The human heart functions as a pump, circulating blood throughout the body. This intricate process is orchestrated by precisely timed electrical signals. Sometimes, these electrical impulses can become disrupted, leading to irregular heartbeats known as arrhythmias. These disruptions can cause the heart to beat too quickly, too slowly, or with an erratic rhythm, impacting its ability to effectively pump blood.
Understanding Heart Rhythms
The heart’s normal electrical activity begins in the sinoatrial (SA) node, the natural pacemaker, located in the upper right chamber. This node generates impulses that spread across the atria, causing them to contract. The signal then travels to the atrioventricular (AV) node, which briefly delays the impulse, allowing the atria to empty blood into the ventricles before they contract.
Finally, the impulse travels through specialized pathways to the ventricles, causing them to pump blood out to the body and lungs. A healthy heart typically beats 60 to 100 times per minute at rest, maintaining a regular rhythm called normal sinus rhythm. An arrhythmia is any deviation from this organized electrical sequence.
Supraventricular Tachycardia Explained
Supraventricular Tachycardia (SVT) is a fast heart rhythm originating in the upper chambers (atria) or the atrioventricular (AV) node. The term “supraventricular” indicates the abnormal electrical activity begins above the ventricles. SVT is characterized by a rapid, usually regular heartbeat, often ranging from 150 to 220 beats per minute.
Episodes of SVT typically begin and end abruptly. Individuals may suddenly feel their heart pounding or racing. Common symptoms include a fluttering sensation in the chest, shortness of breath, lightheadedness, dizziness, and sometimes chest discomfort. While SVT can be alarming, it is generally not life-threatening.
Atrial Fibrillation Explained
Atrial Fibrillation (AFib) is an irregular heart rhythm originating in the atria. In AFib, electrical signals in the atria become disorganized and chaotic, leading to rapid, uncoordinated quivering. This chaotic activity results in an irregular and often rapid ventricular response.
The heart rate during AFib can vary but is often between 100 and 200 beats per minute, with an irregular pattern. Symptoms include palpitations, fatigue, shortness of breath, dizziness, and chest pain. AFib carries an increased risk of blood clots forming in the heart due to blood pooling in the atria. These clots can travel to the brain, potentially causing a stroke.
Comparing SVT and AFib
While both Supraventricular Tachycardia (SVT) and Atrial Fibrillation (AFib) involve rapid heart rates originating above the ventricles, they differ in their electrical mechanisms. SVT typically involves a single, organized electrical circuit that rapidly re-enters itself, leading to a fast but regular heart rhythm. Conversely, AFib is characterized by multiple, disorganized electrical impulses firing chaotically within the atria, resulting in an irregularly irregular heartbeat.
The regularity of the heart rhythm is a primary distinguishing feature: SVT usually presents with a regular, fast rhythm, whereas AFib is distinctly irregular. The onset and offset of SVT episodes are often sudden. AFib can be paroxysmal, persistent, or long-standing, with symptoms that may come and go or be continuous.
Although both conditions can cause similar symptoms, their implications and management approaches differ. SVT is generally less serious and often treated to alleviate symptoms, with a high success rate for curative procedures like ablation. AFib, however, carries a higher risk of complications, particularly stroke, due to potential blood clot formation, often requiring blood thinners. While AFib is technically a type of SVT, it is categorized separately due to its unique characteristics and associated stroke risk.