Heart disease

Congestive heart disease is the leading cause of death of North Americans, generally leading to death by cardiac arrest. It is usually caused by the buildup of arterial plaque in the major arteries providing blood to the heart, which eventually become blocked leading to infarction, heart attack and cardiac arrest. Smoking also leads to such congestive heart failure.
Heart disease generally strikes people later in life, but is not unknown in males as early as their thirties. It is diagnosed by performing such tests as an EKG and an angiogram to measure the flow of blood through the heart.
The best treatment is preventative. Individuals will moderate body mass, a balanced diet and who do not smoke are far less likely to develop heart disease, or will only develop it much later in life. However, once it is diagnosed, it usually requires immediate treatment. There is debate about which treatments are safest and most effective, but all pose risks. In severe cases, a heart bypass (taking arterial grafts and bypassing the flow of blood around the affected area) is often recommended, but this procedure is very risky as it requires heart-lung bypass. Medication that reduces the major symptoms, such as chest pain (angina) have often been shown to be as effective on a five-year mortality basis and less likely to result in sudden death. In all cases, lifestyle changes such as losing weight, exercising, stopping smoking and reducing alcohol intake are also very effective and can be combined with other therapies.
Coronary heart disease at NIH
Heart disease at Wikipedia
Heart disease at Mayo Clinic