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| Arrhythmias |
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| Sometimes the heart can beat too fast, too slow, or it can beat irregularly or skip beats. When the heart beats in any of these ways, a person is said to have an arrhythmia.
Normally the heart beats in a coordinated and regular manner, efficiently pumping blood throughout the body. The electrical impulse that initiates this pumping originates in your sinoatrial (SA) node, located in the upper right chamber (right atrium) of the heart. The SA node is known as the "natural pacemaker" of the heart. This impulse then travels through the atria to the atrioventricular node and on to the ventricles. As the impulses pass through the heart chambers, they cause them to contract, allowing the heart to pump the blood through the heart and to the body. When the electrical signals do not fire in a regular pattern or when they are blocked, the heart beats in an abnormal or arrhythmic pattern. This in turn disrupts the flow of the blood through the body. There are several types of arrhythmias, due to the electrical impulses firing too fast or too slow.
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| Bradycardias |
| Bradycardias are arrhythmias in which your heart beats abnormally slow. This occurs when your SA node does not send the electrical impulses fast enough or when the conduction system of your body prevents the electrical impulses from reaching your ventricles. When this happens, your ventricles may not receive enough charge to contract. Therefore they cannot pump the blood effectively to the rest of your body.
Because your heart beats slower if you have a bradycardia, you may feel symptoms of heart palpitations, which feels like your heart is fluttering and pounding. In addition, if there is not enough blood pumped to your brain, you may feel dizzy or faint.
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| Tachycardias |
| Tachycardias are arrhythmias in which your heart beats too fast because electrical signals are sent more rapidly than normal. When this happens, the ventricles of the heart do not have enough time to fill with blood before they contract again. Therefore, they cannot pump a sufficient amount of blood to the body.
There are several types of tachycardias, some originating in the atria and others originating in the ventricles.
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| Tachycardias Originating in the Atria |
| Atrial flutter: This is a very fast, but steady heartbeat. It is caused when the SA node fires electrical impulses in a steady, rapid succession, which causes the atria to contract more rapidly.
Atrial fibrillation: This is a very fast, but irregular heartbeat (up to 300 beats per minute). Atrial fibrillation is caused when the electrical signals in the atria are fired in a very fast and chaotic manner. As these uncontrolled signals pass through the atria, they cause it to quiver.
Sinus tachycardia: This is an increased heart rate due to the electrical signals from the sinus node being sent more rapidly.
Supraventricular tachycardia (SVT) or paroxysmal atrial tachycardia (PAT): SVT is when your heart rate is faster than normal because the atrium is sending signals faster, causing "short circuits." PAT occurs when these episodes of fast heartbeats begin and end abruptly. People who have SVT and PAT are frequently children, young adults and older adults who do not have heart disease.
Premature atrial contractions (PAC): These occur when the atria send a beat early, causing the heart to beat before it should.
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| Tachycardias Originating in the Ventricles |
| Ventricular tachycardia: These are fast heartbeats caused when the ventricles, rather than the atria, send electrical signals more rapidly than normal. While some ventricular tachycardias still allow the heart to pump blood effectively, others do not. When the ventricles cannot pump the blood effectively, it can cause fainting or sudden cardiac death. Ventricular tachycardias are typically a result of structural heart problems or a scar from a previous heart attack.
Ventricular fibrillation: Ventricular fibrillation is caused when the electrical signals in the ventricles are fired in a very fast and chaotic manner. As these uncontrolled signals pass through the ventricles, they cause them to quiver and prevent them from contracting. Ventricular fibrillation is a life-threatening condition and will cause death within minutes if it is not treated immediately. The only treatment for this condition, however, is defibrillation, which is an electric shock to the heart.
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| Risk Factors and Causes of Arrhythmias |
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An arrhythmia can occur following a heart attack, however most arrhythmias arise from an underlying heart disease or an abnormality a person has from the time of birth. Also some arrhythmias may also result from:- excessive use of coffee, cigarettes or alcohol
- anemia, fever or infection
- pulmonary or lung disease
- thyroid disease
- excessive stress
- a disturbance in the body's level of potassium, magnesium or calcium
- the use of certain drugs, such as some antidepressants
- effects of nasal decongestants or asthma medicines
- a blockage in a coronary artery
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| Symptoms of Arrhythmias |
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In some cases, an abnormal heart rhythm can lead to sudden death. On the other hand, you may not experience any symptoms at all if you have an arrhythmia. Symptoms of an arrhythmia may include:- dizziness
- lightheadedness
- fatigue
- shortness of breath
- nausea
- a feeling of fullness in the chest
- passing out
- palpitations, which are rapid heart flutters or pounding
- an awareness of an irregular heart rate
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