to the heart are dangerously narrowed. In a silent ischemic episode, there is a temporary shortage of blood and oxygen going to the heart. Although this shortage doesn't cause pain, it is still serious. If you have silent ischemia, you may be at risk for a heart attack without warning. Even people who sometimes have the chest pain and pressure of angina can also have episodes of silent ischemia without knowing it.