Ischemia without pain is called silent ischemia. Many people don't know that they have ischemic heart disease and that's why they could suffer a heart attack without any warning before. People with previous heart attacks , diabetes or angina are inclined to developing silent ischemia.
Not all people who suffer from ischemia also have angina. Ischemia without angina is called silent ischemia. The absence of symptoms in the presence of ECG or myocardial ischemia that had already been diagnosed indicates that the person suffers from silent myocardial ischemia. It usually occurs in patients who had a cardiac transplantation or have diabetes.
There are three types of silent ischemia:
1)Type I silent ischemia: Is the most rare form of silent ischemia and it occurs in patients with obstructive CAD that don't suffer from angina. Studies show that patients with myocardial silent ischemia never experience angina pectoris in any of its forms: stable, unstable, variant. That is why patients with type I silent ischemia are considered to have a defective anginal warning system.
2) Type II silent ischemia: Occurs in patients who suffered from MI.
3) Type III silent ischemia: Is the most frequent form of silent ischemia and it occurs in patients with chronic stable angina and variant angina. Patients with this type III silent ischemia experience sometimes ischemia associated with chest discomfort and other times without.
Mechanism of silent ischemia:
~diabetes associated with silent ischemia has been assigned to an autonomic neuropathy.
~silent ischemia is a threshold for other forms of pain like the ones caused by limb ischemia, balloon inflation in the coronary arteries, electric shock.
~patients with hypertension suffering from silent ischemia have a low reaction to tooth-pulp simulation and produce an high amount of endorphins.
~recent studies show that silent ischemia might be caused by a defect in the cerebral cortex because the pain messages transmited from the heart are the subject to abnormal neural processing.