Types of Abnormal Heart Rhythms
Some abnormal heart rhythms or heartbeats (arrhythmias) are fast, others are slow, and some are irregular. How an abnormal heart rhythm is treated depends on the kind of abnormal beat.
Fast heart rhythms (tachycardia)
- Supraventricular tachycardia (SVT) – Instead, it is often the result of tachycardia above the His bundle, and the electrical impulses are generated rapidly, which may result in as high as 280 heartbeats per minute. Treatment is possible with the Valsalva maneuver, in which the patient is asked to strain (bear down) to slow the heart rate. If this isn't effective, medications can slow the heart rate. For those with severe SVT, cardioversion may be recommended. In cardioversion, an electrical shock is delivered to the heart to change an abnormal heart rhythm to a normal one. In many cases, an electrophysiology study may be performed to understand further the mechanism of the SVT, and cardiac ablations may be performed to prevent additional future episodes.
- Atrial flutter – Atrial flutter occurs when rapidly fired signals cause the muscles in the heart's upper chambers (the atria) to contract quickly, leading to a speedy and steady heartbeat. Treatment with medications is possible. Many patients would need to be on anticoagulation medicine to prevent the formation of blood clots in the heart. Like with SVT, cardiac ablations may be performed to treat this.
- Ventricular tachycardia – Ventricular tachycardia is a dangerous type of rapid heart rhythm usually associated with too little blood being ejected from the heart (poor cardiac output). Ventricular tachycardia arises in the heart's lower chambers (the ventricles) from tissues that generate a rapid heart rhythm. Patients with weakened hearts are especially at higher risk. Ventricular tachycardia is a life-threatening emergency that may require cardioversion. Patients typically see cardiac electrophysiologists further to address the management through medical therapy or invasive procedures.
Slow heart rhythms (bradycardia)
An atrioventricular block (AVB) occurs when some or all of the electrical signals traveling from the heart's upper chambers (the atria) to the lower chambers (the ventricles) are impaired or fail to transmit. This is often called "heart block" or "AV block." The atria may contract at an average rate in this condition, but the ventricle signals are "blocked." For example, in the case of a complete heart block, none of the signals pass through the AV node, leaving the ventricles to generate their beat. In other cases, some patients may have sinus nodal dysfunction in which abnormal electrical conduction at the sinus node level results in bradycardia. In addition, patients with slow heart rhythms may present with symptoms such as dizziness or loss of consciousness.
The recommended treatment for patients with bradycardia and symptoms is a pacemaker, which is a small, implanted device that stimulates the heart to beat at a specific rate.
Irregular heart rhythms
- Premature atrial contraction (PAC) – An electrical impulse generated in the upper chamber of the heart "fires" early. This causes the heart to beat earlier than usual, resulting in an irregular heart rhythm. PAC typically doesn't require therapy. However, medications may be prescribed to control it if it's severe.
- Premature ventricular contraction (PVC) – The lower heart chambers (the ventricles) generate an early impulse that causes the heart to beat earlier than usual, resulting in irregular heart rhythm. PVC typically doesn't require therapy, mainly if it occurs infrequently. More frequent PVCs require treatment with medications. The cause of PVC should be investigated, as it may reflect heart muscle disease.
- Atrial fibrillation (Afib) – Many sites within the heart's upper chambers (which may often originate from the left atrium, such as pulmonary veins) generate irregular electrical impulses that cause irregular heartbeat. Afib is unusual in children. Each patient is individualized to determine if anticoagulation is required, as some patients may be at risk of developing blood clots in the heart, which may lead to stroke. In electrical shock therapy (cardioversion), the heart is "shocked" back into normal rhythm, and medications are used to treat Afib. Patients typically see cardiac electrophysiologists for further management. This may be in the form of medical therapy or invasive procedure.