Ecg in supraventricular tachycardia
Ecg in supraventricular tachycardia Supraventricular tachycardia (SVT) is a common arrhythmia characterized by an abnormally rapid heart rate originating above the ventricles. Its hallmark is a sudden onset and termination, making it one of the most recognizable arrhythmias in clinical practice. An essential tool in diagnosing SVT is the electrocardiogram (ECG), which provides vital information about the electrical activity of the heart during episodes of tachycardia.
The ECG in SVT typically displays a narrow QRS complex, usually less than 120 milliseconds, indicating that the impulse originates above the ventricles and that ventricular conduction pathways are functioning normally. The heart rate in SVT often exceeds 150 beats per minute, sometimes reaching up to 250 beats per minute. The rapid rate can cause a loss of the normal atrial and ventricular relationship, although in many cases, atrial activity can be discerned as P waves.
One of the characteristic features of SVT on ECG is the presence of P waves that are either hidden within the QRS complex or appear just after it, often with a short RP interval (the interval from the R wave to the P wave). In some forms, such as atrioventricular nodal reentrant tachycardia (AVNRT), P waves are not visible separately, giving a narrow, regular, and rapid rhythm. In others, like atrioventricular reentrant tachycardia (AVRT), P waves may be seen after the QRS complex, sometimes producing a pseudo-R’ in lead V1 or a pseudo-S wave in inferior leads.
The diagnosis of SVT via ECG hinges on recognizing these features, but it can sometimes be challenging, especially if the episodes are brief or if the patient is not monitored during the event. In acute settings, vagal maneuvers like carotid sinus massage or the Valsalva maneuver can increase vagal tone, often terminating the episode and enabling a clearer ECG recording. When pharmacological intervention is needed, drugs like adenosine are both diagnostic and therapeutic; adenosine temporarily blocks the AV node, revealing underlying atrial activity.
Analyzing the ECG also helps differentiate SVT from other tachyarrhythmias, such as atrial flutter or atrial fibrillation, which often have irregular rhythms and different P wave characteristics. Recognizing the specific type of SVT is critical for guiding treatment, which can range from medication to catheter ablation.
In conclusion, the ECG remains an invaluable tool for diagnosing and understanding supraventricular tachycardia. Its characteristic features—narrow QRS complexes, rapid heart rate, and specific P wave patterns—allow clinicians to distinguish SVT from other arrhythmias quickly. Accurate interpretation of these ECG findings not only aids in diagnosis but also influences management strategies, ultimately improving patient outcomes.
