Rhythm & Arrhythmias
Sinus tachycardia results when the sinoatrial (SA) node sends electrical impulses faster than usual, thus raising the heart rate to meet the increased needs of the body, such as fever or exercise. This is a normal response and, as such, it is considered a normal rhythm.
Atrial and Ventricular Fibrillation
When the a tachyarrhythmia is very fast, the heart muscle begins to fibrillate or quiver continually, and cannot contract normally. When a heart is in a state of atrial or ventricular fibrillation, there is no synchronization between the atria and the ventricles. This may cause the patient to experience a racing sensation – and sometimes discomfort in the chest–and/or to feel light-headed or faint.
Atrial fibrillation (AF) is the most common abnormal heart rhythm. It is a very fast, uncontrolled heart rhythm that occurs when the upper chambers of the heart (the atria) try to beat so fast that they only can quiver. During AF, the upper chambers beat between 350 and 600 times per minute. Normal heart rhythm is between 60 and 100 beats per minute. Due to the erratic rhythm in the upper chambers, the rhythm of the lower chambers of the heart (the ventricles) can also become very irregular.
Because the heart’s pumping function isn’t working properly, the blood is not completely emptied from the heart’s chambers, causing it to pool and sometimes clot. Sometimes, clotted blood dislodges from the atria and results in a stroke. The American Heart Association estimates that of the 700,000 strokes occurring each year in the U.S., 15 percent—about 105,000—occur in people with AF.
Ventricular fibrillation (VF) is a chaotic heart rate resulting from multiple areas of the ventricles attempting to control the heart's rhythm. Ventricular fibrillation can occur spontaneously (generally caused by heart disease) or when ventricular tachycardia has persisted too long. When the ventricles fibrillate, they cannot contract normally, hence, they cannot effectively pump blood. The instant VF begins, effective blood pumping stops. VF quickly becomes more erratic, resulting in sudden cardiac arrest or sudden cardiac death. This arrhythmia must be corrected immediately via a shock from an external defibrillator or an ICD. The defibrillator can stop the chaotic electrical activity and restores normal rhythm.
Did you know?
Facts On: Atrial Fibrillation (AF)