Tachyarrhythmias are abnormally rapid heart rhythms that may lead to potentially serious health complications, such as heart failure.
A narrow-complex tachyarrhythmia refers to a particular type of rhythm in which the ventricles are activated faster than normal. The source of the rhythm disturbance may be in any of several points in the upper portion of your heart.
The term “narrow-complex” refers to how this arrhythmia is reflected on an electrocardiogram (EKG). One complete heartbeat, including the contraction of your heart muscle (systole) and its relaxation (diastole), is shown on an EKG as having five distinct waves: P, Q, R, S, and T.
A narrow-complex tachyarrhythmia is illustrated on an EKG by the Q, R, and S complex being bunched together, suggesting your heart is beating faster than normal.
In contrast, if the Q, R, and S waves are spread apart too far, it means there’s a delay somewhere in the electrical network that causes your heart to beat, usually resulting in an abnormally slow heart rhythm (bradycardia).
Narrow-complex tachyarrhythmia is a broad term to cover any of several types of arrhythmias in which the heart beats faster than 100 beats per minute, and the QRS duration is less than 120 milliseconds.
Most narrow-complex tachyarrhythmias are symptomatic, meaning you can likely feel your heart racing. A 2020 article suggests that about one in five people with the condition experience syncope — fainting caused by a sudden drop in blood pressure.
Narrow-complex tachyarrhythmias include conditions that come and go (paroxysmal) and conditions that persist until treated effectively. Some may be mild and have no obvious symptoms, while others may be so intense that they interfere with your ability to carry out normal, daily functions.
A healthcare professional can diagnose your condition and develop a treatment plan that may include some combination of medications, implanted devices, and lifestyle changes.
Narrow-complex tachyarrhythmias are usually divided into two categories: those that originate in the tissue located within the atria (heart’s upper chambers) and those that originate in the atrioventricular junction — the tissue separating the atria from the ventricles (heart’s lower chambers). Below are examples that originate in atria tissue:
- Atrial fibrillation (AFib): AFib is the rapid, but unpredictable, beating of your atria and the
most commontype of arrhythmia.
- Atrial flutter: Similar to AFib, atrial flutter involves the abnormal beating of your atria but in a more predictable pattern.
- Inappropriate sinus tachycardia: This type of tachycardia is a poorly understood and rare arrhythmia. It affects an estimated
1%of the general population.
- Intraarterial reentrant tachycardia: This is a condition often resulting from a
congenital heart defect.
- Multifocal atrial tachycardia: This type of tachycardia is triggered by ectopic foci, which are abnormal “pacemaker” sites in your heart that interfere with the normal electrical activity that paces your heart’s rhythm.
- Sinoatrial nodal reentrant tachycardia: This is a
raretype of narrow-complex tachyarrhythmia caused by circuits emerging from the sinus node — the portion of your heart that originates the electrical activity controlling your heartbeat.
- Sinus tachycardia: Sinus tachycardia is a problem that occurs with the sinus node sends out electrical impulses faster than normal.
Examples of narrow-complex tachyarrhythmias originating in the atrioventricular junction include:
- Atrioventricular nodal reentrant tachycardia (AVNRT): This is a tachyarrhythmia that originates in the atrioventricular node, the part of your heart that transmits electrical signals from the atria down to the ventricles.
- Atrioventricular reentrant tachycardia (AVNT): This is a paroxysmal condition and one of the more
commonsupraventricular (above the ventricles) arrhythmias.
- Junctional tachycardia: This type of tachycardia starts in the atrioventricular node because the sinus node is injured or otherwise unable to launch the electrical activity needed for the heart to contract and rest.
A narrow-complex tachyarrhythmia can have several possible origins. Among them are:
- cardiovascular disease
- congenital heart defects
- drug or alcohol abuse
- heart attack
- high blood pressure
- sleep apnea
- thyroid disease
The primary means of diagnosing a narrow-complex tachyarrhythmia is with an EKG. As long as the arrhythmia is ongoing, an EKG will be able to identify it and display the narrow QRS complex.
Some people with a narrow-complex tachyarrhythmia or another type of arrhythmia may experience periods when their heart beats normally. In these cases, a doctor may recommend wearing a portable EKG, such as a Holter monitor, to record any abnormal heart rhythms away from a hospital or doctor’s office.
The right treatment for a narrow-complex tachyarrhythmia depends on the specific arrhythmia and its severity and frequency.
Typical treatments can include:
- Anti-arrhythmic drugs: These medications are meant to help preserve a healthy heart rhythm.
- Cardioversion therapy: This therapy uses an electrical signal delivered from outside your chest to restore a healthy, normal heart rhythm.
- Catheter ablation: Catheter ablation is a procedure in which a special catheter is guided through a blood vessel to the part of the heart causing the rhythm disturbance to deliver a small electrical impulse, destroying the suspicious heart tissue.
- Implantable devices: Devices such as pacemakers or implantable cardioverter defibrillators use mild electrical pulses to restore or maintain a healthy rhythm.
- Antihypertensive medication: These medications help to lower blood pressure and can be used to control your heart rate (examples include beta-blockers and calcium channel blockers).
The outlook for someone diagnosed with a narrow-complex tachyarrhythmia depends on several factors, including the individual’s age and overall health, as well as the severity of the arrhythmia and whether any other cardiac problems exist.
Regardless of which type of arrhythmia you have, it’s critically important that you work closely with a cardiologist. You have to keep up with appointments and screenings, as well as stick you to your medication regimen and follow through with other components of your treatment plan.
Are narrow-complex tachyarrhythmias congenital heart conditions?
In some cases, these heart rhythm disturbances may be present at birth. But often they develop as the result of a heart attack or simply due to advancing age.
Following a heart-healthy lifestyle of a balanced diet, regular exercise, no smoking, and control of your blood pressure, cholesterol, and blood glucose levels may lower your risk of developing an arrhythmia.
Do narrow-complex tachyarrhythmias run in families?
Arrhythmias are commonly inherited conditions, though your personal medical history may lead to an arrhythmia that’s not part of your family’s medical history. If you do have a narrow-complex tachyarrhythmia or other heart condition in your family, it’s especially important to take extra precautions to protect your heart.
Are narrow-complex tachyarrhythmias life threatening?
An abnormally rapid heart rate isn’t, by itself, life threatening. However, when your heart stops beating in a normal, efficient manner, blood can pool within your heart and form a blood clot that could make its way to your brain and cause a stroke.
Similarly, if the arrhythmia is forcing your heart to work harder than normal, over time, that burden could weaken the heart and lead to heart failure — a potentially life threatening condition.
You may notice that you have a racing heart, but until you have an EKG that confirms the nature of your arrhythmia, you won’t know exactly what condition you have or how it should be treated.
It’s important to report any change you notice in your heart rate to a doctor and to treat significant changes as serious health concerns that require appropriate medical evaluation.