Characteristics of supraventricular tachycardia
Characteristics of supraventricular tachycardia Supraventricular tachycardia (SVT) is a common cardiac arrhythmia characterized by an abnormally rapid heart rate originating above the ventricles. Typically, it involves a disturbance in the electrical conduction pathways within the atria or the atrioventricular (AV) node, leading to episodes where the heart beats significantly faster than normal. These episodes can vary in duration and severity, often affecting individuals across different age groups, although they are notably prevalent among younger and otherwise healthy individuals.
One of the hallmark features of SVT is its rapid onset and termination. Unlike some arrhythmias that develop gradually, SVT episodes often begin suddenly and can cease just as abruptly. Patients may experience a sudden sensation of a racing heart, described as palpitations, which can be alarming. The heart rate during an SVT episode typically ranges from 150 to 250 beats per minute, much faster than the normal resting rate of 60 to 100 beats per minute. This rapid rate can impair the heart’s ability to fill properly between beats, potentially reducing cardiac output and leading to symptoms such as dizziness, lightheadedness, or even fainting in some cases.
Electrocardiogram (ECG) findings are instrumental in diagnosing SVT. During an episode, the ECG often reveals narrow QRS complexes, indicating that the electrical impulses are traveling through the normal conduction pathway. The P waves, which represent atrial activity, may be difficult to distinguish or may be merged with the T waves because of the rapid rate. In some cases, the P waves are inverted or appear shortly after the QRS complex, helping to differentiate SVT from other arrhythmias. The abrupt start and end of the arrhythmia on ECG are key diagnostic features.
Several types of SVT exist, with the most common being atrioventricular nodal reentrant tachycardia (AVNRT), atrioventricular reentrant tachycardia (AVRT), and atrial flutter or fibrillation with a rapid ventricular response. The underlying mechanism often involves abnormal electrical circuits or pathways that allow impulses to loop back and produce a continuous rapid rhythm. Factors like stress, caffeine, alcohol, certain medications, or underlying heart conditions can precipitate episodes. However, in many cases, SVT occurs in individuals with structurally normal hearts.
Management of SVT focuses on acute termination of episodes and long-term prevention. Vagal maneuvers, such as bearing down or applying cold to the face, can sometimes abort an episode by stimulating the vagus nerve, which slows conduction through the AV node. If these are ineffective, medical interventions like antiarrhythmic drugs or procedures such as catheter ablation may be employed. Catheter ablation has become increasingly popular due to its high success rate and minimal invasiveness, offering a potential cure for recurrent SVT.
Understanding the characteristics of SVT is essential for timely recognition and effective management. Though episodes can be frightening, many individuals live healthy lives with appropriate treatment and lifestyle modifications. Regular follow-up with a cardiologist ensures optimal control and minimizes the risk of complications.
