Heart attack: The death of heart muscle due to the loss of blood supply. The loss of blood supply is usually caused by a complete blockage of a coronary artery, one of the arteries that supplies blood to the heart muscle. Death of the heart muscle, in turn, causes chest pain and electrical instability of the heart muscle tissue.
The electrical instability of the heart causes ventricular fibrillation (chaotic electrical disturbances affecting the ventricles, the lower chambers of the heart). Orderly transmission of electrical signals in the heart is important for the regular beating (and the efficient pumping) of the heart. A heart undergoing ventricular fibrillation simply quivers and can not pump or deliver oxygenated blood to the brain. Permanent brain damage and death can occur unless oxygenated blood flow is restored within five minutes.
A heart attack is also called a myocardial infarction or an MI. Myocardial refers to the myocardium, the heart muscle. Infarction is tissue death due to a local lack of oxygen.
An arrhythmia is any disorder of your heart rate or rhythm. It means that your heart beats too quickly, too slowly
or with an irregular pattern. When the heart beats faster than normal, it is called tachycardia. When the heart beats too slowly, it is called bradycardia.
Many factors can affect your heart’s rhythm, such as having had a heart attack, blood chemistry imbalances or abnormal hormone levels. Some substances or medicines may also cause arrhythmias.
Symptoms of arrhythmias include
- Fast or slow heart beat
- Skipping beats
- Lightheadedness, dizziness
- Chest pain
- Shortness of breath
Tachycardia is a faster than normal heart rate. A healthy adult heart beats 60 to 100 times a minute when a person is at rest. If you have tachycardia, the rate in the upper chambers or lower chambers of the heart, or both, are increased significantly.
Heart rate is controlled by electrical signals sent across heart tissues. Tachycardia occurs when an abnormality in the heart produces rapid electrical signals.
In some cases, tachycardias may cause no symptoms or complications. However, tachycardias can seriously disrupt normal heart function, increase the risk of stroke, or cause sudden cardiac arrest or death.