Supraventricular tachycardia on ecg
Supraventricular tachycardia on ecg Supraventricular tachycardia (SVT) is a rapid heart rhythm originating above the ventricles, primarily in the atria or the atrioventricular (AV) node. It is characterized by episodes of sudden, rapid heartbeat that can last from a few seconds to several hours. Recognizing SVT on an electrocardiogram (ECG) is crucial for diagnosis and management, as the presentation and features on ECG provide vital clues to differentiate it from other arrhythmias.
The hallmark of SVT on an ECG is a narrow QRS complex tachycardia, typically with a rate exceeding 150 beats per minute. This rapid rhythm results from abnormal electrical circuits or impulses within the atria or the AV node, leading to a reentrant mechanism. In many cases, the P waves, which represent atrial depolarization, are either hidden within the QRS complex or appear as retrograde waves following the QRS. This intracardiac activity makes the P waves difficult to discern, often leading to a “sawtooth” pattern in specific types, such as atrial flutter, but in typical SVT, they may be absent or difficult to identify.
One of the classic ECG features of SVT is the regularity of the rhythm. The intervals between successive QRS complexes are consistent, reflecting a stable reentrant circuit. The narrow QRS complexes indicate that ventricular depolarization proceeds via the normal His-Purkinje system, which is typical in supraventricular rhythms. Wide QRS complexes usually suggest aberrant conduction or an alternative diagnosis, such as ventricular tachycardia, which must be distinguished carefully.
Several types of SVT can be identified based on subtle ECG differences. A common form is AV nodal reentrant tachycardia (AVNRT), where reentry occurs within or near the AV node. In AVNRT, P waves are often hidden within or immediately after the QRS complex, leading to a short RP interval. Another type involves accessory pathways, as seen in Wolff-Parkinson-White syndrome, where the preexcitation can produce characteristic delta waves and a widened QRS complex during sinus rhythm, with SVT occurring via the accessory pathway.
Diagnosis of SVT on ECG involves analyzing the rate, rhythm regularity, QRS width, and P wave morphology. In emergency settings, vagal maneuvers (like the Valsalva maneuver) or adenosine administration can temporarily interrupt the reentrant circuit, revealing underlying atrial activity and confirming the diagnosis. Long-term management may include medications such as beta-blockers or calcium channel blockers, and in some cases, catheter ablation to eliminate the reentrant pathway.
In summary, SVT on ECG presents as a rapid, narrow-complex tachycardia with a regular rhythm and often ambiguous P waves. Recognizing these features allows clinicians to differentiate it from other arrhythmias, guiding prompt and effective treatment to alleviate symptoms and prevent potential complications.