The supraventricular tachycardia avnrt ecg
The supraventricular tachycardia avnrt ecg Supraventricular tachycardia (SVT) encompasses a group of rapid heart rhythms originating above the ventricles, with AVNRT (Atrioventricular Nodal Reentrant Tachycardia) being one of the most common subtypes. AVNRT is characterized by a reentrant circuit within or near the atrioventricular node, leading to episodes of rapid heartbeats that can cause palpitations, dizziness, or even fainting. A crucial tool in diagnosing AVNRT is the electrocardiogram (ECG), which provides a visual record of the heart’s electrical activity.
ECG features of AVNRT are distinctive and often diagnostic. During an episode, the heart rate typically ranges from 150 to 250 beats per minute, which is significantly faster than normal sinus rhythm. The P waves, representing atrial activity, can often be hidden within the QRS complexes or appear as retrograde P waves shortly after the QRS complex. This occurs because the reentrant circuit causes atrial activation to occur in a retrograde fashion, making the P waves appear inverted in the inferior leads (II, III, aVF) or sometimes not visible at all.
One key ECG hallmark of AVNRT is the presence of a narrow QRS complex, which indicates that ventricular depolarization occurs normally through the His-Purkinje system. The QRS duration is usually less than 120 milliseconds. The rapid rate and narrow QRS complexes create a characteristic “regular, rapid” rhythm, often described as a “sawtooth” pattern in some cases, especially during certain types of AVNRT. However, the classic “sawtooth” pattern is more typical of atrial flutter than AVNRT; in AVNRT, the hallmark is the sudden onset and termination of the tachycardia with a regular rhythm.
Diagnosis can sometimes be complicated if P waves are obscured or buried within the QRS complexes, but careful analysis of the timing and morphology can reveal retrograde P waves. The presence of P waves shortly after the QRS complex, with a consistent RP interval, supports the diagnosis of AVNRT. Additionally, during an electrophysiological study, specific pacing maneuvers can induce AVNRT, confirming the diagnosis.
Management of AVNRT often begins with acute termination using vagal maneuvers—methods that stimulate the vagus nerve like carotid sinus massage or the Valsalva maneuver—aiming to slow conduction through the AV node. If these are ineffective, pharmacologic agents such as adenosine are used; adenosine transiently blocks AV nodal conduction, often restoring normal rhythm immediately. For recurrent AVNRT, catheter ablation targeting the slow pathway within the AV node offers a curative approach with high success rates.
Understanding the ECG characteristics of AVNRT is vital for rapid diagnosis and appropriate management. Recognizing the typical rate, narrow QRS complexes, and retrograde P waves allows clinicians to differentiate AVNRT from other types of tachycardias, ensuring prompt and effective treatment.
