Heart block is a disorder of the heart which may lead to dizziness, fainting spells, or strokes. It is caused by an interruption of the flow of blood in the heart. It may occur as a result of coronary heart disease, by inflammation of heart muscle, by rheumatic fever, overdose of digitalis drugs, or syphilitic aoritis. If the blockage causes any of the above symptoms, it is usually treated by coronary bypass. Heart blocks occur in about 30 out of 100,000 people annually in the United States.