Supraventricular Tachycardia (SVT) refers to a group of rapid heart rhythms originating above the heart’s lower chambers, the ventricles. Atrial fibrillation (Afib) is a specific type of irregular and often rapid heart rhythm that begins in the upper chambers, known as the atria. Therefore, Afib is indeed a form of SVT, as its electrical impulses originate within the supraventricular region of the heart.
Understanding Supraventricular Tachycardia (SVT)
SVT is an umbrella term encompassing various fast heart rhythms that start in the atria or the atrioventricular (AV) node, both located above the ventricles. These rapid rhythms involve heart rates ranging from 150 to 220 beats per minute, higher than a normal resting heart rate. The abnormal electrical activity in SVT can be due to a short circuit or an area firing too quickly.
Common symptoms of SVT episodes include palpitations, a feeling of the heart pounding or racing, shortness of breath, dizziness, and lightheadedness. Some individuals may also experience chest discomfort or fatigue. Unlike ventricular tachycardias, which originate in the lower heart chambers and can be life-threatening, SVT is not considered a life-threatening rhythm disturbance unless there is underlying heart damage or other conditions. Episodes can start and stop abruptly and may last from minutes to hours.
Understanding Atrial Fibrillation (Afib)
Atrial fibrillation is one of the most common types of irregular heart rhythms, affecting millions of adults. It is characterized by chaotic and disorganized electrical signals in the atria, causing them to quiver or “fibrillate” instead of contracting effectively. This chaotic activity leads to an irregular and often rapid ventricular response, as the lower chambers try to keep pace with the disorganized signals.
Symptoms specific to Afib include irregular heart palpitations, a sensation of fluttering or thumping in the chest, and extreme fatigue. Individuals may also experience shortness of breath, dizziness, and reduced exercise capacity. While some people with Afib may not experience noticeable symptoms, others can have frequent and severe episodes.
The Relationship Between Afib and SVT
Atrial fibrillation is classified as a type of Supraventricular Tachycardia because its origin lies within the atria, which are above the heart’s ventricles. While all Afib is SVT, not all SVTs are Afib; SVT is a comprehensive term that includes other arrhythmias such as atrioventricular nodal reentrant tachycardia (AVNRT) and atrial tachycardia.
The distinction within the SVT umbrella lies in the nature of the electrical activity. Other common SVTs, like AVNRT, involve more organized, rapid rhythms due to re-entry pathways or specific abnormal electrical connections. In contrast, Afib is uniquely characterized by highly chaotic, disorganized electrical signals that result in an “irregularly irregular” ventricular rhythm.
Why the Distinction is Important
Differentiating Afib from other types of SVT is important for accurate diagnosis and effective management. An electrocardiogram (ECG) is a primary tool, revealing distinct patterns: Afib shows an irregularly irregular rhythm with no clear P waves, while other SVTs might present as rapid, regular rhythms with narrow QRS complexes. This diagnostic clarity guides specific treatment approaches.
For instance, Afib carries a risk of blood clot formation in the heart and subsequent stroke, which is a concern not associated with most other SVTs. Therefore, stroke prevention with blood-thinning medications is a primary aspect of Afib management. Treatment for other SVTs focuses on controlling heart rate and rhythm with antiarrhythmic drugs or procedures like catheter ablation, which targets specific electrical pathways. Tailored interventions based on the specific type of SVT can impact patient outcomes and reduce the risk of serious complications.