When the heart's ability to work is greatly reduced for a prolonged time, a life-threatening situation can arise. This may result from ventricular tachycardia and ventricular fibrillation, an extremely fast, chaotic rhythm during which the lower chambers quiver and the heart can't pump any blood, causing cardiac arrest. This is sudden cardiac arrest, which is a medical emergency.
If the heart can continue to pump normally, though, some ventricular tachycardias may be tolerated without fainting (syncope) or cardiac arrest. Tachycardia may be nonsustained (lasting only seconds) or sustained (lasting for minutes or hours).
Tachycardias also can cause serious injury to other organs. For example, the brain, kidneys, lungs or liver may be damaged during prolonged cardiac arrest.
Blood clots can form in the heart's upper chambers because of atrial fibrillation, a disorder in which the atria quiver (like a bowl of gelatin) instead of beating effectively. Blood that isn't pumped completely out of the atria when the heart beats may pool and clot. If a piece of a blood clot in the atria breaks free, it can enter into the circulation. Then it can flow within the bloodstream until it lodges in a narrowed artery leading to or within the brain, causing a stroke. Such clots can also damage other organs.
What is sudden cardiac arrest?
Sudden cardiac arrest is the abrupt loss of heart function in a person who may or may not have diagnosed heart disease. The time and mode of death are unexpected. It occurs instantly or shortly after symptoms appear.
The term "massive heart attack" is often mistakenly used to describe sudden cardiac arrest. While a heart attack may cause cardiac arrest and sudden death, the terms don't mean the same thing. The term "heart attack" (or myocardial infarction) refers to death of heart muscle tissue due to the loss of blood supply, not necessarily resulting in the death of the heart attack victim.
Arrhythmias can cause stroke (View an animation of arrhythmia)
Stroke is a cerebrovascular disease that affects the blood vessels supplying blood to the brain. A stroke occurs when a blood vessel bringing oxygen and nutrients to the brain bursts or is clogged by a blood clot or some other particle. Because of this rupture or blockage, part of the brain doesn't get the blood flow it needs. Deprived of oxygen, brain cells in the affected area can't function and die within minutes. And when brain or nerve cells can't function, the part of the body they control can't function either. The devastating effects of stroke are often permanent because dead brain cells aren't replaced.
There are two types of strokes:
- those caused by a blocked blood vessel to the brain (ischemic stroke)
- those caused by a ruptured blood vessel (hemorrhagic stroke), blood within the brain tissues)
The most common cause of stroke from an arrhythmia is atrial fibrillation. Atrial fibrillation can cause blood clots to form in the atria (top chamber of the heart) where they can be pumped out of the heart, to the brain, blocking a blood vessel and causing a stroke.
Treatment for atrial fibrillation focuses in part on reducing the risk of stroke. It's important to know and manage all your risk factors for stroke, including atrial fibrillation.
This content was last reviewed September 2016.