![]() ![]() A third type of arrhythmia is the ectopic beat.Įctopic beats occur when electrical signals arise intermittently from parts of the heart other than the sinus node. Arrhythmias are usually divided into 2 main types, bradycardias, or slow heart rhythms (less than 50 beats per minute) and tachycardias or fast heart rhythms (faster than 100 beats per minutes). Arrhythmias (abnormal heart rhythms)ĭoctors call abnormal heart rhythms “arrhythmias”. This figure shows the flow of electrical current in the heart: arrows show the electrical current arising in sinus node, travelling through the atria to the AV node, then to the ventricles. This electrical connection has a complicated name, the “atrioventricular-node and His bundle” (from now on, I’ll refer to it as the AV node). The electrical signal then enters a single electrical connection to excite the ventricles. This electric current spreads through all the cells of the atria within about a tenth of a second, causing all these cells to contract virtually simultaneously. The heart beat commences when the heart’s natural pacemaker, the sinus node (this is a small group of cells about the size of a cashew nut) fires off a tiny electrical impulse. The heart uses an electrical system to co-ordinate the contraction of the heart cells. If the cells contract individually rather than together, the heart chambers would wiggle like a sack of worms and the heart’s contraction would be ineffective. In order for the heart to pump blood properly, the cells in the atria must all contract together, followed a fraction of a second later by the cells in the ventricle. It is important that the heart cells contract in a co-ordinated fashion. Each of these chambers is composed of millions of heart cells which are too small to be seen without a microscope. The heart is composed of 4 muscular pumping chambers: 2 atria (singular: atrium) which are relatively small pumping chambers or priming pumps and 2 larger, main pumping chambers, the ventricles. Some background information might help when trying to understand heart rhythms. The name “sinus” rhythm comes from the fact that the normal heart rhythm arises from the sinus node – the heart’s natural pacemaker. Normal or Sinus RhythmĪ normal heart rhythm is called sinus rhythm. The heart rate naturally falls during sleep (sometimes as low as 30 beats per minute in young people) and increases with exercise and emotion. The normal resting heart rate is about 70 beats per minute but rates of between 40 and 90 beats per minute can occur in normal individuals. The normal human heart beats about 100,000 times per day. ![]()
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